# Status Quo of Glycoslation in Cancer: What Is, What Is Not and What Is to Be
## 2 Milestones of Glycoslation in Cancer  
### Analytical Milestones on Glycoslation for Cancer  
Conventional methods like lectin histochemistry, like traditional immunohistochemistry, have been proven as the established method for glycopomarker identification [14]. Both techniques have been popularly used to study glycoconjugates involved in progression and metastasis of cancer. These classical methods have been successful in analyzing glycan biomarkers. However, they have limited scope when it comes to large-scale applications and are unable to cope with the developments in genomics and proteomics. [PERSON] et al., 2019 have elaborately reviewed analytical inputs in glycomics-based biomarker studies using: mass spectrometry (MS), capillary electrophoresis (CE), high-performance liquid chromatography (HPLC), ultra-performance liquid chromatography (UPLC) and liquid chromatography (LC-MS) [14]. We briefly present the milestones achieved in glycosylation in cancer diagnosis and prognosis through the use of these state-of-the-art technologies. LC-MS has been reported as being used to evaluate the changes in glycoproteins in the serum of cancer patients: \(\alpha\)1-antitrypsin (A1 AT) [15], \(\alpha\)1-acid glycoprotein [16], haptoglobin (Hp) [17; 18; 19] and immunoglobulin G (IgG) [20]. These altered glycosulations can be correlated with cancer progression. Glycan separation prior to MS analysis, is achieved using LC coupled with MS for the characterization of the entire glycome. Hydrophilic interaction chromatography (HILIC)-LC, reverse phase (RP)-LC and porous graphitized carbon (PGC)-LC have been successfully used. [PERSON] et al., detected fucosylated N-glycan structures to be upregulated in hepatocellular carcinoma (HCC) in serum Hp using the HILIC-LC-MS method [21]. The same group also detected core fucosylation (CF) levels in serum \(\alpha\)2-macroglobulin (A2 MG) [22] and serum ceruloplasmin (CP) [23] using RP-LC-MS/MS, differentiating between HCC and cirrhosis patients. [PERSON] et al., using RP-LC-MS/MS, evaluated the site-specific N-glycan changes in renal carcinoma patients prior to and subsequent to nephrectomy [24]. Using PGC-LC- tandem mass spectrometry (PGC-LC-MS/MS), [PERSON] et al., identified and determined the relative abundance of N-glycans released from human serum [25]. [PERSON] et al., characterized the total serum N-glycans from advanced breast cancer patients using HPLC coupled with MS. They proved that there was a distinct increase in the sialyl-Lewis X epitope (CESLEX). The sialyl-Lewis X epitope is reported to be a better indicator for breast cancer than the currently used biomarker, CA15-3, since CA15-3 is not a standalone marker [26]. CESLEX in combination with CA15-3 is reported to be useful for monitoring breast cancer patients. The [PERSON] group reported the use of HILIC-LC-MS for quantification of N-glycans in human serum proteins. This significantly improved quantification of the N-glycome compared to the existing traditional quantification methods, making it feasible for quantitative glycomics analysis for biomarker discovery [27]. A novel antibody microarray was used to analyze cancer-related epitopes sLex and sLea in the serum of colon cancer patients [28]. LC-MS determined site specific -linked oligosaccharidesaccharide alterations in oesophageal cancers [29]. HPLC-based analysis of serum glycosylation revealed differences in fucosylation and sialylation in prostate cancer patients [30]. These alterations in serum glycosylation have been used to differentiate different stages of prostate cancer. Using only 10 \(\upmu\)L of patient serum employing quantitative matrix assisted laser desorption/ionization-quadrupole ion trap mass spectrometry (MALDI-QITMS/MS), the [PERSON] group reported elevated fucosylated N-glycans in Hp in pancreatic cancer [31]. They also found a distinct bi-fucosylated tetra-antennary N-glycan in HCC patients, which outperformed alpha-fetoprotein (AFP) in differentiating HCC from cirrhosis [31].