This review was supported by the NIH grants U01 CA117378, R01 EB006177 and U54 ES016015. == Abbreviations Ulixertinib (BVD-523, VRT752271) == advanced glycation end products breast-cancer susceptibility gene conjugated dienes ductal carcinoma in situ enzyme-linked immunosorbent assay estrogen receptor 4-hydroxynonenal high-performance liquid chromatography-electrospray ionization-mass spectroscopy Ulixertinib (BVD-523, VRT752271) immunohistochemistry N-acetylglucosamine N-acetylglucosaminyltransferase V glutathione glutathione S-transferase P1 mitogen-activated protein kinase/extracellular signal-regulated kinase lobular carcinoma in situ matrix-assisted laser desorption ionization-mass spectroscopy nitric oxide 3-nitrotyrosine RAS association family 1 gene phosphoinositide-3 kinase/protein kinase B post-translational modifications Protein Microarray Analysis Tool reactive oxygen species sialyl lewis a sialyl lewis x sialyl Tn Lewis y surface-enhanced laser desorption/ionization time-of-flight mass spectroscopy thiobarbituric acid reactive substances Thomsen-Friedenreich == Footnotes == Disclosures The authors report no conflicts of interest. == References ==. complexity of regulation not only results from variable mRNA splicing and DNA transcription, such that one gene can produce many mRNA and protein sequences, but also because one protein sequence can have multiple functions as a result of covalent modifications after synthesis. These post-translational modifications (PTMs) include phosphorylation, methylation, glycosylation, acylation, oxidation and ubiquitinylation. During cancer progression, many PTMs contribute to abnormal cellular proliferation, adhesion characteristics and morphology.14In breast cancer, recent studies Ulixertinib (BVD-523, VRT752271) suggest that PTM profiles can be used as biochemical foot-prints for tracking and verifying the function and activity of key cellular signaling pathways.57This conclusion suggests that, for early detection, PTMs may be useful biomarkers. Breast cancer is the second most common type of cancer (after lung cancer), and the fifth most common cause of cancer death. According to the American Cancer Society, in 2008, an estimated 182,460 new cases of invasive breast cancer were diagnosed among US women. Approximately 40,480 of these women are expected to die from this disease (http://www.cancer.org/downloads/STT/2008CAFFfinalsecured.pdf). Like many other cancers, breast cancer is the result of multiple environmental and hereditary factors. Although risk factors such as lesions to DNA, failure of immune surveillance, abnormal growth factor signaling, and inherited or somatic genetic defects (e.g. in p53, BRCA1, BRCA2 genes) are associated with breast cancer development, the cause of any individual breast cancer case is typically unknown. As many studies have suggested, changes in gene expression levels for breast cancer may not fully reflect the true state of cancer progression or development.5,8,9This conclusion suggests that many of the differences between normal and cancer tissue may Ulixertinib (BVD-523, VRT752271) be caused by PTMs.1,3,5,6,810 This review mainly focuses on the most recent publications on PTMs (especially oxidation and glycosylation) discovered in blood or tissue from breast cancer patients or from breast cancer cell lines. For more general reviews of PTMs, see prior reviews.14,7,11 == Enzymatic PTMs == Covalent modification of one or more amino acids of a given protein can dramatically alter the biological function of that protein. The likelihood that a particular reactive protein residue will undergo a modification reaction is influenced by the spatial orientation of that amino acid residue(s) in the protein, and is influenced by the adjacent amino acids, which can alter reactivity of the susceptible amino acid by influencing its electrophilic nature. Specific enzymes commonly catalyze these reactions. For example phosphorylation (phosphokinase), methylation (methylase), acetylation (acetyltransferase), and glycosylation (glycosyltransferases) are PTMs Rabbit polyclonal to AKR1E2 that are mediated by the indicated enzyme.14,7,11Many PTMs also result from spontaneous reaction of susceptible residues with certain reactive chemical agents. For example, glycation (commonly called advanced glycation end product, or AGE) is the result of an activated sugar molecule, such as fructose or glucose, bonding to a protein Ulixertinib (BVD-523, VRT752271) without direct enzymatic involvement.12For other PTMs, although enzymes may play an important role in producing the reactive molecule that results in the protein modification, the covalent modification occurs spontaneously without enzymatic activity. For the purposes of this review, we define these PTMs as non-enzymatic if an enzyme is not required for the actual protein modification. For example, peroxynitrite directly reacts with proteins to form nitrotyrosine.1315Although peroxynitrite formation appears to require enzymatic production of reactive precursors, its binding to proteins is non-enzymatic, and therefore we consider nitrotyrosine to be a non-enzymatic PTM. == Phosphorylation == Phosphorylation is well recognized as a key regulator of enzyme activity. As the extensive research in protein phosphorylation has been carefully reviewed by others,1618we only briefly cover this topic here. Abnormal phosphorylation of defined.