Background Esophageal squamous cell carcinoma (ESCC) is the major subtype of esophageal cancer with high aggressiveness and poor prognosis. There is an urgent need for understanding the molecular mechanism underlying the development and progression of ESCC. Methods ESCC tissues and corresponding non-neoplastic tissues were collected. The expression and function of miR-124-3p and BCAT1 in two cell lines KYSE-150 and Eca109 were determined. Results We show downregulation of miR-124-3p expression in ESCC tissues, which is highly correlated with proliferation and migration of ESCC cell lines KYSE-150 and Eca109. miR-124-3p show high correlation with TNM stage and differentiation grade. Furthermore, miR-124-3p directly targets mRNA 3’UTR region of BCAT1, which results in upregulation of BCAT1 expression as observed in ESCC tissues and cell lines. Also, our data indicates that BCAT1 high expression is strongly linked to the disease-free survival, tumor size, pathologic stage, T classification and differentiation grade. On the other hand, we clarified the upstream mechanism regulating miR-124-3p expression in ESCC, which involves in the hypermethylation-silencing regulation mediated by DNA methyltransferase 1(DNMT1), which is of high expression in ESCC tissues and cell lines in the present study. In addition, DNMT1 knockdown or inhibition of DNMT1 function contributes to downregulation of miR-124-3p and BCAT1 expression. Conclusions Our study thus clarifies a new mechanism that DNMT1/miR-124/BCAT1 axis regulates the development and progression of ESCC.

Exhaustion of T cells limits their ability to clear chronic infections or eradicate tumors. Here, in the context of transplant, we investigated whether T cell exhaustion occurs and has a role in determining transplant outcome. A peptide/MHC tetramer‐based approach was used to track exhausted CD8+ T cells in a male‐to‐female skin transplant model. Transplant of large whole‐tail skins, but not small tail skins (0.8 cm × 0.8 cm), led to exhaustion of anti‐male tetramer+ CD8+ T cells and subsequently the acceptance of skin grafts. To study CD4+ T cell exhaustion, we used the TCR‐transgenic B6 TEa cells that recognize a major transplant antigen I‐Eα from Balb/c mice. TEa cells were adoptively transferred either into B6 recipients that received Balb/c donor skins or into CB6F1 mice that contained an excessive amount of I‐Eα antigen. Adoptively transferred TEa cells in skin‐graft recipients were not exhausted. By contrast, virtually all adoptively transferred TEa cells were exhausted in CB6F1 mice. Those exhausted TEa cells lost ability to reject Balb/c skins upon further transfer into lymphopenic B6.Rag1−/− mice. Hence, T cell exhaustion develops in the presence of abundant antigen and promotes transplant acceptance. These findings are essential for better understanding the nature of transplant tolerance.

Achieving transplant tolerance remains the ultimate goal in the field of organ transplantation. We demonstrated previously that ablation of the transcription factor interferon regulatory factor 4 (IRF4) in T cells induced heart transplant acceptance by driving allogeneic CD4+ T cell dysfunction. Herein, we showed that heart‐transplanted mice with T cell‐specific IRF4 deletion were tolerant to donor‐specific antigens and accepted the subsequently transplanted donor‐type but not third‐party skin allografts. Moreover, despite the rejection of the primary heart grafts in T cell-specific Irf4 knockout mice under immune checkpoint blockade, the establishment of donor‐specific tolerance in these mice was unhindered. By tracking alloantigen‐specific CD4+ T cells in vivo, we revealed that checkpoint blockade restored the expression levels of the majority of wild‐type T cell‐expressed genes in Irf4‐deficient T cells on day 6 post‐heart grafting, indicating the initial reinvigoration of Irf4‐deficient T cells. Nevertheless, checkpoint blockade did not restore cell frequency, effector memory cell generation, and IFN‐γ/TNF‐α production of Irf4−/− alloreactive T cells at day 30 post‐heart grafting. Hence, targeting IRF4 represents a potential therapeutic strategy for driving intrinsic T cell dysfunction and achieving alloantigen‐specific transplant tolerance.