Natural adjuvants (PC and G2) induce activated natural killer cells with NKG2D expression and cytotoxic properties in colorectal cancer.

Aim: This study aimed to investigate the effects of natural adjuvants (G2 and PC) to activate natural killer cells in colorectal cancer. Background: Natural killer (NK) cells are an element of the innate immune system that can recognize and kill cancer cells and provide hope for cancer therapy. One of the current methods in cancer immunotherapy is NK cell therapy. Immunotherapy with NK cells has been limited because of the low number and cytotoxicity level of NK cells. Natural adjuvants such as PC and G2 may stimulate the immune system. It seems that these adjuvants could increase cytotoxic NK cells. Methods: Twelve patients with colorectal cancer and six healthy individuals qualified for inclusion in this study. Peripheral blood mononuclear cells (PBMCs) from each patient with two distinctive concentrations (105and 5×104 cells/well) were treated with Interleukin2 (IL2), PC, and G2 adjuvant separately. The NK cell's surface markers, including CD16, CD56, and NKG2D, were evaluated by flow cytometry. The cytotoxicity effect of treated PBMCs as effector cells against NK sensitive cell line (K562) was assessed using the LDH assay method. Results: The results revealed a significant increase in the level of CD16+NKG2D+ NK cells in PBMCs treated with the G2 group compared with the control group in CRC PBMC (p<0.001) as well as the normal PBMC group (p < 0.01). In addition, the results indicated a significant increase in the level of CD56+NKG2D+ cells in the PBMC treated with PC (p < 0.05) and G2 (p < 0.001) groups compared with the PBMC group. The cytotoxicity result of PBMC from CRC patients in 10:1 ratio of the effector: target showed that the cells' cytotoxicity in the PBMCs treated with PC (p<0.01) and G2 (p<0.05) was significantly higher than the untreated PBMC. Conclusion: According to the result of this study, it can be stated that the PC and G2 adjuvants could be candidates for inducing cytotoxic natural killer cells.