Abstract 4799: Nef-M1 peptide inhibits CXCR4 driven Wnt/β-catenin signaling in breast cancer

Introduction: The Nef-M1 peptide (Nef-M1) competes effectively with the natural ligand of CXCR4, SDF-1α, and exhibits anti-tumorigenic activity in breast cancer (BC). However, the molecular mechanisms of action of Nef-M1 on BC remain unclear. In this study, we evaluated the Nef-M1 inhibition of CXCR4 driven Wnt/β-catenin pathway in BC. 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 mice with tumor were treated intraperitoneally either with Nef-M1 or sNef-M1 (control). Preparation of BC tissue, explant complete media, and cultures and treatment for 48 hours was performed for the PDE study. Sections from tumors were evaluated by immunostaining (IHC) for signaling proteins implicating BC 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 Wnt/β-catenin, stem cell or mitogen-activated protein kinase (MAPK) pathways. 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 tumors. 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 activation of MAPK (e.g. p38, ERK) and Akt proteins in BC. Nef-M1 treated BC displayed inhibition of Wnt/β-catenin signaling as demonstrated by an increased expression of p21 and decreased expression of beta-catenin, cyclin D1, Axin 2 and survivin. Cells expressing CXCR4 became susceptible to Nef-M1-induced inhibition of MAPK, Akt, Wnt/beta-catenin and stem cell signaling pathways. Conclusions: These results indicate that Nef-M1 suppresses CXCR4 mediated activation of Wnt/β-catenin and MAPK pathways. Therefore, Nef-M1 inhibition of these signaling pathways may be a promising therapeutic strategy for BC. This work was supported by NIH/NCI Workforce Diversity Grant R21-CA171251. Citation Format: Venkat R. Katkoori, Upender Manne, Harvey L. Bumpers. Nef-M1 peptide inhibits CXCR4 driven Wnt/β-catenin signaling in breast cancer [abstract]. In: Proceedings of the American