Aberrant Glycosylation Promotes Lung Cancer Metastasis through Adhesion to Galectins in the Metastatic Niche

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Abstract
Metastasis is the leading cause of cancer-associated deaths. Although dissemination of tumor cells likely occurs early in tumorigenesis, the constituents of the microenvironment play essential rate-limiting roles in determining whether these cells will form clinically relevant tumors. Recent studies have uncovered many molecular factors that contribute to the establishment of a protumorigenic metastatic niche. Here, we demonstrate that galectin-3, whose expression has clinical associations with advanced malignancy and poor outcome, contributes to metastatic niche formation by binding to carbohydrates on metastatic cells. We show that galectin-3 is expressed early during tumorigenesis by both CD11b+Gr-1+ and CD11b+Ly-6Chi leukocytes. Tumors mobilize these myeloid populations through secretion of soluble factors, including IL6. We find that metastatic cancer cells exhibit elevated presentation of the oncofetal galectin-3 carbohydrate ligand, the Thomsen–Friedenreich antigen, on their surfaces as a result of altered C2GnT2 and St6GalNAc4 glycosyltransferase activity that inhibits further glycosylation of this carbohydrate motif and promotes metastasis. Significance: Although clinical observations of elevated serum galectin-3 levels and altered glycosylation have been associated with malignancy, we identify novel roles for glycosyltransferases in promoting adhesion to galectins in the metastatic niche. This identification of a cytokine–leukocyte–glycosylation axis in metastasis provides mechanistic explanations for clinical associations between malignancy and aberrant glycosylation. Cancer Discov; 5(2); 168–81. ©2014 AACR. See related commentary by Arnal-Estapé and Nguyen, p. 109 This article is highlighted in the In This Issue feature, p. 97

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