Role of Receptor Tyrosine Kinase cross-talk in colorectal cancer

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ABSTRACT: Background: EGF receptor (EGFR) is a receptor tyrosine kinase (RTK) that is overexpressed in over 50% of colorectal cancer (CRC) cases where it is linked to metastasis and poor prognosis. Cetuximab, an EGFR-targeting monoclonal antibody is approved by US-FDA to treat advanced wild-type KRAS CRC. However, cetuximab, as monotherapy, is effective in only about 10% of CRCs and resistance frequently emerges. Thus, there is a pressing need 1) to identify those patients most likely to respond (or not respond) to cetuximab and 2) to devise treatment strategies that would prevent resistance and/or enhance cetuximab response. We propose to address these needs by aggressively pursuing our observations that enhanced activity of multiple RTKs (e.g. MET and RON) confers de novo and acquired cetuximab resistance, which may be overcome by addition of the dual MET/RON inhibitor, crizotinib. Our central hypothesis is that upregulation of RTK activity confers cetuximab resistance in CRC and that it may be a viable therapeutic target. In Aim 1 we will identify the mechanism of RTK cooperation during CRC progression and cetuximab resistance using genetic and chemical modifications in CRC cell lines and patient- derived xenografts (PDXs) and organoids (PDOs). In Aim 2 we will assess the impact of disrupting RTK cooperation in overcoming resistance to EGFR-directed antibodies. In Aim 3 we will identify rational drug combinations and stratify patient populations to overcome resistance to EGFR- directed mAbs. Study design: We will employ our in vitro 3D culture system for CRC cell lines and PDOs and in vivo nude mice xenografts, PDXs, and immune-competent syngeneic mouse CRC models in this grant. We will also employ complementary approaches (Transwell cultures, tumor tissue microarrays, phospho-RTK arrays, and human CRC samples) in relevant sections. Key proteins (EGFR, MET, RON, ERBB3, HGF, HGFL, NRG1 and other positive and negative RTK and ligand regulators) will be manipulated (overexpression, CRISPR-mediated knockout, ligand stimulation, and chemical and antibody-based inhibition) to characterize individual contribution. These experiments will be recorded at subcellular localization, morphological, and phenotypic levels to tease out key differences. These studies will identify and characterize new modes of cetuximab resistance and its prevalence in CRC, while devising means to prevent or overcoming the resistance. This research will help optimize precision medicine and stratify individuals based on their response/resistance profile for better CRC treatment and management.