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Abstract Background: CA125 is elevated in women with ovarian cancer and is the single best ovarian cancer screening biomarker candidate to date, although two randomized screening trials showed no clinically significant difference in ovarian cancer mortality. Consideration of genetic variants that influence blood CA125 levels in healthy women could improve its performance as an ovarian cancer screening biomarker. Furthermore, while studies have suggested CA125 is associated with ovarian carcinogenesis and progression, its biological role remains unclear. Thus, we aimed to identify genetic variants of CA125 in women without ovarian cancer. Methods: We conducted a genome-wide association analysis to identify common genetic variants associated with CA125 using data on 26, 187 women without ovarian cancer, leveraging existing blood CA125 data and genetic data from Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO), European Prospective Investigation into Cancer and Nutrition (EPIC), Nurses’ Health Studies (NHS/NHSII), and New England Case Control Study (NEC). All genotype data were inputted using TOPMed. For blood CA125 measurement, PLCO, NHS/NHSII, and NEC used the CA125II assay and EPIC used the MSD assay. We used multivariable linear regression models adjusting for age, study, and population ancestry (top 4 principal components). Analyses were conducted separately by CA125 assay, genotyping platforms, and menopausal status at blood draw. Because epidemiological predictors of CA125 differ by menopausal status, we conducted analyses stratified by menopausal status. When we meta-analyzed these results, there were no significant heterogeneity by menopausal status in majority of the genome-wide significant SNPs. Therefore, we performed a fixed-effects meta-analysis to combine summary statistics across all the results. Results: We identified 12 independent loci associated with CA125 at a genome-wide significance level (p5 × 10−8), of which one SNP (rs73005869) had been previously linked with CA125 and is located in the MUC16 gene. In our meta-analysis, 7 SNPs were associated with lower and 5 were associated with higher levels of CA125. We discovered SNPs on chromosome 16 in the TET2 gene that were significantly associated with increased CA125 levels. We also discovered SNPs in MSLN, a gene reported to be overexpressed in ovarian tumors that contributes to metastasis in the peritoneal microenvironment, were associated with lower CA125 levels. SNPs in the HIC1 gene on chromosome 17, a tumor suppressor gene whose aberrant methylation has been observed in ovarian tumors, was associated with lower CA125 levels. Conclusion: We identified 12 independent loci associated with blood CA125 levels in women without ovarian cancer, providing novel biological insights on the role of CA125. Accounting for these genetic factors that influence blood CA125 levels could improve the performance of CA125 as ovarian cancer screening biomarker in average risk women, substantially improving survival through earlier detection of this deadly disease. Citation Format: Naoko Sasamoto, Jihye Kim, Constance Turman, Shelley S. Tworoger, Rudolf Kaaks, Renée T. Fortner, Daniel W. Cramer, Kathryn L. Terry, Nicolas Wentzensen, Peter Kraft. Genome-wide association studies of 26, 187 women without ovarian cancer identifies 12 genetic loci of blood CA125 abstract. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84 (5 Suppl₂): Abstract nr B051.
Sasamoto et al. (Mon,) studied this question.