Regulation of EMT-MET and chemoresistance by the Lc3Cer-synthase B3GNT5.

BACKGROUND: Glycosphingolipids (GSL) are essential components of the plasma membrane where they are known to play key structural and functional roles and are known to influence molecular processes involved in cancer malignancy, including multi-drug chemoresistance, the epithelial to mesenchymal transition (EMT), and the activation or receptor tyrosine kinases (RTK). Thus, investigating and understanding how GSLs are regulated in cancer and the impact they have on malignancy have important therapeutic potential. In the GSL biosynthetic pathway, one critical regulator of two of the four major branches of GSLs is the gene product of B3GNT5, which produces the precursor for all GSLs in the lactoside and neolactoside series. METHODS: Publicly available data was mined to determine the types and prevalence of genetic lesions at the B3GNT5 locus in various cancers, and to assess the impact of increased expression on patient outcomes. HeLa cells in which B3GNT5 was partially depleted using CRISPR-Cas9 approaches were used to determine how its expression levels impacted several phenotypic properties associated with cancer malignancy. Mass spectrometry was used to assess the effect of B3GNT5 on the levels of the Lc3Cer precursors glucosylceramide (GlcCer) and lactosylceramide (LacCer). RESULTS: B3GNT5 copy number gain and overexpression are widespread across human cancers and are significantly associated with poor prognosis. Partial depletion of B3GNT5 in HeLa cells led to accumulation of GlcCer and LacCer, increased chemoresistance, altered EMT marker expression, and decreased activation of multiple RTKs following stimulation with serum-suggesting broad signaling and phenotypic shifts. CONCLUSIONS: B3GNT5 is frequently altered in human cancers and correlates with adverse clinical outcomes. Functional depletion reveals its key role in regulating glycosphingolipid metabolism, signaling, and malignant phenotypes. These findings support B3GNT5 as an important target for therapeutic intervention in cancer.