Chulalongkorn Medical Journal


Background ; Streptomycetes serves as an incessant source of novel compounds withthe ability to produce bioactive secondary metabolites, such as,antimicrobial, antiviral, and especially anticancer compounds. In the caseof screening for new anticancer agents, a soil sample was collected fromthe tropical mangrove area in Chantaburi Province, Thailand which mayhave potential effects to induce apoptosis on nasopharyngeal cancer.Objectives ; To study the anticancer and apoptosis induction mechanisms ofStreptomyces strain CH54-4 extract on human nasopharyngeal (KB) cellline.Methods : Streptomyces strain CH54-4 was maintained in ISP2 broth. The cells andmedium were extracted with methanol and ethyl acetate (1:1) and treatedon KB cells. The cell viability was determined by MTT assay. Themolecular apoptotic cell death was evaluated by nuclear staining with4',6-diamidino-2-phenylindole (DAPI), DNA agarose gel electrophoresisassay and evaluated cell cycle by propidium iodide. The activation ofcaspase-3 was analyzed.Results : The IC50 values of strain CH54-4 extract and doxorubicin were found at14.29 ± 1.34 and 1.04 ± 0.21 µg/ml, respectively. Cell death mechanismshave been associated with apoptotic bodies and DNA fragmentationwith broad smearing bands. The nuclei displayed apoptotic nuclearcondensation and fragmentation. The cell cycle analysis showedincreased proportion of sub-diploid cell population. Strain CH54-4extract induced activation of caspase-3 which was reduced bycaspase-3 inhibitor.Conclusions : The findings demonstrate that the apoptotic effects of strain CH54-4extract were mediated through the caspase-3 pathway. This studyprovides good candidates for novel anticancer compounds with highpotency and specificity.


Faculty of Medicine, Chulalongkorn University

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