Double-negative T cells: a promising avenue of adoptive cell therapy in transplant oncology

Double-negative T cells: a promising avenue of adoptive cell therapy in transplant oncology 双阴性T细胞：移植肿瘤学中一种颇具前景的过继细胞疗法 1 2 3 4 5 equal first-author 1 2 3 4 5 equal 1 2 3 4 5 1 3 4 5 6 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 corresp Di LU, zjuludi@zju.edu.cn Di LU, zjuludi@zju.edu.cn zjuludi@zju.edu.cn https://orcid.org/0000-0002-8724-3739 1 2 3 4 5 corresp Xiao XU, zjxu@zju.edu.cn Xiao XU, zjxu@zju.edu.cn zjxu@zju.edu.cn https://orcid.org/0000-0002-2761-2811 浙江大学医学院， 中国杭州市, 310058 浙江大学医学院， 中国杭州市, 310058 Zhejiang University School of Medicine, Hangzhou 310058, China Zhejiang University School of Medicine, Hangzhou 310058, China 肝胆胰外科， 浙江大学医学院附属杭州市第一人民医院，中国杭州市, 310006 肝胆胰外科， 浙江大学医学院附属杭州市第一人民医院，中国杭州市, 310006 Department of Hepatobiliary and Pancreatic Surgery, Affiliated Hangzhou First People’s Hospital, Zhejiang University School of Medicine, Hangzhou 310006, China Department of Hepatobiliary and Pancreatic Surgery, Affiliated Hangzhou First People’s Hospital, Zhejiang University School of Medicine, Hangzhou 310006, China 浙江省肿瘤融合与智能医学重点实验室, 中国杭州市, 310006 浙江省肿瘤融合与智能医学重点实验室, 中国杭州市, 310006 Key Laboratory of Integrated Oncology and Intelligent Medicine of Zhejiang Province, Hangzhou 310006, China Key Laboratory of Integrated Oncology and Intelligent Medicine of Zhejiang Province, Hangzhou 310006, China 浙江大学器官移植研究所, 中国杭州市, 310003 浙江大学器官移植研究所, 中国杭州市, 310003 Institute of Organ Transplantation, Zhejiang University, Hangzhou 310003, China Institute of Organ Transplantation, Zhejiang University, Hangzhou 310003, China 卫健委多器官联合移植重点实验室， 中国杭州市, 310003 卫健委多器官联合移植重点实验室， 中国杭州市, 310003 NHC Key Laboratory of Combined Multi-organ Transplantation, Hangzhou 310003, China NHC Key Laboratory of Combined Multi-organ Transplantation, Hangzhou 310003, China 肝胆胰外科，树兰（杭州）医院， 中国杭州市, 310004 肝胆胰外科，树兰（杭州）医院， 中国杭州市, 310004 Department of Hepatobiliary and Pancreatic Surgery, Shulan (Hangzhou) Hospital, Hangzhou 310004, China Department of Hepatobiliary and Pancreatic Surgery, Shulan (Hangzhou) Hospital, Hangzhou 310004, China Tumor recurrence is one of the major life-threatening complications after liver transplantation for liver cancer. In addition to the common mechanisms underlying tumor recurrence, another unavoidable problem is that the immunosuppressive therapeutic regimen after transplantation could promote tumor recurrence and metastasis. Transplant oncology is an emerging field that addresses oncological challenges in transplantation. In this context, a comprehensive therapeutic management approach is required to balance the anti-tumor treatment and immunosuppressive status of recipients. Double-negative T cells (DNTs) are a cluster of heterogeneous cells mainly consisting of two subsets stratified by T cell receptor (TCR) type. Among them, TCRαβ + DNTs are considered to induce immune suppression in immune-mediated diseases, while TCRγδ + DNTs are widely recognized as tumor killers. As a composite cell therapy, healthy donor-derived DNTs can be propagated to therapeutic numbers in vitro and applied for the treatment of several malignancies without impairing normal tissues or being rejected by the host. In this work, we summarized the biological characteristics and functions of DNTs in oncology, immunology, and transplantation. Based on the multiple roles of DNTs, we propose that a new balance could be achieved in liver transplant oncology using them as an off-the-shelf adoptive cell therapy (ACT). 肿瘤复发是肝癌肝移植术后危及生命的主要并发症之一。除了常见的肿瘤复发机制外，另一个不可避免的问题是移植后的免疫抑制治疗方案可能促进肿瘤复发和转移。移植肿瘤学是一个新兴领域以解决肝移植相关的肿瘤学问题。在此背景下，需要综合治疗管理方法来平衡受者的抗肿瘤治疗和免疫抑制状态。双阴性T细胞（DNTs）是一群异质性细胞，主要由T细胞受体（TCR）不同类型的两个亚群组成。其中，TCRαβ + DNTs被认为在免疫性疾病中诱导免疫抑制，而TCRγδ + DNTs被广泛认为是肿瘤杀伤细胞。作为一种复合细胞疗法，健康供体来源的DNTs可在体外增殖至治疗量级，并应用于多种恶性肿瘤的治疗，同时既不损伤正常组织，也不被宿主排斥。本文就DNTs的生物学特性及其在肿瘤学、免疫学和移植领域等方面的研究进展进行综述。基于DNTs的多重作用，我们建议将其作为一种现成的过继性细胞治疗（ACT），从而为移植肿瘤学提供一种新的平衡。 双阴性T细胞（DNT） 过继细胞疗法（ACT） 肝癌 肝移植 肿瘤学 Double-negative T cell (DNT) Adoptive cell therapy (ACT) Liver cancer Liver transplantation Oncology 1 Introduction 1 Liver transplantation, a lifesaving intervention for patients with end-stage liver disease (ESLD), has grown by leaps and bounds in recent years. Since the transplantability of unresectable hepatocellular carcinoma (HCC) was discussed in the Milan criteria ( Mazzaferro et al., 1996 Mazzaferro et al., 1996 ), a series of studies have been conducted to identify the suitable transplantation criteria for HCC patients ( Takada et al., 2007 Takada et al., 2007 ; Xu X et al., 2016 Xu X et al., 2016 ; Yao et al., 2001 Yao et al., 2001 ). In this context, a new concept named “transplant oncology” has entered the scene. Far beyond the scope of conventional surgery for hepatobiliary malignancies, it is a synthetic concept consisting of multiple disciplines. Generally, four pillars have been promoted to further elucidate the research priorities of transplant oncology: (1) promoting the development of multidisciplinary cancer care; (2) extending the limit of cancer surgery; (3) elucidation of a recognition system by combining tumor and transplant immunology; (4) exploration of the disease mechanism through genomic approaches ( Hibi et al., 2017 Hibi et al., 2017 ; Hibi and Sapisochin, 2019 Hibi and Sapisochin, 2019 ). Designed to extend the bridge between tumor biology and transplantation medicine, transplant oncology aims to create a new era of precise treatment for liver cancer. Currently, with the rapidly growing number of patients who receive transplantation to treat liver cancer, the risk of post-transplant tumor recurrence has attracted increasing attention. Circulating tumor cells (CTCs), released from the primary lesion before transplantation, are considered one of the causes of recurrence ( Ye et al., 2019 Ye et al., 2019 ). Being hard to detect through conventional means, such escaped tumor cells in the peripheral blood provide opportunities for subsequent recurrence or even metastasis. Besides, research showed that an immunosuppressive regimen involving steroids, calcineurin inhibitors, and induction agents could contribute to the recurrence of liver cancer ( Verna et al., 2020 Verna et al., 2020 ). Recently, immune checkpoint inhibitors (ICIs) are becoming a novel strategy to treat liver cancer, but an appropriate degree of immunologic activation must be taken into account, since hyperactivation of the immune system may bring damage to the graft ( Nordness et al., 2020 Nordness et al., 2020 ; Khan et al., 2021 Khan et al., 2021 ). Therefore, it is advisable to derive an integrated therapy that could induce the anti-tumor effect without increasing the immune burden of recipients. 