Curcumin induces apoptosis in p53-null Hep3B cells through a TAp73/DNp73-dependent pathway

Curcumin has anticancer functions in various tumors. It has been shown to induce apoptosis through p53-dependent pathways. p73 gene is a member of the p53 family which encodes both a tumor suppressor (transactivation-competent p73 (TAp73)) and a putative oncogene (dominant-negative p73 (DNp73)); the former shares similarity with the tumor suppressor p53, and the latter behaves as dominant-negative proteins that interfere with the activity of TAp73. To understand the p73-dependent mechanisms that are engaged during curcumin-induced apoptosis, we established a p73 overexpression cell models using p53-deficient Hep3B cells (Hep3B^TAp73/DNp73). Our results demonstrated that curcumin at concentrations of 40 and 80 μM induced DNA damage, increased TAp73/DNp73 ratio, and also led to apoptosis in the Hep3B^TAp73/DNp73 cells. The apoptotic cell death was concurrent with the loss of mitochondrial membrane potential; release of cytochrome c from mitochondria; and the cleavage of caspase 9, caspase 3, and poly(ADP-ribose) polymerase (PARP). These results demonstrated a p73-dependent mechanism for curcumin-induced apoptosis that involves the mitochondria-mediated pathway.