NADPH oxidase 1 supports proliferation of colon cancer cells by modulating reactive oxygen species-dependent signal transduction.
Reactive oxygen species (ROS) play a critical role in cell signaling and proliferation. NADPH oxidase 1 (NOX1), a membrane-bound flavin dehydrogenase that generates O2̇̄, is highly expressed in colon cancer. To investigate the role that NOX1 plays in colon cancer growth, we used shRNA to decrease NOX1 expression stably in HT-29 human colon cancer cells. The 80-90% decrease in NOX1 expression achieved by RNAi produced a significant decline in ROS production and a G1/S block that translated into a 2-3-fold increase in tumor cell doubling time without increased apoptosis. The block at the G1/S checkpoint was associated with a significant decrease in cyclin D1expression and profound inhibition of mitogen-activated protein kinase (MAPK) signaling. Decreased steady-state MAPK phosphorylation occurred concomitant with a significant increase in protein phosphatase activity for two colon cancer cell lines in which NOX1 expression was knocked down by RNAi. Diminished NOX1 expression also contributed to decreased growth, blood vessel density, and VEGF and hypoxia-inducible factor 1α (HIF-1α) expression in HT-29 xenografts initiated from NOX1 knockdown cells. Microarray analysis, supplemented by real-time PCR and Western blotting, revealed that the expression of critical regulators of cell proliferation and angiogenesis, including c-MYC, c-MYB, and VEGF, were down-regulated in association with a decline in hypoxic HIF-1α protein expression downstream of silenced NOX1 in both colon cancer cell lines and xenografts. These studies suggest a role for NOX1 in maintaining the proliferative phenotype of some colon cancers and the potential of NOX1 as a therapeutic target in this disease.
From the Developmental Therapeutics Branch of the Center for Cancer Research.
Agnes
A
Juhasz
the Department of Medical Oncology and Therapeutics Research and.
Susan
S
Markel
the Department of Medical Oncology and Therapeutics Research and.
Shikha
S
Gaur
the Division of Cancer Treatment and Diagnosis, NCI, National Institutes of Health, Bethesda, Maryland 20892.
Han
H
Liu
From the Developmental Therapeutics Branch of the Center for Cancer Research.
Jiamo
J
Lu
From the Developmental Therapeutics Branch of the Center for Cancer Research.
Guojian
G
Jiang
the Bioinformatics Group, City of Hope Comprehensive Cancer Center, Duarte, California 91010.
Xiwei
X
Wu
From the Developmental Therapeutics Branch of the Center for Cancer Research.
Smitha
S
Antony
From the Developmental Therapeutics Branch of the Center for Cancer Research.
Yongzhong
Y
Wu
the Developmental Therapeutics Program, SAIC-Frederick, Inc., NCI at Frederick, Frederick, Maryland 21702, and.
Giovanni
G
Melillo
From the Developmental Therapeutics Branch of the Center for Cancer Research.
Jennifer L
JL
Meitzler
the Pathology/Histotechnology Laboratory, Leidos, Inc./Frederick National Laboratory for Cancer Research, NCI, Frederick, Maryland 21702.
Diana C
DC
Haines
the Pathology/Histotechnology Laboratory, Leidos, Inc./Frederick National Laboratory for Cancer Research, NCI, Frederick, Maryland 21702.
Donna
D
Butcher
the Division of Cancer Treatment and Diagnosis, NCI, National Institutes of Health, Bethesda, Maryland 20892.
Krishnendu
K
Roy
From the Developmental Therapeutics Branch of the Center for Cancer Research, doroshoj@mail.NIH.gov.|the Division of Cancer Treatment and Diagnosis, NCI, National Institutes of Health, Bethesda, Maryland 20892.
James H
JH
Doroshow
D000818:Animals; D017209:Apoptosis; D002453:Cell Cycle; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D003106:Colon / Q000378:metabolism; D003110:Colonic Neoplasms / Q000378:metabolism*; D019938:Cyclin D1 / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D019073:HT29 Cells; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D000074624:NADPH Oxidase 1; D019255:NADPH Oxidases / Q000378:metabolism*; D009368:Neoplasm Transplantation; D010641:Phenotype; D010766:Phosphorylation; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
C530104:CCND1 protein, human; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D019938:Cyclin D1; D000074624:NADPH Oxidase 1; D019255:NADPH Oxidases; C402799:NOX1 protein, human
NADPH oxidase; angiogenesis; cell cycle; colon cancer; cyclin D1; mitogen-activated protein kinase (MAPK); protein phosphatase; reactive oxygen species (ROS)