Human melanoma immunotherapy using tumor antigen-specific T cells generated in humanized mice

Zheng Hu,Wei Fan,Jennifer Wargo,Yong-Guang Yang,Jinxing Xia

doi:10.18632/oncotarget.7044

Abstract

A major factor hindering the exploration of adoptive immunotherapy in preclinical settings is the limited availability of tumor-reactive human T cells. Here we developed a humanized mouse model that permits large-scale production of human T cells expressing the engineered melanoma antigen MART-1-specific TCR. Humanized mice, made by transplantation of human fetal thymic tissue and CD34+ cells virally-transduced with HLA class I-restricted melanoma antigen (MART-1)-specific TCR gene, showed efficient development of MART-1-TCR+ human T cells with predominantly CD8+ cells. Importantly, MART-1-TCR+CD8+ T cells developing in these mice were capable of mounting antigen-specific responses in vivo, as evidenced by their proliferation, phenotypic conversion and IFN-γ production following MART-1 peptide immunization. Moreover, these MART-1-TCR+CD8+ T cells mediated efficient killing of melanoma cells in an HLA/antigen-dependent manner. Adoptive transfer of in vitro expanded MART-1-TCR+CD8+ T cells induced potent antitumor responses that were further enhanced by IL-15 treatment in melanoma-bearing recipients. Finally, a short incubation of MART-1-specific T cells with rapamycin acted synergistically with IL-15, leading to significantly improved tumor-free survival in recipients with metastatic melanoma. These data demonstrate the practicality of using humanized mice to produce potentially unlimited source of tumor-specific human T cells for experimental and preclinical exploration of cancer immunotherapy. This study also suggests that pretreatment of tumor-reactive T cells with rapamycin in combination with IL-15 administration may be a novel strategy to improve the efficacy of adoptive T cell therapy.

Highlights

Infusion of in vitro expanded autologous tumorinfiltrating lymphocytes (TILs) following lymphodepletion has been shown to result in objective tumor regression in up to 70% of patients with metastatic melanoma, and almost a quarter of the treated patients achieved durable complete remission [1]
The hu-mice were made by intravenous injection of TCR-engineered HLA-A*0201+ CD34+ fetal liver cells (FLCs) into NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice grafted with cryopreserved-thawed autologous fetal thymus tissue (FTHY) (Figure 1A)
Using this model in combination with in vitro cell expansion, we were able to produce large quantities of melanoma antigen melanoma-associated antigen recognized by T cell-1 (MART-1)-specific T cells with antigenspecific antitumor activity. This approach provides a practical means of producing potentially unlimited source of tumor-specific human T cells, which can be used in the development and testing of new cancer immunotherapy protocols in the preclinical settings

Summary

Introduction

Infusion of in vitro expanded autologous tumorinfiltrating lymphocytes (TILs) following lymphodepletion has been shown to result in objective tumor regression in up to 70% of patients with metastatic melanoma, and almost a quarter of the treated patients achieved durable complete remission [1]. Emerging evidence indicates that the tumor-induced inhibition of T cell activation is largely attributed to the recruitment of regulatory T cells (Tregs) into the tumor and upregulation of immune inhibitory pathway signaling, which are both driven by T cell immune responses [3, 4]. These studies imply that, for achieving the desired therapeutic effects of adoptive immunotherapy, it is important to develop effective approaches overcoming www.impactjournals.com/oncotarget these immunosuppressive pathways. Such studies have mostly been performed in mice, and the limited availability of tumor-reactive human CTLs that resemble those from patients is one of the key impeding factors

Methods

Results

Conclusion