Blocking 17β hydroxysteroid dehydrogenase type 1 in endometrial cancer: a potential novel endocrine therapeutic approach

Gonda Konings (NL), Karlijn Cornel (NL), Sofia Xanthoulea (NL), Bert Delvoux (NL), Margaretha Skowron (DE), Loes Kooreman (NL), Pasi Koskimies (FI), Camilla Krakstad (NO), Helga Salvesen (NO), Kim van Kuijk (NL), Yannick Schrooders (NL), Marc Vooijs (NL), Arjan Groot (NL), Marlies Bongers (NL), Roy Kruitwagen (NL), Andrea Romano (NL)

[Konings] Maastricht University Medical Centre, [Cornel] Maastricht University Medical Centre, [Xanthoulea] Maastricht University Medical Centre, [Delvoux] Maastricht University Medical Centre, [Skowron] Heinrich Heine University Düsseldorf, [Kooreman] Maastricht University Medical Centre, [Koskimies] Forendo Pharma Ltd., [Krakstad] Haukeland University Hospital, [Salvesen] Haukeland University Hospital, [van Kuijk] Maastricht University Medical Centre, [Schrooders] Maastricht University Medical Centre, [Vooijs] Maastricht University Medical Centre, [Groot] Maastricht University Medical Centre, [Bongers] Maastricht University Medical Centre, [Kruitwagen] Maastricht University Medical Centre, [Romano] Maastricht University Medical Centre

Context: Type 1 17βhydroxysteroid dehydrogenase (17βHSD-1), responsible for generating active 17βestradiol (E2) from low-active estrone (E1), is over-expressed in endometrial cancer (EC) thus implicating an increased intra-tissue generation of E2 in this estrogen-dependent condition. Objective: Explore the possibility to inhibit 17βHSD-1 and impair the generation of E2 from E1 in EC for potential therapeutic purposes. Various in vitro, in vivo and ex vivo models were used. Methods and Patients: We generated EC cell lines derived from the well-differentiated endometrial adenocarcinoma Ishikawa cells and expressing levels of 17βHSD-1 similar to human tissues (Ishi-HSD1). High-performance-liquid-chromatography (HPLC) was used to measure the 17βHSD-1 activity in cell free assay. Estrogen dependent growth and the ability to inhibit 17βHSD-1 activity were assessed in a colony formation assay and in vivo using the chicken chorioallantoic membrane assay (CAM). Two retrospective EC patient cohorts were used to test inhibition (HPLC) and to determine 17βHSD-1 expression (RT-PCR) in paired primary/metastatic lesions. Results: Using Ishi-HSD1 cells, E1 to E2 conversion and 17βHSD-1 activity were blocked by a specific 17βHSD-1 inhibitor in cell-free assay followed by HPLC analysis. In vitro, E1 administration elicited colony formation similar to E2, and this was impaired by 17βHSD-1 inhibition. In vivo, tumours grafted on the CAM demonstrated that E1 upregulated the expression of the estrogen responsive cyclin A similar to E2, which was impaired by 17βHSD-1 inhibition. Neither in vitro nor in vivo effects of E1 were observed using 17βHSD-1 negative cells (negative control). Using a patient cohort of 52 primary ECs, we demonstrated the presence of 17βHSD-1 enzyme activity, which was inhibited using the 17βHSD-1 inhibitor by over 90% in more than 45% of ECs. Since drug treatment is generally indicated for metastatic/recurrent and not primary tumour, we next demonstrated the mRNA expression of the potential drug target, 17βHSD-1, in metastatic lesions using a second cohort of 37 EC patients. Conclusion: 17βHSD-1 inhibition efficiently blocks the generation of E2 from E1 using various EC models. Further preclinical investigations and 17βHSD-1 inhibitor development to make candidate compounds suitable for the first human studies are awaited.