Prognostic significance of urokinase-type plasminogen activator and plasminogen activator inhibitor-1 in primary breast cancer

Abstract

Summary The uPA-mediated pathway of plasminogen activation is central to cancer metastasis. Whether uPA and PAI-1 are related to local recurrence, metastatic spread or both is not clear. We present a retrospective study of 429 primary breast cancer patients with a median followup of 5.1 years, in which the levels of uPA and PAI-1 in tumour extracts were analysed by means of an enzyme-linked immunosorbent assay.The median values of uPA and PAI-1, which were used as cut-off points, were 4.5 and 11.1 ng mg-1 protein respectively. The levels of uPA and PAI-1 were correlated with tumour size, degree of anaplasia, steroid receptor status and number of positive nodes. Patients with high content of either uPA or PAI-1 had increased risk of relapse and death. We demonstrated an independent ability of PAI-1 to predict distant metastasis (relative risk 1.7, confidence limits 1.22 and 2.46) and that neither uPA nor PAI-1 provided any information regarding local recurrence.Keywords: urokinase; plasminogen; PAI-1; breast neoplasm mortality; prognosis Cancer cells undergo the following steps during metastasis: detachment from the primary tumour; migration; invasion of the blood and lymphatic vessels; adhesion to and penetration of the endothelium, allowing colonization at distant sites (Liotta et al, 1991). Tumour progression and metastasis also involve various processes that may be called cancer cell-directed tissue remodelling. Examples are angiogenesis (Folkman, 1995) and desmoplasia (Dvorak et al, 1995).Extracellular proteolysis has been implicated in cancer metastasis for many years, with the basic idea that release of proteolytic enzymes from a tumour leads to breakdown of basement membranes and extracellular matrix (ECM), thus allowing cancer cell invasion into the surrounding normal tissue. This is true for plasminogen activators and metalloproteinases (Dan0 et al, 1985;Liotta et al, 1991;Mignatti and Rifkin, 1993;Andreasen et al, 1997). There are two types of plasminogen activator, the urokinase-type uPA and the tissue-type tPA. Both are capable of catalysing the formation of the broad spectrum proteinase plasmin from the inactive zymogen plasminogen. There seems to be general agreement that uPA is most important for generation of plasmin in events involving degradation of ECM, while the primary role of tPA is to generate plasmin for thrombolysis. In relation to cancer metastasis, therefore, uPA is of main interest. There are two main types of inhibitors of plasminogen activator, PAI-1 and PAI-2. The urokinase receptor (uPAR) serves to localize plasminogen activation to cell surfaces (Dan0 et al, 1985;Andreasen et al, 1990Andreasen et al, , 1997Mignatti and Rifkin, 1993 Recent studies have shown that the levels of uPA and PAI-I in malignant tumours vary considerably and are related to the prognosis of the patient (Andreasen et al, 1997). Whether uPA and PAI-I are related to local recurrence, metastatic spread or both is not clear. None of the research groups has to our knowledge looked specifically into the levels of...

Independent prognostic value of angiogenesis and the level of plasminogen activator inhibitor type 1 in breast cancer patients

“…The 228 patients are a subgroup of this cohort, sampled from a shorter period of time (432 patients), and further restricted to patients having frozen tumour material available. Also, we have earlier reported on uPA and PAI-1 from a larger cohort of 429 patients based on frozen tumour samples (Knoop et al, 1998). Again, the 228 patients are a subgroup of this cohort restricted to the primary catchment area of Odense University Hospital.…”

“…The antigen levels of uPA and PAI-1 were assessed with ELISA as described in detail earlier (Knoop et al, 1998). Briefly, tissue for analysis was taken from À801C, homogenised in a buffer of 0.1 mm Tris (pH 8.1), 0.5% Triton X-100, 10 mm EDTA, 10 mg ml À1 aprotinin (10 ml buffer per mg tissue), and centrifuged.…”

“…Predetermined cutoff points from the earlier studies (Knoop et al, 1998;Hansen et al, 2000b) were used for the prognostic analysis: Chalkley count at 5 and 7 points, PAI-1 at 11.1 ng mg À1 total protein, and uPA at 4.5 ng mg À1 total protein. The relationship between the Chalkley count, the PAI-1 level, and the uPA level were tested by the Spearman correlation test.…”

“…Thus, using eight variables in our Cox models, we assumed that we could achieve a reliable statistical strength of the risk estimates in the multivariate regression analysis. As in the earlier publication (Knoop et al, 1998), the Cox models included the classical prognostic factors (menopausal status, tumour size, malignancy grade, receptor status, and number of positive nodes) together with uPA, PAI-1, and the Chalkley count, in that order. The Cox models were stratified by receptor status, which did not fulfil the assumption of proportional hazard rates.…”

“…Thus, the level of PAI-1 in primary tumours is one of the most informative biochemical prognostic markers in several cancer types (Duffy, 1996;Harbeck et al, 1998;Knoop et al, 1998;Duffy et al, 1999;Look and Foekens, 1999;Janicke et al, 2001;Look et al, 2002).…”