Edinburgh Napier University

  Protein glycosylation is a sequential process that involves many enzymes and aids in protein stability and cell signalling. Protein glycosylation is altered in cancer and can increase its invasive and metastatic potential. Altered glycosylation may be due to the hypoxic tumour microenvironment. Hypoxia inducible transcription factors (HIFs) orchestrate a shift in cellular metabolism towards glycolysis. As glycolytic intermediates are used in protein glycosylation, this shift can alter nucleotide sugar availability and potentially alters glycan structures. Furthermore, changes in gene transcription in hypoxia may also alter glycosylating gene and promote atypical protein glycosylation. Ultimately these may alter glycosylated protein function and confer aggressive tumour growth.

This project aimed to profile changes in glycogene expression in triple negative breast cancer (TNBC) where glycogene expression was analysed in tissue matched TNBC samples by qPCR using a profiler array. Thirty-two glycogenes were upregulated by 2-fold or more. Through qRT-PCR, altered glycogene expression was validated in glycogenes of the: GALNT, B3GNT, B4GALT families in hypoxic MDA-MB-468 TNBC cells, which replicated the tumour environment. Altered glycogene expression was also found in these hypoxic cells. Lectin binding analysis on MDA-MB468 cells elucidated that hypoxia significantly alters the proportions of sugar residues on the cells.

Furthermore, it was identified that HIF-1α expression correlated with the expression of glycogenes: GALNT3, GALNT6, GALNT7, GALNT12, B3GNT2, B4GALT2, B4GALT3, NEU1 and NEU3. SiRNA knockdown of HIF-1α and HIF-2α in hypoxic MDA-MB-468 cells elucidated suppressed HIF-1α significantly altered the expression of B3GNT2, B4GALT3, GALNT6 and GALNT12.