**Author details**

*Proteoforms - Concept and Applications in Medical Sciences*

cardiovascular disease (CVD) [86].

carcinoma pathogenesis [92].

**6. Conclusion**

cost per test.

**Conflict of interest**

The authors declare no conflict of interest.

**5.3 Cancer disease**

HDL. The protein APO C-III has 79 amino acids and can be glycosylated in the residue of Threonine 48. Initially, four APO C-III isoforms were identified by mass spectrometry and later 12 proteoforms. These proteoforms differ by absence of glycosylation (APO C-III Oa), glycosylation (APO C-III Ob), addition of one or two sialic acid residues (APO C-III 1, APO C-III 2) or addition of fucose at glycosylation sites. There are also truncated proteoforms due to amino acid substitution. Increases in APO C-III2 levels are associated with a reduction in TG and LDL levels, and perhaps this is a possible mechanism for dyslipidemia processes and reduced risk of

The identification of novel biomarkers for early clinical-stage cancer detection, targeted molecular therapies, disease monitoring and drug development could impact on the future care of cancer patients. A systematic study of cancer samples using omics technologies, oncoproteomics, is in progress. He et al. summarize the advantages and limitations of the critical technologies used in (onco)proteogenomics [90]. In other studies, Zhan et al. [91]compared MALDI-MS, LC-Q-TOF MS and LC-Orbitrap Velos MS for the identification of proteins within one spot. They described the importance of the development of stable isotope labeling coupled with 2DE-LC/MS in a large-scale study of human proteoforms. This powerful technique platform identified in Blue-stained 2DE spots at least 42 and 63 proteins/ spot in an analysis of a human glioblastoma proteome and a human pituitary adenoma proteome, respectively. A critical study to detect new proteomic markers of medullary thyroid carcinoma, combining MALDI-MSI and nLC-ESI-MS/MS were developed by [92]. They identified proteins as moesin, veriscan and lumican and intratumoural amyloid components, including calcitonin, apolipoprotein E, apolipoprotein IV and vitronectin with a potential role in medullary thyroid

In conclusion, the proteoform identification using a proteomic approach can be an advance in diagnostic routines and development of precision/personalized medicine. Efforts should be concentrated on clinical studies and then on, and one aspect that precludes is the cost and complexity of these tests. Therefore, studies to simplify sample preparation steps and MS platforms need to be performed to reduce

**18**

Jucélia da Silva Araújo and Olga Lima Tavares Machado\* Universidade Estadual do Norte Fluminense-Darcy Ribeiro, Rio de Janeiro, Brazil

\*Address all correspondence to: olga@uenf.br

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
