Liu et al. [40] reported that methylation levels in the promoter or exon regions of four genes, namely COL4A1, COL4A2, ITGA4, and TLX2 could differentiate CRC patients from control subjects in independent populations, with AUC values ranging from 0.95 to 0.98. The gene discussed is COL4A2; the disease is colorectal carcinoma.