CDKN1C and osteosarcoma: As a control, the protein extracts of two cell lines, Hek293 (non-tumoral human embryonal kidney cell line) and U2OS (established from human osteosarcoma), respectively, transfected with an empty pcDNA3.1 plasmid and a vector containing the coding DNA sequence (CDS) for the full-length (FL) human p57 were used.