Project description:Dimerization is believed necessary for receptor tyrosine kinases (RTKs) activation. Here we report that monomeric epidermal growth factor receptor (EGFR) directly phosphorylates the signal transducer and activator of transcription-3 (STAT3) in the absence of transmembrane protein TMEM25 (hereafter referred to as TAMER (Transmembrane protein Antagonizing Monomeric EGF Receptor signaling) to reflect its molecular function). We identified TAMER as a checkpoint for the monomeric-EGFR/STAT3 signaling, and downregulation of TAMER in triple-negative breast cancer (TNBC) results in a persistent activation of STAT3 that is required for TNBC progression, which gives a good explanation why targeting EGFR dimerization by antibodies showed no significant benefit to TNBC patients in clinical trials. Remarkably, supply of TAMER strongly suppressed TNBC progression, presenting a promising targeted therapy for TNBC. Hence, our study demonstrated the first RTK monomer-mediated signaling pathway, introducing an unprecedented pattern of RTK signaling that may play key roles in certain physiological or pathological contexts, which might need to be inspected for therapeutically targeting RTKs in the future.In this paper, RNA-seq were used to identify different gene expression in WT and TMEM25 knockout MDA-MB-231 cells.
Project description:Primary tumor growth and metastasis in triple-negative breast cancer (TNBC) require supporting vasculature, which develop through a combination of endothelial angiogenesis and vasculogenic mimicry (VM), a process associated with aggressive metastatic behavior in which vascular-like structures are lined by tumor cells. We developed αEGFR-E-P125A, an antibody-endostatin fusion protein that delivers a dimeric, mutant endostatin (E-P125A) payload that inhibits TNBC angiogenesis and VM in vitro and in vivo. To characterize the mechanisms associated with induction and inhibition of VM, RNA-seq of MDA-MB-231-4175 TNBC cells grown in a monolayer (2D) was compared to cells plated on Matrigel undergoing VM (3D). We then compared RNA-seq between TNBC cells in 3D and cells in 3D with VM inhibited by αEGFR-E-P125A (αEGFR-E-P125A). Gene set enrichment analysis (GSEA) demonstrated that VM induction activated the IL6-JAK-STAT3 and angiogenesis pathways, which were downregulated by αEGFR-E-P125A treatment. Correlative analysis of the phospho-proteome demonstrated decreased EGFR phosphorylation at Y1069, along with decreased phosphorylation of focal adhesion kinase (FAK) Y397 and STAT3 Y705 sites downstream of α5β1 integrin. Suppression of phosphorylation events downstream of EGFR and α5β1 integrin demonstrated that αEGFR-E-P125A interferes with ligand-receptor activation, inhibits VM, and overcomes oncogenic signaling associated with EGFR and α5β1 integrin crosstalk. In vivo, αEGFR-E-P125A treatment decreased primary tumor growth and VM, reduced lung metastasis, and confirmed the inhibition of signaling events observed in vitro. Simultaneous inhibition of EGFR and α5β1 integrin signaling by αEGFR-E-P125A is a promising strategy for the inhibition of VM, tumor growth, motility, and metastasis in TNBC and other EGFR-overexpressing tumors.
Project description:Inhibitor of apoptosis (IAP) proteins constitute a conserved family of molecules which regulate both apoptosis and receptor signaling. They are often deregulated in cancer cells and represent potential targets for therapy. In our work, we investigated the effect of IAP inhibition in vivo to identify novel downstream genes expressed in an IAP-dependent manner that could contribute to cancer aggressiveness. To this end, immunocompromised mice engrafted subcutaneously with the triple negative breast cancer MDA-MB231 cell line were treated with SM83, a pan-IAP inhibitor developed by us, and tumor nodules were profiled for gene expression. Our work suggests that IAP-targeted therapy could contribute to EGFR inhibition and the reduction of its downstream mediators. This approach could be particularly effective in cells characterized by high levels of EGFR and Snai2, such as triple negative breast cancer.