2 Double-negative T cells (DNTs): fighters, peacemakers, or both? 1 2.1 An overview of DNTs 2 DNTs are a cluster of unconventional and less known cells expressing specific surface markers T cell receptor-positive (TCR + ), cluster of differentiation 3-positive (CD3 + ), CD4 - , CD8 - , and CD56 - , which account for 1%‒3% of peripheral blood mononuclear cells (PBMCs) and 3%‒5% of the peripheral blood mature T lymphocyte pool ( Lee et al., 2018 Lee et al., 2018 ; Yao et al., 2019 Yao et al., 2019 ). To begin with, it is necessary to differentiate DNTs from other CD4 - CD8 - populations ( Table 1 Table 1 ). According to the surface TCRs, DNTs can be divided into two groups: TCRαβ + cells and TCRγδ + cells. TCRαβ + DNTs are referred to as “DN Tregs” for inducing the potent functions of immune regulation and tolerance ( Velikkakam et al., 2022 Velikkakam et al., 2022 ), while TCRγδ + DNTs tend to harbor tumor cytotoxicity and tumor infiltrating ability ( Hoeres et al., 2018 Hoeres et al., 2018 ; Liu and Zhang, 2020 Liu and Zhang, 2020 ; de Gassart et al., 2021 de Gassart et al., 2021 ). Despite these discrepancies, some researchers took the two subsets as a single category in expanded cell products, since comparable anti-tumor functions and cell surface marker expression were detected ( Lee et al., 2018 Lee et al., 2018 , 2019 2019 ; Yao et al., 2019 Yao et al., 2019 ). They also proved that allogeneic human DNTs isolated from healthy donors were able to induce potent anti-tumor function in several hematologic malignancies and solid tumors. More importantly, little rejection or damage to the normal tissues was observed in the related experiments. In practice, a clinical-grade protocol has been developed to isolate and expand healthy donor-derived DNTs in therapeutic numbers ( Lee et al., 2019 Lee et al., 2019 ). To sum up, there is available evidence that DNTs are able to function as both immune regulators and tumor killers, with such integrated characteristics mediated by two different subsets. This group of novel cells is likely to play dual roles of both “fighters” and “peacemakers” in terms of anti-tumor activity. TCR: T cell receptor; DNT: double-negative T cell; MAIT: mucosal-associated invariant T; NKT: natural killer T; MHC: major histocompatibility complex; MR1: MHC class I-related molecule; CD: cluster of differentiation; α-GalCer: α-galactosylceramide. Cell type TCR Restriction Antigen recognition Repertoire DNT TCRαβ + αβ MHC I/MHC II/CD1 (Chowdhary et al., 2017) Peptide (Chowdhary et al., 2017) Polyclonal (Fischer et al., 2005) TCRγδ + γδ MHC I/MHC II/CD1 (Kabelitz et al., 2020) Soluble protein and non-protein antigens (Kabelitz et al., 2020) Oligoclonal/polyclonal (Velikkakam et al., 2022) MAIT Semi-invariant αβ(Zhang et al., 2020) MR1 (Legoux et al., 2017) Microbial-derived vitamin B metabolites (Kjer-Nielsen et al., 2018) Oligoclonal (Kjer-Nielsen et al., 2018) NKT I Semi-invariant αβ (Crosby and Kronenberg, 2018) CD1d (Crosby and Kronenberg, 2018) α-GalCer (Gálvez et al., 2021) Oligoclonal (Gálvez et al., 2021) II αβ CD1d (Almeida et al., 2021) Lipid antigens (Pellicci and Uldrich, 2018) Polyclonal (Pellicci and Uldrich, 2018) 2.2 DNTs as novel adoptive cell therapies (ACTs) for malignancies 2 As early as 2003, the anti-tumor effect of DNTs was first reported in the treatment of lymphoma ( Young et al., 2003 Young et al., 2003 ). Thereafter, numerous successive studies of other hematologic or solid tumors came along, including those on melanoma ( Strippoli et al., 2021 Strippoli et al., 2021 ), acute myeloid leukemia ( Lee et al., 2018 Lee et al., 2018 ), pancreatic cancer ( Chen et al., 2019 Chen et al., 2019 ), and lung cancer ( Yao et al., 2019 Yao et al., 2019 ), in which the anti-tumor mechanisms of DNTs were investigated to varying degrees. In summary, the listed mechanisms can be concluded into two major types: receptor-ligand interaction and secretory factors ( Fig. 1 Fig. 1 ). Of note, previous research showed that the tumor-killing effect of DNTs is independent of TCR with a major histocompatibility complex (MHC)-unrestricted pattern ( Lee et al., 2018 Lee et al., 2018 ), indicating that the two diverse DNT subsets are likely to display an innate-like anti-tumor function. For conventional ACTs, the high heterogeneity of cancer cells and their lack of tumor-specific antigen seriously hamper the recognition and elimination of the target by effector cells, which greatly impairs the therapeutic effect. Given the innate recognition mechanisms, DNTs as a cell therapy may be less affected by known primary or acquired drug resistance. For clarity, we summarized the existing research of DNTs in oncology ( Table 2 Table 2 ). Despite all the above findings that DNTs exert their antitumor effects in a variety of ways, the current research progress in solid tumors is far from unimpeded. Firstly, the existence of tumor microenvironment in solid tumors could greatly impair the tumor-killing effect of ACTs ( Mizukoshi and Kaneko, 2019 Mizukoshi and Kaneko, 2019 ). Besides, the localization of immune infiltration may further affect the therapeutic effect. A tumor model called immune-excluded phenotype showed that malignant tumors with poor prognosis may exclude effector cells from the lesion ( Galluzzi et al., 2018 Galluzzi et al., 2018 ), which may explain the reduced frequency of DNTs in tumor tissue compared with adjacent or normal lung tissue ( Fang et al., 2019 Fang et al., 2019 ). To address this