Mechanism Of MIB1 Promoting Proliferation Of Pancreatic Cancer By Activating β-catenin Signaling

Pancreatic ductal adenocarcinoma(PDAC)is a malignant tumor with high mortality and poor prognosis.Although the level of medical treatment continues to improve,but due to the occult of pancreatic cancer,the early symptoms are not typical,leading to low early diagnosis rate.Most patients have missed the best treatment time when they were diagnosed,the success rate of surgery is not high,and the overall 5-year survival rate is less than 20%.The risk factors of pancreatic cancer are very complex.Although there are more and more studies on pancreatic cancer,there is still no exact evidence to show the pathogenesis of pancreatic cancer.More clinical markers are needed to increase the accuracy of early diagnosis.Radiotherapy and chemotherapy are the main means for the treatment of pancreatic cancer,which play an important role in the recurrence and metastasis of cancer,improving the survival time and slowing down the pain of patients.Gemcitabine(2’,2’-difluorodeoxycytidine,gemcitabine)is an important drug in the treatment of PDAC.However,gemcitabine has no effect after chemotherapy,owing to the drug resistance of pancreatic cancer cells and the insensitivity of some patients to chemotherapy drugs.Therefore,to analyze and reveal the causes and molecular mechanisms of drug resistance in pancreatic cancer cells will provide new targets and research ideas for the treatment of pancreatic cancer.Ubiquitin proteasome system(UPS)is very important for cancer progression.UPS is responsible for protein degradation starting from ubiquitination.E3 ligase recognizes and transfers ubiquitin to lysine residues on specific substrate proteins.More than 600E3 ligases have been found.It has been reported that cancer cells can use UPS to regulate the protein level of tumor suppressor or promoter,so as to promote the growth of cancer cells.Because different E3 ligases recognize different substrates,E3 ligase inhibitors or activators may help to improve the efficiency of cancer treatment.Mind bomb 1(MIB1)is an E3 ligase,playing a critical role in chemotherapy resistance and cancer metastasis.According to the Cancer Genome Atlas(TCGA),MIB1 gene is preferentially amplified in pancreatic cancer.The change of MIB1 gene copy number was associated with poor survival.Gene Expression Omnibus(GEO)also showed that pancreatic cancer with high level of MIB1 m RNA had stronger resistance to gemcitabine,and the expression of MIB1 m RNA in pancreatic carcinoma was higher than that in adjacent normal tissues.In this study,we used Panc-1 and HAPF2 cells and athymic nude mice to explore whether MIB1 promotes the proliferation of pancreatic cancer and its regulatory mechanism.Objects: To investigate whether MIB1 promotes the proliferation of pancreatic cancer and whether it plays a role in activating β-catenin signaling pathway.Methods:In vitro study: Firstly,the copy number variation of MIB1 gene in 69 patients from the TCGA data set was analyzed by GSEA,and the correlation between the copy number variation and the survival time of patients was explored by Kaplan Meier survival analysis.The difference between the expression of MIB1 m RNA in pancreatic cancer tissues and adjacent normal pancreatic tissues in GEO database were analyzed,and the expression level of MIB1 m RNA was correlated with the sensitivity of pancreatic cancer patients to gemcitabine treatment.Secondly,Panc-1 and HPAF2 cells were transfected with MIB1 sh RNA lentivirus,respectively,and the MIB1 expression level was knocked down to detect the proliferation of pancreatic cancer cells.Finally,Panc-1 and HPAF2 cells were treated with β-catenin inhibitors to analyze the correlation between the changes of MIB1 in pancreatic cancer and the β-catenin pathway,and to explore its signaling pathway.In vivo: MIB1 KD pancreatic cancer cells were injected into nude mice to measure their proliferation rate in vivo.To test whether MIB1 KD modulated the drug sensitivity of pancreatic cancer chemotherapy,HPAF2 scramble and MIB1 KD cells were in situ implanted into thymus free nude mice and treated with gemcitabine,respectively.Results:1.The incidence of MIB1 gene copy number variation in pancreatic cancer is not low,and is negatively correlated with poor survival.2.Knocking down MIB1 in Panc-1 and HPAF2 cell lines can significantly inhibit the proliferation and colony formation of pancreatic cancer.The proliferation rate of MIB1 KD pancreatic cancer cells in vivo was also significantly inhibited.Western blot analysis showed that the total level and activity of β-catenin in MIB1 KD cells were decreased compared with control cells.3.β-catenin inhibitors also inhibit the proliferation of Panc-1 and HPAF2 cells.4.In animals,MIB1 KD can modulate the sensitivity of pancreatic cancer to drug chemotherapy.Conclusion: MIB1 can promote the proliferation of pancreatic cancer by activating β-catenin signaling pathway.Therefore,MIB1 may be a new target for the treatment of pancreatic cancer.