Preliminary Studies With Anti-tumor Effects Of Marine Microbial Screening Activity

Ocean provides a rich source of bioactive natural product of medical importance. Exploring and utilizing the natural product provided by marine organism is an important part of the marine development. Especially, marine microorganisms have been the hotspot for searching novel drugs these years.In this work, a screening model of MTT was used to screen antitumor active agents from marine actinomycetes, bacterials, molds and extreme bacterials. The results showed that about 10 percents of actinomycetes, one polar bacterial and two molds have cell toxicity. This indicates that there would be a large number of antitumor agents in marine microorganism. According to the DNA repair test vitality difference between E.coli 343/591 and E.coli 343/636, three positive strains were identified. After treated with the samples, the MGC-803 cells are dyed with the fluorescence dye Hoechst 33258. Observed by the fluorescence microscope, the dense dyeing granulometric and nubby blue fluorescence can be seen in the nucleus of MGC-803 treated with AK-9 and AK-11, the nucleus of some cells smash to small fragments. The nucleus of control MGC-803 present as diffusive and even fluorescence, the size and shape of nucleus is consistent. This indicated AK-9 and AK-11 might produce active agents inducing apoptosis.The determining of pure AK-ll's IC50 to MGC-803 and SMMC-7721 show that the inhibition of AK-11 to tumor cells is slightly greater than Adriamycin and it has high antitumor activity. This indicates that AK-11 having the value for developing a new antitumor drug. Extracting DNA of the cells treated with pure AK-11, the result showed that it could cause DNA of the cells breaking to Mono- and Oligo-nucleosomes. By the Agarose Gel Electrophoresis, we can see regular and 100-200bp intervals "DNA ladder". We analyze the cell cycles of strains AK-11 inducing apoptosis and AK-17 having DDRT toxicity by FCM. Collecting the cells of different time treated with AK-11, dyeing and fixing, the analysis of FCM showed that after treated with 24 hours, the apoptosis peak appear. Along with the increasing of treat time, the degree of apoptosis also increases. After treat with different concentration of AK-11, the degree of apoptosis increases along with the increasing of the concentration. These verify AK-11 can induce the cell apoptosis, the degree of apoptosis increase along with the increasing of the concentration and treat time.The cell cycle analysis with AK-17 showed that it could make the cell light blocking at the period of Ga/M, and along with the increasing the treat time, part of the cells occur apoptosis. Contemporary, the cell cycle was analyzed treated with the positive drug Adriamycin. When treat with the low concentration, the cells are almost completely blocking at the period of G2/M, when the concentration increase, the cells occur apoptosis. AK-17 and Adriamycin having the similar effects to the cell cycle of MGC-803 indicate that they may be have the analogous antitumor approach. The mechanisms of these antitumor drugs will be further research.By the result of nude mouse experiment, it can be determided that AK-11 having the effect of tumor inhibition, its inhibition rate is greater that 30%. But at the sametime, AK-11 have some toxicity, the mouse after injecting occur bad response, wight of the mouse decline. The inhibition rate of AK-17 is less than 30%, effect of tumor inhibition is not obvious.