Abstract 2931: Pharmacological inhibition of 17β-hydroxysteroid dehydrogenase impairs endometrial cancer growth in an orthotopic xenograft mouse model

Endometrial cancer (EC) is the most common gynaecological tumor in developed countries and its incidence is increasing. Approximately 80% of newly diagnosed EC cases are estrogen-dependent. Type 1 17β-hydroxysteroid dehydrogenase (17β-HSD-1) is the enzyme that catalyzes the final step in estrogen biosynthesis by reducing the weak estrogen estrone (E1) to the potent estrogen 17β-estradiol (E2), and previous studies showed that this enzyme is implicated in the local E2 generation in EC. In the present study we employed a recently developed orthotopic and estrogen-dependent xenograft mouse model of EC to show that pharmacological inhibition of the 17β-HSD-1 enzyme inhibits disease development. Tumors were induced in one uterine horn of athymic nude mice by intra-uterine injection of the well-differentiated human endometrial adenocarcinoma Ishikawa cell line that was modified to express 17β-HSD-1 in levels comparable to humans and, in addition, the luciferase and green fluorescent protein reporter genes. After tumor engraftment, controlled estrogen exposure was achieved using subcutaneous MedRod implants that released either E1 or placebo. A subgroup of the E1 supplemented mice received daily gavage of FP4643, a well characterized 17β-HSD-1 inhibitor. Bioluminescence imaging (BLI) was used to measure tumor growth non-invasively. At sacrifice, mice receiving E1 and treated with the FP4643 inhibitor showed a significant reduction in tumor growth by approximately 65% compared to mice receiving E1 alone. Tumors exhibited metastatic spread to the peritoneum, to the lymphovascular space (LVI) and to the thoracic cavity. Metastatic spread and LVI were both reduced in the inhibitor treated group. Transcriptional profiling of tumors indicated that FP4643 treatment reduced the oncogenic potential at the mRNA level. In conclusion, we show that the FP4643 inhibition represents a potential promising novel endocrine treatment for EC Citation Format: Sofia Xanthoulea, Gonda Konings, Niina Saarinen, Bert Delvoux, Loes Kooreman, Pasi Koskimies, Merja Häkkinen, Seppo Auriola, Elisabetta d'Avanzo, Youssef Walid, Frank Verhaegen, Natasja Lieuwes, Florian Caiment, Roy Kruitwagen, Andrea Romano. Pharmacological inhibition of 17β-hydroxysteroid dehydrogenase impairs endometrial cancer growth in an orthotopic xenograft mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Can