Abstract 1484: Inhibition of the glycosylation enzyme Mgat1 blocks migration, invasion and metastasis of malignant cells

Abstract

Abstract N-acetylglucosaminyltransferase I (Mgat1) is the enzyme that initiates the biosynthesis of hybrid and complex N-glycans in medial golgi. As such, it regulates N-glycosylation, a post-translational modification that alters the localization and function of cell surface proteins. Aberrant activity of the N-glycosylation pathway is seen frequently in malignant cells and contributes to their metastatic potential. Here, we have evaluated the effects of Mgat1 inhibition in malignant cells. We knocked down Mgat1 with two independent shRNA in Hela human cervical cancer cells. Target knockdown and inhibition was confirmed by demonstrating mRNA knockdown, decreased cell-surface lectin staining, and inhibition of enzymatic activity. Knockdown of Mgat1 did not induce cell death or inhibit proliferation. Complex N-glycans influence cell migration and invasion. Therefore, we investigated the effect of Mgat1 knockdown on these glycosylation-mediated processes. Hela cells with Mgat1 knockdown and control shRNA were seeded into invasion chambers. Twenty four hours after seeding, we measured cell migration through uncoated chambers and cell invasion through Matrigel-coated chambers. Compared to control shRNA, Mgat1 knockdown significantly decreased Hela cells migration and invasion. ιntegrins influence cell migration and invasion and are N-glycosylated. Therefore, to begin to understand the mechanism by which Mgat1 knockdown inhibits cell migration and invasion, we examined changes in the cell surface expression of β1 integrins. By confocal microscopy, knockdown of Mgat1 decreased cell surface expression of β1 integrins and increased their localization around the nucleus. To assess the effects of Mgat1 on metastasis in vivo, we knocked down Mgat1 with shRNA in RFP-labeled PC3N7 prostate cancer cells. Mgat1 knockdown or control cells were then injected orthotopically into the prostate gland of sublethally irradiated SCID mice. Four weeks after injection, mice were sacrificed and distant tumor formation was imaged with fluorescent microscopy. Mgat1 knockdown decreased the median number of tumors that had metastasized to the lung more than three-fold compared to control. Our preclinical studies, suggest a role for Mgat1 in cancer cell metastasis. Therefore, we examined the association between Mgat1 mRNA expression in primary tumors and the incidence of subsequent metastasis. By analyzing publically available gene expression array data sets from patients with breast cancer, we determined that patients with the lowest levels of Mgat1 mRNA in their primary tumors were least likely to develop metastatic disease after therapy. In summary, this work highlights the role of the N-glycosyltransferase Mgat1 in cancer cell metastasis. As such, Mgat1 may be a novel target for anti-cancer therapies and levels of Mgat1 in primary tumors may help predict the risk of developing metastatic disease. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1484. doi:10.1158/1538-7445.AM2011-1484