Molecular mechanism of silymarin-induced apoptosis of highly metastatic lung cancer cell line(Anip973)

Abstract

Objective To study the molecular mechanism of silymarin-induced apoptosis of highly metastatic lung cancer cell line (Anip973). Methods The apoptosis was analyzed by methyl thiazolyl tetrazolium (MTT) colorimetric assay, morphological observations with inverted microscope and electron microscope, flow cytometry, DNA ladder analysis, expression analysis of PARP as well as the expression and activity analysis of some apoptosis-related proteins including Bax, Bcl-2, caspase-3 and caspase-9. Results(1) Silymarin had significant inhibiting effect to the cellular proliferation of Anip973 cells. (2) When treated with silymarin gradually increased concentraions for 48 hours, the number of Anip973 cells decreased, the cell body became smaller and more circular when observed with inverted microscope till lots of dead cells presented when treated with high concentration. (3) The observation with transmission electron microscope showed that more Anip973 cells presented apoptosis and these cells appeared typical ultrastructural features with the increase of silymarin concentration. (4) The results of flow cytometry indicated that the liar proportion Anip973 cells in GI phase increased, the number of cells in S phase decreased significantly, that in G2 phase reduced slightly and also presented significant apoptotic peak with the prolongation of drug action. (5) The Anip973 cells treated with silymarin presented distinct apoptotic features including DNA ladder, PARP degradation, etc. (6) In Anip973 cells treated with silymarin, the expression of apoptosis-related protein Bax and the enzyme activities of caspase-3 and caspase-9 increased, whilst the expression of Bcl-2 decreased. Conclusion Silymarin con in vitro inhibit the proliferation of human lung adenocarcinoma cell line Anip973 and induce irs apoptosis by activating the mitochondria-dependent caspase cascade pathway. Key words: Silymarin; Cell line,tumor; Lung neoplasms; Apoptosis; Caspase