ABCF2 is a new biomarker of ovarian clear cell adenocarcinoma

5050 Background: Epithelial ovarian cancer (EOC) can be subdivided into five major histologic types (Serous(SC), Mucinous(MC), Endometrioid(EC), Clear cell(CC), Undifferentiated (UC)). Among them, CC generally has a poor response to combination chemotherapy and its overall prognosis is poor. The CC and EC are thought to arise from endometriosis (EM), while a majority of SC are thought to arise from inclusion cysts. In previous reports, we compared gene expression between CC and SC using cDNA microarrays and suggested that ABCF2, which is a new member of the ATP-binding cassette transporter superfamily, gene might be a new biomarker for CC (Proc ASCO 2003 22:448a). In this study, we generated a polyclonal antibody for ABCF2 and further validated the expression of ABCF2 in EOC and EM. Methods: Formalin-fixed surgical samples from 307 EOC and 20 EM patients were included in this study. ABCF2 expression was investigated by immunohistochemostry. The percentage of positive cytoplasmic staining (PCS) for ABCF2 was calculated by examining at least 1000 tumor cells. In 28 cases, quantitative RT-PCR was performed to evaluate the relationship between ABCF2 protein expression and relative mRNA expression. Results: Histologic types, stage and grade were as followed: (SC: 93; MC: 46; EC: 56; CC: 80; UC: 32, EM: 20), (I: 109; II: 34; III: 141; IV: 23) and (GR1: 110; GR2: 90; GR3: 106). In EOC, 166 of 307(54%) cases had ABCF2 expression and relative mRNA expression significantly correlated with levels of ABCF2 protein expression (r=0.504, p=0.006). The relationship between ABCF2 expression and histologic type was shown in table. CC had significantly higher levels of ABCF2 expression than that of other histologic types The positivity rate of ABCF2 in CC was significantly higher than other histologic type. However, there is no significant correlation between ABCF2 expression status and histologic stage or grade. In EM, ABCF2 expression was detected in 6 of 20 cases. Conclusions: ABCF2 expression is a new biomarker for CC. No significant financial relationships to disclose.