All tumor samples in The Cancer Genome Atlas (TCGA, http://cancergenome.nih.gov) and the corresponding normal tissue samples in the Genotype-Tissue Expression (GTEx, https://gtexportal.org/) database were downloaded to analyze the differential expression of HMOX1 in 33 tumors by using the Gene Expression Profiling Interactive Analysis (GEPIA; http://gepia.cancer-pku.cn) database (default parameters: |log2FC|cutoff = 1, q value cutoff = 0.01). The gene discussed is HMOX1; the disease is cancer.