Adenosine deaminase activity in gastric cancer

Prognostic significance of mRNA expression of CASPs in gastric cancer

Current studies suggest that the cysteinyl aspartate specific proteinase (caspase/CASP) family may be closely associated with apoptosis. Scientists have suggested that caspases may be a key to the development of more effective anti-cancer therapies. However, the prognostic value of CASP expression in gastric cancer (GC) remains unclear. Using a Kaplan-Meier plotter online database, the predictive prognostic significance of the expression of 12 CASPs genes (CASP1, CASP2, CASP3, CASP4, CASP5, CASP6, CASP7, CASP8, CASP9, CASP10, CASP12 and CASP14) to overall survival (OS) in different clinicopathological features, including Lauren classification, pathological stages, therapies employed and differentiation in gastric cancer patients was explored. The present study revealed that higher CASP1, 2, 3, 4, 5, 6, 7 and 8 mRNA expression was associated with better OS, whereas higher expression of CASP9, 10, 12 and 14 showed an unfavorable OS in all GC patients. Moreover, CASP1 to 8 were all associated with favorable OS in intestinal type and diffuse type classified by Lauren classification. Therefore, the results of the present study suggested that the CASP family may function as new prognostic indicators in GC and may be helpful in making treatment decisions.

Enhanced oxidative stress and leucocyte activation in neoplastic tissues of the colon

Excess of intracellular reactive oxygen species results in an environment that may modulate gene expression, or damage cellular molecules. These events are assumed to contribute to the process of carcinogenesis. In the present study, we measured the extent of lipid peroxidation and antioxidative status in colonic tumors and normal colonic mucosa obtained from 25 patients with colorectal carcinoma. Levels of lipid peroxides (PD) and of thiobarbituric acid reactive substances (TBARS) were significantly increased, by 54 and 59%, respectively, in tissue specimens obtained from the colonic tumor as compared with normal colonic mucosa (PD, 2.78+/-0.31 versus 1.81+/-0.29 nmol/mg tissue, TBARS, 0.86+/-0.1 versus 0.54+/-0.08 nmol/mg tissue). Activities of the antioxidant enzymes catalase and glutathione peroxidase (GPx) were also higher (by 67 and 29%, respectively) than in normal mucosa, probably in response to the increased free radical stress occurring in cancerous tissues. Myeloperoxidase (MPO) and adenosine deaminase (ADA) are markers of activated leukocytes and are related to the production of oxygen free radicals by these cells. Their activities were significantly elevated in the neoplastic tissue as compared to the normal tissue (MPO, 7.4+/-1.5 versus 4.1+/-0.95 U/mg tissue, ADA, 4.17+/-0.65 versus 2.99+/-0.80 U/g tissue), suggesting a possible involvement of activated leukocytes in the enhanced oxidative stress in the cancerous tissue. Our results demonstrate an enhanced oxidative stress in the neoplastic tissue. Leukocyte activation was also higher in the carcinogenic tissue, indicating a possible contribution of these cells to a further oxidative stress-derived tissue injury. These observations add to previous studies and may encourage therapeutic trials with antioxidants as a means of preventing colorectal cancer and preventing further tissue injury in the neoplastic tissue and its surroundings.

Adenosine deaminase: functional implications and different classes of inhibitors

Adenosine deaminase (ADA) is an enzyme of the purine metabolism which catalyzes the irreversible deamination of adenosine and deoxyadenosine to inosine and deoxyinosine, respectively. This ubiquitous enzyme has been found in a wide variety of microorganisms, plants, and invertebrates. In addition, it is present in all mammalian cells that play a central role in the differentiation and maturation of the lymphoid system. However, despite a number of studies performed to date, the physiological role played by ADA in the different tissues is not clear. Inherited ADA deficiency causes severe combined immunodeficiency disease (ADA-SCID), in which both B-cell and T-cell development is impaired. ADA-SCID has been the first disorder to be treated by gene therapy, using polyethylene glycol-modified bovine ADA (PEG-ADA). Conversely, there are several diseases in which the level of ADA is above normal. A number of ADA inhibitors have been designed and synthesized, classified as ground-state and transition-state inhibitors. They may be used to mimic the genetic deficiency of the enzyme, in lymphoproliferative disorders or immunosuppressive therapy (i.e., in graft rejection), to potentiate the effect of antileukemic or antiviral nucleosides, and, together with adenosine kinase, to reduce breakdown of adenosine in inflammation, hypertension, and ischemic injury.

Studies on purine enzymes in experimental colitis

Although the role of adenosine deaminase (ADA), adenylate deaminase (AMP-DA), purine nucleoside phosphorylase (PNP) is well documented in gastric and intestinal carcinoma, their role in inflammatory bowel diseases remains unknown. In the present study, we investigated the profile of these enzymes in blood and intestinal tissues during colitis. Colitis induced in Wistar rats by acetic acid was monitored by a marker enzyme myeloperoxidase (MPO). The tissue levels of MPO increased on 1, 2, 5 and 6 days post-administration (PA) of acetic acid and declined to the control levels by day 7 PA. In parallel the blood levels of ADA and AMP-DA decreased on days 1, 2 and 5 without any significant change on days 6 and 7 PA. Similar observations were recorded for these enzymes in the cytosolic extracts of colonic tissue specimens. In contrast, PNP remained unaltered in both blood and tissue samples. These findings suggest an inverse-relationship between inflammation and purine deaminases in both blood and tissues.

Adenosine deaminase activity in patients with the intestinal type of gastric carcinoma

Adenosine deaminase activity was studied in tissue slices taken endoscopically from gastric mucosa of patients with the intestinal type of gastric carcinoma. The enzyme activity was measured in mucosal homogenates by determination of ammonia liberated from substrate during 10-min incubation. It was found that: (1) the enzyme activity of de novo gastric cancer was significantly lower than that of recurrent cancer of the gastric remnant; and (2) the enzyme activity of uninvaded gastric mucosa surrounding the neoplastic lesion of non-operated stomach was significantly lower than of the gastric mucosa of partially resected stomach due to malignancy. Since the enzyme activity in gastric cancer and surrounding uninvaded gastric mucosa correlated well with the advance of neoplastic disease estimated by ultrasonography examination, we speculate that some systemic factors associated with tumor progression might be implicated in the regulation of adenosine deaminase activity.