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C-Abl inhibits breast cancer tumorigenesis through reactivation of p53-mediated p21 expression.

ABSTRACT: We previously reported that constitutive c-Abl activity (CST-Abl) abrogates the tumorigenicity of triple-negative breast cancer cells through the combined actions of two cellular events: downregulated matrix metalloproteinase (MMP) and upregulated p21Waf1/Cip1 expression. We now find decreased c-Abl expression to be significantly associated with diminished relapse-fee survival in breast cancer patients, particularly those exhibiting invasive and basal phenotypes. Moreover, CST-Abl expression enabled 4T1 cells to persist innocuously in the mammary glands of mice, doing so by exhausting their supply of cancer stem cells. Restoring MMP-9 expression and activity in CST-Abl-expressing 4T1 cells failed to rescue their malignant phenotypes; however, rendering these same cells deficient in p21 expression not only delayed their acquisition of senescent phenotypes, but also partially restored their tumorigenicity in mice. Although 4T1 cells lacked detectable expression of p53, those engineered to express CST-Abl exhibited robust production and secretion of TGF-?1 that engendered the reactivated expression of p53. Mechanistically, TGF-?-mediated p53 expression transpired through the combined actions of Smad1/5/8 and Smad2, leading to the dramatic upregulation of p21 and its stimulation of TNBC senescence. Collectively, we identified a novel c-Abl:p53:p21 signaling axis that functions as a powerful suppressor of mammary tumorigenesis and metastatic progression.

SUBMITTER: Morrison CD

PROVIDER: S-EPMC5340126 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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c-Abl inhibits breast cancer tumorigenesis through reactivation of p53-mediated p21 expression.

Morrison Chevaun D CD Allington Tressa M TM Thompson Cheryl L CL Gilmore Hannah L HL Chang Jenny C JC Keri Ruth A RA Schiemann William P WP

Oncotarget 20161101 45

We previously reported that constitutive c-Abl activity (CST-Abl) abrogates the tumorigenicity of triple-negative breast cancer cells through the combined actions of two cellular events: downregulated matrix metalloproteinase (MMP) and upregulated p21Waf1/Cip1 expression. We now find decreased c-Abl expression to be significantly associated with diminished relapse-fee survival in breast cancer patients, particularly those exhibiting invasive and basal phenotypes. Moreover, CST-Abl expression ena ...[more]

PMID: 27626309

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Project description:Background:Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer that lacks expression of estrogen receptor (ER) and progesterone receptor (PR) and the human epidermal growth factor receptor 2 (HER2) gene. Chemotherapy remains the standard of care for TNBC treatment, but considerable patients are very resistant to chemotherapy. Mutations or aberrant upregulation of EZH2 occur frequently, and EZH2 inhibitor (EZH2i) showed some preclinic antitumor effects in TNBC. Methods:RNA-seq data of 3 TNBC cell lines either treated with 2 ?M GSK343, or stably transduced with shEHZ2, compared to untreated controls (GSE112378) were analyzed by Limma R package. The Kaplan-Meier plotter (KM plotter) database was used to assess the relevance of FOSB mRNA expression to relapse-free survival (RFS) in TNBC. Cell number counting and colony formation assays were used to detect the biological effect of FOSB on the growth of TNBC cells in vitro. The effect of FOSB on TNBC tumor growth in vivo was investigated in a mice tumor xenograft model. Luciferase reporter and chromatin immunoprecipitation (Chip) assays were used to determine the regulatory roles of C/EBP? on FOSB expression. Results:We found that FOSB, a member of the activator protein-1 complex, was a direct downstream target of EZH2. FOSB was significantly decreased in TNBC samples and associated with better relapse-free survival (RFS). EZH2-mediated histone 3 trimethylated on lysine 27 (H3K27me3), a marker of silent chromatin conformation, at the FOSB promoter inhibited it expression. Depletion of FOSB in TNBC cells promoted cell proliferation in vitro and tumor growth in vitro by inactivating the p53 pathway and conferred resistant to EZH2 inhibitor (EZH2i). Mechanistically, EZH2i promotes the shift from H3K27me3 to H3K27ac at the FOSB promoter, and recruits the transcription factor C/EBP? to activate FOSB gene transcription. Conclusion:Together, our results suggest that EZH2-mediated epigenetic inactivation of FOSB promotes TNBC expression and demonstrate that reactivation of FOSB expression by C/EBP? underlies the anti-TNBC action of EZH2is.

Dataset Information

C-Abl inhibits breast cancer tumorigenesis through reactivation of p53-mediated p21 expression.

Publications

c-Abl inhibits breast cancer tumorigenesis through reactivation of p53-mediated p21 expression.

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