Synergistic anti-tumor efficacy of lovastatin and protein kinase C-beta inhibitor in hepatocellular carcinoma.
OBJECTIVE
Hepatocellular carcinoma (HCC) is characterized by hypervascularity and chemoresistance. Protein kinase C (PKC) participates in cancer progression by enhancing anti-apoptotic signals, angiogenesis, and chemoresistance. Statins have a selective anti-cancer effect due to over-expression of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoAR) in cancer cells, but statins may also activate PKC. Thus, we hypothesized that simultaneous treatment with statin and PKC inhibitor might synergistically enhance their anti-tumor efficacies against HCCs.


METHODS
Hepatocellular carcinoma cell growth was assessed using MTS assays, apoptotic cell death by DAPI staining, and apoptotic signaling cascades were explored by immunoblotting. An in vivo model of HCC was established in C3H mice intradermally implanted with MH134 cells. Lovastatin and/or a PKC inhibitor (enzastaurin) was subsequently administered. Anti-tumor efficacies were evaluated by measuring tumor volumes and quantifying apoptotic cells and microvessel densities (MVD).


RESULTS
Co-treatment with lovastatin and enzastaurin was found to synergistically suppress HCC cell growth in vitro. Lovastatin induced HCC cellular apoptosis by activating mitochondrial apoptotic signals, and although enzastaurin alone did not induce apoptosis, its addition significantly enhanced lovastatin-induced apoptosis. This enhanced apoptosis was attributed to increased caspase-9 activation in these cells. Moreover, tumor growth was significantly suppressed in mice co-treated with lovastatin and enzastaurin, and percentages of TUNEL-positive cells were significantly increased and MVDs were significantly decreased in those mice.


CONCLUSIONS
Combinatorial treatment with statin and PKC inhibitor was found to enhance anti-tumor efficacy in vivo and in vitro. Further studies are warranted to prove anti-tumor efficacy of this potential therapy in human HCCs.
Kim
Won
W
Department of Internal Medicine, Seoul National University Boramae Hospital, Seoul, South Korea.
Yoon
Jung-Hwan
JH
Kim
Jung-Ryul
JR
Jang
In-Jin
IJ
Bang
Yung-Jue
YJ
Kim
Yoon-Jun
YJ
Lee
Hyo-Suk
HS
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000503:physiopathology; D045744:Cell Line, Tumor; D018450:Disease Progression; D004357:Drug Synergism; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology; D020287:In Situ Nick-End Labeling; D007211:Indoles / Q000008:administration & dosage; D008114:Liver Neoplasms, Experimental / Q000188:drug therapy* / Q000503:physiopathology; D008148:Lovastatin / Q000008:administration & dosage; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D055806:Microvessels / Q000473:pathology; D009368:Neoplasm Transplantation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D064546:Protein Kinase C beta
D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007211:Indoles; D008148:Lovastatin; D011493:Protein Kinase C; D064546:Protein Kinase C beta; C504878:enzastaurin