Mechanism of apoptosis of KB cells induced by Topotecan (TPT)

AIM: To study the mechanism of apoptosis of KB cells induced by Topotecan (TPT). METHODS: MTT assay was applied to test the proliferation arrest of KB cells under the treatment of TPT for 12, 24 and 48 h, agarose gel electrophoresis of genomic DNA and flow cytometry (FCM) were used to examine the apoptosis of TPT treated KB cells and Western blot was used to test the phosphorylations of p38MAPK proteins. RESULTS: The inhibition ratio of TPT treated KB cells for 12, 24 and 48 h was (24.4± 9.1)%, (33.7±6.6)% and (45.1±10.4)%, respectively, with significant difference between different treatment duration ( P 0.05). By FCM, the apoptosis rate of the cells was (11.5± 2.8)% at 12h and (31.2±4.1)% at 24 h, with significant difference ( P 0.01). Agarose gel electrophoresis of genomic DNA of TPT treated KB cells for 12 h showed DNA fragmentations, typical index of apoptosis in biochemistry. The phosphorylations of p38 increased gradually with the prolongation of TPT treatment (12, 24 and 48 h) ( n=3, P 0.05). CONCLUSION: TPT induced apoptosis of KB cells in vitro may result from the enhanced activation of p38MAPK.