Plasminogen activator inhibitor,
type 1 (PAI-1)

Plasminogen activator inhibitor, beta-migrating endothelial-cell-derived type
PLANH1

Gene: PLANH1 maps to 7q21-q22. It covers approximately 12.2 kb and consists of 9 exons and 8 introns. An enhancer-like glucocorticoid responsive element within the PLANH1 regions between nucleotides -305 and 75 has been found (van Zonneveld A.J. et al., 1988).
mRNA: 2 distinct species, with sizes of approximately 2.0 kb. They arise by alternative polyadenylation.
Protein: 402 amino acids. Interacts with- and inhibits both tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA).

Cell lines:
- Using breast cancer cell (BCC) lines, it has been suggested that 12-O-tetradecanoylphorbol-13-acetate-responsive in vitro invasive properties that are probably associated with PAI-1 expression may co-vary with progression from hormone-dependent to -independent breast cancer (Ree A.H. et al., 1998).

- tPA activity of MCF-7 BCC treated with estradiol (E₂, 10 nM) was 3-fold higher, that of cells cultured on laminin and treated with E₂ was 15-fold higher, than that of control. Northern-blot analysis showed that tPA mRNA levels were up-regulated by E₂ and laminin, whereas PAI-1 mRNA levels were down-regulated by laminin and not affected by E₂. Concomitant treatment with laminin and E₂ decreased PAI-1 mRNA and increased tPA mRNA levels, accounting for the synergistic increase in tPA activity (Sonohara S. et al., 1998).

- In MDA-MB-231 BCC, TGF-beta1 was shown to increase uPA activity and PAI-1 antigen level (Dong-Le Bourhis X. et al., 1998).

Tumors:
- The concentrations of cathepsin D, uPA, PAI-1, and PAI-2 were analysed in the cytosols of 43 benign and 87 malignant mammary tumors. The mean levels of these markers were significantly higher in malignant tumors than in benign tumors. The increases were about 4-, 5-, 74-, and 29-fold, respectively. PAI-1 was decreased in ER-positive and PgR-positive tumors. When cathepsin D, uPA, PAI-1, and PAI-2 levels in malignant tumors were compared, positive correlations were found for all combinations (Foucré D. et al., 1991).

- In a study of breast tumors from 118 pre- and 72 postmenopausal high-risk patients, the levels of uPA and PAI-1 were strongly correlated. High PAI-1 level was associated with grade of anaplasia in premenopausal patients and with number of tumor-positive lymph nodes in postmenopausal patients. A high PAI-1 level was also associated with low ER and PgR levels in both pre- and postmenopausal patients (Grøndahl-Hansen J. et al., 1993).

- uPA, its receptor uPAR, and PAI-1 were measured in breast cancer cytosol from 111 low-risk premenopausal patients and 184 low-risk postmenopausal patients with a median follow-up of 6.0 years. uPA, uPAR, and PAI-1 levels were all weakly but significantly correlated with each other in both menopausal groups. There were no significant differences in the median levels of uPA, uPAR, and PAI-1 between premenopausal and postmenopausal patients. High levels of tumor cytosolic PAI-1 were significantly associated with short recurrence-free survival in both menopausal groups and short overall survival in postmenopausal patients (Grøndahl-Hansen J. et al., 1997).

- A series of breast cancer tissue specimens was analysed using in situ hybridization and immunohistochemistry. Urokinase-type plasminogen activator (u-PA) mRNA was detected in cancer cells and fibroblasts adjacent to them and its expression was found to be more intense in invasive than in intraductal regions. In invasive but not in intraductal regions, especially those with abundant stroma, plasminogen activator inhibitor-1 (PAI-1) mRNA was observed in cancer cells, fibroblasts, macrophages, and endothelial cells, and PAI-2 mRNA was present in cancer cells, and fibroblasts, macrophages, and lymphocytes around them. These PAI-1- and PAI-2-positive cancer cells were localized at the periphery of the invasive front. Immunohistochemistry yielded basically similar results. A retrospective study of surgically resected breast cancers from 73 patients revealed significant clinical differences associated with u-PA and PAI-2 expression in cancer cells, associated with a poor and a good prognosis, respectively (Umeda T. et al., 1997).

