Overexpression of Urinary Plasminogen Activator (uPA) Protein and mRNA in Thyroid Carcinogenesis

Emerging molecular markers for the prognosis of differentiated thyroid cancer patients

Epithelial thyroid cancers are represented by the differentiated papillary and follicular thyroid carcinomas which, following dedifferentiation, are thought to give rise to the highly aggressive and incurable anaplastic thyroid carcinomas. Although derived from the same cell type, the different thyroid tumors show specific histological features, biological behavior and degree of differentiation as a consequence of different genetic alterations. Over the last few years, our knowledge regarding the molecular alterations underlying thyroid cell malignant transformation and cancer progression has considerably increased; however, the prognosis of differentiated thyroid cancer patients still relies on high-risk clinic-pathological variables. In particular, the actual staging systems provides only a rough prediction for cancer mortality and risk of recurrences, including in each risk group patients with highly different tumor-specific progression, disease-free interval and survival time. In order to improve DTC patient's risk stratification, both the European and the American Thyroid Associations proposed practical guidelines to integrate the actual staging systems with additional clinical features such as the tumor histological variant, the results of post-ablative whole body scan and the serum thyroglobulin levels. Despite that, patients within the same risk group still show a very heterogeneous behavior in terms of disease-free interval. As a consequence, the identification of new prognostic molecular biomarkers able to testify tumor aggressiveness is highly required. Here we'll review recently characterized new molecular markers potentially able to ameliorate the prognosis in DTC patients.

Involvement of urokinase-type plasminogen activator system in cancer: an overview

Currently, there are several studies supporting the role of urokinase-type plasminogen activator (uPA) system in cancer. The association of uPA to its receptor triggers the conversion of plasminogen into plasmin. This process is regulated by the uPA inhibitors (PAI-1 and PAI-2). Plasmin promotes degradation of basement membrane and extracellular matrix (ECM) components as well as activation of ECM latent matrix metalloproteases. Degradation and remodeling of the surrounding tissues is crucial in the early steps of tumor progression by facilitating expansion of the tumor mass, release of tumor growth factors, activation of cytokines as well as induction of tumor cell proliferation, migration, and invasion. Hence, many tumors showed a correlation between uPA system component levels and tumor aggressiveness and survival. Therefore, this review summarizes the structure of the uPA system, its contribution to cancer progression, and the clinical relevance of uPA family members in cancer diagnosis. In addition, the review evaluates the significance of uPA system in the development of cancer-targeted therapies.

Urokinase plasminogen activator and its inhibitor type-1 as prognostic factors in differentiated thyroid carcinoma patients

OBJECTIVE

To investigate the prognostic value of urokinase-type plasminogen activator (uPA) and its inhibitor, type-1 plasminogen activator inhibitor (PAI-1), in differentiated thyroid cancer.

STUDY DESIGN

Prospective cohort study.

SETTING

University hospital.

SUBJECTS AND METHODS

Cytosolic concentrations of uPA and PAI-1 were determined in 105 patients with differentiated thyroid carcinoma and normal matched tissues using an enzyme-linked immunoassay (ELISA).

RESULTS

Both uPA and PAI-1 concentrations were significantly higher in differentiated thyroid tumors (uPA = 0.509 ± 0.767 and PAI-1 = 6.337 ± 6.415 ng/mg) compared to normal tissues (uPA = 0.237 ± 0.051, P < .001; PAI-1 = 2.368 ± 0.418 ng/mg, P < .001). uPA and PAI-1 were significantly higher if extrathyroidal invasion (uPA, P = .015; PAI-1, P < .001) or distant metastasis (PAI-1 P < .001) was present, as well as in tumors whose size exceeded 1 cm in diameter (uPA, P = .002; PAI-1, P = .001). Survival analysis revealed the significant impact of both uPA and PAI-1 on progression-free survival (PFS) (82.22 vs 49.478 months for patients with low and high uPA, respectively, P < .001; 87.068 vs 44.964 months for patients with low and high PAI-1, respectively, P < .001). Univariate analysis showed that gender, tumor size, tumor grade, extrathyroid invasion, local lymph node involvement, distant metastasis, uPA, and PAI-1 were significant predictors of PFS. However, multivariate analysis identified only distant metastasis and tumor tissue uPA and PAI-1 as independent prognostic factors.

