Differential expressions of CYP1A1, CYP1B1, ALDH3A1, GSTA, HMOX1, NQO1, GJA1, TJP2, and DDB2 were used to evaluate transcriptional biomarker responses based on previous research which found these markers to be predictive of PAH carcinogenicity [30,43]. The gene discussed is CYP1A1; the disease is pulmonary arterial hypertension.