Induction of apoptosis by Streptomyces strain CH54-4 extract through activation of caspase-3 in human nasopharyngeal cells

Abstract

Background : Streptomycetes serves as an incessant source of novel compounds with the ability to produce bioactive secondary metabolites, such as, antimicrobial, antiviral, and especially anticancer compounds. In the case of screening for new anticancer agents, a soil sample was collected from the tropical mangrove area in Chantaburi Province, Thailand which may have potential effects to induce apoptosis on nasopharyngeal cancer.

Objectives : To study the anticancer and apoptosis induction mechanisms of Streptomyces strain CH54-4 extract on human nasopharyngeal (KB) cell line.

Methods : Streptomyces strain CH54-4 was maintained in ISP2 broth. The cells and medium were extracted with methanol and ethyl acetate (1:1) and treated on KB cells. The cell viability was determined by MTT assay. The molecular apoptotic cell death was evaluated by nuclear staining with 4',6-diamidino-2-phenylindole (DAPI), DNA agarose gel electrophoresis assay and evaluated cell cycle by propidium iodide. The activation of caspase-3 was analyzed.

Results : The IC₅₀ values of strain CH54-4 extract and doxorubicin were found at 14.29 1.34 and 1.04 0.21 g/ml, respectively. Cell death mechanisms have been associated with apoptotic bodies and DNA fragmentation with broad smearing bands. The nuclei displayed apoptotic nuclear condensation and fragmentation. The cell cycle analysis showed increased proportion of sub-diploid cell population. Strain CH54-4 extract induced activation of caspase-3 which was reduced by caspase-3 inhibitor.

Conclusions : The findings demonstrate that the apoptotic effects of strain CH54-4 extract were mediated through the caspase-3 pathway. This study provides good candidates for novel anticancer compounds with high potency and specificity.