Six of these genes (AP2M1, FKBP11, GALNT6, BDNF, COL9A3 and NR4A1) were selected for validation based on the following criteria: i) high DNA methylation (Δβ-value ≥0.30; Supplementary Table S4) and high gene expression difference (fold change ≥2.0) between the CTC-MCC-41 and the post-treatment CTC lines; and ii) implication in cancer-relevant pathways. The gene discussed is COL9A3; the disease is cancer.