Table 1.
Glycosylation enzymes, glycans and other glycoconjugates involved in breast cancer progression—potential biomarkers and treatment targets.
| Function | Biomarker/Potential Therapeutic Target | Role in Breast Cancer | Reference | |
|---|---|---|---|---|
| ENZYMES | ||||
| Fucosyltransferase 8 | Potentiates TGF-β and EGF signaling in BC cells | Biomarker and potential therapeutic target | Promotes BC metastasis and is associated with an aggressive type of BC | [61,62] |
| 2, 6-sialyltransferase | Potentiates BC cancer cell adhesion to ECM | Biomarker and potential therapeutic target | Contributes to BC cell metastatic ability | [25,63] |
| α2,3-sialyltransferase | Upregulates mediators of malignant invasion: MMP2, COX2 and β1-integrin | Biomarker and potential therapeutic target | Promotes BC metastatic spread | [60] |
| β-1,3-N-acetylglucosaminyl transferase (B3GNT3) | Mediates N-glycosylation of PD-L1 glycoprotein | Biomarker and potential therapeutic target | Enables immune evasion in the tumor microenvironment and improves response to immunotherapy | [36,37,38] |
| Alpha-1,3-mannosyltransferase (ALG3) | N-glycosylation of TGFBR2, which promotes radioresistance of BC | Biomarker and potential therapeutic target | Overexpression of ALG3 is associated with BC radioresistance, early local recurrence, poor clinicopathological characteristics and low OS | [7,44] |
| N-acetylgalactosaminyltransferase 6 (GALNT6) | Controls the first stage of mucin-type O-glycosylation | Biomarker and potential therapeutic target | BC patients with high GALNT6 expression had worse OS than those with low GALNT6 expression | [12] |
| TACAs (GLYCANS) | ||||
| Thomsen-nouvelle antigen (Tn) | Define various behaviors of cancer cells including apoptosis, alteration of the transmembrane receptor tyrosine kinase pathway, angiogenesis, adhesion, invasion, extravasation and metastases, cell survival. |
Biomarker and potential therapeutic target | Overexpressed on BC cells, overexpression associated with increased tumor aggressiveness, lower OS and higher recurrence risks | [66] |
| sialyl-Thomsen-nouvelle antigen (sTn) | ||||
| Thomsen–Friedenreich antigen (TF) antigen | ||||
| sialyl-LewisA (sLeA) and sialyl-LewisX (sLeX) |
Ligands for adhesion receptors expressed on activated endothelial cells | Biomarker and potential therapeutic target | Promotes penetration into distant tissues | [25,45] |
| GLYCOPROTEINS | ||||
| HER2 | Facilitates excessive cell growth and tumorigenesis | Biomarker and potential therapeutic target | Overexpression has a key role in malignant transformation, associated with poor clinical outcomes | [66,67] |
| PROTEOGLYCANS | ||||
| Glypican-3 (GPC3) | Regulates cell proliferation and survival. | Biomarker and potential therapeutic target | Studies suggest a role in inhibition of EMT in BC cells. Requires further elucidation. | [66] |
TGF-β—transforming growth factor β; EGF—epidermal growth factor; BC—breast cancer; ECM—extracellular matrix; MMP-2—matrix metalloproteinase-2; COX2—cyclooxygenase-2; PD-L1—programmed death-ligand 1; TGFBR2—transforming growth factor beta receptor II; OS—overall survival; EMT—epithelial-mesenchymal transition.