Aberrant expression of receptors for platelet-derived growth factor in an anaplastic thyroid carcinoma cell line

Relaxin-2 is a novel biomarker for differentiated thyroid carcinoma in humans

Relaxin's role in differentiated thyroid cancer (DTC) has been suggested but its characterization in a large clinical sample remains limited. We performed immunohistochemistry for relaxin-2 (RLN2), CD68 (total macrophages), CD163 (M2 macrophages) on tissue microarrays from 181 subjects with non-distant metastatic DTC, and 185 subjects with benign thyroid tissue. Mean pixels/area for each marker was compared between tumor and adjacent tissue via paired-t test and between DTC and benign subjects via t-test assuming unequal variances. RNA qPCR was performed for expression of RLN2, RLN1, and RXFP1 in cell lines. Amongst 181 cases, the mean age was 46 years, 75 % were females. Tumoral tissue amongst the DTC cases demonstrated higher mean expression of RLN2 (53.04 vs. 9.79; p < 0.0001) compared to tumor-adjacent tissue. DTC tissue also demonstrated higher mean expression of CD68 (14.46 vs. 4.79; p < 0.0001), and CD163 (23.13 vs. -0.73; p < 0.0001) than benign thyroid. These markers did not differ between tumor-adjacent and benign thyroid tissue groups; and amongst cases, did not differ by demographic or clinicopathologic features. RLN1 and RXFP1 expression was detected in a minority of the cell lines, while RLN2 was expressed by 6/7 cell lines. In conclusion, widespread RLN2 expression in DTC tissue and most cell lines demonstrates that RLN2 acts in a paracrine manner, and that RLN1 and RXFP1 are probably not involved in thyroid cancer cell signaling. RLN2 is a biomarker for thyroid carcinogenesis, being associated with but not secreted by immunosuppressive macrophages. These findings will guide further investigations for therapeutic avenues against thyroid cancer.

Anaplastic Thyroid Carcinoma: Current Issues in Genomics and Therapeutics

PURPOSE OF REVIEW

Anaplastic thyroid carcinoma is a type of thyroid carcinoma with the most aggressive biological behaviour amongst thyroid cancer. Here, we review the current genomic and the impacts of advances in therapies to improve the management of patients with the cancer.

RECENT FINDINGS

Common mutations being identified in anaplastic thyroid carcinoma are p53 and TERT promoter mutations. Other common mutated genes included BRAF, RAS, EIF1AX, PIK3CA, PTEN and AKT1, SWI/SNF, ALK and CDKN2A. Changes in expression of different microRNAs are also involved in the pathogenesis of anaplastic thyroid carcinoma. Curative resection combined with radiotherapy and combination chemotherapies (such as anthracyclines, platins and taxanes) has been shown to have effects in the treatment of some patients with anaplastic thyroid carcinoma. Newer molecular targeted therapies in clinical trials target mostly the cell membrane kinase and downstream proteins. These include targeting the EGFR, FGFR, VEGFR, c-kit, PDGFR and RET on the cell membrane as well as VEGF itself and the downstream targets such as BRAF, MEK and mTOR. Immunotherapy is also being tested in the cancer. Updated knowledge of genomic as well as clinical trials on novel therapies is needed to improve the management of the patients with this aggressive cancer.

The Role of Vitamin D, Platelet-Derived Growth Factor and Insulin-Like Growth Factor 1 in the Progression of Thyroid Diseases

Background:

Thyroid cancer (TC) is a common malignant tumor, however the role of total vitamin D: 25(OH)D, Platelet Derived Growth Factor (PDGF) and Insulin Like Growth Factor 1 (IGF-1) in the development of TC is still unclear.

Aim:

To assess the roles of 25(OH)D, PDGF and IGF-1 in the progression of thyroid diseases. METHODS: The serum levels of 25(OH)D, PDGF and IGF-1 were assessed in 70 patients with papillary thyroid cancer (PTC), 60 patients with benign thyroid nodules (BN) compared to 60 normal controls (NC) using ELISA technique.

