IGHA1 and breast cancer: In addition, the increased level of free and conjugated forms of sialic acids appears to be a frequent phenomenon in cancer, for instance, the increased α2-3-linked sialylation of prostate-specific antigen in prostate cancer [65], the increased serum glycoprotein sialylation in multiple myeloma [66], or an increase in disialobiantennary N-linked glycans on serum IgA1 in breast cancer [53].