Plasminogen activators in normal and malignant oral epithelium in vivo and in vitro

Urinary-type plasminogen activator (uPA) and its receptor (uPAR) in squamous cell carcinoma of the oral cavity

OSCC (oral squamous cell carcinoma) is the most common oral malignancy and is estimated to affect approx. 350000 new patients worldwide this year. OSCC is characterized by a high degree of morbidity and mortality, as most patients exhibit local, regional and distant metastasis at the time of diagnosis. Recent genome-wide screening efforts have identified the serine proteinase uPA (urinary-type plasminogen activator, also known as urokinase) as a strong biomarker for prediction of poor disease outcome and a key candidate for molecular classification of oral neoplasms using a 'gene signature' approach. The proteinase uPA binds a surface-anchored receptor designated uPAR (uPA receptor), focalizing proteolytic activity to the pericellular milieu. Furthermore, uPA-uPAR can interact with transmembrane proteins to modify multiple signal transduction pathways and influence a wide variety of cellular behaviours. Correlative clinical data show elevated uPA-uPAR in oral tumour tissues, with tumours exhibiting high levels of both uPA and uPAR as the most invasive. Combined in vitro, pre-clinical and clinical data support the need for further analysis of uPA-uPAR as a prognostic indicator as well as a potential therapeutic target in OSCC.

Plasminogen activator system in oral squamous cell carcinoma

BACKGROUND

The plasminogen activator system consists of two plasminogen activators, urokinase (uPA) and tissue (tPA); PA inhibitors (PAI-1, and -2), and a cell surface receptor for uPA (uPAR). The plasminogen activator system is involved at many stages of the metastatic cascade, including matrix remodelling, cell proliferation, and migration.

AIMS

To compare tissue concentrations of the components of the plasminogen activator system in paired tumour tissue and normal tissue in patients with oral squamous cell carcinoma, and to correlate these with the histopathological grading of the tumour.

METHODS

Thirty-eight paired tissue samples were analysed by enzyme-linked immunosorbent assays (ELISA; ng/mg protein) for uPA, tPA, uPAR, PAI-1, and PAI-2.

RESULTS

Concentrations of uPA, uPAR, PAI-1, and PAI-2 were significantly higher in tumour than in normal oral tissue (median in uPAR tumour 1.6 (range; 0.1-7.5) ng/mg protein; normal=0.2 (0-2.3), p<0.05). There were strong correlations between the concentrations of certain components of the plasminogen activator system in particular between uPA, uPAR, and PAI-1 (p<0.05). Tissue concentrations of some components of the plasminogen activator system correlated with clinical and pathological indexes of aggression of tumours, including differentiation and T-stage.

CONCLUSION

The relation between components of the plasminogen activator system, in particular uPA, uPAR, and PAI-1 in invasion, metastasis, prognosis, and survival, requires further investigation in oral squamous cell carcinomas.

Urokinase gene 3'-UTR T/C polymorphism is associated with oral cancer

Urokinase is thought to be involved in the formation of oral cancer, although there is a lack of genetic evidence. Our aim was to study single nucleotide polymorphisms in order to investigate the possibility. A total of 130 oral cancer patients and 105 controls were studied. Polymerase chain reaction (PCR) based restriction analysis was used to identify the C/T polymorphism of the urokinase gene, which is located on the 3'-untranslated region (3'-UTR) of chromosome 10. There was a significant difference in the distribution of the urokinase gene 3'-UTR C/T polymorphism frequency between cancer patients and the normal control group (P < 0.05). The "T" allele was prominent in the cancer group. The odds ratio for the risk of the "T" allele in cancer patients was 2.71 (95% CI = 1.325 approximately 5.562). The cancer patients were further categorized according to gender and whether or not they were habitual smokers or betel nut chewers. These clinical parameters were then compared with tumor cell differentiation and tumor progression. No significant differences were found. Therefore, the urokinase gene 3'-UTR "T" allele is associated with oral cancer and may play a role in oral cancer formation. However, we did not find the relationship between tumor progression and this polymorphism.

The plasminogen activating system in periodontal health and disease

The plasminogen activating system is important for extracellular proteolysis and plays a regulatory role in interactions with other tissue degrading systems. Studies on the plasminogen activating system in gingival crevicular fluid (GCF) as well as gingival tissue are reviewed. t-PA, u-PA, PAI-1 and PAI-2 have all been detected in GCF. Especially t-PA and PAI-2 are found in high concentrations. In tissue studies fibrinolytic activity has been found in the gingival pocket epithelium in humans and in animal studies. t-PA and PAI-2 have been detected there immunohistochemically. Local production of the PAs and PAls has been verified with in situ hybridization. In inflammation, a more intense and widespread immunohistochemical staining of t-PA and PAI-2 is seen. Higher concentrations of t-PA and PAI-2 are found in GCF but the balance between them seems to be constant. A systemically disturbed balance of the plasminogen activating system in GCF has been observed during pregnancy, with a possible protective function of PAI-2. In studies of periodontitis, the production of PAI-2 seemed to be locally lowered at impaired sites. In a study of children, a higher inflammatory response to bacterial plaque was accompanied by a higher fibrinolytic ativity in GCF samples. Bacterial LPS has been found to change the ratio of t-PA to PAI-2 in cultured gingival fibroblasts. Interactions between PAI-2 and a protease in the gingival epithelium has been verified through the immunohistochemical detection of relaxed PAI-2.