Project description:We investigate non-genomic mechanisms determining cellular response to EGFR inhibitors in triple negative breast cancer (TNBC). We integrate methods for cellular barcoding and single-cell transcriptomics to enable cell lineage tracing and explore the subclonal evolution of adaptation in an established preclinical model of TNBC in response to incremental concentrations of Afatinib, a second generation EGFR-TKI that irreversibly inhibits both EGFR and HER2. Retrospective lineage tracing data analysis uncovered a pre-existing subpopulation of rare Afatinib-tolerant cells displaying distinct biological features, such as elevated mRNA levels of the IGFBP2 gene. Furthermore, we investigated temporal coordination of transcriptional programs in drug resistant clones with high replication fitness by reordering cells along a pseudotime trajectory. Interestingly, it revealed the activation of biological processes, such as fatty acid metabolism, which have previously been linked to EGFR-TKIs resistance mechanisms.
Project description:Breast cancer is a heterogeneous disease comprised of four molecular subtypes defined by whether the tumor-originating cells are luminal or basal epithelial cells. Breast cancers arising from the luminal mammary duct often express estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth receptor 2 (HER2). Tumors expressing ER and/or PR are treated with anti-hormonal therapies, while tumors overexpressing HER2 are targeted with monoclonal antibodies. Immunohistochemical detection of ER, PR, and HER2 receptors/proteins is a critical step in breast cancer diagnosis and guided treatment. Breast tumors that do not express these proteins are known as “triple negative breast cancer” (TNBC) and are typically basal-like. TNBCs are the most aggressive subtype, with the highest mortality rates and no targeted therapy, so there is a pressing need to identify important TNBC tumor regulators. The signal transducer and activator of transcription 3 (STAT3) transcription factor has been previously implicated as a constitutively active oncogene in TNBC. However, its direct regulatory gene targets and tumorigenic properties have not been well characterized. By integrating RNA-seq and ChIP-seq data from 2 TNBC tumors and 4 cell lines, we discovered novel gene signatures directly regulated by STAT3 that were enriched for processes involving inflammation, immunity, and invasion in TNBC. Functional analysis revealed that STAT3 has a key role regulating invasion and metastasis, a characteristic often associated with TNBC. Our findings suggest therapies targeting STAT3 may be important for preventing TNBC metastasis.
Project description:Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with very limited therapeutic options. We have recently shown that the combined inhibition of EGFR and ROCK in TNBC cells results in cell cycle arrest and ultimately cell death. However, the underlying mechanisms by which co-inhibition of EGFR and ROCK induces cell death remain unclear. To investigate the synergistic effect of the combination treatment on TNBC cells, in the present study we applied a mass spectrometry-based proteomic approach to identify proteins altered upon single and combination treatments.
Project description:Evidence has long suggested that epidermal growth factor receptor (EGFR) may play a prominent role in triple-negative breast cancer (TNBC) pathogenesis, but clinical trials of EGFR inhibitors have yielded disappointing results. Using a candidate drug screen, we discovered that inhibition of cyclin-dependent kinases 12 and 13 (CDK12/13) dramatically sensitizes diverse models of TNBC to EGFR blockade. This combination therapy drives cell death through the 4E-BP1-dependent suppression of the translation and translation-linked turnover of driver oncoproteins, including MYC. A genome-wide CRISPR/Cas9 screen identified the CCR4-NOT complex as a major determinant of sensitivity to the combination therapy whose loss renders 4E-BP1 unresponsive to drug-induced dephosphorylation, thereby rescuing MYC translational suppression and promoting MYC stability. The central roles of CCR4-NOT and 4E-BP1 in response to the combination therapy were further underscored by the observation of CNOT1 loss and rescue of 4E-BP1 phosphorylation in TNBC cells that naturally evolved therapy resistance. Thus, pharmacological inhibition of CDK12/13 reveals a long proposed EGFR dependence in TNBC that functions through the cooperative regulation of translation-coupled oncoprotein stability.
Project description:Antibody-drug conjugate αEGFR-E-P125A reduces triple-negative breast cancer vasculogenic mimicry, motility, and metastasis through inhibition of EGFR, integrin, and FAK/STAT3 signaling