KU-0060648 inhibits hepatocellular carcinoma cells through DNA-PKcs-dependent and DNA-PKcs-independent mechanisms
Abstract
Ideas tested anti-tumor activity of KU-0060648 in preclinical hepatocellular carcinoma (HCC) models. Our results shown that KU-0060648 was anti-proliferative and pro-apoptotic in established (HepG2, Huh-7 and KYN-2 lines) and first human HCC cells, but was non-cytotoxic to non-cancerous HL-7702 hepatocytes. DNA-PKcs (DNA-activated protein kinase catalytic subunit) is a vital although not exclusive target of KU-0060648. DNA-PKcs knockdown or dominant negative mutation inhibited HCC cell proliferation. However, overexpression of untamed-type DNA-PKcs enhanced HepG2 cell proliferation. Importantly, KU-0060648 was still being cytotoxic to DNA-PKcs-silenced or -mutated HepG2 cells, although its activity during these cells was relatively weak. Further studies demonstrated that KU-0060648 inhibited PI3K-AKT-mTOR activation, separate from DNA-PKcs. Introduction of constitutively-active AKT1 (CA-AKT1) restored AKT-mTOR activation after KU-0060648 treatment in HepG2 cells, and alleviated subsequent cytotoxicity. In vivo, intraperitoneal (i.p.) injection of KU-0060648 considerably inhibited HepG2 xenograft development in nude rodents. AKT-mTOR activation seemed to be inhibited in xenografted tumors. Finally, we demonstrated that DNA-PKcs expression was considerably upregulated in human HCC tissues. Yet miRNA-101, an anti-DNA-PKcs miRNA, was downregulated. Over-expression of miR-101 in HepG2 cells inhibited DNA-PKcs expression and cell proliferation. Together, these results indicate that KU-0060648 inhibits HCC cells through DNA-PKcs-dependent and -independent mechanisms.