Abstract. The programmed death-1 (PD-1)/programmed death-ligands (PD-Ls) signal pathway has been implicated as a potential immune escape mechanism in several human cancers. However, the studies of PD-1/PD-Ls pathway in esophageal squamous cell carcinoma (ECSS) are not yet sufficient. The current study investigated the expression of PD-L1, PD-L2 and PD-1 in ESCC tissues. The correlations between the expression of these proteins and clinical histopathological parameters were analyzed. Then the stable transfected Ec109 cell lines overexpressing PD-L1/PD-L2 were established by plasmid transfection successfully. Ec109 and CD8 + T cells were co-cultured to analyze the effects of PD-1/PD-Ls signal pathway on the function of CD8 + T cells including proliferation, apoptosis and interferon-γ production. We found that PD-L1-positive patients had significantly poorer prognosis than the negative patients, while their prognosis was not related to PD-L2 expression. The count of PD-1 + TILs (tumor-infiltrating lymphocytes) was negatively correlated with both PD-L1 and PD-L2 expression. In functional studies, we found that PD-1/PD-Ls signal pathway was able to downregulate the function of CD8 + T lymphocyte and its function could be restored by blocking the signal pathway. This indicates that PD-1/PD-Ls may prevent effective antitumor immunity, which provides important evidence to delineate the cellular immune deficiency mechanism in ESCC. Therefore, PD-1/PD-Ls are predicted to become novel targets for ESCC immunotherapy.

Tryptophan 2,3-dioxygnease 2 (TDO2) is specific for metabolizing tryptophan to kynurenine (KYN), which plays a critical role in mediating immune escape of cancer. Although accumulating evidence demonstrates that TDO2 overexpression is implicated in the development and progression of multiple cancers, its tumor-promoting role in esophageal squamous cell carcinoma (ESCC) remains unclear. Here, we observed that TDO2 was overexpressed in ESCC tissues and correlated significantly with lymph node metastasis, advanced clinical stage, and unfavorable prognosis. Functional experiments showed that TDO2 promoted tumor cell proliferation, migration, and colony formation, which could be prevented by inhibition of TDO2 and aryl hydrocarbon receptor (AHR). Further experimentation demonstrated that TDO2 could promote the tumor growth of KYSE150 tumor-bearing model, tumor burden of C57BL/6 mice with ESCC induced by 4-NQO, enhance the expression of phosphorylated AKT, with subsequent phosphorylation of GSK3 β , and polarization of M2 macrophages by upregulating interleukin-8 (IL-8) to accelerate tumor progression in the tumor microenvironment (TME). Collectively, our results discovered that TDO2 could upregulate IL-8 through AKT/GSK3 β to direct the polarization of M2 macrophages in ESCC, and suggested that TDO2 could represent as an attractive therapeutic target and prognostic marker to ESCC.

Background Esophageal squamous cell carcinoma (ESCC) remains one of the deadly cancer types. Comprehensively dissecting the molecular characterization and the heterogeneity of ESCC paves the way for developing more promising therapeutics. Methods Expression profiles of multiple ESCC datasets were integrated. ATAC-seq and RNA-seq were combined to reveal the chromatin accessibility features. A prognosis-related subtype classifier (PrSC) was constructed, and its association with the tumor microenvironment (TME) and immunotherapy was assessed. The key gene signature was validated in clinical samples. Based on the TME heterogeneity of ESCC patients, potential subtype-specific therapeutic agents were screened. Findings The common differentially expressed genes (cDEGs) in ESCC were identified. Up-regulated genes (HEATR1, TIMELESS, DTL, GINS1, RUVBL1, and ECT2) were found highly important in ESCC cell survival. The expression alterations of PRIM2, HPGD, NELL2, and TFAP2B were associated with chromatin accessibility changes. PrSC was a robust scoring tool that was not only associated with the prognosis of ESCC patients, but also could reflect the TME heterogeneity. TNS1 high fibroblasts were associated with immune exclusion. TG-101348 and Vinorelbine were identified as potential subtype-specific therapeutic agents. Besides, the application of PrSC into two immunotherapy cohorts indicated its potential value in assessing treatment response to immunotherapy. Interpretation Our study depicted the multi-dimensional characterization of ESCC, established a robust scoring tool for the prognosis assessment, highlighted the role of TNS1 high fibroblasts in TME, and identified potential drugs for clinical use. Funding A full list of funding bodies that contributed to this study can be found in the Acknowledgements section.