Results:

There was a significant decrease in the serum level of 25(OH)D in TC patients compared to NC (P<0.001) and BN patients (P=0.006). There was a significant increase in the serum levels of PDGF and IGF-1 in TC patients (P<0.001), and BN patients (P<0.001) compared to NC, while there were no significant differences between TC and BN (P=0.087, and 0.258; respectively). PDGF correlated significantly with IGF-1 (r=0.412, P<0.001), TSH (r=0.146, P=0.045), and inversely correlated with 25(OH)D (r= -0.156, P=0.013) and FT4 (r=-0.178, P=0.014). There was a significant inverse correlation between the serum levels of IGF-1 and FT4 (r=-0.172, P=0.017). Sensitivity and specificity for assessment of TC patients were (65.7% and 58.3%, P= 0.001) for 25(OH)D, (65.7% and 58.3%, P=0.021) for IGF-1, and (68.6% and 61.7%, P=0.006) for PDGF. Multivariate analysis demonstrated that serum 25(OH)D (OR=0.578, 95%CI= 0.426-0.783), IGF-1 (OR=1.019, 95%CI= 1.010-1.029) and PDGF (OR=1.007, 95%CI= 1.004-1.009) were considered independent risk factors for thyroid cancer (P<0.001, for all).

Conclusion:

25(OH) D, IGF-1 and PDGF are significantly different in TC and BN cases compared to control. They have an important role in the progression of TC. However, these data should be validated on a larger sample size.

A Systematic Review of Phase II Targeted Therapy Clinical Trials in Anaplastic Thyroid Cancer

Anaplastic thyroid carcinoma (ATC) is a rare, but devastating disease. Despite multimodal approaches combining surgery, chemotherapy and radiation therapy, ATC is associated with a dire prognosis, with a median overall survival of only three to ten months. Novel treatments are thus urgently needed. Recent efforts towards the characterization of the molecular landscape of ATC have led to the identification of pro-oncogenic targetable alterations, lending promise for novel targeted therapeutic approaches. This systematic review summarizes the results of phase II clinical trials of targeted therapy in ATC, providing an overview of efficacy and safety profiles. The majority of trials to date have consisted of small single-arm studies and have presented modest results. However, only a minority of trials have selected or stratified patients by molecular alterations. In the setting of BRAF V600E mutated ATC, dabrafenib/trametinib combination therapy and vemurafenib monotherapy have both demonstrated efficacy. Everolimus has furthermore shown promising results in patients with PI3K/mTOR/AKT pathway alterations. These studies underscore the importance of molecular profiling of tumors for appropriate patient selection and determination of genomic correlates of response. Clinical trials are underway testing additional targeted therapies as monotherapy, or as a part of multimodal treatment, and in combination with immunotherapy.

The BH3 mimetic drug ABT-737 induces apoptosis and acts synergistically with chemotherapeutic drugs in thyroid carcinoma cells

BACKGROUND

Patients with dedifferentiated and anaplastic thyroid carcinomas that do not take up radioiodine are resistant to chemotherapeutic treatment and external irradiation and thus are difficult to treat. Direct induction of apoptosis is a promising approach in these apoptosis-resistant tumor cells. The BH3 mimetic ABT-737 belongs to a new class of drugs that target anti-apoptotic proteins of the BCL-2 family and facilitate cell death. The purpose of this study was to investigate the effect of ABT-737 alone or in combination with chemotherapeutic drugs on thyroid carcinoma cell lines.

METHODS

A total of 16 cell lines derived from follicular, papillary, and anaplastic thyroid carcinomas were treated with ABT-737. Cell viability was measured with MTT assay. Cell death was determined by cell cycle phase distribution and subG1 peak analyses, determination of caspase 3/7 activity and caspase cleavage products, lactate dehydrogenase (LDH) liberation assays and LC3 analysis by western blot.

