S1: Systems Pharmacogenomics of Aspirin
Systems Pharmacogenomics of Aspirin: A new take on an old exposure
Duke University Medical Center
Identifying individuals at heightened cardiovascular risk is a priority for reducing the global burden of cardiovascular disease. Aspirin is widely used to prevent cardiovascular events, though with variable results. We hypothesized that aspirin exposure would reveal novel biological pathways relevant to the development of cardiovascular events.
Methods: We administered aspirin, followed by peripheral blood RNA microarray profiling, in a discovery cohort of healthy volunteers (n =50, HV1), followed by two validation cohorts of healthy volunteers (n =53, HV2) or outpatient cardiology (OPC, n =25) patients, in conjunction with platelet function testing with the platelet function score (PFS; in HV1 and HV2) or the VerifyNow Aspirin (in OPC) test. Sets of coexpressed genes, or “Factors” were identified via Bayesian sparse factor analysis and associated with platelet function in HV1 and validated in HV2 and OPC. Validated factors were associated with death/myocardial infarction (MI) in observational (n =191) and case:control (n =447) patient cohorts with RNA data collected at the time of cardiac catheterization. Analysis of transcription factor binding data from megakaryocytes was used to identify potential transcription factors that may regulate selected genes. Results: Factor analysis yielded 20 Factors, of which one, Factor 14 (containing 60 genes of platelet origin) was associated with PFS in HV1 (r =-0.31, p =0.03). Factor 14 was associated with platelet function with the same strength and direction in HV2 (r = -0.34, p =0.02) and OPC (one-sided p =0.046 for aspirin-resistant vs. aspirin-sensitive by VerifyNow), thus validating the association. Factor 14 was associated with death/MI in the two patient cohorts, odds ratio (OR) = 1.2, 95% CI [1.02-1.4], p =0.01 and hazard ratio = 1.5, [1.2-1.9], p =0.001, respectively, independent of known cardiovascular risk factors (combined OR =1.3, CI =[1.1, 1.5], p =0.001). Factor 14 and the expression of the Factor 14 transcript most highly correlative of PFS, ITGA2B, improved reclassification compared with traditional risk factors (category-free net reclassification index =31% and 37%, p ≤0.0002 for both). Transcription factor binding studies highlighted the role of transcription factor RUNX1 in regulating Factor 14 genes.
Conclusions: By challenging humans subjects with aspirin, a medication used for cardiovascular risk reduction, we elucidated genes and pathways that may underlie platelet function and mechanisms responsible for cardiovascular death/MI.