Mutant p53 dictates the oncogenic activity of c-Abl in triple-negative breast cancers

Cell Death Dis. 2017 Jun 29;8(6):e2899. doi: 10.1038/cddis.2017.294.

Abstract

We recently established c-Abl as a potent suppressor of triple-negative breast cancer (TNBC) progression through its reactivation of a p53:p21 signaling axis coupled to senescence. Moreover, we observed co-expression of p53 and c-Abl to be essential for normal mammary epithelial cell physiology, as this relationship is lost upon breast cancer progression. Cytoplasmic c-Abl activity is markedly increased in some TNBCs and contributes to disease progression; however, the mechanisms underlying these events remain largely unknown. In addressing this question, we show here that c-Abl is predominantly restricted to the cytoplasm of human MDA-MB-231 TNBC cells, and to the nucleus of human MCF-7 luminal A cells. TTK is a mitotic protein kinase that phosphorylates c-Abl on Thr735, thereby creating a recognition binding motif for 14-3-3 adaptor proteins in response to oxidative stress. By interrogating the METABRIC database, we observed a significant correlation between p53 expression and that of c-Abl and TTK in basal-like breast cancers. Moreover, heterologous expression of TTK in MCF-7 cells significantly stimulated their growth in part via a c-Abl-dependent mechanism. Conversely, depleting TTK expression in MDA-MB-231 cells not only inhibited their organoid growth in 3D-cultures, but also sensitized them to the tumor suppressing activities of c-Abl independent of its subcellular localization. Moreover, we show that mutant p53 forms cytoplasmic complexes with c-Abl, thereby dictating the subcellular localization of c-Abl and the sensitivity of MDA-MB-231 cells to Imatinib. In response to nutrient deprivation, c-Abl:p53 complexes readily accumulate in the nucleus, resulting in the hyperactivation of c-Abl and initiation of its anti-tumor activities. Collectively, we identified a novel mutant p53:c-Abl cytoplasmic signaling complex that promotes MDA-MB-231 cell growth and highlights the contextual cues that confer oncogenic activity to c-Abl in breast cancer.

MeSH terms

  • 14-3-3 Proteins / genetics
  • Apoptosis / drug effects
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Cell Proliferation / drug effects
  • Cytoplasm / genetics
  • Drug Resistance, Neoplasm / genetics
  • Female
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • Imatinib Mesylate / administration & dosage
  • Imatinib Mesylate / adverse effects
  • MCF-7 Cells
  • Multiprotein Complexes / genetics
  • Mutant Proteins / genetics*
  • Mutant Proteins / metabolism
  • Protein Binding
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism
  • Protein-Tyrosine Kinases / genetics
  • Protein-Tyrosine Kinases / metabolism
  • Proto-Oncogene Proteins c-abl / genetics*
  • Proto-Oncogene Proteins c-abl / metabolism
  • Triple Negative Breast Neoplasms / drug therapy*
  • Triple Negative Breast Neoplasms / genetics
  • Triple Negative Breast Neoplasms / pathology
  • Tumor Suppressor Protein p53 / genetics*
  • Tumor Suppressor Protein p53 / metabolism

Substances

  • 14-3-3 Proteins
  • Cell Cycle Proteins
  • Multiprotein Complexes
  • Mutant Proteins
  • TP53 protein, human
  • Tumor Suppressor Protein p53
  • Imatinib Mesylate
  • Protein-Tyrosine Kinases
  • Proto-Oncogene Proteins c-abl
  • Protein Serine-Threonine Kinases
  • TTK protein, human