T cells in testicular germ cell tumors: new evidence of fundamental contributions by rare subsets
Tumor-infiltrating T cells in testicular germ cell tumors (TGCT) remain poorly understood. Therefore, along with immunohistochemistry and flow cytometry, single-cell RNA sequencing (scRNA-seq) was performed on different human TGCT testes to identify immune cell composition, with particular emphasis on delineating T cell subtypes. There are various tumor-infiltrating T cells including regulatory T (Treg) and follicular helper T (Tfh) cells that are found in other cancer entities, but their contributions to TGCT are unknown. In this study, we found that T cells including Treg and Tfh were most abundant in seminoma compared to mixed tumors and embryonal carcinoma. Taken together, despite significant heterogeneity between patients, this study demonstrated that T cell subtypes form a key component of the TGCT microenvironment. The novel finding of rare Treg and Tfh cells in the human testis suggests their involvement in TGCT pathobiology, with implications for understanding tumor progression, assessing patient prognosis, and as putative targets for personalized immunotherapy. Overall design: To analyze the cellular composition, with particular emphasis on immune cells, in human testicular germ cell tumor (TGCT), scRNA-seq was performed using 10x genomics on testes from four TGCT patients.