The k-core factor was then applied to identify key regulatory genes, which likely play pivotal roles in gene interactions and regulation (Fig. 6d), including for key cancer genes, such as p21, FAS, CCND1, and CDK2; real-time PCR confirmed these genes after knockdown of HOXC-AS3 (Additional file 3: Figure S2B). The gene discussed is CCND1; the disease is cancer.