RESULTS

The number of viable cells was decreased in all cell lines examined after ABT-737 treatment, with IC50 values ranging from 0.73 to 15.6 μM. Biochemical markers of apoptosis like caspase activities, caspase cleavage products and DNA fragmentation determined as SubG1 peak were elevated after ABT-737 treatment, but no LC3 cleavage was induced by ABT-737 indicating no autophagic processes. In combination with doxorubicin and gemcitabine, ABT-737 showed synergistic effects on cell viability.

CONCLUSIONS

With these experiments we demonstrated the efficacy of the BH3 mimetic drug ABT-737 against dedifferentiated thyroid carcinoma cells of various histological origins and showed synergistic effects with chemotherapeutic drugs. ABT-737-treated cells underwent an apoptotic cell death. ABT-737 and related BH3 mimetic drugs, alone or in combination, may thus be of value as a new therapeutic option for dedifferentiated thyroid carcinomas.

Induction of atypical cell death in thyroid carcinoma cells by the indirubin derivative 7-bromoindirubin-3'-oxime (7BIO)

BACKGROUND

The indirubin derivative 7-bromoindirubin-3'-oxime (7BIO) has already shown anticancer properties by causing cell death in some tumour cell lines and may be a new therapeutic option for treatment-resistant tumour cells. Since dedifferentiated and anaplastic thyroid carcinomas do not take up radioiodine and are insensitive to chemotherapeutic treatment and external radiation, direct cell death induction in these tumour cells may be a promising approach. We thus investigated the effect of 7BIO on thyroid carcinoma cell lines of different histological origins and characterized the type of cell death induction by 7BIO.

METHODS

Cell viability was measured with MTT assay. Cell death was analysed by caspase 3/7 activity, lactate dehydrogenase liberation, caspase cleavage products, DNA fragmentation, cell cycle phase distribution and LC3B analysis.

RESULTS

After 7BIO treatment, cell viability was reduced in all 14 thyroid carcinoma cell lines investigated. Treated cells showed DNA fragmentation, cell cycle arrest and lactate dehydrogenase liberation but no LC3B cleavage. Caspase activation following 7BIO treatment was found in five of six cell lines investigated. Interestingly, inhibition of caspases had no effect on viability of the cells after 7BIO incubation.

CONCLUSIONS

Our results indicate that 7BIO efficiently killed dedifferentiated thyroid carcinoma cells. It induced a non-classical kind of cell death that was caspase-independent and includes DNA fragmentation. 7BIO and related indirubin components thus may have value as a new therapeutic option for dedifferentiated thyroid cancer irrespective of the exact target molecules and the kind of cell death they induce.

Cell death induction by the BH3 mimetic GX15-070 in thyroid carcinoma cells

Background

The evasion of cell death is one of the hallmarks of cancer, contributing to both tumor progression and resistance to therapy. Dedifferentiated and anaplastic thyroid carcinomas that do not take up radioiodine are resistant to conventional anticancer treatments and patients with these tumors are difficult to treat. BH3 mimetics are a new class of drugs that target anti-apoptotic proteins of the BCL-2 family and promote cell death. The purpose of this study was to analyze the molecular effects of the BH3 mimetic GX15-070 on thyroid carcinoma cell lines and to characterize cell death induced by GX15-070.

Methods

A total of 17 cell lines derived from follicular, papillary, and anaplastic thyroid carcinomas were treated with GX15-070. Cell viability was measured with MTT assay while cell cycle phase distribution and subG1 peaks were determined after propidium iodide staining. We assessed cell death via the caspase 3/7 activity, caspase cleavage products, lactate dehydrogenase (LDH) liberation assays, and a LC3 analysis by western blot. Ultrastructural changes were analysed by electron microscopy of GX15-070-treated cells.