CONCLUSION

These findings indicate that high uPA and PAI-1 levels represent independent unfavorable prognostic factors in patients with differentiated thyroid carcinoma.

Clinical utility of level-of-evidence-1 disease forecast cancer biomarkers uPA and its inhibitor PAI-1

The prognostic and/or predictive value of the cancer biomarkers, urokinase-type plasminogen activator (uPA) and its inhibitor (plasminogen activator inhibitor [PAI]-1), determined by ELISA in tumor-tissue extracts, was demonstrated for several cancer types in numerous clinically relevant retrospective or prospective studies, including a multicenter breast cancer therapy trial (Chemo-N0). Consequently, for the first time ever for any cancer biomarker for breast cancer, uPA and PAI-1 have reached the highest level of evidence, level-of-evidence-1. At present, two other breast cancer therapy trials, NNBC-3 and Plan B, also incorporating uPA and PAI-1 as treatment-assignment tools are in effect. Furthermore, small synthetic molecules targeting uPA are currently in Phase II clinical trials in patients afflicted with advanced cancer of the ovary, breast or pancreas.

Clinical and molecular features of papillary thyroid cancer in adolescents and young adults

BACKGROUND

Age disparities in thyroid cancer incidence and outcome among adolescents and young adults (AYAs) with thyroid cancer are under reported. In this study, the authors compared the molecular and clinical features of papillary thyroid cancer (PTC) in AYAs with the same features among patients in other age groups.

METHODS

One thousand eleven patients underwent initial treatment for PTC at the University of California at San Francisco. Patients were subdivided into 2 age groups: ages 15 to 39 years (the AYA group) and aged ≥40 years. Demographic, clinical, and survival data in the cohort also were compared with data from the National Cancer Instsitute's Surveillance, Epidemiology, and End Results (SEER) Program. In a subset of the study cohort, the primary tumors were analyzed by genome-wide expression analyses, genotyping for common somatic mutations, and pathway-specific gene expression arrays between the age groups.

RESULTS

The percentage of women and the lymph node metastasis rate were significantly higher in the AYA group. In the AYA group, the rate of distant metastasis was lower. Disease-free survival and median overall survival were significantly higher in the AYA group. The better survival in AYA patients also was apparent in the national SEER data. An unsupervised cluster analysis of gene expression data revealed no distinct clustering by age in 96 PTC samples. The frequency and type of somatic mutations in the primary tumors did not differ significantly between age groups (the AYA group vs the group aged ≥40 years). Six genes (extracellular matrix protein 1 [ECM1], v-erb-2 erythroblastic leukemia viral oncogene homolog 2 [ERBB2], urinary plasminogen activator [UPA], 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 2 [PFKFB2], meis homeobox 2 [MEIS2], and carbonic anhydrase II [CA2]) had significant differential expression between age groups.

CONCLUSIONS

The extent of disease at presentation and the survival of patients with PTC differed between AYAs and older patients. The current results indicated that these differences may be caused by several candidate genes and that these genes are expressed differentially and may play an important role in tumor cell biology. However, no distinct gene expression profiles exist for patients with PTC that distinguish between AYAs and patients aged ≥40 years.

