INTRODUCTION: Endometrial carcinoma (EMC) is the most common gynecologic malignancy and is highly lethal in the metastatic setting with an overall survival of 1.5-2 years due to chemotherapy resistance. Uterine carcinosarcoma (UCS) is a rare but aggressive biphasic subtype that comprises only 3-4% of EMCs but accounts for greater than 16% of uterine cancer deaths. Sulfatase 2 (SULF2) is an extracellular enzyme that activates pro-tumorigenic growth factor signaling, including transforming growth factor β (TGFβ). SULF2 is overexpressed in many cancers and is associated with tumor progression and poor prognosis. TCGA data reveal that the SULF2 gene is commonly amplified or mutated in UCS (17.5%) and may be a viable therapeutic target. OKN-007, a disulfonyl derivative of phenyl-tert-butyl nitrone, interrupts the TGFβ pathway and decreases downstream markers of epithelial mesenchymal transition (EMT) through inhibition of SULF2 in the tumor extracellular matrix. As such, assessment of OKN-007 was undertaken in UCS and EMC.METHODS: The anticancer effect of OKN-007 was evaluated in a UCS cell line (CS99) and EMC cell lines (Ishikawa, AN3CA, Hec1A, and RL95-2A). Cell viability, migration, colony-formation, and protein expression of SULF2, TGFβ, and EMT markers were evaluated in 2D and 3D culture conditions in vitro. The effect of OKN-007 alone or in combination with chemotherapy (carboplatin and paclitaxel) on tumor growth was evaluated in an intraperitoneal UCS xenograft mouse model. In vivo tumor growth was monitored using magnetic resonance imaging. TGFβ, SULF2, and EMT markers were investigated by western blot. RESULTS: SULF2 was highly expressed in UCS and EMC cells in 2D and 3D conditions. Decreased cell viability, migration, and colony-forming ability were observed with OKN-007 treatment with differences observed in IC50 values in 2D vs 3D conditions. Mice treated with OKN-007 demonstrated no observable toxicity, had decreased mean tumor volume (p<0.0001), and had prolonged survival compared to untreated mice (p<0.01). This effect was also observed when OKN-007 was given in combination with chemotherapy (p<0.05). Immunoblotting demonstrated a 30% reduction in SULF2 expression in OKN-007 treated tumors. Decreased expression of TGFβ and matrix metalloprotease 9 (MMP9) was also noted. CONCLUSION: OKN-007 is an effective agent in UCS and EMC. The anticancer activity of OKN-007 across histologic subtypes of EMC is associated with inhibition of the SULF2-TGFβ signaling pathway which decreases cellular proliferation, migration and viability in vitro and in vivo.

Citation Format: Anjalika Gandhi, Samrita Dogra, Rheal Towner, Bethany N. Hannafon, Katherine Moxley. OKN-007 suppresses uterine carcinosarcoma by inhibiting extracellular sulfatase 2 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB137.