Abstract C7: Role of β1,6 branched N linked oligosaccharides and associated terminal substitutions in organ-specific metastasis.
Authors: Dange Manohar , Srinivasan Nithya , Kalraiya Rajiv D. 
Published: August 2014

Metastasis involves complex interplay of multitude of events which aid dissemination of tumour cells from primary site to a distant, non-contiguous organ site. The cell surface molecules along with their associated posttranslational modifications are known to play an important role in these events. One such widely studied modification is altered expression of β1,6 branched N-glycans on cell surface glycoproteins. These oligosaccharides have been strongly associated with invasive as well as metastastic potential of human and murine tumours and cancer cell lines. One of the interesting features of the cell lines which express these oligosaccharides is that they either metastasize to the lungs or to the liver. The cells expressing β1,6 branched N-oligosaccharides substituted with Lewis antigens have been shown to metastasize preferentially to liver, the mechanism by which they facilitate lung metastasis is not clear. Low (B16F1) and high (B16F10) metastatic variants of B16 Melanoma has been used as a model to investigate the role of these oligosaccharides in lung metastasis. The model provides cell lines with vastly different metastatic potential which metastasize in organ specific manner to lungs and also express β1,6 branched N-glycans. Previously, poly N-acetyl lactosamine (polylacNAc) substituted β1,6 branched N-glycans were shown to facilitate lung homing via galectin-3. Galectin-3 was shown to be expressed in highest amounts on the lungs on all the major compartments and constitutively on the surface of lung vascular endothelium. Galectin-3 not only provides initial adhesion on the lung vascular endothelium, but also stabilizes adhesion by promoting spreading of cells. Further, it facilitates degradation of vascular basement membrane and mobility into organ parenchyma.

To confirm the role of polylacNAc on β1,6 branched N-glycans, we generated inducible lentiviral (pTRIPZ) mediated shRNA clones which target galactosyl transferase genes (GalTI and GalTV) involved in synthesis of polylacNAc. Real time PCR results showed reduction in expression of GalTI and GalTV genes at transcript levels. The cell surface levels of polylacNAc were analysed by flow cytometry using biotinylated Lycopersicum Esculantum (LEA) lectin as well as by biotinylated galectin-3.The downregulation of polylacNAc on B16F10 cells also results in inhibition of processes critical for metastasis including cell adhesion, cell spreading and motility of cells on galectin-3 and galectin-3 induced secretion of MMP-9. In summary, polylacNAc on β1,6 branched N-glycans is an important determinant of lung specific metastasis of murine melanoma cells.

Citation Format: Manohar Dange, Nithya Srinivasan, Rajiv D. Kalraiya. Role of β1,6 branched N linked oligosaccharides and associated terminal substitutions in organ-specific metastasis.. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr C7.