Results

After GX15-070 treatment, the number of viable cells was decreased in all cell lines examined, with IC50 values ranging from 48nM to 3.25 μM. We observed biochemical markers of autophagic cell death and necrosis like LC3 conversion and LDH release after the GX15-070 treatment. Electron microscopy revealed several common characteristic ultrastructural changes like swelling of mitochondria, dilatation of rough endoplasmic reticulum, membrane blebbing and formation of vacuoles. GX15-070 treatment induced DNA fragmentation detected by subG1-peak induction and an arrest in G1 phase of the cell cycle. Caspase activation after GX15-070 incubation was detected but had no effect on viability of cells.

Conclusions

With these experiments we demonstrated the efficacy of the BH3 mimetic drug GX15-070 acting against dedifferentiated thyroid carcinoma cells of various histological origins by the induction of cell death. GX15-070-treated cells underwent non-classical cell death with signs of apoptosis, autophagy and necrosis in parallel. GX15-07 and related compounds thus may be a new therapeutic option for dedifferentiated thyroid carcinoma of various histological subtypes.

Sorafenib inhibits intracellular signaling pathways and induces cell cycle arrest and cell death in thyroid carcinoma cells irrespective of histological origin or BRAF mutational status

BACKGROUND

Patients with dedifferentiated or anaplastic thyroid carcinomas currently lack appropriate treatment options. Kinase inhibitors are among the most promising new agents as alternative strategies. The BRAF- and multi-kinase inhibitor, sorafenib, has already shown antitumor effects in thyroid carcinoma patients in a phase III clinical trial. In this study we aim to better characterize molecular effects and efficacy of sorafenib against thyroid carcinoma cells with various histological origins and different BRAF mutational status. Analysis of different signaling pathways affected by sorafenib may contribute to assist a more specific therapy choice with fewer side effects. Twelve thyroid carcinoma cell lines derived from anaplastic, follicular and papillary thyroid carcinomas with wildtype or mutationally activated BRAF were treated with sorafenib. Growth inhibition, cell cycle arrest, cell death induction and inhibition of intracellular signaling pathways were then comprehensively analyzed.

METHODS

Cell viability was analyzed by MTT assay, and the cell cycle was assessed by flow cytometry after propidium iodide staining. Cell death was assessed by lactate dehydrogenase liberation assays, caspase activity assays and subG1 peak determinations. Inhibition of intracellular pathways was analyzed in dot blot and western blot analyses.

RESULTS

Sorafenib inhibited proliferation of all thyroid carcinoma cell lines tested with IC50 values ranging between 1.85 and 4.2 μM. Cells derived from papillary carcinoma harboring the mutant BRAF (V600E) allele were slightly more sensitive to sorafenib than those harboring wildtype BRAF. Cell cycle analyses and caspase assays showed a sorafenib-dependent induction of apoptosis in all cell lines, whereas increased lactate dehydrogenase release suggested cell membrane disruption. Sorafenib treatment caused a rapid inhibition of various MAP kinases in addition to inhibiting AKT and receptor tyrosine kinases.

CONCLUSIONS

Sorafenib inhibited multiple intracellular signaling pathways in thyroid carcinoma cells, which resulted in cell cycle arrest and the initiation of apoptosis. Sorafenib was effective against all thyroid carcinoma cell lines regardless of their tumor subtype origin or BRAF status, confirming that sorafenib is therapeutically beneficial for patients with any subtype of dedifferentiated thyroid cancer. Inhibition of single intracellular targets of sorafenib in thyroid carcinoma cells may allow the development of more specific therapeutic intervention with less side effects.

Managing anaplastic thyroid carcinoma

Anaplastic thyroid cancer is one of the most lethal malignancies, with dismal prognosis, resistance to multimodal treatments and a median survival of only 5-6 months. Advances in the discovery of genetic pathway aberrations involved in this aggressive disease have been made, and multiple novel therapies targeting these pathways are undergoing clinical trials. So far, there is no single effective treatment for this disease; however, multimodal therapies with a combination of surgery, radiation and chemotherapy hold some promise. We conducted a PubMed search using the words thyroid neoplasm, anaplastic thyroid carcinoma, anaplastic thyroid cancer and anaplastic thyroid neoplasm, revealing 1673 publications. We review the pathophysiology, current treatments and advances made in identifying the alterations in genetic pathways, as well as novel therapies targeting these pathways.

