Human carbonyl reductase 1 upregulated by hypoxia renders resistance to apoptosis in hepatocellular carcinoma cells.
OBJECTIVE
Human carbonyl reductase1 (CBR1) has been reported to protect cells against lipid peroxidation. Since human hepatocellular carcinoma (HCC) cells are under oxidative stress in hypoxic conditions, we tested if CBR1 is upregulated by hypoxia inducible factor (HIF)-1α, helps tumor growth under hypoxia, and renders chemoresistance to cisplatin and doxorubicin in HCC.


METHODS
Luciferase, EMSA, and chromatin immunoprecipitation (ChIP) assays were performed to analyze whether HIF-1α transactivates CBR1 promoter. CBR1 overexpression, siRNA, and inhibitors were used to study the role of CBR1 in tumor survival under hypoxia and chemoresistance to cisplatin and doxorubicin in HCC. FACS and Western blot analysis for oxidative stress markers were performed to measure ROS. Immunohistochemistry (IHC) was performed to analyze CBR1 expression in 78 cases of HCC and 123 cases of colon cancer tissues.


RESULTS
The CBR1 promoter was activated by HIF-1α. CBR1 overexpression enhanced cell survival by decreasing oxidative stress under hypoxia, cisplatin, and doxorubicin treatment. CBR1-siRNA increased apoptosis via increasing oxidative stress. Combinational therapy of CBR1 inhibitors with cisplatin or doxorubicin enhanced cell death in HCC cells. IHC showed CBR1 overexpression in 56 (72%) out of 78 HCC and 88 (72%) out of 123 colon cancer cases.


CONCLUSIONS
Overexpressed CBR1 by HIF-1α plays important roles in tumor growth under hypoxia and chemoresistance to anticancer drugs. The inhibition of CBR1 by specific inhibitors enhances anticancer drug efficacy in HCC. Therefore, we concluded that CBR1 is a good molecular target for the development of anticancer drugs for HCC patients.
Department of Biochemistry and Molecular Biology, School of Medicine, Kyung Hee University, Seoul 130-701, Republic of Korea.
Eunyoung
E
Tak
Seonmin
S
Lee
Jisun
J
Lee
M A
MA
Rashid
Youn Wha
YW
Kim
Jae-Hoon
JH
Park
Won Sang
WS
Park
Kevan M
KM
Shokat
Joohun
J
Ha
Sung Soo
SS
Kim
D000429:Alcohol Oxidoreductases / Q000235:genetics*; D017209:Apoptosis / Q000187:drug effects*; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology; D003110:Colonic Neoplasms / Q000201:enzymology; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000502:physiology; D008113:Liver Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D018384:Oxidative Stress; D011401:Promoter Regions, Genetic; D015854:Up-Regulation
C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D004317:Doxorubicin; D000429:Alcohol Oxidoreductases; C531129:CBR1 protein, human; D002945:Cisplatin