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Drug resistance is a major problem in cancer chemotherapy. Aberrant glycosylation has been known to be associated with cancer chemoresistance. Aim of this work is to investigate the alterations of glycogene and N-glycan involved in multidrug resistance (MDR) in human breast cancer cell lines. Using real-time polymerase chain reaction (PCR) for quantification of glycogenes, fluorescein isothiocyanate (FITC)-lectin binding for glycan profiling, and mass spectrometry for N-glycan composition, the expression of glycogenes, glycan profiling, and N-glycan composition differed between drug-resistant MCF/ ADR cells and the parental MCF-7 line. Further analysis of the N-glycan regulation by tunicamycin (TM) application or PNGase F treatment in MCF/ADR cells showed partial inhibition of the N-glycan biosynthesis and increased sensitivity to chemotherapeutic drugs dramatically both in vitro and in vivo. Using an RNA interference strategy, we showed that the downregulation of MGAT5 in MCF/ADR cells could enhance the chemosensitivity to antitumor drugs both in vitro and in vivo. Conversely, a stable high expression of MGAT5 in MCF-7 cells could increase resistance to chemotherapeutic drugs both in vitro and in vivo. In conclusion, the alterations of glycogene and N-glycan in human breast cancer cells correlate with tumor sensitivity to chemotherapeutic drug and have significant implications for the development of new treatment strategies. V C 2013 IUBMB Life, 65(5): 409-422, 2013.

Tumor necrosis factor α-induced protein 8-like-1 (TIPE1) functions as an activator or a repressor in a tumor cell type-specific manner. However, the role of TIPE1 in breast cancer, especially regarding metastasis, is unknown. In this study, we aimed to investigate the TIPE1 expression in breast cancer tissues, the biological functions, and the underlying mechanisms of TIPE1 regarding the metastatic properties of breast cancer cells. The results of immunohistochemical staining and western blot analysis indicated that TIPE1 expression was associated with tumor size and lymph node metastasis, and the expression of TIPE1 was downregulated in the tissues of patients with lymph node metastasis. Transwell and wound healing assay results showed that TIPE1 inhibited the invasive and migratory capacities of breast cancer cells. Moreover, the epithelial-mesenchymal transition (EMT) was suppressed in TIPE1-overexpressing cells, as demonstrated by western blot analysis. In addition, western blot analysis also showed that TIPE1 reduced the expression levels of MMP2 and MMP9 and decreased the phosphorylation level of ERK. These results suggested that TIPE1 might suppress the invasion and migration of breast cancer cells and inhibit EMT primarily via the ERK signaling pathway. Our findings revealed the anti-tumor metastasis role of TIPE1 in breast cancer and TIPE1 might be a new candidate prognostic indicator and a potential molecular target for the treatment of breast cancer.

Alteration of Axl glycosylation can attenuate neoplastic lymphatic metastasis. Axl N-glycans may be a universal target for chemotherapy.

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