Abstract 5151: Deciphering the molecular mechanisms driving infiltrative histopathological type of colorectal cancer liver metastases

Abstract

Abstract Colorectal carcinoma (CRC) remains the second leading cause of cancer death in the western world. Over 50% of CRC patients develop liver metastases (LM) and 90% will succumb to their disease. Liver resection of the LMs provides the only possibility of cure, but only 20% of colorectal cancer liver metastases (CRCLM) patients are resectable. The combination of angiogenic inhibitors (AI: anti-VEGF) with chemotherapy is the current form of treatment. Unfortunately, 65-70% of the patients continue on chemotherapy until resistance develops and then are treated with second, third and some times a fourth line of treatment, with an expected median overall survival of 24-28 months. We have no way of identifying those CRCLM patients that would respond/benefit to the addition of anti-angiogenic therapies (e.g. Bevacizumab). Recently we have identified two CRCLM histologic growth patterns (HGP) that predict treatment response and survival: 1) Desmoplastic (DHGP), a desmoplastic ring separating cancer cells from the liver parenchyma and lesions grow by angiogenesis; 2) Replacement or infiltrative (RHGP), tumor cells infiltrate the parenchymal cells in the liver as the lesions grow by co-opting the sinusoidal blood vessels between the liver cell plates. We showed that CRCLM patients with predominantly desmoplastic HGP metastasis receiving AIs plus chemotherapy have more than double the 5-year overall survival compared to patients with replacement HGP who have received the same treatment. In addition, our clinical data revealed that Angiogenic Inhibitors could negatively affect outcomes in patients with replacement HGPs. These non-angiogenic lesions do not respond to angiogenic inhibitors. To further our understanding of the molecular differences between the two HGPs we demonstrated by knocking out ARPC3 (Actin-related protein 2/3 complex subunit 3, involved in actin polymerization) in the human colon cancer cell line, HT-29, that cancer cell motility is a crucial process that regulates histological growth pattern in CRCLM. HT29 CRC cells injected directly into the mouse liver grow into replacement HGPs, while HT29s silenced for ARPC3 grow into desmoplastic HGPs lesions. However, the molecular mechanisms that regulate ARPC3 in CRCLM remain unknown. To further dissect the molecular mechanisms differentiating desmoplastic from replacement HGPs, we performed RNA-seq analysis of CRCLM lesions from chemonaïve patients. Our data revealed that both TGFβ1 and RUNX1 were upregulated in RHGP comparing to DHGP lesions. This has been further validated by immunoblotting and immunohistochemistry. Consistently, RUNX1 has been reported as a downstream of TGFβ1 and transcriptional factor for ARPC3. Collectively, our data suggests that TGFβ1 and RUNX1 contribute to the formation of infiltrative type of colorectal cancer liver metastases possibly through upregulation of ARPC3. Note: This abstract was not presented at the meeting. Citation Format: Miran Rada, Anthoula Lazaris, Stephanie Petrillo, Abdellatif Amri, Peter Metrakos. Deciphering the molecular mechanisms driving infiltrative histopathological type of colorectal cancer liver metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5151.