Effects of Combination of Anti-CTLA-4 and Anti-PD-1 on Gastric Cancer Cells Proliferation, Apoptosis and Metastasis

Background/Aims: Gastric cancer (GC) is one of the most common and lethal varieties of cancers. Anticancer activities of anti-CTLA-4 and anti-PD-1 antibodies have been explored in different cancers, including GC. The study aimed to explore the role of combination therapy with anti-CTLA-4 and anti-PD-1 antibodies in GC cells, and understand the possible underlying molecular mechanism. Methods: MKN-45 and MGC-803 cells were divided into four groups, namely control, CTLA-4, PD-1, and CTLA-4&PD-1. Cell viability, cell cycle, apoptosis, migration and invasion were measured by MTT, flow cytometry, and transwell assays, respectively. Expression levels of different mRNAs and proteins associated with apoptosis, epithelial mesenchymal transition (EMT), β-catenin, MAPK, and PI3K/AKT pathways were assessed by RT-qPCR and western blot analysis, respectively. The tumor formation in vivo was examined by tumor Xenograft model assay. Results: Combination with anti-CTLA-4 and anti-PD-1 antibodies significantly suppressed cell proliferation, induced apoptosis, as well as inhibited migration, invasion, and EMT in MKN-45 and MGC-803 cells. Western blotting revealed that combination with anti-CTLA-4 and anti-PD-1 antibodies declined the activation of β-catenin, MAPK and PI3K/AKT signal pathways. Moreover, combination of anti-CTLA-4 and anti-PD-1 antibodies inhibited tumor formation in vivo. Furthermore, the mRNA levels of CTLA-4 and PD-1 were significantly decreased in si-CTLA and si-PD-1 transfected cells, and combination with si-CTLA and si-PD-1 also suppressed cell proliferation, migration, invasion, EMT and induced apoptosis in MKN-45 cells. Conclusion: Combination therapy with anti-CTLA-4 and anti-PD-1 antibodies presented the promising outcomes in GC, although further investigations are warranted.