Abstract 5951: Synergistic efficacy of sulforaphane and progesterone against endometrial cancer
Authors: Rai Rajani , Choudhary Swati , Benbrook Doris M. , Chandra Vishal 
Published: June 2022

Introduction: Worldwide, endometrial cancer (EC) is the most common gynecological malignancy with increasing rate of incidence and mortality. While progesterone-based hormone therapy is a well-accepted conservative therapeutic option for EC patients, loss of progesterone receptor (PR) in long-term treatment leading to hormonal resistance and disease recurrence is still an area of concern. We demonstrated potent anti-cancerous activity of sulforaphane against EC in vitro and in vivo and hypothesized that it will activate PR and overcome progesterone therapy limitations. The purpose of this study was to evaluate the interaction of sulforaphane and progesterone against EC.

Methods: The in vitro synergistic interaction between sulforaphane and progesterone was investigated with isobologram analysis of plotting MTT metabolic viability assay results of EC cells treated with drugs individually and in combination using CompuSyn software. ATP, soft-agar colony formation and invasion assays were performed to evaluate the combined drug effects on cell viability, anchorage independent colony formation and invasion properties, respectively. Mitochondrial membrane potential and caspase-3 activity were measured by JC-1 and caspase-3 detection ELISA kit, respectively. Protein expression was accessed by western blot. Progesterone resistant EC cells were developed by treating cells with 30µM of progesterone for more than 3 months.

Results: Sulforaphane demonstrated strong synergy or additive effects with progesterone in the EC cell lines tested. Sulforaphane in combination with progesterone significantly decreased levels of cellular ATP, anchorage-independent colony formation, invasion and mitochondrial membrane potential. Furthermore, combination of sulforaphane and progesterone increased caspase-3 activity as compared to individual drug or controls, suggesting induction of apoptosis. Western blot results demonstrated an increased expression of cleaved PARP, with reduced expression of total caspase-3 and PCNA in the combination groups as compared to control and individual drugs. Sulforaphane alone or in combination showed increased expression of PR-A while it had minimal effects on PR-B. Further, in all EC cell lines, the combination of sulforaphane and progesterone demonstrated upregulation of PR-A/PR-B ratio. The progesterone resistant cells demonstrated less sensitivity to progesterone as compared to parent cell lines, however it was found to be sensitive to sulforaphane.

Conclusions: Sulforaphane demonstrated synergistic activity with progesterone leading to increased apoptosis and reduced proliferation. Furthermore, sulforaphane exhibited potent toxicity to progesterone resistance cells. Sulforaphane in combination with progesterone could overcome progesterone therapy limitation by re-activation of PR.

Funding: Administrative Suppl (P30CA225520) and PHF (GRF00005456)

Citation Format: Rajani Rai, Swati Choudhary, Doris M. Benbrook, Vishal Chandra. Synergistic efficacy of sulforaphane and progesterone against endometrial cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5951.