title: Gain-of-function p53 mutant with 21-bp deletion confers susceptibility to multidrug resistance in MCF-7 cells.
abstract: The majority of p53 mutations, which are responsible for gain of oncogenic function, are missense mutations in hotspot codons. However, in our previous study, we demonstrated that a deletion spanning codons 127-133 in the p53 gene (designated as del p53) was detected in doxorubicin-resistant MCF-7 cell lines following various induction processes. In the present study, we aimed to investigate the role of del p53 and its association with the proliferation, metastasis and drug resistance of MCF-7 cells. The MCF-7/del p53 cell line is a representative of the del p53 stably expressed clones which were constructed by transfection of the del p53-containing construct into MCF-7/wt cells. Markers of multidrug resistance (MDR), epithelial-mesenchymal transition (EMT) and stem cell-like properties were examined in the MCF-7/del p53 cells. The results revealed that the MCF-7/del p53 cells expressed full-length p53 and del p53 mRNA and protein, as well as P-glycoprotein (P-gp). The MCF-7/del p53 cells acquired resistance to doxorubicin with increased P-gp efflux function. Using a transient expression assay, the mdr1 promoter was found to be significantly activated by external or integrated del p53 (P<0.001). The inhibition of nuclear factor (NF)-κB by cyclosporine sensitized the MCF-7/del p53 cells to doxorubicin toxicity. In addition, the morphological characteristics of the MCF-7/del p53 and MCF-7/adr were similar. EMT was observed in the MCF-7/del p53 cells as demonstrated by the presence of the mesenchymal markers, Slug and vimentin, and the decrease in the epithelial marker, cadherin 1, type 1, E-cadherin (CDH1), as well as an enhanced migration ability (P<0.001). Furthermore, the number of cells expressing the cancer stem cell-like marker, CD44, increased, accompanied by mammosphere formation. Taken together, these findings indicate that the expression of del p53 in MCF-7/del p53 cells enables the cells to partially acquire doxorubicin resistance characteristics of the MCF-7/adr cells. Thus, del p53 may be an important factor in non-invasive MCF-7 cells, activating NF-κB signaling and the mdr1 promoter and partially attributing to EMT; the cells thus acquire stem cell‑like properties, which facilitates drug resistance. Therefore, the 21-bp deletion of p53 may prove to be a therapeutic strategy with which to prevent cancer cells from acquiring resistance to drugs.
authors.affiliation: Graduate Institute of Pharmaceutical Sciences, School of Pharmacy, College of Medicine, National Taiwan University, Taipei 10050, Taiwan, R.O.C.
authors.forename: Shang-Hsun
authors.initials: SH
authors.lastname: Tsou
authors.affiliation: Graduate Institute of Pharmaceutical Sciences, School of Pharmacy, College of Medicine, National Taiwan University, Taipei 10050, Taiwan, R.O.C.
authors.forename: Ming-Hung
authors.initials: MH
authors.lastname: Hou
authors.affiliation: Graduate Institute of Pharmaceutical Sciences, School of Pharmacy, College of Medicine, National Taiwan University, Taipei 10050, Taiwan, R.O.C.
authors.forename: Lih-Ching
authors.initials: LC
authors.lastname: Hsu
authors.affiliation: Department of Obstetrics and Gynecology, College of Medicine, National Taiwan University, Taipei 10050, Taiwan, R.O.C.
authors.forename: Tzer-Ming
authors.initials: TM
authors.lastname: Chen
authors.affiliation: Graduate Institute of Pharmaceutical Sciences, School of Pharmacy, College of Medicine, National Taiwan University, Taipei 10050, Taiwan, R.O.C.
authors.forename: Yen-Hui
authors.initials: YH
authors.lastname: Chen
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D001483:Base Sequence; D001940:Breast / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D003062:Codon / Q000235:genetics; D004317:Doxorubicin / Q000494:pharmacology*; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D058750:Epithelial-Mesenchymal Transition; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D061986:MCF-7 Cells; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D014411:Neoplastic Stem Cells / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017384:Sequence Deletion; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D000903:Antibiotics, Antineoplastic; D003062:Codon; D016328:NF-kappa B; D016159:Tumor Suppressor Protein p53; D004317:Doxorubicin