Abstract
ObjectiveBlood type A and the A1 allele have been associated with increased ovarian cancer risk. With only two small studies published to date, evidence for an association between ABO blood type and ovarian cancer survival is limited.MethodsWe conducted a retrospective cohort study of Tumor Registry confirmed ovarian cancer cases from the Vanderbilt University Medical Center with blood type from linked laboratory reports and ABO variants from linked Illumina Exome BeadChip data. Associations with overall survival (OS) were quantified by hazard ratios (HR) and confidence intervals (CI) from proportional hazards regression models; covariates included age, race, stage, grade, histologic subtype, and year of diagnosis.ResultsABO phenotype (N = 694) and/or genotype (N = 154) data were available for 713 predominantly Caucasian (89.3%) cases. In multivariable models, blood type A had significantly better OS compared to either O (HR: 0.75, 95% CI: 0.60–0.93) or all non-A (HR: 0.77, 95% CI: 0.63–0.94) cases. Similarly, missense rs1053878 minor allele carriers (A2) had better OS (HR: 0.50, 95% CI: 0.25–0.99). Among Caucasians, this phenotype association was strengthened, but the genotype association was attenuated; instead, four variants sharing moderate linkage disequilibrium with the O variant were associated with better OS (HR: 0.62, 95% CI: 0.39–0.99) in unadjusted models.ConclusionsBlood type A was significantly associated with longer ovarian cancer survival in the largest such study to date. This finding was supported by genetic analysis, which implicated the A2 allele, although O related variants also had suggestive associations. Further research on ABO and ovarian cancer survival is warranted.
Highlights
Ovarian cancer is the 5th leading cause of cancer deaths among women in the United States (US), with an estimated 22,280 new cases and 14,240 deaths in 2016 [1]
Blood type A had significantly better overall survival (OS) compared to either O (HR: 0.75, 95% Confidence Interval (CI): 0.60–0.93) or all non-A (HR: 0.77, 95% CI: 0.63–0.94) cases
Among Caucasians, this phenotype association was strengthened, but the genotype association was attenuated; instead, four variants sharing moderate linkage disequilibrium with the O variant were associated with better OS (HR: 0.62, 95% CI: 0.39–0.99) in unadjusted models
Summary
Ovarian cancer is the 5th leading cause of cancer deaths among women in the United States (US), with an estimated 22,280 new cases and 14,240 deaths in 2016 [1]. In addition to transfusion medicine, blood type gained a prominent role in genetics as one of the first traits with a Mendelian mode of inheritance and population-specific phenotypic variation. We know that blood type is determined by genetic variation in the ABO gene on chromosome 9q34. Common variants result in different glycosyltransferases, oligosaccharide antigens, and phenotypes: N-acetylgalactosamine for blood type A, D-galactose for blood type B, both for blood type AB, and neither for an unmodified H antigen in blood type O. Blood type A and B differ predominantly by four amino acid substitutions (R176G, G235S, L266M, and G268A) from four common missense variants (rs7853989, rs8176743, r8176746, and rs8176747), while blood type O is predominantly due to a single nucleotide deletion (rs8176719) which shifts the reading frame and results in early protein termination [2,3,4,5,6]. Multiple alleles, new mutations, and frequent recombination events add complexity to the genetic diversity of the ABO locus [3,4]
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