Investigação de biomarcadores a partir do peptidoma sérico e mapeamento de proteases de pacientes com câncer gástrico

• Autor(a) principal: Oliveira, Talita Mendes De [UNIFESP]
• Data de Publicação: 2019
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UNIFESP
• Texto Completo: https://sucupira.capes.gov.br/sucupira/public/consultas/coleta/trabalhoConclusao/viewTrabalhoConclusao.jsf?popup=true&id_trabalho=7892094; https://repositorio.unifesp.br/handle/11600/59807
• topic: Gastric Cancer; Serum Peptidome; Proteases; Phosphorylation; Câncer Gástrico; Peptidoma Sérico; Proteases; Fosforilação

Introduction: Gastric cancer (GC) is the fifth most diagnosed malignant neoplasms and the third leading cause of death associated with cancer worldwide. In Brazil, 21.000 new cases were estimated for the biennium 2018-2019. GC is frequently diagnosed at an advanced stage, causing a reduction in therapeutic efficacy rate, and therefore the identification of biomarkers that allows an early diagnosis may result in a better survival. The aims of this study were to perform a comparative analysis of the endogenous peptides (peptidome) of patients diagnosed with gastric adenocarcinoma (GAC) and non-tumor (control) subject, and then mapping the proteases involved in the production of these peptides. Methods: Fifteen GAC serum samples (stage I-IV) and fifteen controls, from which the extracted peptides were pooled of random mode into 5 biological replicates (n = 3) per group and submitted to liquid chromatography coupled to spectrometry mass in tandem (nanoLC-ESI-MS / MS), followed by peptidome-based protease prediction. From the principalcomponents analysis (PCA) based on ions intensity resulting, it was possible to show the correlations between samples pools of each group and the difference between them. Results: A total of 191 peptides were identified corresponding to the cleavage products of 36 proteins involved mainly in the degranulation of platelets and neutrophils, regulation of exocytosis, proteolytic activity and immune response. Further, 29 Serine-, 19 Metallo-, 8 Cysteine-, and 3 Aspartyl-protease was predicted, in which Prothrombin, Plasminogen, MMP14, MMP7, and MMP3 were associated with the highest number of cleavages. From the relative quantification of peptides (label-free quantification), 33 peptides presented significant differences (fold change ≥ 1.5; p-value < 0.05), being 19 increased and 14 reduced in GAC samples. The peptide sequences increased in GAC belong to the Poly-Ig receptor, Cystatin S and Complement C3 proteins, whereas sequences decreased are derived from Prothrombin, Apolipoprotein A-I, Coagulation factor XIII A chain, Inter-alpha-trypsin inhibitor heavy chain H4, Alpha-2-HS-glycoprotein, and Transthyretin. In addition, fibrinogens A and B yielded the majority of the peptides, with significant differences in both groups varying by size, of which the longer sequences were reduced in GAC samples, while the smaller ones increased. Using these peptides, 9 proteases had increased predicted activity in GAC samples. Additionally, increasing the phosphopeptide 20ADpSGEGDFLAEGGGVR35 (Fibrinopeptide A) was verified in GAC samples, while their non-phosphorylated counterpart was decreased. Conclusion: The comparison between peptidomes showed the presence of peptides that could be used as potential indicators of tumorigenesis. Increases in proteolytic activity and phosphorylation of fibrinopeptide A may be tumoral biomarkers in serum samples.