Background
N-glycolylneuraminic acid (Neu5Gc) is an aberrant glycosylation found in human tumor cells and has been proposed as a cancer biomarker. An engineered B subunit of Escherichia coli subtilase cytotoxin (SubB), SubB2M, is highly specific for Neu5Gc-containing glycans and can detect elevated Neu5Gc in serum samples from ovarian cancer patients. Here we use SubB2M to detect Neu5Gc tumor biomarkers in sera from breast cancer patients.
Patients and Methods
We first supplemented the known breast cancer biomarker, MUC1, into normal human serum and used surface plasmon resonance (SPR) with SubB2M for detection to establish a dose response. We then analysed 22 serum samples from normal human females, 12 serum samples from patients with stage I breast cancer, 12 with stage II breast cancer, 12 with stage III breast cancer and 24 with stage IV breast cancer.
Results
We demonstrate that SubB2M can detect human MUC1 in a highly sensitive and specific fashion in human serum. Serum from patients with all stages of breast cancer had significantly elevated mean levels of Neu5Gc glycans compared to normal controls. Serum from late stage disease patients all had highly elevated levels of Neu5Gc glycans. Receiver operating characteristic analyses showed that serum Neu5Gc levels can discriminate early stage breast cancer from normal individuals with high sensitivity and specificity, and can discriminate late stage breast cancer from normal individuals with 100% sensitivity and specificity.
Conclusion
Detection of Neu5Gc-glycans using SubB2M may be useful as a diagnostic test for breast cancer and as a tool for monitoring treatment and progression in late stage disease.