issue, Vasic et al. (2022) Vasic et al. (2022) have developed a new strategy to use DNTs as chimeric antigen receptor (CAR) T cell therapy platforms, of which effective infiltration and anti-tumor function in lung cancer were observed. Nonetheless, more research is needed to improve the efficacy of DNTs against solid tumors. * Refers to the in vitro cell experiments or in vivo animal experiments conducted in the corresponding article. DNTs: double-negative T cells; TCR: T cell receptor; Fas: factor-associated suicide; FasL: Fas ligand; PBMCs: peripheral blood mononuclear cells; AML: acute myeloid leukemia; NKG2D: natural-killer group 2, member D; MICA: major histocompatibility complex class I-related antigens A; NKG2DL: NKG2D ligand; DNAM-1: DNAX accessory molecule-1; DNAM-1L: DNAM-1 ligand; IFNγ: interferon-γ; TNFα: tumor necrosis factor α; CD: cluster of differentiation; EBV-LCL: Epstein-Barr virus lymphoblastoid cell line; Nrf2: nuclear factor erythroid 2-related factor 2; TRAIL: TNF-related apoptosis-inducing ligand; TRAILR: TRAIL receptor; NCR3: natural cytotoxicity triggering receptor 3; B-ALL: B-cell acute lymphoblastic leukemia; CAR: chimeric antigen receptor; LFA-1: lymphocyte function-associated antigen-1. 2 Tumor type 2 Subset of DNTs 2 Source of DNTs 2 Experiment * 2 Mechanism involved 2 Reference In vitro In vivo Lymphoma TCRαβ + Spleens of mice Yes Yes Fas/FasL Young et al., 2003 Young et al., 2003 Melanoma TCRαβ + PBMCs of a melanoma patient Yes No Perforin/granzyme B Voelkl et al., 2009 Voelkl et al., 2009 AML TCRαβ + TCRγδ + PBMCs of AML patients Yes No Perforin Merims et al., 2011 Merims et al., 2011 Pancreatic carcinoma TCRαβ + TCRγδ + PBMCs of healthy donors No Yes NKG2D/MICA Xu H et al., 2016 Xu H et al., 2016 AML TCRαβ + TCRγδ + PBMCs of AML patients and healthy donors Yes Yes NKG2D/NKG2DL, DNAM-1/DNAM-1L Chen et al., 2018 Chen et al., 2018 AML TCRαβ + TCRγδ + PBMCs of healthy donors Yes Yes NKG2D/NKG2DL, DNAM-1/DNAM-1L, IFNγ Lee et al., 2018 Lee et al., 2018 Pancreatic carcinoma TCRαβ + TCRγδ + PBMCs of healthy donors Yes Yes Fas/FasL Chen et al., 2019 Chen et al., 2019 Non-small celllung cancer TCRαβ + TCRγδ + PBMCs of healthy donors Yes Yes IFNγ, TNFα, perforin/granzyme B, CD107a Fang et al., 2019 Fang et al., 2019 Myeloma, Burkitt lymphoma, AML,EBV-LCL, large celllung cancer, and adenocarcinoma TCRαβ + TCRγδ + PBMCs of healthy donors Yes Yes Lee et al., 2019 Lee et al., 2019 Pancreatic carcinoma TCRαβ + PBMCs of healthy donors Yes No Fas/FasL, Nrf2, IFNγ Lu et al., 2019 Lu et al., 2019 Sarcoma TCRαβ + Spleens of mice Yes Yes IFNγ Ponzetta et al., 2019 Ponzetta et al., 2019 Non-small celllung cancer TCRαβ + TCRγδ + PBMCs of healthy donors Yes Yes NKG2D/NKG2DL, DNAM-1/DNAM-1L, TRAILR/TRAIL, NCR3, IFNγ, perforin/granzyme B Yao et al., 2019 Yao et al., 2019 AML TCRαβ + TCRγδ + PBMCs of healthy donors Yes Yes CD64 Soares et al., 2021 Soares et al., 2021 B-ALL and lung cancer TCRαβ + TCRγδ + PBMCs of healthy donors Yes Yes Anti-CD19-CAR,LFA-1, perforin/granzyme B Vasic et al., 2022 Vasic et al., 2022 2.3 Immune tolerance induced by TCRαβ + DNTs 2 At present, in terms of immune tolerance and suppression, TCRαβ + DNTs comprise the main subset of DNTs to be studied. During the process of liver allograft rejection, activated CD8 + cytotoxic T cells are known as the main effector lymphocytes to induce graft injury ( Ronca et al., 2020 Ronca et al., 2020 ). For CD8 + T cells, the immunoregulation of TCRαβ + DNTs can be summarized into three approaches ( Ford et al., 2002 Ford et al., 2002 ) ( Fig. 2 Fig. 2 ). Importantly, the above processes are conducted through an antigen-specific manner, which means that only those immune cells of the host that threaten the allograft would be attacked by TCRαβ + DNTs, and vice versa. Based on their potent function of immune regulation, TCRαβ + DNTs have been promising therapeutic agents in transplantation. Graft versus host disease (GVHD), a serious post-transplant complication, occurs when donor T cells are activated by the recipient alloantigen, which tends to cause multisystem organ failure ( Chakraverty and Teshima, 2021 Chakraverty and Teshima, 2021 ). Achita et al. (2018) Achita et al. (2018) have confirmed that the infusion of allogeneic or xenogeneic TCRαβ + DNTs alone does not cause GVHD due to the MHC-unrestricted characteristics, while adoptive CD4 + or CD8 + T cells are associated with a significantly high risk. In their study, DNTs were also observed to alleviate GVHD caused by other grafts. In addition to GVHD, host versus graft (HVG) rejection is another issue of major concern. Research showed that allogeneic DNTs are able to evade rejection by host immune cells ( Lee et al., 2019 Lee et al., 2019 ), though the detailed mechanism remains elusive. For the allograft, studies have proved that a direct infusion of TCRαβ + DNTs could inhibit the rejection and induce the long-term survival of cardiac, skin, and islet grafts ( Young et al., 2002 Young et al., 2002 ; Chen et al., 2005 Chen et al., 2005 ; Juvet and Zhang, 2012 Juvet and Zhang, 2012 ). As an important immunosuppressant, rapamycin is recommended in patients with HCC after liver transplantation ( Ling et al., 2022 Ling et al., 2022 ). Interestingly, rapamycin enhanced the immunosuppressive function of TCRαβ + DNTs in vitro and in vivo ( Achita et al., 2018 Achita et al., 2018 ). The above-mentioned properties, albeit preliminary, could be indeed considered as a positive sign of future development and the potential application of DNTs to alleviate the immune burden of recipients in transplant oncology. 3 Future directions in the use of DNTs in transplant oncology 1 In practice, the infusion of allogeneic DNTs hardly brings about GVHD or damage to normal cells and tissues ( Achita et al., 2018 Achita et al., 2018 ), thus ensuring their therapeutic safety as an ACT. Given the success of application in hematological malignancies ( Lee et al., 2018 Lee et al., 2018 , 2019 2019 ), DNTs are likely to become an effective ACT in tumor immunotherapy. Despite the lack of extensive data on the application of DNTs in patients after liver transplantation, the remarkable correlation of DNT infusion with an increased survival potential of organs in model animals still brings us great encouragement ( Hu et al., 2021 Hu et al., 2021 ; Bafor et al., 2022 Bafor et al., 2022 ; Newman-Rivera et al., 2022 Newman-Rivera et al., 2022 ). We have divided the potential applications of DNTs in liver transplant oncology into two main fields: prevention and treatment ( Fig. 3 Fig. 3 ). 