Significantly high expression of platelet-derived growth factor (PDGF) in benign nodules of the thyroid: relevance in the development of goitre recurrence?

PURPOSE

Platelet-derived growth factor (PDGF) is a critical regulator of cell proliferation and influences the development of tumors. The role of PDGF in benign thyroid diseases is presently not well-determined. The purpose is to evaluate PDGF isoforms and receptors in primary culture of thyrocytes isolated from human thyroid tissue.

METHODS

Forty patients with uninodular (n = 11), multinodular (n = 15) and recurrent goitre (n = 14) were investigated. Nodular and corresponding paranodular thyroid tissues were characterized. RNA and protein were extracted from primary thyrocyte monoculture. RT-PCR, western blot and ELISA were performed to evaluate PDGF isoforms AA, BB, CC, DD and PDGF receptors α and β.

RESULTS

Significantly higher mRNA expression of PDGF-AA, -BB, -CC and PDGFR molecules α and β was measured by RT-PCR in thyrocytes from uninodular and recurrent nodular tissue compared with corresponding paranodular tissue. Elevated PDGF protein and PDGFR-α and -β were confirmed by western blot. Likewise, higher secretion of PDGF-AA and -BB was detected in the supernatant of thyrocyte culture from all nodular tissue compared with paranodular tissue. Interestingly, comparison of nodular and corresponding paranodular tissues in multinodular goitre did not show significant difference of expression levels of PDGF isoforms or receptors.

CONCLUSION

These findings suggest that the overexpression of PDGF isoforms and receptors may play a crucial role in the development of thyroid nodules and recurrent goitre.

A phase II study of imatinib in patients with advanced anaplastic thyroid cancer

BACKGROUND

Currently, there is no standard treatment for metastatic anaplastic thyroid cancer (ATC). DNA microarray analysis has shown platelet-dervived growth factor receptor (PDGFR) overexpression in ATC relative to well-differentiated thyroid cancer. In p53-mutated/deficient ATC cell lines, cABL is overexpressed, and selective inhibition of cABL results in a cytostatic effect. Imatinib inhibits tyrosine kinase activity of Bcr-ABL and PDGF. We hypothesize that patients with ATC that over-expresses PDGF receptors or cABL will respond to imatinib.

METHODS

Patients with histologically confirmed ATC who had measurable disease and whose disease expressed PDGF receptors by immunohistochemistry were eligible for study. Imatinib was administered at 400 mg orally twice daily without drug holiday. Response to treatment was assessed every 8 weeks. Patients with complete response, partial responses, or stable disease were treated until disease progression. The study was terminated early due to poor accrual.

RESULTS

From February 2004 to May 2007, 11 patients were enrolled and were started on imatinib. At baseline, 4/11 had locoregional disease, 5/11 had distant metastases, and 2/11 had both. Nine of 11 had prior chemoradiation, and 7/11 had thyroidectomy. Eight of 11 were evaluable for response; 4 were excluded for lack of follow-up with radiologic evaluation. The overall response rates at 8 weeks were complete response 0/8, partial response 2/8, and stable disease 4/8. The median time to follow-up was 26 months (ranges 23-30 months). The rate of 6-month progression-free survival was 36% (95% confidence interval, 9%-65%). The rate of 6-month overall survival was 45% (95% confidence interval, 16%-70%). The most common grade 3 toxicity was edema in 25%; other grade 3 toxicities included fatigue and hyponatremia (12.5% each). There were no grade 4 toxicities or treatment related deaths.

CONCLUSIONS

Imatinib appears to have activity in advanced ATC and is well tolerated. Due to difficulty of accruing patients with a rare malignancy at a single institution, further investigation of imatinib in ATC may be warranted in a multi-institutional setting.

