Project description:Goal of this study was to investigate gene expression profiling across different molecular subtypes of breast cancers, such as Estrogen Receptor (ER) positive, HER2 amplified, Triple negative Basal A, Triple negative Basal B.
Project description:Breast tumors are highly heterogeneous and for many molecular subtypes no targeted therapies are available. These include breast cancers that display hallmarks of epithelial to mesenchymal transition (EMT), a process related to metastasis and enriched in triple negative breast cancers (TNBCs). To determine whether this EMT cellular state could be therapeutically exploited, we performed a large-scale chemical genetic screen. We identified a group of structurally related compounds, including the clinically advanced drug PKC412 (midostaurin), that targeted post-EMT breast cancer cells. PKC412 induced apoptosis specifically in basal-like TNBC cells and inhibited tumor growth in vivo. Structure activity relationship (SAR) studies, chemical proteomics, and computational modeling identified the kinase SYK as a critical PKC412 target. Specific SYK inhibitors and PKC412 displayed a similar profile across a large panel of breast cancer cell lines, indicating a shared mode of action. Phosphoproteomics analysis revealed that SYK activates STAT3, and chemical or genetic inhibition of STAT3 resulted in cell death in basal-like breast cancer cells. This non-oncogene addiction of basal-like breast cancer cells to SYK suggests that chemical SYK inhibition may be beneficial for a specific subset of triple negative breast cancer patients.
Project description:The dire need for more effective treatments for clinically aggressive breast cancers has motivated intensive investigations into their cellular and molecular etiology. Breast cancers that are “triple-negative” for the clinical markers, ESR1, PGR, and HER2, typically belong to the Basal-like molecular subtype. Defective Rb, p53, and Brca1 pathways are each associated with triple-negative and Basal-like subtypes. Our mouse genetic studies demonstrate that concomitant inactivation of all three pathways in mammary epithelium has an additive effect on tumor latency, and predisposes highly penetrant, metastatic, adenocarcinomas. These tumors are poorly differentiated with histologic features that are common among human Brca1-mutated tumors, including heterogeneous morphology, metaplasia, and necrosis. Transcriptomic analyses demonstrated that the tumors shared attributes of both Basal-like and Claudin-low signatures, two molecular subtypes encompassed by the broader triple-negative category defined by clinical markers. Ex vivo tumorsphere formation, which was suppressed by Notch and Wnt pathway inhibition, and tumor antigen profiles and are consistent with enrichment of stem-like and luminal progenitor cells among these tumors. These studies establish a novel mouse model of malignant breast cancer based on events in the human disease and underscore the non-reciprocal requirements of three canonical tumor suppressor pathways in breast cancer evolution. Morphogenetic pathways may provide additional avenues for targeted therapeutic intervention. Gene expression analysis of mouse mammary tumors with perturbation of Rb family pathways, p53, and/or Brca1 are compared to other mouse model tumors (n=152)