3.1 Prophylactic administration of DNTs 2 Based on the characteristics of the two cell subsets, DNTs are likely to become novel cell prophylactics that may prevent tumor recurrence without disturbing the immunosuppressive environment. Usually, liver cancer recurrences emerge in the liver and other sites with abundant vascularity such as lung, bone, adrenal glands, and even soft tissue ( Verna et al., 2020 Verna et al., 2020 ), suggesting that CTCs left in the blood play a pivotal role after the complete removal of the primary lesion. Therefore, TCRγδ + DNTs may work even better against this part of tumor cells circulating in the blood, exactly as they would behave in the treatment of hematologic malignancies, contributing to an overall decreased recurrence rate. Another inevitable issue lies in how to protect the allograft function. As an indispensable component, TCRαβ + DNTs tend to maintain an immune microenvironment conducive to subsequent graft survival with relatively low levels of CD4 + and CD8 + T cells ( Juvet and Zhang, 2012 Juvet and Zhang, 2012 ) that play a key role in the HVG reaction. Early allograft dysfunction (EAD), as a life-threatening postoperative complication, is deemed to be largely the result of ischemia/reperfusion injury (IRI) caused by the transplant operation ( Yang et al., 2021 Yang et al., 2021 ; Lu et al., 2022 Lu et al., 2022 ). In the lung and kidney, TCRαβ + DNTs are corroborated to function as important participants and play a protective role in response to IRI ( Hsu et al., 2021 Hsu et al., 2021 ), which makes the prophylactic use of DNTs more practical in transplant surgery. The above two aspects may be simply achieved through intravenous injection before and after the reception of transplant. 3.2 Therapeutic administration of DNTs 2 Other than acting as a form of prophylaxis in the peripheral blood, DNTs are expected to induce a direct killing effect inside the tumor. In acute myeloid leukemia, DNTs have been approved as an ACT for a human clinical trial (NCT03027102). Given the cytotoxicity of TCRγδ + DNTs, other clinical trials have also been conducted in lung, breast, and renal cancers ( Hoeres et al., 2018 Hoeres et al., 2018 ; Pauza et al., 2018 Pauza et al., 2018 ; Yao et al., 2019 Yao et al., 2019 ). Yet due to the general weakness of ACTs to treat solid tumors, most trials have shown limited efficacy. Intratumoral immunotherapy may help solve this problem ( Marabelle et al., 2017 Marabelle et al., 2017 ). By applying direct injections, DNTs can be easily enriched in situ. Besides, transarterial chemoembolization (TACE) has become the standard-of-care for the treatment of intermediate-stage HCC ( Raoul et al., 2019 Raoul et al., 2019 ), the mechanisms of which involve drug local delivery and tumor embolization. Thus, it might also be effective to transfer our drugs into tumors by replacing the cytotoxic agents with DNTs. Moreover, among all sorts of cell therapies, autologous CAR T cells have great significance; such therapies are associated with little allogeneic reaction but usually stymied by T cell dysfunction ( Thommen and Schumacher, 2018 Thommen and Schumacher, 2018 ), while allogeneic CAR T cells possess stable function but are likely to cause rejection ( Depil et al., 2020 Depil et al., 2020 ). By contrast, CAR DNT therapy as an emerging ACT has shown great superiority, of which the cytotoxicity against solid tumors has been partly confirmed in previous research ( Capsomidis et al., 2018 Capsomidis et al., 2018 ; Vasic et al., 2022 Vasic et al., 2022 ). However, for the lack of direct evidence, the above attempts require further exploration before being expanded to clinical treatment alternatives of liver cancer. Patient-derived xenograft (PDX) models may provide ideal ways for such preclinical research in oncology ( Zhuo et al., 2020 Zhuo et al., 2020 ; Sun et al., 2021 Sun et al., 2021 ). To shorten the modeling time, patient-derived organoid (PDO) is another reliable model for validation ( Broutier et al., 2017 Broutier et al., 2017 ; Tuveson and Clevers, 2019 Tuveson and Clevers, 2019 ). The above modern tools offer great convenience for the future applications of DNTs. To sum up, by virtue of the unique characteristics of DNTs, they could play important roles in the treatment of liver cancer and prevention of its recurrence, especially under the background of transplantation. By not increasing the immune burden, DNTs can also make up for the shortcomings of traditional immunotherapies typified by ICI in transplantation. Notably, the administration of DNTs before liver transplantation may act as both a downstaging and a prophylactic strategy, which makes DNTs potential sequential therapeutics in transplant oncology. 