DDX5 and osteosarcoma: In MCF-2 cells and U2OS cells (osteosarcoma cell line), DDX5 is recruited to the promoters of several p53-responsive genes, including those of the cell cycle arrest gene p21WAF1 and the proapoptotic genes Bax and PUMA; however, DDX5 appears to be required for selective p21WAF1 induction but not for proapoptotic genes (70).