NO is a free radical and is now thought to be an important intracellular signaling molecule. It in low concentrations, can act as a pro-oxidant presumably by forming peroxynitrite with superoxide, whereas at higher concentrations its antioxidant action predominates. There is convincing evidence that cellular pro-oxidant states-i.e., increased concentrations of active oxygen species and organic peroxides and radicals can promote initiated cells to neoplastic growth. On the other hand, pro- oxidant states can be prevented or suppressed by the enzymes of the cellular antioxidant defense system and many antioxidants are anti-promoters and anti-carcinogens. It is, therefore, not surprising that NO has been shown to involve cellular transformation and stimulation of neoplastic growth, whereas other studies indicate that NO has a cytostatic and/or cytotoxic effect on tumor cells. The overall hypothesis to be tested is that """"""""NO has a biphasic action on human breast cancer cell lines, i.e. at low steady state concentrations, it increases cell proliferation, whereas at high steady state concentrations, it decreases cell proliferation. This biphasic action is due to its actions on cyclin D1-cyclin dependent kinase (CDK)-retinoblastoma protein (pRG) cascade. NO also acts as an intermediary in some of the actions of estradiol leading to cell proliferation."""""""" This hypothesis will be tested under 4 specific aims. They are as follows:
Specific Aim 1. We will determine the effects of different concentrations of NO on cell cycle and proliferation and DNA synthesis of human breast cancer (HBC) cell lines.
Specific Aim 2. We will determine the effects of low steady state concentrations of NO to modulate phosphorylation of pRB in HBC cell lines, increase cyclin D1 expression, and elucidate the step(s) at which NO may be acting on the cyclin D1-CDK-pRB cascade.
Specific Aim 3. We will determine the effects of high steady state concentrations of NO (determined under specific aim 1) to modulate the phosphorylation of pRB and elucidate the step(s) at which NO may be acting on the cyclin D1-CDK-pRB cascade in HBC cell lines.
Specific Aim 4. We will determine the ability of inhibitors of NO synthesis to modulate the estradiol induced increase in breast cancer cell proliferation in vitro; shorten the G0/G1 phase of the cell cycle and the molecular mechanisms involved in this phenomenon.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Reproductive Endocrinology Study Section (REN)
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Freeman, Colette S
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University of California Los Angeles
Obstetrics & Gynecology
Schools of Medicine
Los Angeles
United States
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Pervin, Shehla; Chaudhuri, Gautam; Singh, Rajan (2010) NO to breast: when, why and why not? Curr Pharm Des 16:451-62
Pervin, Shehla; Tran, An H; Zekavati, Shaghayegh et al. (2008) Increased susceptibility of breast cancer cells to stress mediated inhibition of protein synthesis. Cancer Res 68:4862-74
Pervin, Shehla; Singh, Rajan; Hernandez, Estebes et al. (2007) Nitric oxide in physiologic concentrations targets the translational machinery to increase the proliferation of human breast cancer cells: involvement of mammalian target of rapamycin/eIF4E pathway. Cancer Res 67:289-99
Pervin, Shehla; Singh, Rajan; Freije, William A et al. (2003) MKP-1-induced dephosphorylation of extracellular signal-regulated kinase is essential for triggering nitric oxide-induced apoptosis in human breast cancer cell lines: implications in breast cancer. Cancer Res 63:8853-60
Pervin, Shehla; Singh, Rajan; Chaudhuri, Gautam (2003) Nitric-oxide-induced Bax integration into the mitochondrial membrane commits MDA-MB-468 cells to apoptosis: essential role of Akt. Cancer Res 63:5470-9
Singh, Rajan; Pervin, Shehla; Chaudhuri, Gautam (2002) Caspase-8-mediated BID cleavage and release of mitochondrial cytochrome c during Nomega-hydroxy-L-arginine-induced apoptosis in MDA-MB-468 cells. Antagonistic effects of L-ornithine. J Biol Chem 277:37630-6
Pervin, S; Singh, R; Chaudhuri, G (2001) Nitric oxide-induced cytostasis and cell cycle arrest of a human breast cancer cell line (MDA-MB-231): potential role of cyclin D1. Proc Natl Acad Sci U S A 98:3583-8
Pervin, S; Singh, R; Gau, C L et al. (2001) Potentiation of nitric oxide-induced apoptosis of MDA-MB-468 cells by farnesyltransferase inhibitor: implications in breast cancer. Cancer Res 61:4701-6
Singh, R; Pervin, S; Wu, G et al. (2001) Activation of caspase-3 activity and apoptosis in MDA-MB-468 cells by N(omega)-hydroxy-L-arginine, an inhibitor of arginase, is not solely dependent on reduction in intracellular polyamines. Carcinogenesis 22:1863-9