Abstract 3879: Inhibition of CXCR4 driven colorectal cancer progression by Nef-M1 peptide

Abstract

Abstract Introduction: The Nef-M1 peptide (Nef-M1) competes effectively with the natural ligand of CXCR4, SDF-1α, and exhibits anti-tumorigenic activity in human colorectal cancer (CRC). However, the molecular mechanisms of action of Nef-M1 on CRC remain unclear. In this study, we evaluated the inhibition of CXCR4 driven molecular signaling mechanisms that is involved in CRC progression. Experimental Design: Cell line derived xenografts (CDX), patient derived explant (PDE) and in vitro cell based models were used to examine the mechanisms of action of Nef-M1. The severe combined immunodeficient (SCID) mice with tumor were treated intraperitoneally with either Nef-M1 or scrambled amino acids sequence Nef-M1 (sNef-M1) that is the control. Preparation of CRC tissue, explant complete media, and cultures and treatment for 48 hours were performed for the PDE study. Sections from tumors were evaluated by immunostaining (IHC) for signaling proteins thus, implicating CRC progression. Western blot (WB) analyses were also performed on lysates of both cell lines and tumors to assess the effect of Nef-M1 on the signaling pathways that promote CRC progression. Results: The present study revealed that PDE recapitulate multiple biological features of the disease and these were found to be very similar to the corresponding original CRC. CXCR4 overexpressing CRC cells displayed activation of CXCR4/CREB signaling as demonstrated by an increased activation of CREB, and expression of B-Myb and APOBEC3B (A3B). IHC analysis for Ub-H2B, a stem cell signaling protein that correlates with advanced disease and metastasis indicated that Nef-M1 treated CDX or PDE tumors had low expression of Ub-H2B. However, sNef-M1 treated tumors had high expression of Ub-H2B. WB analyses indicated that Nef-M1 not only suppressed the expression of Ub-H2B, but also significantly suppressed the expression of A3B. Cells expressing CXCR4 became susceptible to Nef-M1-induced inhibition of Akt, mTOR activation and Ub-H2B expression. Conclusions: These results indicate that Nef-M1 suppresses CXCR4 driven activation of CXCR4/CREB signaling and the expression of Ub-H2B. Therefore, Nef-M1 inhibition of these signaling pathways may be a promising therapeutic strategy for CRC. This work was supported by NIH/NCI Workforce Diversity Grant R21-CA171251. Citation Format: Venkat R. Katkoori, Zeynoire Anderson, Upender Manne, Harvey Bumpers. Inhibition of CXCR4 driven colorectal cancer progression by Nef-M1 peptide [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 3879.