3-Nitro-naphthalimide and nitrogen mustard conjugate NNM-25 induces hepatocellular carcinoma apoptosis via PARP-1/p53 pathway

Abstract

Hepatocellular carcinoma (HCC) is one of the main causes of death in cancer. Some naphthalimide derivatives exert high anti-proliferative effects on HCC. In this study, it is confirmed that 3-nitro-naphthalimide and nitrogen mustard conjugate (NNM-25), a novel compound conjugated by NNM-25, displayed more potent therapeutic action on HCC, both in vivo and in vitro, than amonafide, a naphthalimide drug in clinical trials. More importantly, preliminary toxicological evaluation also supported that NNM-25 exhibited less systemic toxicity than amonafide at the therapeutic dose. The antitumor mechanism of conjugates of naphthalimides with nitrogen mustard remains poorly understood up to now. Here, we first reported that apoptosis might be the terminal fate of cancer cells treated with NNM-25. Inhibition of p53 by siRNA resulted in a significant decrease of NNM-25-induced apoptosis, which corroborated that p53 played a vital role in the cell apoptosis triggered by NNM-25. NNM-25 inhibited the PARP-1 activity, AKT phosphorylation, up-regulated the protein expression of p53, Bad, and mTOR as well as down-regulating the protein expression of Bcl-2 and decreasing mitochondrial membrane potential. It also facilitated cytochrome c release from mitochondria to cytoplasm, activated caspase 8, caspase 9, and caspase 3 in HepG2 cells in vitro, as also authenticated in H22 tumor-bearing mice in vivo. Collectively, the conjugation of naphthalimides with nitrogen mustard provides favorable biological activity and thus is a valuable strategy for future drug design in HCC therapy.