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J Biol Chem. 2017 May 12;292(19):7866-7887. doi: 10.1074/jbc.M116.768283. Epub 2017 Mar 22.

NADPH oxidase 1 supports proliferation of colon cancer cells by modulating reactive oxygen species-dependent signal transduction.

Author information

1
From the Developmental Therapeutics Branch of the Center for Cancer Research.
2
the Department of Medical Oncology and Therapeutics Research and.
3
the Division of Cancer Treatment and Diagnosis, NCI, National Institutes of Health, Bethesda, Maryland 20892.
4
the Bioinformatics Group, City of Hope Comprehensive Cancer Center, Duarte, California 91010.
5
the Developmental Therapeutics Program, SAIC-Frederick, Inc., NCI at Frederick, Frederick, Maryland 21702, and.
6
the Pathology/Histotechnology Laboratory, Leidos, Inc./Frederick National Laboratory for Cancer Research, NCI, Frederick, Maryland 21702.
7
From the Developmental Therapeutics Branch of the Center for Cancer Research, doroshoj@mail.NIH.gov.

Abstract

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 D1 expression 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.

KEYWORDS:

NADPH oxidase; angiogenesis; cell cycle; colon cancer; cyclin D1; mitogen-activated protein kinase (MAPK); protein phosphatase; reactive oxygen species (ROS)

PMID:
28330872
PMCID:
PMC5427267
DOI:
10.1074/jbc.M116.768283
[Indexed for MEDLINE]
Free PMC Article

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