CGRP-carrying Liposome Nano-delivery System Inhibits Hypoxia-induced Immune Escape of Prostate Cancer Cells Through NO-cGMP Signaling Pathway

Background Prostate cancer is one of the most common malignancies in men, and immune escape is one of the major challenges in development and treatment. In a hypoxic environment, tumor cells may reduce or stop expressing antigens, thereby avoiding recognition by the immune system and increasing the risk of immune escape. Purpose The purpose of this study is to explore the inhibitory effect of the calcitonin gene-related peptide (CGRP)-carrying liposome nano-delivery system on the immune escape of prostate cancer cells under hypoxic conditions and further to study its related mechanism with the nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) signaling pathway. Materials and Methods A hypoxic PC-3 culture model was constructed and divided into four groups: Control group (no treatment of prostate cancer cells), Low_Oxygen_1 group (5% hypoxic environment + prostate cancer cells), Low_Oxygen_2 group (3% hypoxic environment + prostate cancer cells), Low_Oxygen_3 group (1% hypoxic environment + prostate cancer cells). For the co-cultivation of the obtained CGRP-low-density lipoprotein (LDL) delivery system with PC-3 cells, they were divided into Low_Oxygen + CGRP-LDL + hypoxia group, CGRP-LDL group, CGRP group, and Low_Oxygen + CGRP group. The apoptosis rate was detected, and the key protein of immune escape of PC-3 cells was analyzed to determine whether the immunosuppressive effect of CGRP-LDL on PC-3 under hypoxic conditions was realized through the NO-cGMP pathway. Results GRP-liposome carrying liposome (LCL) was successfully constructed, and the immune escape of prostate cancer cells was found in a hypoxic environment; the lower the oxygen concentration, the higher the degree of escape. The Low_Oxygen_2 group (3% hypoxic environment + CGRP-LCL group) had the most significant anti-cancer effect in the hypoxic environment, with the lowest proliferation and highest apoptosis (vs. other groups, p < .05). Liposome nano-delivery system carrying CGRP has a good anti-cancer effect. Further endothelial nitric oxide synthase (eNOS) messenger ribonucleic acid (mRNA) silencing and comparative verification using the nitric oxide synthase (NOS) inhibitor NG-nitro- l -arginine methyl ester (L-NAME) revealed that the nano-delivery system had a positive effect on the NO-cGMP signaling pathway of prostate cancer cells in a hypoxic environment. The 3% hypoxic environment + GCRP-LCL system group had the best intervention effect, and the G protein, cGMP concentration, and NO synthase activity were the highest (vs. other groups, p < .001). We added the NOS inhibitor L-NAME group and detected related proteins, and found that the CGRP-LCL group was significantly lower than the NOS inhibitor L-NAME group, which indicated that CGRP-LCL inhibited the immune escape of PC-3 cells. Conclusion A hypoxic environment can increase the phenomenon of immune escape of tumor cells, but the application of the CGRP-LCL nano-delivery system can intervene in this process. CGRP-LCL nano-delivery system can inhibit the immune escape of prostate cancer cells in a hypoxic environment. The expression of key proteins is inhibited, and this inhibitory effect is mainly exerted through the activation of the NO-cGMP signaling pathway.