Pancreatic secretions as a clue to the presence of pancreatic cancer

PPIGCF: A Protein-Protein Interaction-Based Gene Correlation Filter for Optimal Gene Selection

Biological data at the omics level are highly complex, requiring powerful computational approaches to identifying significant intrinsic characteristics to further search for informative markers involved in the studied phenotype. In this paper, we propose a novel dimension reduction technique, protein-protein interaction-based gene correlation filtration (PPIGCF), which builds on gene ontology (GO) and protein-protein interaction (PPI) structures to analyze microarray gene expression data. PPIGCF first extracts the gene symbols with their expression from the experimental dataset, and then, classifies them based on GO biological process (BP) and cellular component (CC) annotations. Every classification group inherits all the information on its CCs, corresponding to the BPs, to establish a PPI network. Then, the gene correlation filter (regarding gene rank and the proposed correlation coefficient) is computed on every network and eradicates a few weakly correlated genes connected with their corresponding networks. PPIGCF finds the information content (IC) of the other genes related to the PPI network and takes only the genes with the highest IC values. The satisfactory results of PPIGCF are used to prioritize significant genes. We performed a comparison with current methods to demonstrate our technique's efficiency. From the experiment, it can be concluded that PPIGCF needs fewer genes to reach reasonable accuracy (~99%) for cancer classification. This paper reduces the computational complexity and enhances the time complexity of biomarker discovery from datasets.

Pancreatic secretory abnormalities precede appearance of tumors of the pancreas in hamsters treated with bis-(2-oxopropyl)-N-nitrosamine

The possibility that pancreatic secretory abnormalities might precede the appearance of pancreatic neoplasms and thus provide clues to early detection of this malignancy has been investigated in an animal model. Syrian golden hamsters were treated with bis-(2-oxopropyl)-N-nitrosamine on two successive weeks (2 mg/100 g body weight/week). Pancreatic secretions from treated and untreated control animals were studied at approximately monthly intervals. The animals were anesthetized, their pancreatic ducts cannulated, and basal pancreatic juice collected for 30 min. Pancreatic secretion was then stimulated by sequential intravenous injection of secretin (50 ng/100 g) and C-terminal octapeptide of cholecystokinin (4 ng/100 g) 1 hr later. Four consecutive 15-min collections of fluid were made following secretin stimulation and four additional collections after CCK administration. Each collection was examined for volume, total protein, trypsin, chymotrypsin, elastase, arylsulfatase, beta-D-glucuronidase, alpha-D-glucosidase, and leucine naphthylamidase. In addition two trypsinogen variants present in pancreatic secretions were determined. The pancreas and other organs were removed and examined histologically at the end of each experiment. Cytological atypia appeared 3 months, ductal hyperplasia 4 months, and pancreatic neoplasms 6 months after the last injection of carcinogen. Striking decreases in flow rate and output of trypsin and chymotrypsin were observed several months prior to the appearance of histologically recognizable pancreatic tumors. By contrast, output of beta-D-glucuronidase and alpha-D-glucosidase in pancreatic juice increased markedly in the last 2 months preceding the emergence of neoplasms. The diagnostic significance of these premalignant abnormalities is illustrated most dramatically in the form of ratios of lysosomal to digestive enzymes, such as beta-D-glucuronidase-trypsin or alpha-D-glucosidase-chymotrypsin. Highly significant increases in these ratios were observed consistently, not only in hamsters with pancreatic neoplasms, but also in animals with preneoplastic lesions (ductular hyperplasia) which preceded malignancies by about 2 months.

Abnormalities in pancreatic secretory profiles of patients with cancer of the pancreas

Pancreatic secretory profiles for 11 pancreatic enzymes and proteins were established in nine patients with cancer of the pancreas by analysis of minute-to-minute collections of pure pancreatic juice after sequential administration of secretin and cholecystokinin. Aspiration of pancreatic fluid sufficient for this study was successful in less than one quarter of the patients investigated because of ductal obstruction and/or the effect of the disease on pancreatic exocrine function. Flow rates in patients generally were lower than in healthy individuals, and secretion of total protein, trypsin inhibitor, and activity of digestive enzymes were in the lowest part of or below the normal range. Normal flow rates in four patients precluded ductal obstruction as the sole cause of impaired enzyme secretion. Activity of lysosomal hydrolases in pancreatic juice of these patients, in contrast to that of digestive enzymes, remained within or rose above the normal range. The tumor appeared to have a diametrically opposite effect on the two different groups of enzymes. This is illustrated most dramatically in the form of ratios of lysosomal to digestive enzymes. Virtually all of 10 such ratios were far above the normal average in all patients, and none was below. In an analogous investigation of 25 patients with chronic pancreatitis only three exhibited the ratio pattern characteristic of pancreatic cancer patients. Pancreatic secretory profiles appear to be capable of discriminating between cancer of the pancreas and chronic pancreatitis in a high percentage of cases. Extension and refinement of this approach may facilitate early detection of cancer of the pancreas.