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. Objectives: 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.