Study On Antitumor Effects Of Four Species Of Dendrobium

Dendrobiurn huoshanense,Dendrobium candidum,Dendrobium nobile and Dendrobium fimbriatum are used in traditional Chinese medicine.In order to protect and exploit their resources reasonably,their antitumor effects have carried out with two human carcinoma cell lines(HelaS3,HepG2)in this paper.MTT assay was performed to investigate in vitro inhibitory effect of different polar solvent extracts from Dendrobium species on HelaS3 and HepG2 cells. Hoechst33342/PI double staining and agarose gel electrophorosis(AGE)were used as qualitative methods to identify apoptosis.The expression of proto-oncogenes c-myc was measured by RT-PCR.The results indicated that water extracts,petroleum ether extracts,ethyl acetate extracts,n-butanol extracts from four Dendrobium species could inhibit the growth of HelaS3 and HepG2 cells at different levels.The effect seemed to be dose-dependent and time-dependent in the range of trial concentrations.It was found that inhibitory rate rose first and descended later with the prolonging of culture time. The highest inhibitory rate appeared at the fourth day.The inhibitory effect was better when HelaS3 cells treated by water extracts from Dendrobium huoshanense, ethyl acetate extracts from Dendrobium candidum,water extracts from Dendrobium nobile and Dendrobium fimbriatum,respectively.Their median lethal concentrations(IC₅₀)were 11.63 mg/ml,14.18 mg/ml,15.11 mg/ml and 5.89 mg/ml, respectively.The inhibitory effect was better when HepG2 cells treated by petroleum ether extracts from Dendrobium huoshanense and Dendrobium candidum,water extracts from Dendrobium nobile and Dendrobium fimbriatum,respectively.Their median lethal concentrations(IC₅₀)were 8.53 mg/ml,10.81 mg/ml,3.80 mg/ml and 17.76 mg/ml,respectively.The morphological observation showed that the cells of control group appeared blue and the structure of nucleus were normal,but the red cells increased when treated by extracts,the nucleus were round in shape and chromatin agglutination was clear,resulting in cell death.Degradation of the nuclear DNAs of apoptotic cells was demonstrated by visualization of "DNA Ladders" on gel electrophorosis 72 h after treatment,showing that "DNA Ladders" was clearer in higher concentration of extracts.The outcome of RT-PCR indicated that the expression of proto-oncogene c-myc was notably decreased when the dose of extracts was increased. In conclusion,different polar solvent extracts from Dendrobium huoshanense, Dendrobium candidum,Dendrobium nobile and Dendrobium fimbriatum could inhibit the growth of HelaS3 cells and HepG2 cells at different levels.The expression of proto-oncogenc c-myc was decreased after treated by extracts from Dendrobium species.Tremendous evidences indicate that tumor genesis has close relations with the expression of proto-oncogenc c-myc.Our study may imply that Dendrobium could treat cancer by inhibiting the expression of c-myc,which may be one of its molecular mechanisms of antitumor.