Abstract LB-176: HE4 antigen-autoantibody complexes complement CA125 for detecting early stage ovarian cancer and can be elevated with CA125 in preclinical ovarian cancer

Abstract

Abstract Early detection of ovarian cancer could significantly improve patient outcomes. Serial monitoring of CA125 with the Risk of Ovarian Cancer Algorithm (ROCA) can attain sufficient specificity for cost effective screening when combined with transvaginal sonography, but not all early stage disease can be detected with CA125 alone. Sensitivity could be improved by combining CA125 with other biomarkers. Different autoantibodies (AAb) have been evaluated including TP53 AAb, but antigen-autoantibody (Ag-Ab) complexes have received less attention. We have measured AAb reactive with the serum biomarker human epididymal protein 4 (HE4) and Ag-Ab complexes containing HE4 in sera from patients with epithelial ovarian cancer at the time of conventional diagnosis and from asymptomatic women with or without ovarian cancer enrolled in the Normal Risk Ovarian Cancer Screening Study (NROSS). We developed a Magplex-based immunoassay to measure autoantibodies against HE4 in human serum. Immune complexes were dissociated in pH3 buffer for 30 min, separated on a desalting spin column and assayed for HE4 AAb. When sera from patients with early stage (I-II) ovarian cancer (n=72) and from healthy women (n=213) in the NROSS trial were assayed for free HE4 autoantibody, 4 cases (5.6%) had autoantibodies against HE4 at 98% specificity using a cut-off of 80 ng/mL. HE4 Ag-Ab complexes were detected in sera from 29 of 72 ovarian cancer cases (40.3%) at early stage (I-II) at the time of conventional diagnosis using a cut-off of 730 ng/mL to achieve a specificity of 98.2%. Complementarity was observed between HE4 Ag-Ab complexes and CA125 levels in early stage cancer cases. Either HE4 Ag-Ab complexes or CA125 were detected in 58 of 72 sera (80.2%) in cancer cases. This result suggests that combining assays for HE4 Ag-Ab complexes and for CA125 might improve detection of early stage ovarian cancer. To determine whether HE4 Ag-Ab complexes could be detected at an earlier interval than CA125, we assayed preclinical serum samples from 16 ovarian cancer patients, 2 women with endometrial cancer and 5 with benign pelvic disease from the NROSS study. Elevated HE4 Ag-Ab complexes were detected in 5 of 16 ovarian cancer cases (31.2%) and exhibited a strong correlation with rising CA125. Free HE4 AAb was found in 2 cases immediately before diagnosis. Consequently, HE4 AAb and Ag-Ab complexes, in contrast to TP53 AAb, appear to arise at the time of CA125 elevation, but can still detect early stage disease, complement CA125 and deserve further evaluation for screening and early detection. Citation Format: Wei-Lei Yang, Zhen Lu, Karen H. Lu, Usha Menon, Makoto Kobayashi, Samir Hanash, Steven Skates, Robert C. Bast. HE4 antigen-autoantibody complexes complement CA125 for detecting early stage ovarian cancer and can be elevated with CA125 in preclinical ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-176.