Three subsets of genes whose tissue specific expression is sex and age-dependent can be identified within the rat alpha 2u-globulin family

PARP-1 Val762Ala polymorphism, CagA+ H. pylori infection and risk for gastric cancer in Han Chinese population

INTRODUCTION

PARP-1 plays important role in the BER (base excision repair) and maintenance of genomic integrity. Previous study found the Val762Ala genetic variant in the PARP-1 gene contributed to susceptibility of some cancers and decreased PARP-1 enzyme activity in response to oxidative damage. Helicobacter pylori (H. pylori) infection was thought to be one of the major causes of gastric cancer. In this study, we investigated the association between the PARP-1 Val762Ala polymorphism, CagA(+) H. pylori infection, and the risk for gastric cancer.

METHODS

This hospital-based, case-control study was performed involving 556 individuals (236 cases with gastric cancer and 320 controls without evidence of neoplasm and gastrointestinal disease) using a PCR-RFLP method. Chi-square test and logistic regression analysis were used to count OR and 95% CI.

RESULTS

762Ala/Ala genotype was overrepresented in the cases (16.9%) compared with controls (10.3%), (OR, 1.942; 95% CI, 1.157-3.257, P = 0.011). Multivariate analysis showed that two factors were significantly associated with risk of gastric cancer, including CagA(+) H. pylori infection (OR, 2.562; 95% CI, 1.174-5.240, P = 0.037), PARP-1 762AA genotype (OR, 1.772; 95% CI, 1.065-3.867; P = 0.042). Stratification analysis indicated that among Cag(+) H. pylori positive subjects, 762Ala/Ala carriers had higher risk for developing gastric cancer compared with 762Val/Val carrier (OR, 2.337; 95% CI, 1.148-4.758; P = 0.017).

CONCLUSION

PARP-1 762Ala/Ala could be a risk factor for gastric cancer in Han Chinese population; PARP-1 762Val/Ala polymorphism and Cag(+) H. pylori infection jointly contribute to higher risk for gastric cancer.

Specific down-regulation of interleukin-12 signaling through induction of phospho-STAT4 protein degradation

Interleukin-12 (IL-12) plays a critical role in modulating the function of T lymphocytes and natural killer cells. IL-12 has potent antitumor effects in animal models, mediated primarily by its ability to enhance cytolytic activity and secretion of interferon-gamma (IFN-gamma). Unfortunately, the antitumor effect of IL-12 has not been demonstrated in clinical trials. Repeated administration of IL-12 in humans results in decreasing levels of IFN-gamma secretion. To understand the mechanism underlying this loss of responsiveness, the effect of IL-12 on its own signaling in activated human T cells was examined. These experiments demonstrate that the level of the signal transducer and activator of transcription 4 (STAT4) protein, a critical IL-12 signaling component, is dramatically decreased 24 hours after IL-12 stimulation, whereas levels of STAT4 messenger RNA are not affected. The decrease of STAT4 protein appears to be due to specific degradation of phospho-STAT4, possibly through the proteasome degradation pathway. Decreased levels of STAT4 protein lead to decreased STAT4 DNA-binding activity and reduced proliferation and secretion of IFN-gamma. This down-regulation of STAT4 is specific for IL-12 signaling, presumably owing to the prolonged activation of STAT4 induced by IL-12. IFN-alpha stimulation, which leads to transient phosphorylation of STAT4, does not reduce the level of STAT4 protein. These findings provide new insights into the regulation of IL-12 signaling in human T cells, where IL-12 promotes T(H)1 responses, but persistent IL-12 stimulation may also limit this response. The cellular depletion of STAT4 following prolonged IL-12 stimulation may also explain the loss of responsiveness following the repeated administration of IL-12 in clinical trials. (Blood. 2001;97:3860-3866)