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The Effects of Nitric Oxide and Peroxynitrite on Cancer Cells

by Choi, Ji Yeon

Abstract (Summary)
Cancer is a group of diseases characterized by uncontrolled growth and this spread of abnormal cells is caused by various external and internal reasons. This study elucidated the relationship between the growth of cancer cells and concentration of NO and ONOO¯. Nanosensors were applied to measure nitric oxide and peroxynitrite concentration in cancer and normal cells. The ratio between NO/ONOO¯ concentrations was used as an indicator of oxidative stress in cancer cells. ONOO¯ concentration measured from HT1080 cancer cells (fibrosacoma) and MRC-5 normal cells (fibroblasts) was higher than NO concentration. ONOO¯ released from HT1080 cancer and MRC-5 normal cells was similar, while NO concentration in HT1080 cancer cells was significantly higher than in MRC-5 normal cells. Enzyme levels were measured by using Western blotting and correlated with NO and ONOO¯ levels in normal and cancer cells treated with 3-morpholinosydnonimine hydrochloride (SIN-1) (ONOO¯ donor) and sodium nitroprusside (SNP) (NO donor), respectively. After the preincubation with SNP and SIN-1 in MRC-5 cells, a significant decrease in eNOS expression was observed compared to HT1080 cancer cells. This indicates that MRC-5 normal cells were more sensitive to the changes of exogenous NO and ONOO¯. It indicated that exogenous NO or ONOO¯ downregulate eNOS expression in both cancer and normal cells. A treatment of CACO-2 cancer cells with SNP decreased eNOS expression more significantly that a treatment with SIN-1. In this study, we found that NO not only affected eNOS expression but also cell growths. The effect of NO and ONOO¯ on cell growth was investigated by preincubating HT1080 cancer and MRC-5 normal cells with L-arginine, NO substrate and L-NAME, a NOS inhibitor. L-arginine treatment promoted HT1080 cancer cell growth and increased the number of viable cells. HT1080 cancer cells preincubated with L-arginine promoted cell growth and increased the cells number. NO had a greater in promoting effect growth of HT1080 cancer cells. MRC-5 cell growth after treatment, with L-arginine, was slower than the rate observed for HT1080. L-NAME, an eNOS inhibitor, did not effect MRC-5 normal cell growth and cell numbers significantly. The pretreatment of CACO-2 cancer cells with SNP and L-arginine showed higher cell growth than those treated with SIN-1 or L-NAME. SNP and L-arginine inhibited the cell growth, and cell number of CACO-2. SIN-1 treatment inhibited CACO-2 cell growth through increased ONOO¯ level. In CACO-2 cancer cells, NO effects cell growth and further study are needed to identify the level at which NO becomes cytotoxic to CACO-2 cancer cells. NO promotes normal colon epithelial growth, but inhibited CACO-2 colon cancer cell growth. This finding can be potentially useful in determining a strategy for colon cancer treatment.
Bibliographical Information:

Advisor:

School:Ohio University

School Location:USA - Ohio

Source Type:Master's Thesis

Keywords:cancer nitric oxide peroxynitrite cell growth

ISBN:

Date of Publication:01/01/2008

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