Glycosylation in cancer: its application as a biomarker and recent advances of analytical techniques

Despite significant worldwide investment in research, cancer remains one of the most common cause of death in the world. Early detection and reliable diagnosis are the keys to effectively treating cancer and improving the long-term survival of cancer patients. Therefore, there is an urgent need to develop a single, non-invasive biomarker with high sensitivity and specificity. Aberrant glycosylation is well defined as a hallmark of cancer and represents a promising source of potential biomarkers. Tumor-associated carbohydrate epitopes have long been detected by using monoclonal antibodies and lectins. Recent advances in analytical technologies allow us to analyze cancer-specific glycoforms on a target protein in a variety of clinical samples. A number of glycan analysis techniques, such as lectin-based detection methods and mass spectrometry combined with various types of chromatography, have been developed to establish novel glycoform-specific cancer biomarkers. Several glycan-based cancer biomarkers are already in clinical use. The aim of this review is to outline the role of glycan as a cancer biomarker and to summarize the current status and the potential for contribution of the serum glycoproteome to cancer diagnostics, monitoring, and prognostics.