Abstract 300: A new combination therapy to treat metastatic breast cancer

Abstract

Abstract Poly (ADP-ribose) polymerase (PARP) resulting poly (ADP-ribosyl)ation is an early player in modification of proteins detected at single strand breaks and double strand breaks contributing to DNA repair. PARP1, 2 and 3 are involved in this process. However, PARP3 is unique in that, it is also required for efficient mitotic progression, specifically in stabilization of the mitotic spindle. The vinca alkaloids such as vinorelbine, arrest cells in metaphase due to inhibition of the assembly and dynamics of microtubules. Nontoxic concentrations of 2 PARP3 inhibitors, ME-0328 and olaparib, sensitized various her-2 negative and triple negative breast cancer cell lines greater than or equal to 10 fold to vinorelbine associated with potentiation of vinorelbine’s interaction with tubulin and also vinorelbine-induced PARP3 inhibition, mitotic arrest, and apoptosis without evidence of a DNA repair mechanism involved in this sensitization (Sharif-Askari B et al. Breast Cancer Res Treat. 2018 Nov;172(1):23-32). Eribulin is a Halichondrin B analogue, an antitubulin drug, with a unique mechanism of action; it inhibits microtubule dynamics via a novel mechanism of action which seems to involve binding to a unique site on tubulin resulting in the suppression of microtubule polymerization without affecting depolymerization along with sequestration of tubulin into nonfunctional aggregate. After impressive results in phase III trials (including one of the rare trials to show prolongation of survival in comparison to standard of care in heavily pretreated metastatic breast cancer patients) the U.S. Food and Drug Administration approved eribulin for treatment of patients with metastatic breast cancer. PARP3 inhibitors again sensitized at least 5 fold her-2 negative and triple negative breast cancer cell lines to eribulin. We will do similar studies with eribulin as we have done with vinorelbine including in-vivo studies. These studies could define a new therapy in the treatment of metastatic triple negative and ER+/her-2 negative breast cancer. The inhibition of PARP3 may increase the sensitivity of tumor cells to mitotic spindle poison chemotherapies. Our results should stimulate development of specific PARP3 inhibitors for clinical use. Citation Format: Bahram Sharif-Askari, Raquel Aloyz, Lawrence Panasci. A new combination therapy to treat metastatic breast cancer [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 300.