Studies On Regulations Of Tumor Cells Growth By Oxidized Injury

The previous studies showed that nitric oxide possesses a wide range of biological characters, which involving in regulations on a lot kind of gene expressions, inhibition tumor cells proliferations, and so on; free radicals- inducing dysfunctions of biological macromolecules can mediate multi-changes of gene expressions. For the further research of regulations and mechanisms on tumor cells growth by free radicals, our experiments were designed to display ways of some photosensitive substance, such as riboflavin, composed photonuclease and L-arginine; those which act as donor of free radicals play different biological characters in different concentrations. In this research, the inhibition effects of oxidation on tumor cells and its mechanisms were studied.1 The inhibition rate of tumor cells is dose-dependent on L-arginine\ riboflavin\ composed photonuclease MTT assay was used to estimate the inhibition rate of different drugs. Adding L-arginine in concentrations of 0 ~ 30mmol/L could depresss cells proliferation. The inhibition rate was positive correlation with the dose. Same with L-arginine, groups of riboflavin under 0.016 to 32 mol/L showed positive correlation with the dose. Groups of high L-argininedose(30 ~ 100mmol/L) have a trend of promoting cells proliferation.2 Studies on photosensitive riboflavin induced cell apoptosis Riboflavin-given groups 32, 3.2 ju mol/L showed 4.02 and 1.99 in apoptosis index while the blank group is 1.08, which proved riboflavin could induce cell apoptosis.3 Photosensitive riboflavin oxidizing guanine into 8-hydroxy-guanine Immnohistochemical studies by using Anti-8-hydroxyguanine antibody showed that guanine could be oxidized into 8-hydroxyguanine in both 32 and 3.2umol/L riboflavin- given groups. The high dose group appeared membranes and nucleolus positive while the low dose only showed nucleolus positive.4 Telomere length is positive correlation with illumination time In cultured cell system, after given 32 u mol/L riboflavin and then illuminate different times, the telomere length was measured by southern blot and the results indicated that there was a continuous telomere shortens with time; in the time of 0, 0.5, 1, 2, 4h dealt with photosensitiv riboflavin, the telomere length are 4.61, 4.36, 4.10, 3.92, 3.79kb, respectively;5 The DNA damage related gene expression changes had been found by Microarray after dealt with riboflavin The Hela cells dealt with 32 u mol/L riboflavin, and then isolated mRNA was analysised by GEArray. The results indicated that gene expressions of GADD45, 53Bpl, BRCA 2, BTG 2, P55cdc, CENP-E, MCAK, UNG 2 changedobviously. Some of these expression changes were related to DNA damage and repair in response to stress stimuli. The data in our experiment showed that FOXO3a gene has no significant expression changes under our experimental condition. GADD45 expression may first not activate the FOXO3a-mediate DNA repair response but a p53 or other genes regulated pathway.In conclusion, those experiment systems showed that free radicals could control the proliferations of tumor cells. The mechanism may relate with free radicals initiated damage of DNA, resulting in multi-gene expressions variation and oxidized incising and shorten telomere.