PDGFR-Î’ Signals Induce Doxorubicin Resistance Via Mutant P53 In MDA-MB-231 Cells

Breast cancer(BC) is one of the most-frequent-malignancy of women in the world. Triple negative breast cancer(TNBC, ER-/PR-/HER2low) has accounted for 10%-20% incidence of breast cancer, characterized by poor differentiation, high heterogeneity, fast progress, high transfer rate and postoperative recurrence rate, and poor response to treatment. Cancer metastasis, chemoresistance, and recurrence closely correlate with each other and greatly enhance the mortality of patients with breast cancer.Many transcription factors inducing epithelial mesenchymal transition(EMT) and stem-related genes have been involved in tumorigenesis,metastasis and chemoresistance. However, the underlying molecular mechanisms regulating these processes are still opaque. Here, we report that mutant p53, a kind mutation of p53 DNA-binding domain, acts as an Co-promoter of stemness traits and EMT, positively regulated by the exogenous signals of platelet-derived growth factor receptor-β(PDGFR-β),and eventually promotes cancer drug resistance.ObjectiveTo investigate the role and mechanism of PDGFR-β signals indoxorubicin(Dox) resistance of MDA-MB-231 cells.MethodsThe rates of G2 cell cycle, apoptosis and viability were detected by Flow cytometry or MTS in Dox or(and) platelet-derived growth factor-DD(PDGF-DD, a PDGFR-β specific ligand) incubated cells. The expression levels of mutant p53, Cdk1, PDGFR-β, p21, Bax, Hsp90(heat shock protein 90) and TopBP1[topoisomerase(DNA) II binding protein 1]were determined by qPCR and WB to study the effects of PDGF-DD and Wortmannin(a PI3 K inhibitor) on mutant p53 expression and its functions.qPCR was used to measure the mRNA levels of resistant genes in cells treated with P53 siRNA or(and) PDGF-DD.ResultsPDGF-DD significantly reduced the rates of cell death, apoptosis and partly relieved G2/M cell cycle arrest caused by Dox. It greatly improved the protein level of p53 and seriously altered the expression of its downstream genes(like Cdk1, PDGFR-β, p21 and Bax), but with the negligible change of p53 mRNA(P >0.05). Meanwhile the elevated mRNA and protein levels of Hsp90(a mtp53 protein-stabilizing factor) and TopBP1(a mtp53 function-promoting protein) induced by PDGF-DD heavily decreased after Wortmannin treatment. Moreover, the improvement of the mRNA levels of resistant genes(as FOXC2, Twist, Snail, Nanog and Oct4) induced by PDGF-DD were seriously limited via knockingdownmutant p53 through siRNA.ConclusionPDGF-DD/PDGFR-β induces Dox resistance in MDA-MB-231 cells by stabilizing mutant p53 protein and promoting mutant p53-mediated resistance via the transcriptional level up-regulated expressions of Hsp90 and TopBP1 through the PI3 K signaling pathway.