Everolimus Plus Ku0063794 Regimen Promotes Anticancer Effects against Hepatocellular Carcinoma Cells through the Paradoxical Inhibition of Autophagy.
- Author:
Sang Chul LEE
1
;
Kee Hwan KIM
;
Ok Hee KIM
;
Sang Kuon LEE
;
Ha Eun HONG
;
Byung Jo CHOI
;
Wonjun JEONG
;
Say June KIM
Author Information
- Publication Type:Original Article
- Keywords: Autophagy; Everolimus; TOR serine-threonine kinases; Hepatocellular carcinoma; Sirtuin 1
- MeSH: Animals; Apoptosis; Autophagy*; Carcinoma, Hepatocellular*; Cell Proliferation; Coloring Agents; Down-Regulation; Everolimus*; Fluorescent Antibody Technique; Hep G2 Cells; Heterografts; In Vitro Techniques; Mice; Mice, Nude; Sirolimus; Sirtuin 1; TOR Serine-Threonine Kinases
- From:Cancer Research and Treatment 2018;50(3):1023-1038
- CountryRepublic of Korea
- Language:English
- Abstract: PURPOSE: Everolimus only inhibits mammalian target of rapamycin complex 1 (mTORC1), whereas Ku0063794 inhibits both mTORC1 and mTORC2. Although they have similar anticancer effects, their combination has a synergistic effect against hepatocellular carcinoma (HCC) cells. We aimed to determine the mechanism underlying the synergistic effects of everolimus and Ku0063794 associated with autophagy in HCC cells. MATERIALS AND METHODS: We compared the effects of everolimus and Ku0063794, individually or in combination, on both the in vitro and in vivo models of HCCs. RESULTS: HepG2 cells treated with both agents had significantly lower rates of cell proliferation and higher apoptosis than the individual monotherapies (p < 0.05). Autophagic studies consistently indicated that, unlike the monotherapies, the combination therapy significantly reduced autophagy (p < 0.05). Autophagic blockage directly promoted the pro-apoptotic effects of combination therapy, suggesting autophagy as the survival mechanism of HCC cells. Unlike the monotherapies, combination therapy showed the potential to inhibit sirtuin 1 (SIRT1), the positive regulator of autophagy. SIRT1 overexpression abrogated the autophagy-inhibiting and pro-apoptotic effects of combination therapy. In a nude mouse xenograft model, the shrinkage of tumors was more prominent in mice treated with combination therapy than in mice treated with the respective monotherapies (p < 0.05). The immunohistochemical and immunofluorescence stains of the tumor obtained from the xenograft model showed that combination therapy had the potential of reducing autophagy and promoting apoptosis. CONCLUSION: The combination of everolimus and Ku0063794 potentiates anticancer effects on HCCs through a decrease in autophagy, which is prompted by SIRT1 downregulation.
