CDKN1A (p21), which is a major regulator of cell senescence among pro-senescence genes and was altered in most cases in addition to growth factors and DNA repair genes, was downregulated in both p53 negative colon cancer and osteosarcoma cells, suggesting that this regulator may be involved in control of senescence in multiple cell types. This evidence concerns the gene CDKN1A and malignant colon neoplasm.