Effect And Significance Of PORCN Expression In Tumor DNA Damage Repair

Background: On the basis of extensive exploration of the basic mechanisms of tumor development,early diagnosis,early treatment and precise treatment of tumors have developed rapidly.Our understanding of the disease of tumors has been more in-depth,and it has significantly improved the survival rate and quality of life of cancer patients.However,the resistance of tumor to chemotherapy,radiotherapy and targeted therapy is increasing rapidly,which result in slow progress in tumor treatment.To find new therapeutic targets and to increase the sensitivity of tumor to adjuvant therapy are still major problems to be solved.In the previous study,we found that LGK974,a specific inhibitor of PORCN protein,can increase the radiosensitivity of tumor cells.Then we speculated that PORCN also affects the chemosensitivity of tumor cells.Furthermore,we formulate a hypothesis that the specific mechanism is that PORCN participates in DNA damage repair process.The purpose of this study is to investigate the role of PORCN in DNA damage repair of tumor cells and PORCN’s clinical significance.Methods: In this study,the influence of PORCN on chemosensitivity of tumor cells was studied by cytological experiments,and the role of PORCN in DNA damage repair of tumor cells was also preliminarily explored.Furthermore,the relationship between the expression of PORCN and the survival of tumor patients was analyzed by bioinformatics.First,we used LGK974 to specifically inhibits PORCN.Then we tested the effect of PORCN on chemosensitivity by MTS assay after treating tumor cells with cisplatin.Next,we used sh RNA to knock down PORCN and established a stable transfected cell line.Subsequently,DNA damage of tumor cells was induced by ionizing radiation,and the DNA damage repair ability of PORCN-deficient cells was detected by experiments such as immunofluorescence,comet assay and western blot.Finally,through the analysis of TCGA database data by website GEPIA,to explore the correlation between the expression of PORCN and the m RNA expression of DNA PKCs,as well as the correlation with the survival of different cancer patients.Results:(1)Inhibition of PORCN increased chemotherapy sensitivity of tumor cells to platinum drugs;(2)the focal duration of γ-H2 AX increased,the tail moment of comet assay increased,and DNA damage and repair defects appeared in PORCN deficient cells.(3)TCGA data analysis showed that the m RNA expression of PORCN and DNA PKCs was positively correlated in 20 kinds of tumors.The total survival time of Luminal A breast cancer patients with low expression of PORCN was longer,which was statistically significant.Conclusion: Specific inhibition of PORCN can increase the chemosensitivity of tumor cells.PORCN plays an important role in the process of DNA damage and repair in tumor cells.Inhibition or knock down of PORCN cause the dysfunction of DNA damage repair in tumor cells.The expression of PORCN in many kinds of tumor tissues is positively correlated with the expression of DNA-PKCs,which is a key protein in DNA damage repair process.The overall survival(OS)of cancer patients with low expression of PORCN was higher than that of patients with high expression of PORCN.This study showed the effect of PORCN on the radiosensitivity and chemosensitivity of tumor cells,its important role in the process of DNA damage repair and its correlation with the total survival time of specific types of breast cancer patients.Based on these findings,we can further explore the use of PORCN as a new therapeutic target for tumor and a potential marker for cancer patients’ survival.