The Role Of Notch Signaling Pathway And C-Myc In Cell Proliferation Of Clear Cell Renal Cell Carcinoma

Objective: Notch signaling pathway and proto-oncogene c-Myc both play a critical rolein cell cycle progression and cell proliferation and they may collaborate intumorigenesis. C-Myc was a direct target gene of Notch signaling pathway in T-ALLand breast cancer. In current study, we serve to clarify the contribution of Notchsignaling pathway and c-Myc to clear cell renal cell carcinoma and their potentialrelationships, so as to find a new therapy target independent of VHL/HIF signaling.Materials and Methods:①Message RNA and protein levels of Notch1, Notch2andc-Myc were detected in27clear cell renal cell carcinoma (ccRCC) tissue samples andtheir corresponding adjacent normal tissue samples by real-time polymerase chainreaction (PCR) and western-blot, respectively. Then, correlation analyses were utilizedbetween mRNA expressions of Notch1, Notch2and c-Myc.②Cell cycle assays andcell proliferation were detected by flow cytometer and MTS in ccRCC cell line786-Oand human kidney tubule epithelial cell line HKC, which were pre-treated by Notchinhibitor DAPT and equal quantity of solution DMSO.③Basal expressions of Notch1,Notch2and c-Myc in HKC and786-O and the expression of c-Myc in cells with orwithout DAPT treatments were detected by triplicate real-time PCR and western-blot.Results:①Notch1, Notch2and c-Myc were all upregulated in ccRCC samplesrelative to adjacent normal tissue samples (all p<0.001). Correlation analyses showedthat in ccRCC samples c-Myc mRNA expression was closely positive correlated withNotch2mRNA expression in ccRCC (r=0.629, p<0.001), but not with Notch1mRNAexpression (p=0.389). However, in adjacent normal tissue samples, there were nocorrelations between c-Myc and Notch1or Notch2(both p>0.05).②When Notchsignaling pathway was blocked by DAPT treatments, cell proliferations was attenuatedin both cell lines (both p<0.05) and cell cycles were G0/G1arrested (16.54%in786-Oand9.75%in HKC, respectively, both p<0.001);③With HKC cells as control,mRNA expressions of Notch1, Notch2and c-Myc were all upregulated in786-O cells(1.87±0.15folds,2.56±0.18folds and2.54±0.24folds, respectively, all p <0.05).After DAPT treatment, c-Myc expressions in786-O and HKC were both downregulated (2.93±0.26folds and1.41±0.13folds, respectively, both p<0.05). Conclusions:Up-regulated Notch1, Notch2and c-Myc may associate with ccRCC and they maycollaborate in tumorigenesis. Downregulation of c-Myc may contribute to proliferationattenuation of kidney normal and cancer cells treated by Notch inhibitor DAPT.