Identification of Glycoprotein Biomarkers in Breast Cancer by MALDI.

Protein glycosylation plays a pivotal role in breast cancer biology, influencing cell proliferation, adhesion, migration, and immune evasion. Aberrant N- and O-glycosylation are hallmarks of neoplastic transformation and serve as sensitive indicators of disease progression. This review aims to characterize glycoprotein biomarkers in breast cancer identified using Matrix-Assisted Laser Desorption/Ionization (MALDI) Mass Spectrometry. We examine specific glycosylation alterations-including hypersialylation, fucosylation, and truncated O-glycans-across different molecular subtypes (Luminal A/B, HER2-positive, TNBC) and assess their diagnostic and prognostic potential. Methodologically, the review contrasts MALDI-based profiling and Imaging Mass Spectrometry (MALDI-IMS) with other proteomic techniques, highlighting MALDI's advantages in throughput and spatial resolution alongside its technical limitations. Furthermore, we discuss emerging frontiers in the field, such as the shift from whole-serum analysis to "liquid biopsy" components (e.g., extracellular vesicles). Ultimately, we argue that implementing quantitative glycoproteomics is essential for advancing personalized oncology.