Circulating Forms of Urokinase-Type Plasminogen Activator Receptor in Plasma Can Predict Recurrence and Survival in Patients with Urothelial Carcinoma of the Bladder

Simple Summary

Bladder cancer is an aggressive disease and after operation many patients are at risk of recurrence and shortened survival. Specific proteins are known to be of importance in the development of cancers. One of these proteins is the urokinase-type plasminogen activator receptor (uPAR) which exists in different forms. We here investigate the presence of the different uPAR forms in plasma from patients with bladder cancer, and we associate the elevated amount of uPAR forms with survival. We find that high levels of all uPAR forms is associated with short survival in patients with bladder cancer and suggest that this in the future might help improve handling of the disease.

Abstract

Urothelial carcinoma of the bladder is a highly aggressive disease characterised by a very heterogeneous clinical outcome. Despite cystectomy, patients still have a high recurrence risk and shortened survival. Urokinase-type plasminogen activator receptor (uPAR) is present in tumour tissue specimens from patients with urothelial carcinoma. The different uPAR forms in blood are strong prognostic markers in other cancer types. We investigate the presence of different uPAR forms in tumour tissue and test the hypothesis that preoperative plasma levels of the uPAR forms predict recurrence free survival, cancer specific survival, and overall survival in patients treated with cystectomy for urothelial carcinoma. Using Western blotting we analyse neoplasia and adjacent benign-appearing urothelium from randomly selected patients for the presence of intact and cleaved uPAR forms. Prospectively collected preoperative plasma samples from 107 patients who underwent radical cystectomy for urothelial carcinoma are analysed. The different uPAR forms are measured by time-resolved fluorescence immunoassays. uPAR in tumour tissue from patients with urothelial carcinoma is demonstrated in both an intact and cleaved form. The different uPAR forms in plasma are all significantly associated with both recurrence free survival, cancer specific survival, and overall survival, high concentrations predicting short survival. uPAR (I) has the strongest association with a HR of 2.56 for overall survival. In the multivariable survival analysis uPAR (I) is significantly associated with cancer specific survival and overall survival.

Crystal structure of the unoccupied murine urokinase-type plasminogen activator receptor (uPAR) reveals a tightly packed DII-DIII unit

The urokinase-type plasminogen activator receptor (uPAR) is a cell surface receptor that is capable of binding to a range of extracellular proteins and triggering a series of proteolytic and signaling events. Previous structural studies of uPAR with its ligands uPA and vitronectin revealed that its three domains (DI, DII, and DIII) form a large hydrophobic cavity to accommodate uPA. In the present study, the structure of unoccupied murine uPAR (muPAR) is determined. The structure of DII and DIII of muPAR is well defined and forms a compact globular unit, while DI could not be traced. Molecular dynamic simulations further confirm the rigid binding interface between DII and DIII. This study shows overall structural flexibility of uPAR in the absence of uPA.

Involvement of urokinase receptor in the cross-talk between human hematopoietic stem cells and bone marrow microenvironment

Hematopoietic stem cells (HSCs) reside in bone marrow (BM) and can be induced to mobilize into the circulation for transplantation. Homing and lodgement into BM of transplanted HSCs are the first critical steps in their engraftment and involve multiple interactions between HSCs and the BM microenvironment.uPAR is a three domain receptor (DIDIIDIII) which binds urokinase, vitronectin, integrins. uPAR can be cleaved and shed from the cell surface generating full-length and cleaved soluble forms (suPAR and DIIDIII-suPAR). DIIDIII-suPAR can bind fMLF receptors through the SRSRY sequence (residues 88-92).We previously reported the involvement of soluble uPAR in HSC mobilization. We now investigate its possible role in HSC homing and engraftment.We show similar levels of circulating full-length suPAR in healthy donors and in acute myeloid leukemia (AML) patients before and after the pre-transplant conditioning regimen. By contrast, levels of circulating DIIDIII-suPAR in AML patients are higher as compared to controls and significantly decrease after the conditioning.We found that suPAR and uPAR84-95, a uPAR-derived peptide which mimics active DIIDIII-suPAR, induce a significant increase in Long Term Culture (LTC)-Initiating Cells (ICs) and in the release of clonogenic progenitors from LTCs of CD34+ HSCs. Further, suPAR increases adhesion and survival of CD34+ KG1 AML cells, whereas uPAR84-95 increases their proliferation.Thus, circulating DIIDIII-suPAR, strongly increased in HSC mobilization, is indeed down-regulated by pre-transplant conditioning, probably to favour HSC homing. BM full-length suPAR and DIIDIII-suPAR may be involved in HSC lodgement within the BM by contributing to a suitable microenvironment.