ABSTRACT
Kinase inhibitors have limited success in cancer treatment because tumors circumvent their action. Using a quantitative proteomics approach, we assessed kinome activity in response to MEK inhibition in triple-negative breast cancer (TNBC) cells and genetically engineered mice (GEMMs). MEK inhibition caused acute ERK activity loss, resulting in rapid c-Myc degradation that induced expression and activation of several receptor tyrosine kinases (RTKs). RNAi knockdown of ERK or c-Myc mimicked RTK induction by MEK inhibitors, and prevention of proteasomal c-Myc degradation blocked kinome reprogramming. MEK inhibitor-induced RTK stimulation overcame MEK2 inhibition, but not MEK1 inhibition, reactivating ERK and producing drug resistance. The C3Tag GEMM for TNBC similarly induced RTKs in response to MEK inhibition. The inhibitor-induced RTK profile suggested a kinase inhibitor combination therapy that produced GEMM tumor apoptosis and regression where single agents were ineffective. This approach defines mechanisms of drug resistance, allowing rational design of combination therapies for cancer.
Subject(s)
Breast Neoplasms/drug therapy , Breast Neoplasms/metabolism , Drug Resistance, Neoplasm , MAP Kinase Kinase 1/antagonists & inhibitors , Protein Kinases/genetics , Proteome/analysis , Animals , Antineoplastic Agents/therapeutic use , Benzenesulfonates/therapeutic use , Benzimidazoles/therapeutic use , Disease Models, Animal , Extracellular Signal-Regulated MAP Kinases/antagonists & inhibitors , Female , Gene Expression Regulation, Neoplastic , Humans , Male , Mice , Niacinamide/analogs & derivatives , Phenylurea Compounds , Protein Kinase Inhibitors/therapeutic use , Protein Kinases/metabolism , Proto-Oncogene Proteins c-myc/metabolism , Pyridines/therapeutic use , Receptor Protein-Tyrosine Kinases/genetics , SorafenibABSTRACT
Epithelial stem cells self-renew while maintaining multipotency, but the dependence of stem cell properties on maintenance of the epithelial phenotype is unclear. We previously showed that trophoblast stem (TS) cells lacking the protein kinase MAP3K4 maintain properties of both stemness and epithelial-mesenchymal transition (EMT). Here, we show that MAP3K4 controls the activity of the histone acetyltransferase CBP, and that acetylation of histones H2A and H2B by CBP is required to maintain the epithelial phenotype. Combined loss of MAP3K4/CBP activity represses expression of epithelial genes and causes TS cells to undergo EMT while maintaining their self-renewal and multipotency properties. The expression profile of MAP3K4-deficient TS cells defines an H2B acetylation-regulated gene signature that closely overlaps with that of human breast cancer cells. Taken together, our data define an epigenetic switch that maintains the epithelial phenotype in TS cells and reveals previously unrecognized genes potentially contributing to breast cancer.
