To investigate the interaction between BMP9 and angiogenic factors in HCC, we first explored the gene expression correlation between BMP9 (GDF2) and the angiogenic proteins VEGFR2 (KDR) and HIF-1α (HIF1A) in The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC) cohort. The gene discussed is HIF1A; the disease is hepatocellular carcinoma.