ABSTRACT
AIM:To study the effect of Taxol on the proliferation, apoptosis, and mRNA expressions of α2,6-sialic acid (SA) and α2,6-sialyltransferase (ST6Gal) in mouse cervical cancer cell line U14.METHODS:After the U14 cells were treated with Taxol, the IC50 value of Taxol to U14 cells was detected by MTT assay.The expression of α2,6-SA and apoptosis-related factors (Bcl-2, Bax, caspase 8 and caspase 3), the apoptosis rate and cell cycle were determined by flow cytometry.The mRNA expression of ST6Gal1 and ST6Gal2 was detected by qPCR.RESULTS:As compared with control group, Taxol induced obvious U14 cell growth inhibition, reduced α2,6-SA expression, up-regulated Bax, down-regulated Bcl-2, decreased the ratio of Bcl-2/Bax, enhanced caspase 8 and caspase 3 activity, increased the apoptotic rate and cell proportions of Sub-G1 and S phases, and induced G2/M phase arrest.Taxol also down-regulated the mRNA expression of ST6Gal1, and slightly up-regulated the mRNA expression of ST6Gal2.CONCLUSION:α2,6-SA and ST6Gal are involved in the multiple effects of Taxol on modulation of the cell cycle and apoptosis in U14 cells.
ABSTRACT
The level of β-galactoside α2,6-sialyltransferase I (ST6Gal I) mRNA, encoded by the gene siat1, is increased in malignant tissues. Expression is regulated by different promoters – P1, P2 and P3 – generating three mRNA isoforms H, X and YZ. In cervical cancer tissue the mRNA isoform H, which results from P1 promoter activity, is increased. To study the regulation of P1 promoter, different constructs from P1 promoter were evaluated by luciferase assays in cervical and hepatic cell lines. Deletion of a fragment of 1048 bp (−89 to +24 bp) increased 5- and 3-fold the promoter activity in C33A and HepG2 cell lines, respectively. The minimal region with promoter activity was a 37 bp fragment in C33A cells. The activity of this region does not require the presence of an initiator sequence. In HepG2 cells the minimal promoter activity was detected in the 66 bp fragment. Sp1 (−32) mutation increased the promoter activity only in HepG2 cells. HNF1 mutation decreased promoter activity in HepG2 cell line but not in C33A cells. We identified a large region that plays a negative regulation role. The regulation of promoter activity is cell type specific. Our study provides new insights into the complex transcriptional regulation of siat1 gene.