Carcinogenesis Advance Access originally published online on September 22, 2009
Carcinogenesis 2009 30(11):1865-1871; doi:10.1093/carcin/bgp225
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The cyclin-dependent kinase inhibitor, p21WAF1, promotes angiogenesis by repressing gene transcription of thioredoxin-binding protein 2 in cancer cells
Children's Cancer Institute Australia for Medical Research, University of New South Wales, Sydney 2031, Australia
1 Parc de Recerca Biomèdica de Barcelona, Doctor Aiguader, 88 Barcelona E-08003, Spain
2 Centre for Children's Cancer and Blood Disorders, Sydney Children's Hospital, Randwick, Sydney 2031, Australia
* To whom correspondence should be addressed. Tel: +61 2 93821721; Fax: +61 2 93821789; Email: glenn.marshall{at}sesiahs.health.nsw.gov.au
The cyclin-dependent kinase inhibitor, p21WAF1, induces cell-cycle arrest and can act as a tumor suppressor. However, increasing evidence indicates that p21WAF1 can also increase resistance to some anticancer therapies and thus promote tumor growth. The mechanisms explaining this paradox have not been explained. We found that conditioned media from MCF-7 breast cancer cells transfected with a p21WAF1-specific small interfering RNA (siRNA) significantly reduced endothelial cell migration, invasion and vascular sprouting. Liquid chromatography/mass spectrometry analysis of the conditioned media revealed that p21WAF1 knockdown significantly reduced secretion of thioredoxin (Trx), a redox protein known to promote tumor angiogenesis. p21WAF1 knockdown decreased Trx enzymatic activity in cancer cells, by effects on the expression levels of intracellular thioredoxin-binding protein 2 (TBP2), known to bind and inactivate Trx. Consistent with these findings, media from cancer cells transfected with TBP2 siRNA promoted endothelial cell invasion and blocked the anti-angiogenic effect of p21WAF1 siRNA. Addition of Trx siRNA blocked the pro-angiogenic effects of TBP2 siRNA. Chromatin immunoprecipitation assays showed p21WAF1 bound TBP2 gene promoter. Taken together, our data suggests that p21WAF1 can induce Trx secretion and angiogenesis in cancer cells, by direct transcriptional repression of the TBP2 promoter.
Abbreviations: HUVEC, human umbilical vein endothelial cell; mRNA, messenger RNA; PCR, polymerase chain reaction; siRNA, small interfering RNA; Trx, thioredoxin; TBP2, thioredoxin-binding protein 2
Received June 18, 2009; revised August 28, 2009; accepted September 7, 2009.