OGA and neoplasm: As a corollary, we next tested the overall role of the O-GlcNAc modification in mediating tumor cell line response to inhibition of PI3K by GDC-0941, by using PUGNAc, a pharmacological inhibitor of OGA, the glycosidase that removes the O-GlcNAc moiety, thus increasing the overall cellular levels of O-GlcNAc [25].