Targeting ß-TrCP regulators to improve CRC response to chemotherapy

PROJECT SUMMARY Improved treatment of colorectal cancer (CRC) requires better understanding of key regulators of survival and proliferation of intestinal epithelial cells and their crosstalk with immune system. Upregulation and hyperactivation of the β-TrCP E3 ubiquitin ligase underlie CRC pathogenesis and poor responses to chemotherapy. While directly inhibiting β-TrCP proved to be practically difficult, here we propose to target the key regulators of β-TrCP in CRC including proteins that stabilize its mRNA (IGF2BP1) and protein (PARP11). Our published and preliminary data indicate that IGF2BP1 and PARP11 act within malignant cells as well as within benign immune cells of the tumor microenvironment (TME) to stimulate colorectal tumors growth and progression and limit their responses to chemotherapeutic regimens. These data support an overarching hypothesis that targeting IGF2BP1 and PARP11 should elicit potent anti-tumor effects and improve the efficacy of anti-cancer chemotherapies. We will test this hypothesis in three independent yet integrated Specific Aims. In Aim 1 we will determine the roles of IGF2BP1 in cancer cells and in the pro-tumorigenic TME and in responses to therapy. We will utilize genetic modulation of IGF2BP1 expression in CRC cells and cells of the TME to understand the role of IGF2BP1 for tumor growth, metastases, and sensitivity to the FOLFOX regimen, which is a standard of care chemotherapy for CRC patients. Mechanisms governing IGF2BP1 expression in TME as well as mechanisms of TME-dependent involvement of IGF2BP1 in sensitivity to chemotherapy will be investigated. Aim 2 will determine the importance of PARP11 in growth and progression of intestinal tumors as well as their responses to anti-tumor therapy. We will use genetic, molecular, and pharmacologic approaches to modulate PARP11 in colon adenocarcinoma cells or in the non-malignant TME cells to determine the importance of PARP11 in pro-tumorigenic phenotypes in vitro and ability to form orthotopic tumors and liver metastases in vivo. PARP11-dependent mechanisms underlying control of malignant cells by anti-tumor immune system and responsiveness of tumors to chemotherapy will be investigated. Aim 3 will examine the effects of pharmacological targeting of the regulators of β-TrCP to improve the responses of colon adenocarcinoma tumors to chemotherapy. We will determine the anti-tumor effects of novel, potent and highly selective inhibitors of IGF2BP1 (AVJ16) and PARP11 (ITK7) as mono-agents and their ability to improve the responses to FOLFOX regimen. Completion of these studies should gain the insight on the importance of IGF2BP1 and PARP11 in colorectal tumor growth and metastasis, and characterize these regulators as potential vulnerabilities, which could be exploited for improving chemotherapy of CRC.