Résumé
Objective: To investigate a new method for altering the secondary metabolism of inactive actinomycete strain by magnetic nanoparticle-aided microwave mutagenesis to obtain antitumor mutants. Methods: HLF-43, a marine-derived actinomycete strain without antitumor activity with the inhibition rate of 3.9% at the 1000 μg/ml sample concentration on K562 cells, was used as the initial strain in the present study. The spore suspension of HLF-43 was exposed to the microwave radiation (the frequency 2450 MHz, the power 464 W)under the presence of Fe3O4 magnetic nanoparticles, then spread on neomycin-containing plates and the neomycin-resistant (neo) mutants were selected during incubation at 28°C for 4-14 days. The initial strain HLF-43 and its neo mutants were fermented to obtain fermentation samples and the antitumor neo mutants were obtained by the test of antitumor activity for these samples at 100 μg/ml. The antitumor activity was assayed by the MTT method using K562 cells. Results: A new method has been created for altering the secondary metabolism of actinomycete strain by magnetic nanoparticle-aided microwave mutagenesis. By the method coupled with the neo mutant selection, a total of 80 neo mutants were obtained from the inactive-initial strain HLF-43 and 28 of them were antitumor mutants with the inhibition rates over 20% at the 100 μg/ml sample concentration on the K562 cells. The antitumor mutants could be obtained at quite high frequency of 35% (28/80). Conclusion: Compared with the microwave mutagenesis without the aid of Fe3O4 magnetic nanoparticles, the Fe3O4 magnetic nanoparticle-aided microwave mutagenesis is more favorable to obtain the neo mutants resistant to higher concentration of neomycin and to obtain the antitumor neo mutants at higher frequency.