CXCR4 as a target for colon cancer chemoprevention

The risk of colorectal cancer (CRC) is substantially higher in populations consuming Western diets (WDs). WDs also increase tumors in experimental CRC models. In this study we will use pharmacological and genetic strategies to test CXCR4 requirements and down-stream signals in WD-promoted tumorigenesis. We will also dissect the genetic and epigenetic regulation of CXCR4 modulated by diet and malignant transformation. Finally, we will screen a natural product (NP) library for anti-CXCR4 activity and test chemopreventive efficacy of promising agents in CRC models. Since CXCR4 is up-regulated by WD in non-transformed colonocytes and its inhibition suppresses tumor development, studies dissecting CXCR4 regulation and effector signals and identifying NP inhibitors could uncover new targets for CRC prevention. Aim 1a To assess the ability of CXCR4 inhibitor MSX-122 to suppress AOM tumorigenesis. We will compare effects of standard diet and WD on initiation and progression phases by RNAseq and EGFR signals. 1b To genetically establish CXCR4 role in CRC using mutant cdx2-CreERT-ApcΔ/Δ, CXCR4Δ/Δ mice (with CXCR4+/Δ as controls). We will measure tumor incidence and progression and assess RNAseq changes and EGFR signals. Aim 2a To determine effects of WD and neoplastic progression on TFs and histone modifications controlling CXCR4 using ChIP-PCR and global effects of WD and tumorigenesis on chromatin structure by ATAC-seq and DNA methylation by nano-5hmC-seal in Cdx-2 Cre Apc+/Δ CRC model. 2b To assess CXCR4 regulatory events in human colonic malignant progression using organoids derived from primary colonocytes and cancers. Aim 3a To screen a natural product library for CXCR4 inhibitory activity. CXCR4-labeled colon cancer cells will be pretreated with natural products (Cellular Screening Core) and activated with Sdf1α. An ELISA detecting CXCR4 internalization will be used to monitor CXCR4 activation. 3b Promising agents identified in aim3a, with in vitro inhibitory activity and predicted or established low toxicity and acceptable bioavailability, will be tested for chemopreventive efficacy using AOM and cdx-2-Cre Apc+/Δ models.