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| Antileukemia Properties of Different Aqueous Extracts from Cordyceps militaris In vitro |
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Abstract As a well-known medicinal fungus, Cordyceps militaris has been widely used as a crude drug and folk tonic food in East Asia. It has been proved that C. militaris has the therapeutic actions against various kinds of cancer cells, while studies concerning the leukemia cells are not common, especially with fermentation products of this fungus. In this study, the effects of three aqueous extracts of C. militaris on human leukemia Jurkat and K562 cells were investigated. All aqueous extracts from C. militaris mycelium (CMME), fermentation broth (CMBE) and whole fermentation product (CMPE, extracts from both mycelium and fermentation broth) significantly inhibited the growth of Jurkat and K562 cells in a concentration- and time-dependent manner and the cytotoxic effects were clearly evident even from the early time point (24 h) using methylthiazoletetrazolium (MTT) assay. In comparison with CMBE, both CMME and CMPE showed a remarkably higher inhibitory effect on human leukemia cells, while no significant difference was observed between the two. Additionally, for the three extracts from liquid culture of C. militaris, IC50 value (inhibitory concentration for 50% growth inhibition) followed the ascending sequence: CMME＜CMPE＜CMBE. Further, the Annexin V-FITC/PI staining and flow cytometric analysis showed that the cytotoxic effects observed in response to the CMME and CMPE were associated with the induction of apoptotic cell death, and both early and late apoptosis rates were increased in a dose dependent manner in both Jurkat and K562 cells after the treatments. Both CMME and CMPE showed similar effects on the Jurkat cell apoptosis induction, although the former induced more K562 cells to undergo apoptosis than the latter. Generally, among the three extracts, CMME showed a stronger effect on cell viability and apoptosis than both CMBE and CMPE. In response to CMME, the level of anti-apoptosis B-cell lymphoma-extra large(Bcl-xL) expression was significantly inhibited in Jurkat cells after a relatively long time (48 h) at the concentration of 4.00 mg/mL, but slightly decreased in K562 cells (up to 60 h of treatment) at a higher concentration of 8.00 mg/mL. Taken together, the results here suggested that the anti-proliferative properties of C. militaris aqueous extracts were associated with the apoptotic induction and that CMME might have a great therapeutic potential in human leukemia treatment than the other two extracts. Antileukemia activities of the three aqueous extracts from C. militaris reported here indicated that the effective compounds were produced intracellularly rather than extracellularly. Further investigation may focus more on the mycelium production rather than fermentation broth. The results provide references for future study on application of C. militaris products in leukemia treatments and other related research.
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Received: 09 April 2014
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