Lack of association between level of Plasminogen Activator Inhibitor-1 and estimates of tumor angiogenesis in early breast cancer

A comparison among HER2, TP53, PAI-1, angiogenesis, and proliferation activity as prognostic variables in tumours from 408 patients diagnosed with early breast cancer

BACKGROUND

The prognostic potential of HER2, TP53 mutations, PAI-1 protein levels, angiogenesis and proliferation were investigated in tumours from 408 patients with early breast cancer followed >10 years. One hundred and sixty seven patients (41%) died from breast cancer.

MATERIALS AND METHODS

Tumour sections were stained for HER2, CD34, and MIB-1. HER2 scores were based on staining intensity, 3+ being considered HER2+. Angiogenesis was scored by the Chalkley method. MIB-1 was evaluated using systematic random sampling. PAI-1 was measured by ELISA. TP53 mutations were evaluated by DGGE analysis and DNA sequencing.

RESULTS

Ninety one patients (22%) were HER2 positive. TP53 was mutated in 101 cases (25%). Median PAI-1, Chalkley and MIB-1 was 0.72 ng/mg protein (range, 0-90 ng/mg protein), 5.00 (range, 2.67-12.00) and 15% (range, 1-83%). MIB-1 was correlated with HER2+, Chalkley counts, TP53 mutations (all p <0.0001), and PAI-1 (p =0.002). In univariate analyses with DSS as endpoint, HER2+ (p <0.0001), mutated TP53 (p <0.0001), high Chalkley (p =0.008), MIB-1 (p =0.002), tumour size (p =0.008), grade (p <0.0001), negative estrogen receptor (p =0.0001), and lymph node status (p <0.0001) were prognostic markers. Among node-negative patients, HER2+ (p =0.0002), mutated TP53 (p =0.001), high PAI-1 levels (p =0.02), and grade (p =0.03) indicated poor DSS. In node-positive patients, HER2+ (p =0.0002), mutated TP53 (p <0.0001), MIB-1 (p =0.01), Chalkley scores (p =0.007), negative estrogen receptor (p <0.0001) and grade (p =0.001) indicated poor prognosis. In multivariate analysis, metastatic nodes (1-3 positive: RR 1.56 95% CI 1.02-2.38; >3 positive: RR 3.70 95% CI 2.54-5.38), HER2+ (RR 1.91, 95% CI 1.35-2.70), mutated TP53 (RR 1.70, 95% CI 1.21-2.38), PAI-1 (RR 1.04, 95% CI 1.01-1.07) and grade 3 (RR 1.96, 95% CI 1.83-3.22) were independent markers of poor outcome.

CONCLUSION

Compared to PAI-1 protein levels, Chalkley counts and MIB-1, HER2+ and mutations of TP53 were the strongest independent markers of poor prognosis irrespective of nodal status.

The plasminogen activator inhibitor "paradox" in cancer

Proteolysis in general and specifically the plasminogen activating system regulated by urokinase (uPA) its specific receptor, the GPI membrane anchored urokinase receptor (uPAR) and the specific plasminogen activator inhibitor 1 (PAI-1) plays a major role in tumorigenesis, tumor progression, tumor invasion and metastasis formation. This is exemplified by a body of published work showing a positive correlation between the expression of uPA or uPAR in several tumors and their malignancy. It is generally assumed that such a "pro-malignant" effect of the uPA-uPAR system is mediated by increased local proteolysis thus favoring tumor invasion, by a pro-angiogenic effect of this system and also by uPA-uPAR signaling towards the tumor thereby shifting the tumor phenotype to a more "malignant" one. However, when tumor patients are analyzed for long term survival, those with high levels of the inhibitor of the system, PAI-1 have a much worse prognosis than those with lower PAI-1 levels. This indicates that increased overall proteolysis alone cannot be made responsible for the adverse effects of the plasminogen activating system in tumors. Moreover, it becomes increasingly evident that components of the fibrinolytic system secreted by the tumor cells themselves are not solely responsible for a correlation between the plasminogen activating system and tumor malignancy; components of the plasminogen activating system secreted by stroma cells or cells of the immune system such as macrophages contribute also to the impact of fibrinolysis on malignancy. This review summarizes the evidence for the role of plasminogen activator inhibitor-1 in mediating the malignant phenotype and possible mechanism thereby trying to explain the "PAI-1 paradox in cancer" on a molecular level.