Good or bad: Paradox of plasminogen activator inhibitor 1 (PAI-1) in digestive system tumors

The fibrinolytic system is involved in many physiological functions, among which the important members can interact with each other, either synergistically or antagonistically to participate in the pathogenesis of many diseases. Plasminogen activator inhibitor 1 (PAI-1) acts as a crucial element of the fibrinolytic system and functions in an anti-fibrinolytic manner in the normal coagulation process. It inhibits plasminogen activator, and affects the relationship between cells and extracellular matrix. PAI-1 not only involved in blood diseases, inflammation, obesity and metabolic syndrome but also in tumor pathology. Especially PAI-1 plays a different role in different digestive tumors as an oncogene or cancer suppressor, even a dual role for the same cancer. We term this phenomenon "PAI-1 paradox". PAI-1 is acknowledged to have both uPA-dependent and -independent effects, and its different actions can result in both beneficial and adverse consequences. Therefore, this review will elaborate on PAI-1 structure, the dual value of PAI-1 in different digestive system tumors, gene polymorphisms, the uPA-dependent and -independent mechanisms of regulatory networks, and the drugs targeted by PAI-1 to deepen the comprehensive understanding of PAI-1 in digestive system tumors.

SERPINE1, PAI-1 protein coding gene, methylation levels and epigenetic relationships with adiposity changes in obese subjects with metabolic syndrome features under dietary restriction

Plasminogen activator inhibitor 1 (PAI-1) has been associated with metabolic disorders, through different mechanisms, which could involve changes in DNA methylation. This work aimed to assess the potential relationships of the cytosine methylation levels within SERPINE1 gene transcriptional regulatory region, which codes for PAI-1, in peripheral white blood cells with anthropometrical, metabolic and inflammatory features. Forty-six obese subjects with metabolic syndrome features followed Control or Metabolic Syndrome Reduction in Navarra (RESMENA) energy-restricted (−30%E) diets for 8 weeks. SERPINE1 transcriptional regulatory region methylation at baseline was analyzed by a microarray technical. Both dietary strategies reduced anthropometric and biochemical parameters. The Control group significantly reduced plasma PAI-1 concentrations but not the RESMENA group. Participants from both nutritional interventions with higher SERPINE1 methylation levels at baseline showed significantly major reductions in body weight, total fat mass, android fat mass, total cholesterol and triglycerides, as compared with those with lower initial SERPINE1 methylation levels. In conclusion, the DNA methylation levels of SERPINE1 transcriptional regulatory region were associated with some metabolic and anthropometric changes in obese subjects with metabolic syndrome under energy restriction, suggesting a complex epigenetic network in the regulation of this recognized pro-inflammatory marker. (www.clinicaltrials.gov; NCT01087086)

Deregulated expression of urokinase and its inhibitor type 1 in prostate cancer cells: role of epigenetic mechanisms

Plasminogen activator inhibitor-1 (PAI-1) and urokinase-type plasminogen activator (uPA) play a crucial role in cancer progression. In the present study we examined the regulation of PAI-1 and uPA expressions in normal prostate epithelial cells (PrEC) and the prostate cancer cell lines LNCaP, DU-145, and PC-3. The antigen and mRNA levels of PAI-1 were down-regulated in cancer cells, especially in LNCaP and DU-145. In the presence of proinflammatory cytokines, an increase of PAI-1 mRNA levels was observed in PrEC, LNCaP and PC-3, but not in DU-145 cells. Treatment with demethylating agent, 5-aza-2'-deoxycytidine increased the level of PAI-1 transcript in DU-145 cells and restored the inducing effect of cytokines on PAI-1 expression. An aberrant methylation of PAI-1 promoter in DU-145 and LNCaP cells was shown by methylation-sensitive high resolution melting (MS-HRM) analysis. PAI-1 methylation was also significantly increased in tumor samples (23.2±1.7%) in comparison to adjacent non-tumor tissue (6.0±0.8%). Furthermore, the expression of uPA was increased in high invasive cell lines DU-145 and PC-3 in comparison to PrEC and low invasive LNCaP cells. MS-HRM analysis revealed aberrant methylation of uPA promoter in LNCaP cells, but not in PrEC, DU-145 and PC-3 cells, as well as in normal and prostate cancer tissue samples. In conclusion, the study shows that PAI-1 and uPA expressions were changed in opposite directions in high invasive prostate cancer cell lines resulting in a strong decrease of PAI-1/uPA ratio, which may indicate a shift towards proteolytic activities. Methylation of the PAI-1 gene is suggested as one of the molecular mechanisms involved in the cancer-associated down-regulation of the PAI-1 expression.