Follicle-Stimulating Hormone Receptor Is Expressed by Most Ovarian Cancer Subtypes and Is a Safe and Effective Immunotherapeutic Target

Abstract

To define the safety and effectiveness of T cells redirected against follicle-stimulating hormone receptor (FSHR)-expressing ovarian cancer cells. FSHR expression was determined by Western blotting, immunohistochemistry, and qPCR in 77 human ovarian cancer specimens from 6 different histologic subtypes and 20 human healthy tissues. The effectiveness of human T cells targeted with full-length FSH in vivo was determined against a panel of patient-derived xenografts. Safety and effectiveness were confirmed in immunocompetent tumor-bearing mice, using constructs targeting murine FSHR and syngeneic T cells. FSHR is expressed in gynecologic malignancies of different histologic types but not in nonovarian healthy tissues. Accordingly, T cells expressing full-length FSHR-redirected chimeric receptors mediate significant therapeutic effects (including tumor rejection) against a panel of patient-derived tumors in vivo In immunocompetent mice growing syngeneic, orthotopic, and aggressive ovarian tumors, fully murine FSHR-targeted T cells also increased survival without any measurable toxicity. Notably, chimeric receptors enhanced the ability of endogenous tumor-reactive T cells to abrogate malignant progression upon adoptive transfer into naïve recipients subsequently challenged with the same tumor. Interestingly, FSHR-targeted T cells persisted as memory lymphocytes without noticeable PD-1-dependent exhaustion during end-stage disease, in the absence of tumor cell immunoediting. However, exosomes in advanced tumor ascites diverted the effector activity of this and other chimeric receptor-transduced T cells away from targeted tumor cells. T cells redirected against FSHR+ tumor cells with full-length FSH represent a promising therapeutic alternative against a broad range of ovarian malignancies, with negligible toxicity even in the presence of cognate targets in tumor-free ovaries. Clin Cancer Res; 23(2); 441-53. ©2016 AACR.