Secretome-based identification and characterization of potential biomarkers in thyroid cancer

In search of thyroid cancer biomarkers, proteins secreted by thyroid cancer cell lines, papillary-derived TPC-1 and anaplastic-derived CAL62, were analyzed using liquid chromatography-tandem mass spectrometry. Of 46 high-confidence identifications, 6 proteins were considered for verification in thyroid cancer patients' tissue and blood. The localization of two proteins, nucleolin and prothymosin-α (PTMA), was confirmed in TPC-1 and CAL62 cells by confocal microscopy and immunohistochemically in xenografts of TPC-1 cells in NOD/SCID/γ mice and human thyroid cancers (48 tissues). Increased nuclear and cytoplasmic expression of PTMA was observed in anaplastic compared to papillary and poorly differentiated carcinomas. Nuclear expression of nucleolin was observed in all subtypes of thyroid carcinomas, along with faint cytoplasmic expression in anaplastic cancers. Importantly, PTMA, nucleolin, clusterin, cysteine-rich angiogenic inducer 61, enolase 1, and biotinidase were detected in thyroid cancer patients' sera, warranting future analysis to confirm their potential as blood-based thyroid cancer markers. In conclusion, we demonstrated the potential of secretome analysis of thyroid cancer cell lines to identify novel proteins that can be independently verified in cell lines, xenografts, tumor tissues, and blood samples of thyroid cancer patients. These observations support their potential utility as minimally invasive biomarkers for thyroid carcinomas and their application in management of these diseases upon future validation.

Inhibition of uPAR and uPA reduces invasion in papillary thyroid carcinoma cells

OBJECTIVES/HYPOTHESIS

We analyzed the expression of urokinase plasminogen activator (uPA) and its receptor (uPAR) in papillary thyroid carcinoma (PTC) and normal thyroid tissue and examined in vitro how uPA and uPAR contribute to an invasive/metastatic phenotype, and the functional consequences of inhibiting this system.

STUDY DESIGN

Retrospective chart review of PTC patients, followed by prospective study using previously obtained patient tissue and PTC cellular models.

METHODS

uPA and uPAR RNA and protein levels were analyzed in PTC patient tissue samples, PTC and normal thyroid tissue culture cells, and conditioned media (CM) using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and/or Western blotting. The plasminogen-activating ability of CM was examined using dark-quenched casein fluorimetry and casein-plasminogen gel zymography. The invasive potentials of the PTC and normal thyroid epithelial cell lines were assessed using an in vitro cellular invasion/migration system.

RESULTS

uPA and uPAR RNA and protein levels were increased in PTC patient samples and PTC cells relative to controls. uPA and uPAR RNA were also significantly higher in patients with metastatic disease. Casein-plasminogen zymography and Western blotting demonstrated increased active uPA secreted by PTC cells compared with normal thyroid cells. Fluorimetric assays revealed that the PTC cells' CM was able to activate plasminogen, resulting in measurable casein hydrolysis. This casein hydrolysis was prevented by the addition of several specific uPA inhibitors. Finally, the in vitro invasion phenotypes of PTC cells were augmented by the addition of plasminogen, and this augmentation was reversed by inhibitory anti-uPA and anti-uPAR antibodies.

CONCLUSIONS

These data provide new functional evidence of the uPA/uPAR system's role in PTC invasion/metastasis and demonstrate the attractiveness of uPA and uPAR as molecular biomarkers and therapeutic targets.

Inhibitory effects of retinoic acid on invasiveness of human thyroid carcinoma cell lines in vitro

BACKGROUND

The prognosis of patients with metastasized thyroid carcinoma is not optimistic, necessitating the search for new treatment options.

AIM

Beneficial effects of retinoic acid (RA) have been suggested in thyroid cancer differentiation and the present study was performed to investigate the anti-metastatic potential of RA in respect of important determinants of metastatic behavior in thyroid carcinoma, focusing on the role of invasion-associated proteins.

