OBJECTIVETo study the effects of small interfering RNA (siRNA) and antisense oligonucleotides (ASOs) targeting ST6Gal I on adhesion and invasiveness of human colonic carcinoma cell line SW480 over-expressing ST6Gal I.

METHODSsiRNA and ASOs targeting ST6Gal I were constructed and transfected into SW480 cells via lipofectmine 2000. SW480 cells were cultured and divided into 7 groups, namely the blank control group, liposome group, siRNA group (transfected with ST6Gal I siRNA), ASO(1) group (transfected with ST6Gal I ASO whose target site is different from the siRNA), ASO(2) group (transfected with ST6Gal I ASO targeting the same site as siRNA), siRNA+ASO(1) group (transfected with siRNA and ASO(1)), siRNA+ASO(2) group (transfected with siRNA and ASO(2)). RT-PCR was used to examine ST6Gal I mRNA expression following the treatment. Flow cytometry was used to examine the amount of alpha2,6-sialylation on SW480 cell surface. SW480 cell adhesion and invasiveness to the extracellular matrix (ECM) were analyzed using CytoMatrix kit and cell invasion assay kit, respectively.

RESULTSThe expression of ST6Gal I mRNA, the amount of alpha2,6-sialylation on the cell surface and cell adhesion and invasion to ECM decreased remarkably in groups siRNA, ASO(1), ASO(2), siRNA+ASO(1) and siRNA+ASO(2), all significantly lower than those of the blank control and liposome groups (all P<0.05), especially in siRNA+ASO(1) group. Significant difference was noted between siRNA+ASO(1) and siRNA groups (P<0.05), but not between siRNA+ASO(2) and siRNA groups, or between blank control and liposome groups (all P>0.05).

CONCLUSIONChemically synthesized specific siRNA targeting ST6Gal I effectively inhibits SW480 cell ST6Gal I expression and leads to diminished cell adhesion and invasiveness to ECM, suggesting a combined effect of siRNA and ASO with different targeting sites.