PIK3CA and cancer: These observations suggest a potential causal relationship between heightened O‐GlcNAcylation and tumorigenesis, although an analysis of 33 cancer types in the Cancer Genome Atlas database showed that mutations in O‐GlcNAcylation cycling enzymes are rare compared with highly mutated genes, such as p53 and PIK3CA [34], indicating that increased O‐GlcNAcylation may be a phenotypic consequence of cancer progression.