No biomarker has yet to achieve this level of performance. As stated previously, proteomic studies in OvCa have been performed mainly through mass spectrometry (MS) as this platform allows for the simultaneous examination of thousands of proteins in a biological sample. In a typical MS-based experiment, proteins are converted to peptides through enzyme digestion. These peptides can be fractionated offline or placed directly into the mass spectrometer for separation and ionization. Following ionization, the peptides are fragmented in a process known as collision-induced

dissociation. The m/z (mass-to-charge) ratios of the product ions provide information on the amino acid sequence of the peptide which can be subsequently identified through the mass spectrum generated and bioinformatics [29]. Such MS-based JNK inhibitor discovery experiments – also known as shotgun proteomics – have represented the majority of OvCa biomarker studies. Since 2002, over 100 studies have been published investigating the proteome of various biological samples relevant to OvCa for novel biomarkers including serum, proximal fluid, cell lines, and tumoral tissues. Unfortunately, very few of these putative markers have passed clinical validation due to inadequate sensitivity and specificity for OvCa. As a result, a number

of strategies for check details OvCa biomarker discovery beyond classical MS-based proteomics have emerged in the past decade. In the following sections, we will examine some of these recent alternative approaches that are being increasingly ID-8 adopted in the search for novel OvCa biomarkers. Glycomics is the global study of proteins with carbohydrate post-translational modifications (PTMs) and has also served as a growing avenue for biomarker discovery over the past decade. The addition of carbohydrates to nascent proteins, also known as glycosylation, is one of the most common PTMs and is biologically implicated in protein folding, stability, localization, and cell communication [30]. Due to its extensive involvement in cellular processes, it is speculated that glycosylation is accordingly affected or differentially regulated in malignant states.

As a result, proteins are aberrantly glycosylated and these abnormal glycoforms can be used to detect the presence of disease. While glycomic analysis of biological specimens still faces challenges (these will be discussed later), major advances in both pre-analytical separation methods and MS have allowed for increasingly comprehensive characterization of glycomes and cancer-specific glycoproteins [31] and [32]. With respect to OvCa, the majority of glycomic-based biomarker studies have employed the use of matrix-assisted laser desorption/ionization (MALDI) MS coupled with extensive pre-analytical enrichment methods for glycans (such as peptide-N-glycosidase digestion, chromatographic separation, and solid phase permethylation) [30]. In a study by Alley Jr. et al.