- In a retrospective study of 429 primary breast cancer patients (median follow-up of 5.1 years), the levels of uPA and PAI-1 in tumour extracts were analysed by means of an enzyme-linked immunosorbent assay. Patients with high content of either uPA or PAI-1 had increased risk of relapse and death. An independent ability of PAI-1 to predict distant metastasis was demonstrated (Knoop A. et al., 1998).

- In a study of 152 breast cancer samples, no significant relationship was found between either of the nm23 isoforms (nm23-H1 and nm23-H2) and PAI-1 (Russell R.L. et al., 1998).

- It has been suggested that uPA family members, including PAI-1, and sex steroid receptors may be measured in the same cytosol fraction from breast tumor homogenates (Descotes F. et al., 1998).

- In a prospective study of 130 patients with node-negative invasive breast cancer who underwent radical operation (the median follow-up was 52.6 months), patients with high u-PA, high PAI-1, or low t-PA had significantly higher relapse rates than did those with low u-PA, low PAI-1, or high t-PA, respectively, by the Kaplan-Meier method (P = 0.006, 0.032, and 0.028, respectively). Analyses of the combinations of both u-PA and PAI-1 or both u-PA and t-PA showed that the differences in relapse rate between the high- and low-risk groups were statistically very significant. In the univariate analysis, u-PA, PAI-1, t-PA, progesterone receptor, and tumor size (T3 versus T1) were significantly correlated with relapse. However, the multivariate analysis revealed that only u-PA (P = 0.023) was an independent prognostic factor (Kim S.J. et al., 1998).

- PAI-1 protein and mRNA (determined by RT-PCR) levels were found to be significantly correlated in a series of 37 breast tumors. The mRNA expression of PAI-1 was not associated with the mRNA levels for ER, PgR, and pS2 in a series of 100 breast tumors. PAI-1 was also found to be independent of tumor size, grade, and lymph node involvement (Tong D. et al., 1999).

- uPA and PAI-1 were measured by ELISA in samples derived from 892 patients with primary breast cancer (median follow-up 99 months). The assays were performed in cytosolic extracts as well as in corresponding detergent extracts of pellets obtained after ultracentrifugation, which was carried out when preparing the cytosolic fractions for routine steroid hormone receptor determination. High cytosolic levels of uPA or PAI-1 were significantly associated with increased rates of relapse and death. The levels of uPA and PAI-1 in the pellet extracts also provided prognostic information, although to a lesser extent compared with the cytosolic extracts (de Witte J.H. et al., 1999).

- Comparison of immunohistochemistry with immunoassay (ELISA) for the detection of uPA, tPA, PAI-1 and uPAR in a compound group consisting of 33 cancer lesions of various origin, including breast, concluded that that the two techniques are not directly interchangeable and that their value for clinical purposes may be different (Ferrier C.M. et al., 1999).

- An ELISA has been described for the assessment of complexes between the urokinase-type (uPA) and the tissue-type plasminogen (tPA) activators with their inhibitor type-1 (PAI-1) in cell-culture medium and cytosolic extracts of breast tumours (Grebenschikov N. et al., 1999). - PAI-1 was found to remain a strong and independent prognostic factor in node-negative breast cancer after extended 6-year median follow-up (Harbeck N. et al., 1999a). PAI-1 levels in the primary tumor were also a significant prognostic marker for survival after first relapse (Harbeck N. et al., 1999b).

- A kinetic sandwich format immunoassay for specific quantification of the uPA:PAI-1 complex was developed, validated, and applied to plasma from 19 advanced-stage breast cancer patients, 39 age-matched healthy women, and 31 men. 18 cancer patients had a measurable complex concentration (median, 68 ng/L; range, <16 to 8700 ng/L), whereas for healthy females and males the median signal values were below the detection limit (median, <16 ng/L; range, <16 to 200 ng/L; P <0.0001). For patient plasma, a comparison with total uPA and PAI-1 showed that the complex represented a variable, minor fraction of the uPA and PAI-1 concentrations of each sample (Pedersen A.N. et al., 1999).

