Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer subtype characterized by a remarkable molecular heterogeneity and resistance to treatment. Here, we report the generation of a unique mouse model (MMTV-R26 Met mice) in which a subtle increase in the expression levels of the wild-type MET receptor tyrosine kinase leads to spontaneous, exclusive TNBC formation, recapitulating TNBC heterogeneity. We further exploited the MMTV-R26 Met TNBC model by exploring signaling alterations through proteomics to search for TNBC vulnerability. We identified a new drug combination based on combinatorial targeting of WEE1 and BCL-XL that efficiently kills TNBC cells. Mechanistically, we show that BCL-XL inhibition exacerbates the dependency of TNBC cells on WEE1 function, leading to Histone H3 and phosphoS 33 RPA32 upregulation, RRM2 downregulation, cell cycle perturbation, and depletion of oncogenic signals, resulting in mitotic catastrophe and apoptosis. Our findings suggest that combination therapy with BCL-XL and WEE1 inhibitors warrants further evaluation in clinical trials.
Statement of significanceWe have developed a new TNBC mouse model that recapitulates resistance to chemotherapy and heterogeneity. We uncovered that combined inhibition of WEE1 and BCL-XL selectively kills mouse and human TNBC cells, and provided mechanistic insights underlying this combined targeting. We propose that BCL-XL inhibition exacerbates WEE1 requirement for TNBC survival. cancer subtypes, TNBC is characterized by the earliest age of onset, a higher prevalence in African-Americans, a high propensity for metastasis, and the worst prognosis in terms of relapse and survival rate (6,7). Over 80% of TNBC patients exhibit alterations in the TP53 locus (8), whereas a smaller fraction has mutations in genes controlling the PI3K pathway and homologous recombination including BRCA1/2 negative. A molecular feature of TNBC is the dependency of cancer cells on signals that are rarely mutated, a phenomenon defined as "non-oncogene addiction" (9). It is the case, for example, of components of the receptor tyrosine kinase (RTK) core pathway (7,10). Collectively, these traits are 4 among the leading cause of limited efficacy of current TNBC therapies. Radiation therapy and chemotherapy, applied before and after surgery, are the mainstay of treatment, although frequently associated with drug resistance and recurrent disease.Extensive efforts have been made to search for molecular targeted therapies effective for TNBC treatment. Although some targeted therapies approved for treatment of other cancer types have been proposed in TNBC, they rarely turned out to be clinically relevant (11). These limited responses are associated with the high heterogeneity of the disease and the lack of suitable immunocompetent preclinical models that recapitulate the molecular diversity of TNBC. Among potential targets for TNBC subsets are PARP1, androgen receptor (AR), vascular endothelial growth factor receptor (VEGFR), epidermal growth factor receptor (EGFR...