Quantitative proteomics reveals proteins involved in the progression from non-cancerous lesions to gastric cancer.

Gastric cancer is one of the most aggressive malignancies affecting humankind. With almost a million cases globally, it sits in fifth position in terms of incidence, and third in terms of mortality. The progression of this disease is slow, with prolonged and sequential precancerous stages including chronic gastritis, intestinal metaplasia, dysplasia, and finally gastric cancer. Here we used the iTRAQ approach combined with high-resolution mass spectrometry analysis to describe the spectrum of the gastric cancer cascade. Biopsies from three stages: chronic gastritis, intestinal metaplasia, and gastric adenocarcinoma, were selected for analysis by quantitative proteomics. We identified and reported quantitative data for 3914 different proteins quantified with high confidence, uncovering pathways and processes dysregulated between the different stages. Intestinal metaplasia is characterized by the down-regulation of ribosomal proteins, with overexpression of cell survival proteins such as GSTP1 and EPCAM. The transformation to gastric cancer involves overexpression of the DNA replication and the spliceosome pathways. The impairment of mitochondrial pathways was correlated with down-regulation of SIRT3 and SIRT5, and overexpression of enzymes supporting the glycolytic phenotype, such as HK3 and PCK2. Several proteins found dysregulated during the progression of gastric cancer have potential to be used as specific biomarkers and/or therapeutic targets.