title: Synergistic growth inhibition by acyclic retinoid and vitamin K2 in human hepatocellular carcinoma cells.
abstract: Hepatocellular carcinoma (HCC) is one of the most prevalent cancers worldwide. However, effective chemopreventive and chemotherapeutic agents for this cancer have not yet been developed. In clinical trials acyclic retinoid (ACR) and vitamin K(2) (VK(2)) decreased the recurrence rate of HCC. In the present study we examined the possible combined effects of ACR or another retinoid 9-cis retinoic acid (9cRA) plus VK(2) in the HuH7 human HCC cell line. We found that the combination of 1.0 microM ACR or 1.0 microM 9cRA plus 10 microM VK(2) synergistically inhibited the growth of HuH7 cells without affecting the growth of Hc normal human hepatocytes. The combined treatment with ACR plus VK(2) also acted synergistically to induce apoptosis in HuH7 cells. Treatment with VK(2) alone inhibited phosphorylation of the retinoid X receptor (RXR)alpha protein, which is regarded as a critical factor for liver carcinogenesis, through inhibition of Ras activation and extracellular signal-regulated kinase phosphorylation. Moreover, the inhibition of RXRalpha phosphorylation by VK(2) was enhanced when the cells were cotreated with ACR. The combination of retinoids plus VK(2) markedly increased both the retinoic acid receptor responsive element and retinoid X receptor responsive element promoter activities in HuH7 cells. Our results suggest that retinoids (especially ACR) and VK(2) cooperatively inhibit activation of the Ras/MAPK signaling pathway, subsequently inhibiting the phosphorylation of RXRalpha and the growth of HCC cells. This combination might therefore be effective for the chemoprevention and chemotherapy of HCC.
authors.affiliation: Department of Medicine, Gifu University School of Medicine, Gifu, Japan.
authors.forename: Toh
authors.initials: T
authors.lastname: Kanamori
authors.forename: Masahito
authors.initials: M
authors.lastname: Shimizu
authors.forename: Masataka
authors.initials: M
authors.lastname: Okuno
authors.forename: Rie
authors.initials: R
authors.lastname: Matsushima-Nishiwaki
authors.forename: Hisashi
authors.initials: H
authors.lastname: Tsurumi
authors.forename: Soichi
authors.initials: S
authors.lastname: Kojima
authors.forename: Hisataka
authors.initials: H
authors.lastname: Moriwaki
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D014212:Tretinoin / Q000031:analogs & derivatives* / Q000627:therapeutic use; D024482:Vitamin K 2 / Q000627:therapeutic use*
chemical_list: D000970:Antineoplastic Agents; D024482:Vitamin K 2; D014212:Tretinoin; C034534:3,7,11,15-tetramethyl-2,4,6,10,14-hexadecapentaenoic acid