4 Conclusions 1 Transplant oncology is a wide-ranging field, where anti-tumor effects and the maintenance of a suitable immune status are crucial issues to be investigated for a better prognosis of transplant recipients. DNTs are a cluster of immune cells mainly composed of two cell populations, including TCRαβ + and TCRγδ + DNTs, with great potential in terms of varying degrees of anti-tumor and immunosuppressive effects. Herein, we propose that DNTs could act as both “fighters” against liver cancer and “peacemakers” to maintain a suitable immune status of patients. Hopefully, further research will highlight the potential of this group of cells to act as a new ACT and provide an immunological equilibrium in transplant oncology. References Achita P , Dervovic D , Ly D , et al. , 2018 . Infusion of ex-vivo expanded human TCR-αβ + double-negative regulatory T cells delays onset of xenogeneic graft- versus -host disease . Clin Exp Immunol , 193 ( 3 ): 386 - 399 . https://doi.org/10.1111/cei.13145 https://doi.org/10.1111/cei.13145 Infusion of ex-vivo expanded human TCR-αβ+ double-negative regulatory T cells delays onset of xenogeneic graft-versus-host disease Almeida CF , Smith DGM , Cheng TY , et al. , 2021 . Benzofuran sulfonates and small self-lipid antigens activate type II NKT cells via CD1d . Proc Natl Acad Sci USA , 118 ( 34 ): e2104420118 . https://doi.org/10.1073/PNAS.2104420118 https://doi.org/10.1073/PNAS.2104420118 Benzofuran sulfonates and small self-lipid antigens activate type II NKT cells via CD1d Bafor EE , Valencia JC , Young HA , 2022 . Double negative T regulatory cells: an emerging paradigm shift in reproductive immune tolerance? Front Immunol , 13 : 886645 . https://doi.org/10.3389/fimmu.2022.886645 https://doi.org/10.3389/fimmu.2022.886645 Double negative T regulatory cells: an emerging paradigm shift in reproductive immune tolerance? Broutier L , Mastrogiovanni G , Verstegen MMA , et al. , 2017 . Human primary liver cancer-derived organoid cultures for disease modeling and drug screening . Nat Med , 23 ( 12 ): 1424 - 1435 . https://doi.org/10.1038/nm.4438 https://doi.org/10.1038/nm.4438 Human primary liver cancer-derived organoid cultures for disease modeling and drug screening Capsomidis A , Benthall G , van Acker HH , et al. , 2018 . Chimeric antigen receptor-engineered human gamma delta T cells: enhanced cytotoxicity with retention of cross presentation . Mol Ther , 26 ( 2 ): 354 - 365 . https://doi.org/10.1016/j.ymthe.2017.12.001 https://doi.org/10.1016/j.ymthe.2017.12.001 Chimeric antigen receptor-engineered human gamma delta T cells: enhanced cytotoxicity with retention of cross presentation Chakraverty R , Teshima T , 2021 . Graft-versus-host disease: a disorder of tissue regeneration and repair . Blood , 138 ( 18 ): 1657 - 1665 . https://doi.org/10.1182/blood.2021011867 https://doi.org/10.1182/blood.2021011867 Graft-versus-host disease: a disorder of tissue regeneration and repair Chen B , Lee JB , Kang H , et al. , 2018 . Targeting chemotherapy-resistant leukemia by combining DNT cellular therapy with conventional chemotherapy . J Exp Clin Cancer Res , 37 : 88 . https://doi.org/10.1186/s13046-018-0756-9 https://doi.org/10.1186/s13046-018-0756-9 Targeting chemotherapy-resistant leukemia by combining DNT cellular therapy with conventional chemotherapy Chen J , Hu PB , Wu GH , et al. , 2019 . Antipancreatic cancer effect of DNT cells and the underlying mechanism . Pancreatology , 19 ( 1 ): 105 - 113 . https://doi.org/10.1016/j.pan.2018.12.006 https://doi.org/10.1016/j.pan.2018.12.006 Antipancreatic cancer effect of DNT cells and the underlying mechanism Chen WH , Zhou DJ , Torrealba JR , et al. , 2005 . Donor lymphocyte infusion induces long-term donor-specific cardiac xenograft survival through activation of recipient double-negative regulatory T cells . J Immunol , 175 ( 5 ): 3409 - 3416 . https://doi.org/10.4049/jimmunol.175.5.3409 https://doi.org/10.4049/jimmunol.175.5.3409 Donor lymphocyte infusion induces long-term donor-specific cardiac xenograft survival through activation of recipient double-negative regulatory T cells Chowdhary VR , Krogman A , Tilahun AY , et al. , 2017 . Concomitant disruption of CD4 and CD8 genes facilitates the development of double negative αβTCR + peripheral T cells that respond robustly to staphylococcal superantigen . J Immunol , 198 ( 1 ): 4413 - 4424 . https://doi.org/10.4049/jimmunol.1601991 https://doi.org/10.4049/jimmunol.1601991 Concomitant disruption of CD4 and CD8 genes facilitates the development of double negative αβTCR+ peripheral T cells that respond robustly to staphylococcal superantigen Crosby CM , Kronenberg M , 2018 . Tissue-specific functions of invariant natural killer T cells . Nat Rev Immunol , 18 ( 9 ): 559 - 574 . https://doi.org/10.1038/s41577-018-0034-2 https://doi.org/10.1038/s41577-018-0034-2 Tissue-specific functions of invariant natural killer T cells de Gassart A , Le KS , Brune P , et al. , 2021 . Development of ICT01, a first-in-class, anti-BTN3A antibody for activating Vγ9Vδ2 T cell-mediated antitumor immune response . Sci Transl Med , 13 ( 616 ): eabj0835 . https://doi.org/10.1126/scitranslmed.abj0835 https://doi.org/10.1126/scitranslmed.abj0835 Development of ICT01, a first-in-class, anti-BTN3A antibody for activating Vγ9Vδ2 T cell-mediated antitumor immune response Depil S , Duchateau P , Grupp SA , et al. , 2020 . ‘Off-the-shelf’ allogeneic CAR T cells: development and challenges . Nat Rev Drug Discov , 19 ( 3 ): 185 - 199 . https://doi.org/10.1038/s41573-019-0051-2 https://doi.org/10.1038/s41573-019-0051-2 ‘Off-the-shelf’ allogeneic CAR T cells: development and challenges Fang LN , Ly D , Wang SS , et al. , 2019 . Targeting late-stage non-small cell lung cancer with a combination of DNT cellular therapy and PD-1 checkpoint blockade . J Exp Clin Cancer Res , 38 : 123 . https://doi.org/10.1186/s13046-019-1126-y https://doi.org/10.1186/s13046-019-1126-y Targeting late-stage non-small cell lung cancer with a combination of DNT cellular therapy and PD-1 checkpoint blockade Fischer K , Voelkl S , Heymann J , et al. , 2005 . Isolation and characterization of human antigen-specific TCRαβ + CD4 - CD8 - double-negative regulatory T cells . Blood , 105 ( 7 ): 2828 - 2835 . https://doi.org/10.1182/blood-2004-07-2583 https://doi.org/10.1182/blood-2004-07-2583 Isolation and characterization of human antigen-specific TCRαβ+ CD4-CD8- double-negative regulatory T cells Ford MS , Young KJ , Zhang ZX , et al. , 2002 . The immune regulatory function of lymphoproliferative double negative T cells in vitro and in vivo . J Exp Med , 196 ( 2 ): 261 - 267 . https://doi.org/10.1084/jem.20020029 https://doi.org/10.1084/jem.20020029 The immune regulatory function of lymphoproliferative double negative T cells in vitro and in vivo Galluzzi L , Chan TA , Kroemer G , et al. , 2018 . The hallmarks of successful anticancer immunotherapy . Sci Transl Med , 10 ( 459 ): eaat7807 . https://doi.org/10.1126/scitranslmed.aat7807 