Abstract 4119: CXCR4/CB2 heterodimer antagonizes CXCR4-mediated metastasis and tumor growth in vivo
Authors: Pennant Nakea Michelle , Hartono Alifiani B. , Liu Shiqin , Massey Christopher , Lee Chung , Stoyanova Tanya , Hinton Cimona V. 
Published: March 2024

Abstract
The G-protein-coupled chemokine receptor (GPCR), CXCR4, is ubiquitously expressed in malignant tumor tissues, and controls migration and other tumor survival mechanisms upon interaction with its chemokine agonist, stromal cell-derived 1α (SDF1α). The CXCR4/SDF1α axis is relevant to shaping the tumor microenvironment mainly the metastatic spread of primary tumors to distal organs and immune response; thus, expression of CXCR4 in tumors is vital to tumor aggressiveness, survival probability, and metastasis-associated mortality. CXCR4 signals through a homodimer, but also forms heterodimers with other chemokine and non-chemokine GPCRs. We’ve demonstrated that CXCR4 forms a heterodimer with the GPCR, cannabinoid receptor 2 (CB2), in human breast and prostate cell lines in vitro. The cannabinoid system has earned interest as anticancer therapeutic targets by modulating growth, migration, angiogenesis, etc. In our model, CXCR4-mediated, pro-tumor signaling was reduced by the physical heterodimer, and the dimer was induced by simultaneous treatment with agonists (SDF1α and AM1241) for respective receptors. The resultant heterodimer negatively interfered with migration, cytoskeletal rearrangement, motility associated proteins, and signaling that coordinates movement. Given that cannabinoids have been shown to reduce metastasis and profession of clinical tumors, we hypothesize that a heterodimer of CXCR4 and CB2 disrupts CXCR4-mediated metastasis, and ultimately, decrease tumor progression in vivo.Herein, we tested our hypothesis in an in vivo model of spontaneous metastasis NSG male mice. Luciferase-containing human prostate cancer cells (DU145 RFP/Luc) were implanted subcutaneously. Once tumors reached 40mm3, mice were randomized by volume, weight and age, and divided into 4 treatments: vehicle, SDF1α, AM124, and SDF1α/AM124(combo) for daily intraperitoneal injections. Tumors reaching 400mm3 were excised, and treatments continued for 3 weeks. Spontaneous metastasis was monitored via IVIS imaging at 2- and 3-weeks post-tumor removal. We observed reduced tumor growth, and decreased incidence rates of metastasis to the lung in the combination treatment group, which, based on our in vitro data, is representative of a CXCR4/CB2 heterodimer. This novel definition of heterodimerization could reveal and exploit new mechanisms for CXCR4 regulation in tumor metastasis. The CXCR4/CB2 heterodimer may attenuate responses triggered individually by CXCR4 without toxicity and side effects experienced with current CXCR4 antagonists.
Citation Format: Nakea Michelle Pennant, Alifiani B. Hartono, Shiqin Liu, Christopher Massey, Chung Lee, Tanya Stoyanova, Cimona V. Hinton. CXCR4/CB2 heterodimer antagonizes CXCR4-mediated metastasis and tumor growth in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4119.