Congqi Dai, Fengjuan Lin, Ruixuan Gen, Xiaoxiao Ge, Wenbo Tang, Jinjia Chang, Zheng Wu, Xinyang Liu, Ying Lin, Zhe Zhang, Jin Li

Department of Medical Oncology, Fudan University Shanghai Cancer Center

Objective:Cytokine-induced killer (CIK) cells represent a realistic approach in cancer immunotherapy with confirmed survival benefits in the context of metastatic solid tumors that are unmanageable using standard treatments. However, its therapeutic effects are limited to a fraction of patients. The aim of the study was to identify immune-resistance mechanism underlying cancer immunotherapy in the context of metastatic solid tumors and evaluate ideal combinational therapy with CIK cells infusion. Method: Flow cytometry was used to identify the phenotype and immune-features of CIK cells. Non-radioactive cytotoxicity assays were performed to evaluate anti-tumor activity of CIK cells against gastric and colorectal cancer cells. Lentiviral transduction and Western blot were used to create and validate varying levels of PD-L1 on the tumor cells. RT-PCR was used to detect mRNA levels in gastric cancer samples. Result:Cytotoxic activity of CIK cells could be indirectly affected by varying levels of PD-L1 on the tumor cells. The levels of PD-1 and PD-L1 on CIK cells were elevated substantially, as well as the PD-L1 expression on tumor cells upon co-culture. Neutralizing of PD-L1/PD-1 signaling resulted in an increased cytotoxicity of CIK cells against gastric and colorectal cancer cells, and NKG2D was identified as a mediator of the mechanism of PD-L1/PD-1 signaling blockade boosting the lytic activity of CIK cells in the presence of other immune-promoting molecules support. Gastric specimens analysis indicates clinical significance of NKG2D receptors as an independent prognostic indicator for patients outcomes. Conclusion: All the data support that simultaneous CIK infusion and blockade of PD-L1/PD-1 pathways should be put forward as a novel promising candidate for clinical trial, especially in the setting of unresectable metastatic cancers.

Key Words: PD-L1/PD-1  CIK  NKG2D