Abstract PR014: Cytokine mediated epigenetic reprogramming of CRC primary tumors drives liver metastasis
Authors: Rennhack Jonathan , Dwivedi Arika , Wu Nathan , Shim Brian , Font-Tello Alba , Kesten Nikolas , Aguirre Andrew , Long Henry , Ng Kimmie , Hahn William C. 
Published: January 2023

Abstract
An emerging hypothesis is that metastatic potential is determined largely by the combination of genetic alterations that initiate the primary tumor and subsequent transcriptional reprogramming through epigenetic mechanisms. Here we leverage integrative, multi-omic profiling of primary and metastatic colorectal cancer tumors in combination with functional screens and disease models to understand drivers of liver metastasis. Through performing bulk and single cell RNA-sequencing, whole exome sequencing, and H3K27Ac ChIP-seq of primary tumors and metastatic lesions in the liver, we identified dramatic enhancer remodeling in metastatic disease. In specific, we identified a region on chromosome 20 upstream of the signaling protein SIRPA containing 7 differentially active enhancers in metastatic disease. Not only do the enhancers show an in silico enrichment for TCF7 binding sites but we showed them in vitro to be reliant upon TCF7 through the use of a reporter system. To confirm the regulatory potential of TCF7 on SIRPA we performed CRISPRa mediated overexpression of TCF7. This resulted in significant increase in SIRPA levels. We then showed each gene to be functional drivers of metastasis and migration with in vitro and in vivo models. Through CRISPR mediated KO and CRISPRa mediated overexpression, we showed both genes to be necessary and sufficient for migration in a wound healing assay and invasion in a transwell assay. When the lines were transplanted orthotopically to the cecum, we saw a reduction in metastatic burden in the liver with the loss of either gene. To identify liver microenvironmental factors that lead to the upregulation of TCF7 and subsequent activity of SIRPA we assayed conditioned media derived from immortalized hepatocytes. Through the use of a cytokine array, we have shown the hepatocyte produced CCL2 is able to induce TCF7 and subsequently SIRPA in a panel of CRC cell lines and organoids. Importantly we showed the continued production of CCL2 is important for the survival of the cancer cell in the liver microenvironment through both genetic and drug intervention experiments. Together this data indicates an important signaling node in colorectal cancer metastasis to the liver. Here we propose a model in which secreted liver factors, such as CCL2, reprogram genes within the tumor cell to promote growth and survival of the liver. These genes, SIRPA, and TCF7, represent potential therapeutic targets. Targeting these proteins may kill existing metastatic lesions as well as block new metastases from forming which will be important in improving the outcomes of patients with oligometastatic and premetastatic disease.
Citation Format: Jonathan Rennhack, Arika Dwivedi, Nathan Wu, Brian Shim, Alba Font-Tello, Nikolas Kesten, Andrew Aguirre, Henry Long, Kimmie Ng, William C. Hahn. Cytokine mediated epigenetic reprogramming of CRC primary tumors drives liver metastasis [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr PR014.