Biomarkers and targeted therapies for ovarian granulosa cell tumors

Adult-type granulosa cell tumor (AGCT) is a unique subtype of ovarian cancer, accounting for 5% of all ovarian malignancies. The prognosis of AGCTs is often favorable, however these tumors have a tendency for late relapse. Eventually AGCT recurs in every third patient, and half of them succumb to the disease. Surgery is the mainstay of treatment. Platinum-based chemotherapy is used in advanced and inoperable AGCTs, although its efficacy is only modest. The objectives of this study were to improve the preoperative diagnostics of AGCTs and to uncover targeted treatments for AGCT. Serum markers HE4 and CA125 are commonly used in the preoperative evaluation of unknown ovarian masses, but their roles in AGCTs are unknown. Based on our results, HE4 levels are not elevated in AGCTs. We detected increased CA125 levels in a subset of AGCTs; however, the marker had no prognostic significance. These results underline the possibility of malignant ovarian tumor even in situations where CA125 and HE4 are both normal. Based on our and previous findings, inhibin B and AMH are the most specific markers in distinguishing AGCT from other malignant or benign ovarian tumors. The equilibrium between proliferation and apoptosis is crucial in the physiology of normal granulosa cells and it has been proposed to be disturbed in AGCTs. We evaluated the role of TNF-related apoptosis inducing ligand (TRAIL) in clinical AGCT samples and detected a significant correlation of TRAIL to its receptors (DR4 and DR5) in AGCT tissue samples, indicating active TRAIL signaling in AGCTs. Furthermore, both circulating and tissue TRAIL expressions were decreased in patients with large AGCTs, implying a tumor suppressive role for TRAIL in AGCTs. Our results suggest a potential role for TRAIL in AGCT treatment. We characterized the hormonal milieu of AGCTs in a vast collection of AGCT samples and studied the functional effects of follicle-stimulating hormone (FSH) and estradiol (E2) in tumor proliferation by using cell culture assays. FSH receptor and estrogen receptor beta were found to be expressed in the majority of tumors whereas the expression of aromatase, a crucial enzyme in estrogen synthesis, varied significantly among the studied tumors. In functional assays, FSH increased the viable cell number in subset of AGCTs, whereas E2 increased the cell number only at high concentrations. The aromatase inhibitor letrozole was able to block E2 synthesis in AGCTs but had no effect on cell viability. To systematically screen for new targeted therapies for AGCTs, we performed drug sensitivity and resistance testing and transcriptomic profiling. Seven AGCT primary cell cultures were exposed to a collection of 230 oncologic regimens. Among these compounds, a multi tyrosine kinase inhibitor dasatinib emerged as the most effective targeted treatment. Furthermore, dasatinib in combination with the traditional chemotherapeutic paclitaxel showed a synergistic effect, suggesting clinical testing of these regimens in patients with advanced AGCT. In conclusion, we verified that inhibin B and AMH are the most specific serum markers in AGCT preoperative diagnostics. Even though aromatase inhibitors showed no efficacy in inhibition of AGCT cell growth, further clinical studies are needed to verify the role of hormonal treatments in AGCTs. Importantly, our results suggest a role for TRAIL and dasatinib in AGCT treatment and encourage clinical testing of these regimens.