Pecam-1 Targeting Extends Overall Survival In Various Advanced Metastatic Mouse Tumor Models

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Objectives: Patients who die from cancer succumb to advanced metastatic progression (AMP). While targeted therapies are available that address tumor cell derived regulators of metastasis, few therapeutics are being developed to address the molecular mechanisms of AMP. Our group has previously shown that vascular endothelial cell (VEC) PECAM-1 is a critical molecular master switch which regulates AMP by controlling the release of VEC-derived, paracrine growth factors that drive its progression. Anti-PECAM-1 monoclonal antibody (mAb) effectively and safely treats even pre-terminal cancers in AMP-bearing mice. The current experiments were performed to assess whether, to what extent and how widely targeting PECAM-1 can improve overall survival in mice bearing advanced metastases. Methods: Groups of wildtype (WT) C57Bl/6 mice, together with age and gender matched PECAM-1 knockout (KO) mice were intravenously injected with 25,000 murine B16-F10 melanoma cells, 30,000 murine EL4 lymphoma cells or 1,000,000 murine MC38 colon cancer cells. We then injected matched groups of PECAM-1 KO vs WT mice with 1,000,000 B16-F10 cells, to model maximally aggressive AMP. All groups were assessed for overall survival, using IACUC approved guidelines. Results: In all cases, overall survival (OS) was significantly prolonged in PECAM-1 KO vs WT controls (Kaplan-Meier ranged from p = 0.018 to p = 0.0002). Targeting microenvironmental PECAM-1 was as effective in increasing OS in mice receiving the very high tumor burden of 1,000,000 B16-F10 cells as in mice receiving 25,000 cells, further confirming the efficacy of targeting PECAM-1 against the most advanced models of metastasis that can be achieved preclinically. Furthermore, anti-PECAM-1 mAb-based therapy of B16-F10 metastase was as effective as the PECAM-1 KO genotype in increasing OS. Conclusion: To date, many approved mAb- and small molecule-inhibitor based targeted-therapies have shown limited abilities to either prolong OS as single agents, or to effectively treat multiple different solid tumor types. These results suggest that anti-PECAM-1 mAb therapy, which specifically targets VEC and paracrine factors they produce, has the potential to significantly increase OS in the setting of lethal advanced metastatic progression, independent of tumor type. Anti-PECAM-1 mAb therapy is as effective as a PECAM-1 knockout in improving OS. Phase 1 clinical trials are planned within 2 years. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2847. doi:1538-7445.AM2012-2847