title: Combination of acyclic retinoid with branched-chain amino acids inhibits xenograft growth of human hepatoma cells in nude mice.
abstract: OBJECTIVE
  Combination chemoprevention is a promising strategy to improve the prognosis of hepatocellular carcinoma (HCC). A malfunction of retinoid X receptor-α (RXR-α) due to phosphorylation by Ras/mitogen-activated protein kinase is closely associated with liver carcinogenesis and acyclic retinoid (ACR) can prevent HCC development by inhibiting RXR-α phosphorylation. The present study examined the possible combined effects of ACR plus branched-chain amino acids (BCAA), which can also prevent the development of HCC in obese patients with liver cirrhosis, in human HCC xenografts in nude mice.
  
  
  METHODS
  This study examined the effects of the combination of ACR plus BCAA on the growth of Huh7 human HCC xenografts in nude mice. The effects of the combination on the phosphorylation of RXR-α, extracellular signal-regulated kinase (ERK), Akt and insulin-like growth factor-1 receptor (IGF-1R) proteins, and on the expression levels of retinoic acid receptor-β (RAR-β) and p21(CIP1)  mRNA, were also examined by western blot and real-time reverse transcription polymerase chain reaction analyses, respectively.
  
  
  RESULTS
  The combined treatment with ACR plus BCAA significantly inhibited the growth of Huh7 xenografts. The combination of these agents caused a marked inhibition of the phosphorylation of RXR-α, ERK, Akt and IGF-1R proteins in the xenografts. In addition, the expression levels of RAR-β and p21(CIP1)  mRNA significantly increased by these agents.
  
  
  CONCLUSIONS
  The combination of ACR and BCAA restores the function of RXR-α by inhibiting its phosphorylation and increasing the level of RAR-β, a heterodimeric partner for RXR-α, and thus suppresses the growth of HCC xenografts. Therefore, this combination might be an effective regimen for the treatment and, probably, chemoprevention of HCC.
authors.affiliation: Department of Medicine, Gifu University Graduate School of Medicine, Gifu, Japan.
authors.forename: Masahito
authors.initials: M
authors.lastname: Shimizu
authors.forename: Yohei
authors.initials: Y
authors.lastname: Shirakami
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Sakai
authors.forename: Junpei
authors.initials: J
authors.lastname: Iwasa
authors.forename: Makoto
authors.initials: M
authors.lastname: Shiraki
authors.forename: Koji
authors.initials: K
authors.lastname: Takai
authors.forename: Takafumi
authors.initials: T
authors.lastname: Naiki
authors.forename: Hisataka
authors.initials: H
authors.lastname: Moriwaki