Tissue extraction procedures for investigation of urokinase plasminogen activator (uPA) and its inhibitors PAI-1 and PAI-2 in human breast carcinomas

In vitro modulation of multidrug resistance by pregnane steroids and in vivo inhibition of tumour development by 7α-OBz-11α(R)-OTHP-5β-pregnanedione in K562/R7 and H295R cell xenografts

Synthetic progesterone and 5α/β-pregnane-3,20-dione derivatives were evaluated as in vitro and in vivo modulators of multidrug-resistance (MDR) using two P-gp-expressing human cell lines, the non-steroidogenic K562/R7 erythroleukaemia cells and the steroidogenic NCI-H295R adrenocortical carcinoma cells, both resistant to doxorubicin. The maximal effect in both cell lines was observed for 7α-O-benzoyloxy,11α(R)-O-tetrahydropyranyloxy-5β-pregnane-3,20-dione 4. This modulator co-injected with doxorubicin significantly decreased the tumour size and increased the survival time of immunodeficient mice xenografted with NCI-H295R or K562/R7 cells.

The Prognostic Value of Vascular Endothelial Growth Factor, Urokinase Plasminogen Activator and Plasminogen Activator Inhibitor-1 in Node-Negative Breast Cancer

The vascular endothelial growth factor (VEGF) and the plasminogen activator system play an essential role in solid tumor angiogenesis and in tumor invasion and metastasis. In the present study we investigated the relationship between patient outcome and levels of VEGF, urokinase plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1) in tumor cytosols of 196 node-negative primary invasive breast cancer patients who did not receive any adjuvant therapy. The median follow-up was 65 months. VEGF, uPA and PAI-1 were measured by commercially available enzyme-linked immunosorbent assays. Cox's univariate analysis showed that pT (p=0.0007), uPA (p=0.0156) and PAI-1 (p=0.0015) had a significant impact on relapse-free survival, whereas VEGF did not have any prognostic value (p=0.18). Bivariate analysis showed significant interactions between uPA and PAI-1 (p=0.0035) and between VEGF and PAI-1 (p=0.006). Our study confirms that uPA and PAI-1 cytosol levels can be considered as prognostic factors for relapse-free survival in node-negative breast cancer. Moreover, the interaction between VEGF and PAI-1 warrants further investigation into the relationship between the biomarkers of angiogenesis and those of the protease cascade.

IGF binding proteins (IGFBPs) and regulation of breast cancer biology

The IGFBP family comprises six proteins with high affinity for the IGFs. Changes in the balance of the components of the IGF system may contribute to the progression of breast cancer. In tumours the abundance of IGFBPs relates to the estrogen receptor status and their production in the breast is controlled by hormones, principally estrogen and progesterone. Important interactions occur between IGFBPs and key growth regulators such as TGF-beta, PTEN and EGF which are reviewed. The conflicting observations between the effects of IGFBPs on the risk of breast cancer, in particular IGFBP-3, obtained from epidemiology studies in comparison to in vivo observations are highlighted and potential explanations provided. The functional activity of IGFBPs can also be affected by proteolysis, phosphorylation and glycosylation and the implications of these are described. The IGFs are generally present at levels far in excess of that required for maximal receptor stimulation, and the IGFBPs are critical regulators of their cellular actions. IGFBPs can affect cell function in an IGF-dependent or independent manner. The key mechanisms underlying the intrinsic actions of the IGFBPs are still in debate. IGF bioactivity locally in the breast is influenced not only by local tissue expression and regulation of IGFs, IGFBPs and IGFBP proteases, but also by these factors delivered from the circulation. Finally, the therapeutic potential of IGFBPs-2 and -3 are considered together with key questions that still need to be addressed.

Plasminogen activator inhibitor type 1 is the most significant of the usual tissue prognostic factors in node-negative breast ductal adenocarcinoma independent of urokinase-type plasminogen activator

PURPOSE

The aim of the present investigation was to evaluate the prognostic significance of urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1) tissue contents in primary breast adenocarcinoma.

PATIENTS AND METHODS

Patients from 3 medical centers were included between 1994 and 2001. Biologic factors in tumor extracts were all assayed in the same laboratory. PAI-1 and uPA were treated as continuous or dichotomized variables. Metastasis-free survival analyses were performed using the Cox model and the classification algorithm and regression tree (CART) in the whole population and in the subsets of node-negative (pN0) or positive (pN+) cases. Kaplan curves of metastasis-free survival were designed for different groups in relation to uPA/PAI-1 combinations. Urokinase-type plasminogen activator tumor level appears related to the anatomic degree of extension; conversely, PAI-1 tumor content is independent of tumor size and nodal extension.