Descotes F. et al. (1998) Tissue extraction procedures for investigation of urokinase plasminogen activator (uPA) and its inhibitors PAI-1 and PAI-2 in human breast carcinomas. Breast Cancer Res. Treat. 49, 135-143.
de Witte J.H. et al. (1999) Prognostic impact of urokinase-type plasminogen activator (uPA) and its inhibitor (PAI-1) in cytosols and pellet extracts derived from 892 breast cancer patients. Br. J. Cancer 79, 1190-1198.
Dong-Le Bourhis X. et al. (1998) Transforming growth factor beta 1 and sodium butyrate differentially modulate urokinase plasminogen activator and plasminogen activator inhibitor-1 in human breast normal and cancer cells. Br. J. Cancer 77, 396-403.
Ferrier C.M. et al. (1999) Comparison of immunohistochemistry with immunoassay (ELISA) for the detection of components of the plasminogen activation system in human tumour tissue. Br. J. Cancer 79, 1534-1541.
Foucré D. et al. (1991) Relationship between cathepsin D, urokinase, and plasminogen activator inhibitors in malignant vs benign breast tumours. Br. J. Cancer 64, 926-932.
Ginsburg D. et al. (1986) cDNA cloning of human plasminogen activator-inhibitor from endothelial cells. J. Clin. Invest. 78, 1673-1680.
Grebenschikov N. et al. (1999) ELISA for complexes of urokinase-type and tissue-type plasminogen activators with their type-1 inhibitor (uPA-PAI-1 and tPA-PAI-1). Int. J. Cancer 81, 598-606.
Grøndahl-Hansen J. et al. (1993) High levels of urokinase-type plasminogen activator and its inhibitor PAI-1 in cytosolic extracts of breast carcinomas are associated with poor prognosis. Cancer Res. 53, 2513-2521.
Grøndahl-Hansen J. et al. (1997) Plasminogen activator inhibitor type 1 in cytosolic tumor extracts predicts prognosis in low-risk breast cancer patients. Clin. Cancer Res. 3, 233-239.
Harbeck N. et al. (1999a) Risk-group discrimination in node-negative breast cancer using invasion and proliferation markers: 6-year median follow-up. Br. J. Cancer 80, 419-426.
Harbeck N. et al. (1999b) Invasion marker PAI-1 remains a strong prognostic factor after long-term follow-up both for primary breast cancer and following first relapse. Breast Cancer Res. Treat. 54, 147-157.
Kim S.J. et al. (1998) Prognostic impact of urokinase-type plasminogen activator (PA), PA inhibitor type-1, and tissue-type PA antigen levels in node-negative breast cancer: a prospective study on multicenter basis. Clin. Cancer Res. 4, 177-182.
Knoop A. et al. (1998) Prognostic significance of urokinase-type plasminogen activator and plasminogen activator inhibitor-1 in primary breast cancer. Br. J. Cancer 77, 932-940.
Pedersen A.N. et al. (1999) Determination of the complex between urokinase and its type-1 inhibitor in plasma from healthy donors and breast cancer patients. Clin. Chem. 45, 1206-1213.
Ree A.H. et al. (1998) Regulation of tissue-degrading factors and in vitro invasiveness in progression of breast cancer cells. Clin. Exp. Metastasis 16, 205-215.
Russell R.L. et al. (1998) Relationship of nm23 to proteolytic factors, proliferation and motility in breast cancer tissues and cell lines. Br. J. Cancer 78, 710-717.
Schwartz C.E. et al. (1991) Deletion mapping of plasminogen activator inhibitor, type I (PLANH1) and beta-glucuronidase (GUSB) in 7q21-q22. Cytogenet. Cell Genet. 51, 152-153.
Sonohara S. et al. (1998) Laminin and estradiol regulation of the plasminogen-activator system in MCF-7 breast-carcinoma cells. Int. J. Cancer 76, 77-85.
Tong D. et al. (1999) Messenger RNA determination of estrogen receptor, progesterone receptor, pS2, and plasminogen activator inhibitor-1 by competitive reverse transcription-polymerase chain reaction in human breast cancer. Clin. Cancer Res. 5, 1497-1502.
Umeda T. et al. (1997) Cellular localization of urokinase-type plasminogen activator, its inhibitors, and their mRNAs in breast cancer tissues. J. Pathol. 183, 388-397.
van Zonneveld A.J. et al. (1988) Type 1 plasminogen activator inhibitor gene: functional analysis and glucocorticoid regulation of its promoter. Proc. Nat. Acad. Sci. USA 85, 5525-5529.

Plasminogen activator inhibitor, type 2 (PAI-2), tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPA)