title: Synergistic anti-tumor efficacy of doxorubicin and flavopiridol in an in vivo hepatocellular carcinoma model.
abstract: OBJECTIVE
  A previous study showed that flavopiridol increased doxorubicin sensitivity in hypoxic hepatocellular carcinoma (HCC) cells by increasing apoptosis through suppressing hypoxia-inducible N-myc downstream-regulated gene-1 (NDRG1) expression. However, this has not been investigated in an in vivo HCC model. Therefore, we aimed to elucidate whether the combination of doxorubicin and flavopiridol has a synergistic anti-tumor effect in an in vivo HCC model.
  
  
  METHODS
  An HCC mouse model was established by implanting C3H/He mouse with MH134 cells. Then, doxorubicin with or without flavopiridol was injected. The anti-tumor efficacy was assessed by evaluating tumor volumes, and the underlying mechanism was investigated by quantifying apoptotic cells, the Ki-67 proliferation index, and microvessel densities (MVDs). Immunohistochemistry of NDRG1 was performed to determine the underlying mechanism.
  
  
  RESULTS
  Tumor growth was significantly suppressed in the doxorubicin + flavopiridol combination group compared to the other three groups. The percentage of apoptotic cells was significantly higher, and Ki-67-positive proliferating cells were significantly lower in the combination group compared to the other groups; however, MVDs were not significantly different across the groups. Increased apoptosis by flavopiridol occurred by suppressing hypoxia-inducible NDRG1 expression.
  
  
  CONCLUSIONS
  These results show that a combination of doxorubicin and flavopiridol has a synergistic anti-tumor effect in an in vivo HCC model. This synergistic effect of combination therapy was attributed to increased apoptosis and decreased proliferation of tumor cells rather than decreased angiogenesis. These findings suggest that flavopiridol might be an effective adjuvant therapy to doxorubicin-resistant HCC cells by inducing apoptosis through suppression of NDRG1 expression.
authors.affiliation: Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, 28 Yungun-dong, Chongno-gu, Seoul, 110-744, Korea.|Department of Internal Medicine, Healthcare Research Institute, Healthcare System Gangnam Center, Seoul National University Hospital, Seoul, Korea.
authors.forename: Min-Sun
authors.initials: MS
authors.lastname: Kwak
authors.affiliation: Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, 28 Yungun-dong, Chongno-gu, Seoul, 110-744, Korea.
authors.forename: Su Jong
authors.initials: SJ
authors.lastname: Yu
authors.affiliation: Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, 28 Yungun-dong, Chongno-gu, Seoul, 110-744, Korea. yoonjh@snu.ac.kr.
authors.forename: Jung-Hwan
authors.initials: JH
authors.lastname: Yoon
authors.affiliation: Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, 28 Yungun-dong, Chongno-gu, Seoul, 110-744, Korea.
authors.forename: Sung-Hee
authors.initials: SH
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, 28 Yungun-dong, Chongno-gu, Seoul, 110-744, Korea.
authors.forename: Soo-Mi
authors.initials: SM
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, 28 Yungun-dong, Chongno-gu, Seoul, 110-744, Korea.
authors.forename: Jeong-Hoon
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, 28 Yungun-dong, Chongno-gu, Seoul, 110-744, Korea.
authors.forename: Yoon Jun
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, 28 Yungun-dong, Chongno-gu, Seoul, 110-744, Korea.
authors.forename: Hyo-Suk
authors.initials: HS
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, 28 Yungun-dong, Chongno-gu, Seoul, 110-744, Korea.
authors.forename: Chung Yong
authors.initials: CY
authors.lastname: Kim
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000627:therapeutic use; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000473:pathology; D018797:Cell Cycle Proteins / Q000096:biosynthesis* / Q000235:genetics; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D004317:Doxorubicin / Q000627:therapeutic use*; D004357:Drug Synergism; D005419:Flavonoids / Q000627:therapeutic use*; D006593:Hexokinase / Q000235:genetics; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics; D047908:Intracellular Signaling Peptides and Proteins / Q000096:biosynthesis* / Q000235:genetics; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000473:pathology; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D009368:Neoplasm Transplantation; D010880:Piperidines / Q000627:therapeutic use*; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use; D047368:Tumor Burden / Q000187:drug effects; D000099259:N-myc Downstream-Regulated Gene 1 Protein
chemical_list: D000903:Antibiotics, Antineoplastic; D018797:Cell Cycle Proteins; D004317:Doxorubicin; D005419:Flavonoids; D006593:Hexokinase; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D047908:Intracellular Signaling Peptides and Proteins; D010880:Piperidines; D047428:Protein Kinase Inhibitors; D000099259:N-myc Downstream-Regulated Gene 1 Protein; C497443:Hif1a protein, mouse; C077990:alvocidib
keywords: Apoptosis; Doxorubicin; Flavopiridol; Hepatocellular carcinoma; Hypoxia