Experimental and Clinical Evidence Supports the Use of Urokinase Plasminogen Activation System Components as Clinically Relevant Biomarkers in Gastroesophageal Adenocarcinoma

Simple Summary

Patients with gastric and oesophageal adenocarcinomas (GOCs) have short life expectancies as their tumours spread to other sites early. This is facilitated by the increased expression of the urokinase plasminogen activation system (uPAS); a feature of the majority of GOCs. There is increasing appreciation of the importance of uPAS expression in a range of cell types within the tumour microenvironment. Abundant clinical evidence indicates that altered expression of uPAS proteins is associated with worse outcomes, including time to tumour recurrence and patient survival. Emerging technologies, including liquid biopsy, suggest a role of uPAS for the detection of circulating tumour cells, which are responsible for the dissemination of cancers. We review and summarise pre-clinical and clinical data that supports the use of uPAS as a biomarker in GOC.

Abstract

Gastric and oesophageal cancers (GOCs) are lethal cancers which metastasise early and recur frequently, even after definitive surgery. The urokinase plasminogen activator system (uPAS) is strongly implicated in the invasion and metastasis of many aggressive tumours including GOCs. Urokinase plasminogen activator (uPA) interaction with its receptor, urokinase plasminogen activator receptor (uPAR), leads to proteolytic activation of plasminogen to plasmin, a broad-spectrum protease which enables tumour cell invasion and dissemination to distant sites. uPA, uPAR and the plasminogen activator inhibitor type 1 (PAI-1) are overexpressed in some GOCs. Accumulating evidence points to a causal role of activated receptor tyrosine kinase pathways enhancing uPAS expression in GOCs. Expression of these components are associated with poorer clinicopathological features and patient survival. Stromal cells, including tumour-associated macrophages and myofibroblasts, also express the key uPAS proteins, supporting the argument of stromal involvement in GOC progression and adverse effect on patient survival. uPAS proteins can be detected on circulating leucocytes, circulating tumour cells and within the serum; all have the potential to be developed into circulating biomarkers of GOC. Herein, we review the experimental and clinical evidence supporting uPAS expression as clinical biomarker in GOC, with the goal of developing targeted therapeutics against the uPAS.

Clinical significance of urokinase-type plasminogen activator (uPA) and its type-1 inhibitor (PAI-1) for metastatic sentinel lymph node involvement in breast cancer

Urokinase-type plasminogen activator (uPA) and its type-1 inhibitor (PAI-1) are key factors for tumor invasion and development of metastases in breast cancer. Prospective studies confirmed the prognostic significance of these factors for development of distant metastases. The predictive impact of uPA and PAI-1 for metastatic sentinel lymph node involvement is unclear.

PATIENTS AND METHODS

Between 2006 and 2008 uPA and PAI-1 were measured in 184 out of 1,035 patients for primary breast cancer. uPA and PAI-1 were analyzed with an ELISA assay. Measured concentrations were considered as negative for uPA <3 ng/ml and for PAI-1 <14 ng/ml.

RESULTS

In a retrospective analysis, 173/184 women had a negative sentinel lymph node and 11/184 women had a metastatic sentinel lymph node. From the 11 women with a positive sentinel lymph node 7 had elevated values for uPA and 4 had elevated values for PAI-1. Four and 7 women were uPA- and PAI-1-negative, respectively. Sensitivity, specificity, positive and negative predictive values for uPA were 63.3%, 50.9%, 7.6%, 95.6% and for PAI-1 36%, 52.6%, 4.7%, 92.9%. Even the combination of both uPA and PAI-1 values did not detect 3/11 women with metastatic lymph node involvement.

CONCLUSION

uPA and PAI-1 alone or in combination did not identify all patients with metastatic lymph node involvement. Thus, uPA and PAI-1 cannot be considered as predictive selection parameters to avoid sentinel lymph node biopsy in case of negative values for uPA or PAI-1.