Prognostic value of ABCF2 in ovarian clear cell adenocarcinoma

Abstract

5037 Background: Ovarian clear cell adenocarcinoma (CC) generally shows little response to combination chemotherapy and the overall prognosis is poor. However, the molecular pathobiology of CC remains largely unknown, because this is a rare type of ovarian cancer. We previously reported that ABCF2, which is a new member of the ATP-binding cassette transporter superfamily, gene might be a new biomarker for CC using cDNA microarray analysis (Proc ASCO 2003 22:448a). In this study, we raised a polyclonal antibody directed against ABCF2 and evaluated the relationship between ABCF2 expression and the response to chemotherapy or overall survival (OS) in CC patients. Methods: Formalin-fixed surgical samples were obtained from 61 CC patients and ABCF2 expression was investigated by immunohistochemostry. The percentage of positive cytoplasmic staining for ABCF2 was calculated by examining at least 1000 tumor cells. In 28 patients, quantitative RT-PCR was performed to evaluate the relationship between level of ABCF2 protein expression and relative mRNA expression. Results: The clinical stage was I in 28 patients, II in 10 patients, III in 22 patients, and IV in 1 patients. Fifty six patients received platinum-based chemotherapy after primary debulking surgery and the response to chemotherapy was evaluable in 12 of them. Forty-three out of 61 (70.5%) patients showed ABCF2 expression in the cytoplasm of tumor cells and the relative mRNA expression was significantly correlated with level of ABCF2 protein expression (r=0.504, p=0.006). There was no significant difference of ABCF2 protein expression between stages I+II and stages III+IV. A clinical response to chemotherapy was obtained in 5 cases. Non responders had significantly higher level of ABCF2 protein expression than responders (58.6% vs. 25%, p=0.0007). For the entire cohort, the OS was 75.4% (median follow-up of 36 months). The OS of 67.4% (median follow-up of 36 months) for patients with ABCF2 expression in their tumors was significantly worse than the OS of 94.4% (median follow-up of 37 months) for patients without tumor ABCF2 expression (p=0.03). Conclusions: The present results indicate that ABCF2 expression may predict the response to chemotherapy and survival of CC patients. No significant financial relationships to disclose.