MATERIALS AND METHODS

Differentiated thyroid carcinoma cell lines FTC- 133 and XTC.UC1, and anaplastic thyroid cancer cell lines C643 and HTH74 were studied. All cell lines were cultured with alltrans- RA (ATRA) or the solvent ethanol. Invasion and adhesion potency in vitro was studied by transwell experiment and short-term adhesion assay. The involvement of invasion-associated proteins, urokinase type plasminogen activator (uPA), uPA receptor (uPAR), matrix metalloproteinase-2 (MMP-2) and E-cadherin, were investigated by semi-quantitative RT-PCR and Western blot.

RESULTS

In vitro invasion assay revealed that ATRA treatment could reduce the invasive potency in all the thyroid cancer cell lines, with the most significant effect in anaplastic cancer cells. Short-term adhesion assay suggested that ATRA increases cancer cell adhesion to extracellular matrix (ECM) in C643, HTH74 and XTC.UC1, probably through a transcriptional and translational regulation of some attachment molecules. RT-PCR andWestern blot both revealed diminished expression of uPAR in all four carcinoma cell lines. In C643 and HTH74 cell lines, the expression of uPA was reduced and the expression of E-cadherin was increased, whereas the MMP-2 expression was not significantly down-regulated in ATRA-treated group. In ATRA-treated FTC-133 and XTC.UC1 cell lines, MMP-2 expression was decreased, but no significant changes in uPA and E-cadherin expression were observed.

CONCLUSIONS

The present study demonstrates the influence of ATRA on both important determinants of metastatic behavior ("de-adhesion" and proteolysis) in thyroid carcinoma cell lines, especially in anaplastic cancer cells. These findings may add to the explanations for beneficial effects of RA in the treatment of metastatic thyroid carcinomas.

What is New on Thyroid Cancer Biomarkers

Thyroid cancer harbours in about 5% of thyroid nodules. The majority of them are well-differentiated cancers originating from the follicular epithelium, and are subdivided into papillary and follicular carcinomas. Undifferentiated carcinomas and medullary thyroid carcinomas arising from C cells are less common.

Although most thyroid nodules are benign, distinguishing thyroid cancer from benign lesions is crucial for an appropriate treatment and follow-up. The fine needle aspiration cytology (FNAC) allows the diagnosis of nature of thyroid nodules in the majority of cases. However, FNAC has some limitations, particularly in the presence of follicular lesions which can appear dubious in rare instances even at histology.

In an effort to improve diagnostic accuracy and offer new prognostic criteria, several immunohistochemical and molecular markers have been proposed. However, most of them have to be validated on large series before being used in routine practice.

Urokinase-type plasminogen activator and its inhibitor in thyroid neoplasms: a cytosol study

PURPOSE

Higher levels of urokinase-type plasminogen activator (uPA) and its inhibitor (PAI-1) are linked to the poor prognosis in a variety of malignances. uPA and PAI-1 were expressed in most thyroid carcinomas, as had been measured immunohistochemically. However, no relationship between their expression and clinicopathological parameters were found. Aim of the present study was to investigate the expression and clinical relevance of uPA and PAI-1 in thyroid cancer.

PATIENTS AND METHODS

uPA and PAI-1 in paired cytosol samples of thyroid tumor and normal tissue were determined in 23 patients using enzyme-linked immunosorbent assay and correlated to the known prognostic features.

