Sialylation is one of the altered glycosylation patterns associated with
cancer progression. In this study, we investigated the N-
glycan profiles of
breast cancer patients and cell lines to reveal sialylation associated with
breast cancer progression, and provided new evidences of
miRNA-mediated sialylation. MALDI-TOF MS analysis revealed that N-
glycans found in
breast cancer tissues and
breast cancer cell MDA-MB-231 featured increased levels of sialylation compared with adjacent tissues and normal breast epithelial cell MCF-10A. The expressional profiles of 20
sialyltransferase genes were then analyzed and found significantly different comparing
breast cancer samples with adjacent tissues, and two
breast cancer cell lines MDA-MB-231 and MCF-7 with different metastatic potential and MCF-10A cells.
Tumor tissues and highly metastatic
breast cancer cell line MDA-MB-231 exhibited higher levels of ST8SIA4. Knocking down ST8SIA4 in
breast cancer cell lines significantly inhibited their malignant behaviors including cell proliferation and invasion in a
sialyltransferase-dependent manner. By applying bioinformatic approaches for the prediction of
miRNA targeting 3'-UTR of ST8SIA4, we identified ST8SIA4 as one of the miR-26a/26b-targeted genes. Further data analysis revealed the inversely related expression of ST8SIA4 and miR-26a/26b in
breast cancer cells,
tumor tissues and corresponding adjacent tissues. The ability of miR-26a/26b to interact specifically with and regulate the 3'-UTR of ST8SIA4 was demonstrated via a
luciferase reporter assay. The forced expression of miR-26a/26b was able to induce a decrease of ST8SIA4 level and also to affect
breast cancer cells progression, while altered expression of ST8SIA4 in
breast cancer cells modulated progression upon transfection with miR-26a/26b mimics or inhibiter. Taken together, these results indicate that changes in the glycosylation patterns and sialylation levels may be useful markers of the progression of
breast cancer, as well as miR-26a/26b may be widely involved in the regulation of sialylation machinery by targeting ST8SIA4.