Effect of tumor-infiltrating T-lymphocytes on the aggressiveness of epithelial ovarian tumors.

Abstract

5053 Background: Borderline ovarian tumors (BOT) are a low-grade form of ovarian malignancy with significantly less aggressive behavior than epithelial ovarian cancer (EOC). Since there is neither convincing scientific evidence nor a marker capable of predicting BOT’s behavior, we analyzed the role of immune tolerance in differential disease outcome. EOC and BOT were chosen due to similar disease etiology, despite different disease courses. Increased numbers of T-cell subpopulations infiltrate malignant tumors, so we used epigenetic tests to determine the prevalence of regulatory T-cells (Treg) and overall-T-Lymphocytes (oTL) in EOC and BOT. Methods: The ovarian cancer samples were provided by the European multicentric OVCAD study. The BOT samples were obtained from Tumor Bank Ovarian Cancer at Charité Campus Virchow (Germany). Samples and clinical data were prospectively collected and documented using validated SOPs. DNA was bisulphite-converted and forwarded to methylation-specific RT-PCR for CD3 and FOXP3 loci. Results: We evaluated 90 high-grade EOC, 12 BOT with invasive implants and 25 non-invasive BOT samples. Higher oTL-values correlate with mortality (p=0.008) and recurrence (p<0.001), while higher Treg levels correlate with recurrence (p=0.028). Patients with non-invasive BOT have lower oTL (p=0.019) and Treg (p=0.0005) levels than patients with invasive BOT and EOC, while BOT (both invasive and non-invasive) patients have lower Treg-to-oTL ratios than EOC patients (p=0.0005). Finally, oTL levels associate with overall survival in EOC (p=0.042). Conclusions: We observed a strict correlation between tumor-type, Treg and oTL levels, as well as Treg-to-oTL ratio. This is in agreement with our hypothesis that disease aggressiveness is associated with the amount tumor-infiltrating lymphocytes and may provide the explanation for differing disease courses in EOC and BOT.