https://doi.org/10.1126/scitranslmed.aat7807 The hallmarks of successful anticancer immunotherapy Gálvez NMS , Bohmwald K , Pacheco GA , et al. , 2021 . Type I natural killer T cells as key regulators of the immune response to infectious diseases . Clin Microbiol Rev , 34 ( 2 ): e00232-20 . https://doi.org/10.1128/CMR.00232-20 https://doi.org/10.1128/CMR.00232-20 Type I natural killer T cells as key regulators of the immune response to infectious diseases Hibi T , Sapisochin G , 2019 . What is transplant oncology? Surgery , 165 ( 2 ): 281 - 285 . https://doi.org/10.1016/j.surg.2018.10.024 https://doi.org/10.1016/j.surg.2018.10.024 What is transplant oncology? Hibi T , Itano O , Shinoda M , et al. , 2017 . Liver transplantation for hepatobiliary malignancies: a new era of “Transplant Oncology” has begun . Surg Today , 47 ( 4 ): 403 - 415 . https://doi.org/10.1007/s00595-016-1337-1 https://doi.org/10.1007/s00595-016-1337-1 Liver transplantation for hepatobiliary malignancies: a new era of “Transplant Oncology” has begun Hoeres T , Smetak M , Pretscher D , et al. , 2018 . Improving the efficiency of Vγ9Vδ2 T-Cell immunotherapy in cancer . Front Immunol , 9 : 800 . https://doi.org/10.3389/fimmu.2018.00800 https://doi.org/10.3389/fimmu.2018.00800 Improving the efficiency of Vγ9Vδ2 T-Cell immunotherapy in cancer Hsu J , Krishnan A , Lee SA , et al. , 2021 . CD3 + CD4 - CD8 - double-negative αβ T cells attenuate lung ischemia-reperfusion injury . J Thorac Cardiovasc Surg , 161 ( 1 ): E81 - E90 . https://doi.org/10.1016/j.jtcvs.2019.09.188 https://doi.org/10.1016/j.jtcvs.2019.09.188 CD3+CD4-CD8- double-negative αβ T cells attenuate lung ischemia-reperfusion injury Hu SH , Zhang LH , Gao J , et al. , 2021 . NKG2D enhances double-negative T cell regulation of B cells . Front Immunol , 12 : 650788 . https://doi.org/10.3389/fimmu.2021.650788 https://doi.org/10.3389/fimmu.2021.650788 NKG2D enhances double-negative T cell regulation of B cells Juvet SC , Zhang L , 2012 . Double negative regulatory T cells in transplantation and autoimmunity: recent progress and future directions . J Mol Cell Biol , 4 ( 1 ): 48 - 58 . https://doi.org/10.1093/jmcb/mjr043 https://doi.org/10.1093/jmcb/mjr043 Double negative regulatory T cells in transplantation and autoimmunity: recent progress and future directions Kabelitz D , Serrano R , Kouakanou L , et al. , 2020 . Cancer immunotherapy with γδ T cells: many paths ahead of us . Cell Mol Immunol , 17 ( 9 ): 925 - 939 . https://doi.org/10.1038/s41423-020-0504-x https://doi.org/10.1038/s41423-020-0504-x Cancer immunotherapy with γδ T cells: many paths ahead of us Khan AA , Liu ZK , Xu X , 2021 . Recent advances in immunotherapy for hepatocellular carcinoma . Hepatobiliary Pancreat Dis Int , 20 ( 6 ): 511 - 520 . https://doi.org/10.1016/j.hbpd.2021.06.010 https://doi.org/10.1016/j.hbpd.2021.06.010 Recent advances in immunotherapy for hepatocellular carcinoma Kjer-Nielsen L , Corbett AJ , Chen ZJ , et al. , 2018 . An overview on the identification of MAIT cell antigens . Immunol Cell Biol , 96 ( 6 ): 573 - 587 . https://doi.org/10.1111/imcb.12057 https://doi.org/10.1111/imcb.12057 An overview on the identification of MAIT cell antigens Lee JB , Minden MD , Chen WC , et al. , 2018 . Allogeneic human double negative T cells as a novel immunotherapy for acute myeloid leukemia and its underlying mechanisms . Clin Cancer Res , 24 ( 2 ): 370 - 382 . https://doi.org/10.1158/1078-0432.CCR-17-2228 https://doi.org/10.1158/1078-0432.CCR-17-2228 Allogeneic human double negative T cells as a novel immunotherapy for acute myeloid leukemia and its underlying mechanisms Lee JB , Kang H , Fang LN , et al. , 2019 . Developing allogeneic double-negative T cells as a novel off-the-shelf adoptive cellular therapy for cancer . Clin Cancer Res , 25 ( 7 ): 2241 - 2253 . https://doi.org/10.1158/1078-0432.CCR-18-2291 https://doi.org/10.1158/1078-0432.CCR-18-2291 Developing allogeneic double-negative T cells as a novel off-the-shelf adoptive cellular therapy for cancer Legoux F , Salou M , Lantz O , 2017 . Unconventional or preset αβ T cells: evolutionarily conserved tissue-resident T cells recognizing nonpeptidic ligands . Annu Rev Cell Dev Biol , 33 : 511 - 535 . https://doi.org/10.1146/annurev-cellbio-100616-060725 https://doi.org/10.1146/annurev-cellbio-100616-060725 Unconventional or preset αβ T cells: evolutionarily conserved tissue-resident T cells recognizing nonpeptidic ligands Ling SB , Zhan QF , Jiang GJ , et al. , 2022 . E2F7 promotes mammalian target of rapamycin inhibitor resistance in hepatocellular carcinoma after liver transplantation . Am J Transplant , 22 ( 10 ): 2323 - 2336 . https://doi.org/10.1111/ajt.17124 https://doi.org/10.1111/ajt.17124 E2F7 promotes mammalian target of rapamycin inhibitor resistance in hepatocellular carcinoma after liver transplantation Liu YX , Zhang C , 2020 . The role of human γδ T cells in anti-tumor immunity and their potential for cancer immunotherapy . Cells , 9 ( 5 ): 1206 . https://doi.org/10.3390/cells9051206 https://doi.org/10.3390/cells9051206 The role of human γδ T cells in anti-tumor immunity and their potential for cancer immunotherapy Lu JQ , Liu JY , Li A , 2022 . Roles of neutrophil reactive oxygen species (ROS) generation in organ function impairment in sepsis . J Zhejiang Univ-Sci B (Biomed & Biotechnol) , 23 ( 6 ): 437 - 450 . https://doi.org/10.1631/jzus.B2101075 https://doi.org/10.1631/jzus.B2101075 Roles of neutrophil reactive oxygen species (ROS) generation in organ function impairment in sepsis Lu Y , Hu PB , Zhou HB , et al. , 2019 . Double-negative T cells inhibit proliferation and invasion of human pancreatic cancer cells in co-culture . Anticancer Res , 39 ( 11 ): 5911 - 5918 . https://doi.org/10.21873/anticanres.13795 https://doi.org/10.21873/anticanres.13795 Double-negative T cells inhibit proliferation and invasion of human pancreatic cancer cells in co-culture Marabelle A , Tselikas L , de Baere T , et al. , 2017 . Intratumoral immunotherapy: using the tumor as the remedy . Ann Oncol , 28 : xii33 - xii43 . https://doi.org/10.1093/annonc/mdx683 https://doi.org/10.1093/annonc/mdx683 Intratumoral immunotherapy: using the tumor as the remedy Mazzaferro V , Regalia E , Doci R , et al. , 1996 . Liver transplantation for the treatment of small hepatocellular carcin omas in patients with cirrhosis. N Engl J Med , 334 ( 11 ): 693 - 700 . https://doi.org/10.1056/NEJM199603143341104 https://doi.org/10.1056/NEJM199603143341104 Liver transplantation for the treatment of small hepatocellular carcin Merims S , Li X , Joe B , et al. , 2011 . Anti-leukemia effect of ex vivo expanded DNT cells from AML patients: a potential novel autologous T-cell adoptive immunotherapy . Leukemia , 25 ( 9 ): 1415 - 1422 . https://doi.org/10.1038/leu.2011.99 https://doi.org/10.1038/leu.2011.99 Anti-leukemia effect of ex vivo expanded DNT cells from AML patients: a potential novel autologous T-cell adoptive immunotherapy Mizukoshi E , Kaneko S , 2019 . Immune cell therapy for hepatocellular carcinoma . J Hematol Oncol , 12 : 52 . https://doi.org/10.1186/s13045-019-0742-5 https://doi.org/10.1186/s13045-019-0742-5 Immune cell therapy for hepatocellular carcinoma Newman-Rivera AM , Kurzhagen JT , Rabb H , 2022 . TCRαβ + CD4 - /CD8 - “double negative” T cells in health and disease-implications for the kidney . Kidney Int , 102 ( 1 ): 25 - 37 . https://doi.org/10.1016/j.kint.2022.02.035 https://doi.org/10.1016/j.kint.2022.02.035 TCRαβ+ CD4-/CD8- “double negative” T cells in health and disease-implications for the kidney Nordness MF , Hamel S , Godfrey CM , et al. , 2020 . Fatal hep atic necrosis after nivolumab as a bridge to liver transplant for HCC: are checkpoint inhibitors safe for the pretransplant patient? Am J Transplant , 20 ( 3 ): 879 - 883 . https://doi.org/10.1111/ajt.15617 https://doi.org/10.1111/ajt.15617 Fatal hep Pauza CD , Liou ML , Lahusen T , et al. , 2018 . Gamma delta T cell therapy for cancer: it is good to be local . Front Immunol , 9 : 1305 . https://doi.org/10.3389/fimmu.2018.01305 https://doi.org/10.3389/fimmu.2018.01305 Gamma delta T cell therapy for cancer: it is good to be local Pellicci DG , Uldrich AP , 2018 . Unappreciated diversity within the pool of CD1d-restricted T cells . Semin Cell Dev Biol , 84 : 42 - 47 . https://doi.org/10.1016/j.semcdb.2017.11.031 https://doi.org/10.1016/j.semcdb.2017.11.031 Unappreciated diversity within the pool of CD1d-restricted T cells Ponzetta A , Carriero R , Carnevale S , et al. , 2019 . Neutrophils driving unconventional T cells mediate resistance against murine sarcomas and selected human tumors . Cell , 178 ( 2 ): 346 - 360.e24 . https://doi.org/10.1016/j.cell.2019.05.04 https://doi.org/10.1016/j.cell.2019.05.04 Neutrophils driving unconventional T cells mediate resistance against murine sarcomas and selected human tumors Raoul JL , Forner A , Bolondi L , et al. , 2019 . Updated use of TACE for hepatocellular carcinoma treatment: how and when to use it based on clinical evidence . Cancer Treat Rev , 72 : 28 - 36 . https://doi.org/10.1016/j.ctrv.2018.11.002 https://doi.org/10.1016/j.ctrv.2018.11.002 Updated use of TACE for hepatocellular carcinoma treatment: how and when to use it based on clinical evidence Ronca V , Wootton G , Milani C , et al. , 2020 . The immunological basis of liver allograft rejection . Front Immunol , 11 : 2155 . https://doi.org/10.3389/fimmu.2020.02155 https://doi.org/10.3389/fimmu.2020.02155 The immunological basis of liver allograft rejection Soares F , Chen B , Lee JB , et al. , 2021 . CRISPR screen identifies genes that sensitize AML cells to double-negative T-cell therapy . Blood , 137 ( 16 ): 2171 - 2181 . https://doi.org/10.1182/blood.2019004108 https://doi.org/10.1182/blood.2019004108 CRISPR screen identifies genes that sensitize AML cells to double-negative T-cell therapy Strippoli S , Fanizzi A , Negri A , et al. , 2021 . Examining the relationship between circulating CD4 - CD8 - double-negative T cells and outcomes of immuno-checkpoint inhibitor therapy—looking for biomarkers and therapeutic targets in metastatic melanoma . Cells , 10 ( 2 ): 406 . https://doi.org/10.3390/cells10020406 https://doi.org/10.3390/cells10020406 Examining the relationship between circulating CD4-CD8- double-negative T cells and outcomes of immuno-checkpoint inhibitor therapy—looking for biomarkers and therapeutic targets in metastatic melanoma Sun H , Cao S , Mashl RJ , et al. , 2021 . Comprehensive characterization of 536 patient-derived xenograft models prioritizes candidatesfor targeted treatment . Nat Commun , 12 : 5086 . https://doi.org/10.1038/s41467-021-25177-3 https://doi.org/10.1038/s41467-021-25177-3 Comprehensive characterization of 536 patient-derived xenograft models prioritizes candidatesfor targeted treatment Takada Y , Ito T , Ueda M , et al. , 2007 . Living donor liver transplantation for patients with HCC exceeding the Milan criteria: a proposal of expanded criteria . Dig Dis , 25 ( 4 ): 299 - 302 . https://doi.org/10.1159/000106908 https://doi.org/10.1159/000106908 Living donor liver transplantation for patients with HCC exceeding the Milan criteria: a proposal of expanded criteria Thommen DS , Schumacher TN , 2018 . T cell dysfunction in cancer . Cancer Cell , 33 ( 4 ): 547 - 562 . https://doi.org/10.1016/j.ccell.2018.03.012 https://doi.org/10.1016/j.ccell.2018.03.012 T cell dysfunction in cancer Tuveson D , Clevers H , 2019 . Cancer modeling meets human organoid technology . Science , 364 ( 6444 ): 952 - 955 . https://doi.org/10.1126/science.aaw6985 https://doi.org/10.1126/science.aaw6985 Cancer modeling meets human organoid technology Vasic D , Lee JB , Leung Y , et al. , 2022 . Allogeneic double-negative CAR-T cells inhibit tumor growth without off-tumor toxicities . Sci Immunol , 7 ( 70 ): eabl3642 . https://doi.org/10.1126/sciimmunol.abl3642 https://doi.org/10.1126/sciimmunol.abl3642 Allogeneic double-negative CAR-T cells inhibit tumor growth without off-tumor toxicities Velikkakam T , Gollob KJ , Dutra WO , 2022 . Double-negative T cells: setting the stage for disease control or progression . Immunology , 165 ( 4 ): 371 - 385 . https://doi.org/10.1111/imm.13441 