Role of nitric oxide in human gastric cancer cells treated with 5-fluorouracil

Effects of endogenous nitric oxide induced by 5-fluorouracil and L-Arg on liver carcinoma in nude mice

AIM: To study the effects of endogeous nitric oxide induced by 5-fluorouracil (5-FU) and L-arginine (L-Arg) on the human liver carcinoma model in nude mice.

METHODS: The human liver carcinoma model in nude mice was established with BEL-7402 cells and normal saline (NS), 5-FU and 5-FU + L-Arg injected intraperitoneally. The tumor size was measured. The necrotic degree and range were observed under microscope. The apoptosis of cancer cell was detected by turmina deoxynucleotidyl transferanse mediated dUTP nick end labeling (TUNEL) method. Immunohistochemical method was performed to determine the expression of iNOS, P16, BAX. The chemical colorimetry was used to test the activity and nitrate reductase method was adopted to test the concentration of nitric oxide (NO) in the tumor tissue. The BI2000 pathological image analyzer was used to analyze the result of immunohistochemistry.

RESULTS: 5-FU combined with L-Arg could inhibit the tumor growth apparently. In NS, 5-FU and 5-FU+L-Arg groups, the changes of tumor volumes were 257.978 ± 59.0, 172.232 ± 66.0 and 91.523 ± 26.7 mm³, respectively (P < 0.05 5-FU vs 5-FU + L-Arg group; P < 0.05 NS vs 5-FU + L-Arg group; P < 0.05, NS vs 5-FU group). The necrotic range and apoptosis index were significantly increased after the drug injection. The necrotic range was biggest in 5-FU + L-Arg group (χ² = 15.963, P < 0.05).

The apoptosis indexes were as follows: NS, 17.4% ± 6.19%; 5-FU, 31.3% ± 12.3%; and 5-FU + L-Arg, 46% ± 15.24% (P < 0.05, 5-FU vs 5-FU + L-Arg; P < 0.05, NS vs 5-FU + L-Arg; P < 0.05, NS vs 5-FU). The expression and activity of iNOS were increased in the tumor tissue. The concentration of NO was also increased. F of optical density of iNOS, iNOS activity and NO concentration are 31.693, 21.949, and 33.909, respectively, P < 0.05. The concentration of NO was related to the expression of P16 and BAX. The correlation coefficient was 0.764 and 0.554.

CONCLUSION: 5-FU combined with L-Arg can inhibit the growth of tumor in nude mice. The effect may be related to inducing the synthesis and increasing the activity of iNOS. The production of NO is increased, and it can enhance the expression of apoptosis-related gene and antioncogene.

Effects of lipopolysaccharide with L-arginine on proliferation and apoptosis of human hepatocellular carcinomacell line Bel-7402

AIM: To study the effect of endogenous nitric oxide (NO) on the proliferation and apoptosis in human liver carcinoma cell line 7402 through regulation of the speed limit enzyme and the concentration of substrate in the process of No production.

METHODS: The speed limit enzyme in the process of NO production in 7402 cell is inducible nitric oxide synthase (iNOS), and its substrate is L-arginine (L-Arg).The cells were cultured in the Dulbecco's modified Eagle medium, which was without L-Arg. Different concentration of L-Arg was added into the culture medium and lipopolysaccharide (LPS) of 100 ng/L was added at the same time. MTT method was adopted to describe the proliferation of the cells. Immunohistochemical method was performed to determine the expression of iNOS. The TUNEL method was used to detect the apoptosis in situ.

RESULTS: Without change of the expression and activity of iNOS, L-Arg of 0.625 mmol/L produced NO with low concentration, it could promote the proliferation of the cells. On the contrary, L-Arg of 2.5 mmol/L inhibited the proliferation of the cells and improved the apoptotic rate of the cells. LPS of 100 ng/L could promote the expression and activity of iNOS in the cells. The production of NO in unit time was increased if the substrate was enough.

CONCLUSION: Low concentration of NO promotes the proliferation of the cells. High concentration of NO can inhibit the proliferation and promote the apoptosis of the cells. Increasing the production of endogenous NO by stimulating the expression and activity of its own iNOS is an effective way to inhibit the cells proliferation and promote its apoptosis.