RESULTS

In univariate analysis, adjusted on usual prognostic factors, the metastasis risk increased with PAI-1 level in all patients (HR [hazard ratio], 3.1; P < .001), in pN0 (HR, 4.3; P < .001), and pN+ patients (HR, 2.3; P = .019). It increased also with uPA in all patients (HR, 2.6; P = 0.006). In multivariate analysis, when both variables were included, PAI-1 remained significant in all patients (HR, 2.4; P = .002) and pN0 patients (HR, 3.2; P = .003) but not uPA. CART analyses confirmed that the best partitioning factor was PAI-1.

CONCLUSION

There was no evidence for any additional impact of uPA. PAI-1 is an independent prognostic factor in particular in pN0 breast ductal carcinoma.

The complex between urokinase (uPA) and its type-1 inhibitor (PAI-1) in pulmonary adenocarcinoma: Relation to prognosis

In a lung cancer population comprising tumor tissue from 99 pulmonary adenocarcinoma patients, the relationship between tumor tissue level of the complex formed of urokinase (uPA) and its type-1 inhibitor (PAI-1) and survival was studied. The study included patient material previously investigated for the prognostic impact of PAI-1 on survival. Standard clinical parameters were available and the patients had a median survival time of 25 months. An ELISA established to measure preformed uPA-PAI-1 complexes was applied to the tumor extracts and previously measured data on uPA and PAI-1 levels were available. The amounts of uPA-PAI-1 complex measured in pulmonary adenocarcinoma tissue were within the same range as previously reported in breast cancer tissue (0.11-5.74 ng/mg protein). uPA and PAI-1 levels were weakly correlated to the uPA-PAI-1 complex, r = 0.52 and r = 0.47, respectively, and no relation was found between uPA-PAI-1 complex and any of the clinical parameters. However, a significant prognostic impact of PAI-1 on prognosis was demonstrated (HR = 1.62, p = 0.04). Patients with high PAI-1 and low uPA-PAI-1 complex were found to have a significantly poorer survival than patients with low PAI-1 and high uPA-PAI-1 complex (HR = 3.06, p = 0.01). This is the first investigation of the prognostic impact of uPA-PAI-1 complex in a tumor type other than breast cancer, showing low levels of uPA-PAI-1 complex in combination with high levels of PAI-1 to be associated with poor prognosis. To understand these interactions and the clinical importance of the tissue levels of uPA, PAI-1 and uPA-PAI-1 complex, the results suggest further exploratory studies of the components in pulmonary adenocarcinomas and other cancers.

Immunoassays of urokinase (uPA) and its type-1 inhibitor (PAI-1) in detergent extracts of breast cancer tissue

Two immunoassays for quantitation of the biological markers uPA and PAI-1 were evaluated for their use with detergent extracts of breast cancer tissue. Both assays were based on murine monoclonal capture antibodies and rabbit polyclonal detector antibodies. Horseradish peroxidase-conjugated goat anti-rabbit antibodies enabled measurement of the bound antigen. The detection limit of the uPA assay was 13 pg/ml, with a linear dose-response relationship up to 350 pg/ml. The assay detected free uPA as well as uPA in complex with PAI-1 and/or with its receptor. The detection limit of the PAI-1 assay was 50 pg/ml, with a linear dose-response relationship up to 1500 pg/ml. The assay detected both free PAI-1 and uPA:PAI-1 complex. Both assays were validated for detergent extracts using immunoabsorption and recovery tests. Highly significant associations between tumour tissue uPA and PAI-1 levels and prognosis were verified in a cohort of 164 lymph node-negative primary breast cancer patients. It is concluded that the two immunoassays are well-suited for the quantitation of uPA and PAI-1 in detergent extracts of breast cancer tissues.

Insulin-like growth factor binding proteins (IGFBPs) in breast cancer

The IGFBP family comprises six proteins with high affinity for the IGFs and several lower affinity IGFBP-related proteins. Their production in the breast is controlled by hormones, other local regulators and in tumors relates to the estrogen receptor status. Their functional activity can also be affected by various post-translational modifications. The IGFs are generally present at levels far in excess of that required for maximal receptor stimulation, and the IGFBPs are critical regulators of cellular action. IGFBPs can affect cell function in an IGF-dependent or independent manner. IGF bioactivity locally in the breast is influenced not only by local tissue expression and regulation of IGFs, IGFBPs, and IGFBP proteases, but also by these factors delivered from the circulation. Changes in the balance of the components of the IGF system may lead to a disruption of tissue homeostasis.