https://doi.org/10.1111/imm.13441 Double-negative T cells: setting the stage for disease control or progression Verna EC , Patel YA , Aggarwal A , et al. , 2020 . Liver transplantation for hepatocellular carcinoma: management after the transplant . Am J Transplant , 20 ( 2 ): 333 - 347 . https://doi.org/10.1111/ajt.15697 https://doi.org/10.1111/ajt.15697 Liver transplantation for hepatocellular carcinoma: management after the transplant Voelkl S , Moore TV , Rehli M , et al. , 2009 . Characterization of MHC class-I restricted TCRαβ + CD4 - CD8 - double negative T cells recognizing the gp100 antigen from a melanoma patient after gp100 vaccination . Cancer Immunol Immunother , 58 ( 5 ): 709 - 718 . https://doi.org/10.1007/s00262-008-0593-3 https://doi.org/10.1007/s00262-008-0593-3 Characterization of MHC class-I restricted TCRαβ+ CD4- CD8- double negative T cells recognizing the gp100 antigen from a melanoma patient after gp100 vaccination Xu H , Zhu XX , Chen J , 2016 . DNT cell inhibits the growth of pancreatic carcinoma via abnormal expressions of NKG2D and MICA in vivo . Biochem Biophys Res Commun , 469 ( 2 ): 145 - 150 . https://doi.org/10.1016/j.bbrc.2015.11.085 https://doi.org/10.1016/j.bbrc.2015.11.085 DNT cell inhibits the growth of pancreatic carcinoma via abnormal expressions of NKG2D and MICA in vivo Xu X , Lu D , Ling Q , et al. , 2016 . Liver transplantation for hepatocellular carcinoma beyond the Milan criteria . Gut , 65 ( 6 ): 1035 - 1041 . https://doi.org/10.1136/gutjnl-2014-308513 https://doi.org/10.1136/gutjnl-2014-308513 Liver transplantation for hepatocellular carcinoma beyond the Milan criteria Yang XY , Lu D , Wang R , et al. , 2021 . Single-cell profiling reveals distinct immune phenotypes that contribute to ischaemia-reperfusion injury after steatotic liver transplantation . Cell Prolif , 54 ( 10 ): e13116 . https://doi.org/10.1111/CPR.13116 https://doi.org/10.1111/CPR.13116 Single-cell profiling reveals distinct immune phenotypes that contribute to ischaemia-reperfusion injury after steatotic liver transplantation Yao FY , Ferrell L , Bass NM , et al. , 2001 . Liver transplantation for hepatocellular carcinoma: expansion of the tumor size limits does not adversely impact survival . Hepatology , 33 ( 6 ): 1394 - 1403 . https://doi.org/10.1053/jhep.2001.24563 https://doi.org/10.1053/jhep.2001.24563 Liver transplantation for hepatocellular carcinoma: expansion of the tumor size limits does not adversely impact survival Yao JL , Ly D , Dervovic D , et al. , 2019 . Human double negative T cells target lung cancer via ligand-dependent mechanisms that can be enhanced by IL-15 . J Immunother Cancer , 7 ( 1 ): 17 . https://doi.org/10.1186/s40425-019-0507-2 https://doi.org/10.1186/s40425-019-0507-2 Human double negative T cells target lung cancer via ligand-dependent mechanisms that can be enhanced by IL-15 Ye QW , Ling SB , Zheng SS , et al. , 2019 . Liquid biopsy in hepatocellular carcinoma: circulating tumor cells and circu lating tumor DNA. Mol Cancer , 18 : 114 . https://doi.org/10.1186/s12943-019-1043-x https://doi.org/10.1186/s12943-019-1043-x Liquid biopsy in hepatocellular carcinoma: circulating tumor cells and circu Young KJ , Yang LM , Phillips MJ , et al. , 2002 . Donor-lymphocyte infusion induces transplantation tolerance by activating systemic and graft-infiltrating double-negative regulatory T cells . Blood , 100 ( 9 ): 3408 - 3414 . https://doi.org/10.1182/blood-2002-01-0235 https://doi.org/10.1182/blood-2002-01-0235 Donor-lymphocyte infusion induces transplantation tolerance by activating systemic and graft-infiltrating double-negative regulatory T cells Young KJ , Kay LS , Phillips MJ , et al. , 2003 . Antitumor activity mediated by double-negative T cells . Cancer Res , 63 ( 22 ): 8014 - 8021 . Antitumor activity mediated by double-negative T cells Zhang YJ , Kong DR , Wang H , 2020 . Mucosal-associated invariant T cell in liver diseases . Int J Biol Sci , 16 ( 3 ): 460 - 470 . https://doi.org/10.7150/ijbs.39016 https://doi.org/10.7150/ijbs.39016 Mucosal-associated invariant T cell in liver diseases Zhuo JY , Su RY , Tan WY , et al. , 2020 . The ongoing trends of patient-derived xenograft models in oncology . Cancer Commun (Lond) , 40 ( 11 ): 559 - 563 . https://doi.org/10.1002/cac2.12096 https://doi.org/10.1002/cac2.12096 The ongoing trends of patient-derived xenograft models in oncology Zhihang HU: writing ‒ original draft. Modan YANG: data curation and visualization. Xiao XU and Di LU: conceptualization and writing ‒ review & editing. Hao CHEN, Chiyu HE, Zuyuan LIN, Xinyu YANG, Huigang LI, and Wei SHEN: supervision and writing ‒ review & editing. All authors have read and approved the final manuscript, and therefore, have full access to all the data in the study and take responsibility for the integrity and security of the data. This work was supported by the Key Research & Development Plan of Zhejiang Province (Nos. 2019C03050 and 2021C03118), the National Key Research and Development Program of China (No. 2021YFA1100500), and the National Natural Science Foundation of China (No. 92159202). 10.1631/jzus.B2200528 1673-1581（2023）05-0387-10 胡志航,杨墨丹,陈昊等.双阴性T细胞：移植肿瘤学中一种颇具前景的过继细胞疗法[J].浙江大学学报（英文版）（B辑：生物医学和生物技术）,2023,24(05):387-396. 胡志航,杨墨丹,陈昊等.双阴性T细胞：移植肿瘤学中一种颇具前景的过继细胞疗法[J].浙江大学学报（英文版）（B辑：生物医学和生物技术）,2023,24(05):387-396. This work was supported by the Key Research & Development Plan of Zhejiang Province (Nos. 2019C03050 and 2021C03118), the National Key Research and Development Program of China (No. 2021YFA1100500), and the National Natural Science Foundation of China (No. 92159202). 2022-10-17 2023-02-19 2023-05-15 2023-05-15 2023-03-31 Copyright © Zhejiang University and Springer-Verlag GmbH Germany, part of Springer Nature 2022 2023 浙江大学出版社 37538254 Zhihang HU, Modan YANG, Hao CHEN, Chiyu HE, Zuyuan LIN, Xinyu YANG, Huigang LI, Wei SHEN, Di LU, and Xiao XU declare that they have no conflict of interest. This article does not contain any studies with human or animal subjects performed by any of the authors. Compliance with ethics guidelines 浙江大学学报（英文版）（B辑：生物医学和生物技术） 5 24