One example where hypersialylation can be counterproductive in cancer, our group has shown that sialic acid derived from 1,3,4-O-Bu3ManNAc sensitizes drug-resistant pancreatic cancer cells to tyrosine kinase inhibitors (erlotinib and gefitinib [22]) through attenuation of EGFR signaling [23]. Here, EGFR is linked to familial pancreatic carcinoma.