RESULTS

Both uPA and PAI-1 concentrations were significantly higher in malignant thyroid tumors (uPA=1.342 +/- 2.944 and PAI-1=17.615 +/- 31.933 ng/mg protein) than in normal tissue (uPA=0.002 +/- 0.009, P=0.011 and PAI-1=2.333 +/- 0.338 ng/mg protein, P=0.001) with positive correlation of the two proteins in the tumors. There were no differences in proteins' levels between benign tumors and normal tissue. Both proteins' concentrations were significantly different among various histological grades (uPA P=0.024 and PAI-1 P=0.017), showing higher values in higher tumor grades (grade I uPA=0.116 +/- 0.247 and PAI-1=4.802 +/- 4.151 ng/mg protein; grade III uPA=8.45 +/- 2.192 and PAI-1=94.65 +/- 59.468 ng/mg protein). The uPA and PAI-1 levels showed significant differences among different histological types of thyroid cancer (uPA P=0.049 and PAI-1=0.017). The lowest values were in adenomas (uPA=0.013 +/- 0.025 and PAI-1=2.785 +/- 1.069 ng/mg protein) and the highest in anaplastic carcinomas (uPA=8.45 +/- 2.192 and PAI-1=94.65 +/- 59.468 ng/mg protein). uPA and PAI-1 were significantly higher in anaplastic vs. well-differentiated cancers (uPA P=0.014 and PAI-1 P=0.026), if extrathyroidal invasion (uPA P=0.019 and PAI-1 P=0.009) or distant metastases (uPA P=0.006 and PAI-1 P=0.003) had been present, and in tumors whose size exceeded 1 cm in diameter (uPA P=0.009 and PAI-1 P=0.035). Only PAI-1, but not uPA was significantly higher in multicentric vs. solitary tumors (P=0.012) and lymph node positive compared to lymph node negative patients (P=0.042). The differences of uPA and PAI-1 did not reach the significant level when patients with well-differentiated tumors below and above 40 years of age had been compared. Survival analysis revealed the significant impact of both uPA and PAI-1 on the Progression-Free Survival (PFS) (38.84 vs. 3.67 months for patients with low and high uPA, respectively, P<0.001; 38.2 vs. 12 months for patients with low and high PAI-1, respectively, P=0.016).

CONCLUSIONS

The correlation of high uPA and PAI-1 with the known prognostic factors of poorer outcome and with lower PFS rate in patients with thyroid cancers proved that these proteins could be an additional prognostic parameter.

Amplification of the urokinase gene and the sensitivity of prostate cancer cells to urokinase inhibitors

OBJECTIVES

To evaluate the frequency of the urokinase-type plasminogen activator (uPA) gene amplification and the sensitivity of prostate cancer cells to uPA inhibition, as we previously found one hormone-refractory prostate tumour with high-level amplification of the uPA (alias PLAU) gene, and also showed that a uPA inhibitor, amiloride, can effectively reduce the invasion potential of the PC-3 prostate cancer cell line.

MATERIALS AND METHODS

Sixty-three locally recurrent hormone-refractory tumours and 78 hormone-refractory metastases from 29 patients who died from prostate cancer were analysed for uPA gene-copy number using fluorescence in situ hybridization. The Matrigel invasion assay was used to study the influence of uPA inhibitors on the invasive potential of prostate cancer cell lines.

RESULTS

Of the locally recurrent hormone-refractory tumours, 21% had an increased copy number of uPA, but no high-level amplifications were found; 31% of the metastases had increased copy number and one high-level amplification of the uPA. Matrigel invasion assays with two specific uPA inhibitors, B428 and p-aminobenzamidine, showed that invasion of a prostate cancer cell line containing uPA gene amplification was inhibited by these small-molecule uPA inhibitors, while invasion of prostate cell lines without uPA gene amplification were not.

CONCLUSION

These results suggest that selective inhibition of the uPA pathway in individuals whose tumours contain uPA gene amplification may provide therapeutic benefit.

A plasminogen-like protein, present in the apical extracellular environment of thyroid epithelial cells, degrades thyroglobulin in vitro

The prothyroid hormone, thyroglobulin (Tg), is stored at high concentrations in the thyroid follicular lumen as a soluble 19S homo-dimer and as heavier soluble (27S and 37S) and insoluble (Tgm) forms. Follicular degradation of Tg may contribute to maintaining Tg concentrations compatible with follicle integrity. Here, we report on the presence of a plasminogen-like protein in the follicular lumen of normal human thyroids and its synthesis and apical secretion by cultured epithelial thyroid cells. Since all the main luminal forms of Tg are cleaved by this plasminogen-like protein, we suggest that it contributes to Tg degradation in the follicular lumen.