PD-1 and CTLA-4 antibodies offer great hope for cancer immunotherapy. However, many patients are incapable of responding to PD-1 and CTLA-4 blockade and show low response rates due to insufficient immune activation. The combination of checkpoint blockers has been proposed to increase the response rates. Besides, antibody drugs have disadvantages such as inclined to cause immune-related adverse events and infiltration problems. In this study, we developed a cyclic peptide C25 by using Ph.D.-C7C phage display technology targeting LAG-3. As a result, C25 showed a relative high affinity with human LAG-3 protein and could effectively interfere the binding between LAG-3 and HLA-DR (MHC-II). Additionally, C25 could significantly stimulate CD8 T cell activation in human PBMCs. The results also demonstrated that C25 could inhibit tumor growth of CT26, B16 and B16-OVA bearing mice, and the infiltration of CD8 T cells was significantly increased while FOXP3 Tregs significantly decreased in the tumor site. Furthermore, the secretion of IFN- by CD8 T cells in spleen, draining lymph nodes and especially in the tumors was promoted. Simultaneously, we exploited T cells depletion models to study the anti-tumor mechanisms for C25 peptide, and the results combined with MTT assay confirmed that C25 exerted anti-tumor effects CD8 T cells but not direct killing. In conclusion, cyclic peptide C25 provides a rationale for targeting the immune checkpoint, by blockade of LAG-3/HLA-DR interaction in order to enhance anti-tumor immunity, and C25 may provide an alternative for cancer immunotherapy besides antibody drugs.

【Objective】 To explore the correlation between CSAG1 expression and the prognosis and tumor-infiltrating lymphocytes in renal clear cell carcinoma (RCCC), and to predict the survival and tumor progression. 【Methods】 The gene expression profiles and clinical information of CSAG1 were downloaded from the Cancer Genome Atlas (TCGA). Based on the differential mRNA expression, GO annotation and KEGG pathway analysis were performed. The relationship between CSAG1 and tumor immune infiltration was assessed with Tumor Immunoassay Resource (Timer 2.0) database. The mRNA expression of CSAG1 in human RCCC specimens was validated with qRT-PCR. 【Results】 CSAG1 expression was significantly higher in RCCC tissues than in normal tissues (P<0.05). The qRT-PCR results revealed that the mRNA level of CSAG1 was consistent with that predicted by bioinformatic analysis. The KEGG analysis and GO annotation indicated high GSAG1 expression in RCCC was related to transmembrane transport, tricarboxylic acid cycle and lysosome. CSAG1 expression was positively related to the infiltration of pDC, aDC, CD8⁺ T cells, cytotoxic cells, TFH, TH1 cells, Tem, NK CD56^dm cells, Treg and T cells, but negatively correlated with macrophage infiltration. 【Conclusion】 CSAG1 may be associated with poor prognosis of RCCC and become a potential immunotherapy target.

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