High OX40 expression in recurrent ovarian carcinoma is indicative for response to repeated chemotherapy.

Background: Ovarian carcinoma (OC) is the fifth most common female cancer and mostly diagnosed at an advanced stage. Surgical debulking is usually followed by adjuvant platinum-based chemotherapy. Only few biomarkers are known to be related to chemosensitivity. OX40 is a TNF receptor member and expressed on activated CD4+ and CD8+ T cells. It is known that OX40 signaling promotes survival and responds to various immune cells of the innate and adaptive immune system. Therefore we investigated the indicative value of OX40 expression for recurrence and survival in OC.

Methods: A tissue microarray of biopsies of mostly high-grade primary serous OC and matched recurrences of 47 patients was stained with OX40. Recurrence within 6 months of the completion of platinum-based chemotherapy was defined as chemoresistance.

Results: Chemosensitivity correlated significantly with high OX40 positive immune cell density in primary cancer biopsies (p = 0.027). Furthermore patients with a higher OX40 expression in recurrent cancer biopsies showed a better outcome in recurrence free survival (RFS) (p = 0.017) and high OX40 expression was associated with chemosensitivity (p = 0.008). OX40 positive TICI in recurrent carcinomas significantly correlated with IL-17 positive tumor infiltrating immune cells in primary carcinomas (r  = 0.34; p = 0.023). Univariate cox regression analysis revealed a significant longer RFS and higher numbers of chemotherapy cycles for high OX40 tumor cell expression in recurrent cancer biopsies (HR 0.39, 95%CI 0.16-0.94, p = 0.036 and 1.28, 95%CI 1.05-1.55; p = 0.013).

Conclusion: High OX40 expression in OC is correlated with chemosensitivity and improved RFS in OC. Patients might therefore benefit from a second line therapy.