Angiogenesis inhibition in cancer therapy: platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) and their receptors: biological functions and role in malignancy

Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen in vitro and an angiogenic inducer in a variety of in vivo models. VEGF gene transcription is induced in particular in hypoxic cells. In developmental angiogenesis, the role of VEGF is demonstrated by the finding that the loss of a single VEGF allele results in defective vascularization and early embryonic lethality. Substantial evidence also implicates VEGF as a mediator of pathological angiogenesis. In situ hybridization studies demonstrate expression of VEGF mRNA in the majority of human tumors. Platelet-derived growth factor (PDGF) is mainly believed to be an important mitogen for connective tissue, and also has important roles during embryonal development. Its overexpression has been linked to different types of malignancies. Thus, it is important to understand the physiology of VEGF and PDGF and their receptors as well as their roles in malignancies in order to develop antiangiogenic strategies for the treatment of malignant disease.

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.

PDGFRalpha: a new therapeutic target in the treatment of hepatocellular carcinoma?

BACKGROUND

Hepatocellular carcinoma (HCC) develops most often in a background of chronic inflammatory liver injury from viral infection or alcohol use. Most HCCs are diagnosed at a stage at which surgical resection is not feasible. Even in patients receiving surgery rates of recurrence and metastasis remain high. There are few effective HCC therapies and hence a need for novel, rational approaches to treatment. Platelet derived growth factor receptor-alpha (PDGFR-alpha) is involved in tumor angiogenesis and maintenance of the tumor microenvironment and has been implicated in development and metastasis of HCC.

OBJECTIVE

To examine PDGFR-alpha as a target for therapy of HCC and explore opportunities and strategies for PDGFR-alpha inhibition.

METHODS

A review of relevant literature.

RESULTS/CONCLUSIONS

Targeted inhibition of PDGFR-alpha is a rational strategy for prevention and therapy of HCC.

Receptor tyrosine kinase inhibitors in thyroid cancer

Thyroid cancer is frequently associated with the oncogenic conversion of receptor tyrosine kinases (RTKs) or their downstream signalling molecules. Hence, there is a strong biological rationale for assessing the efficacy of RTK blockade to treat patients who are resistant to or not candidates for treatment with radioactive iodine. The first results of clinical trials based on the use of RTK inhibitors in thyroid cancer patients have recently been published. Here we discuss targeting of specific RTKs as a potential therapeutic strategy for the treatment of thyroid cancer.

Role of platelet-derived growth factors in physiology and medicine

Platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) have served as prototypes for growth factor and receptor tyrosine kinase function for more than 25 years. Studies of PDGFs and PDGFRs in animal development have revealed roles for PDGFR-alpha signaling in gastrulation and in the development of the cranial and cardiac neural crest, gonads, lung, intestine, skin, CNS, and skeleton. Similarly, roles for PDGFR-beta signaling have been established in blood vessel formation and early hematopoiesis. PDGF signaling is implicated in a range of diseases. Autocrine activation of PDGF signaling pathways is involved in certain gliomas, sarcomas, and leukemias. Paracrine PDGF signaling is commonly observed in epithelial cancers, where it triggers stromal recruitment and may be involved in epithelial-mesenchymal transition, thereby affecting tumor growth, angiogenesis, invasion, and metastasis. PDGFs drive pathological mesenchymal responses in vascular disorders such as atherosclerosis, restenosis, pulmonary hypertension, and retinal diseases, as well as in fibrotic diseases, including pulmonary fibrosis, liver cirrhosis, scleroderma, glomerulosclerosis, and cardiac fibrosis. We review basic aspects of the PDGF ligands and receptors, their developmental and pathological functions, principles of their pharmacological inhibition, and results using PDGF pathway-inhibitory or stimulatory drugs in preclinical and clinical contexts.

Growth factor receptors expression in anaplastic thyroid carcinoma: potential markers for therapeutic stratification

Anaplastic thyroid carcinoma is a rare and universally fatal disease. Therefore, novel biomarkers are needed as surrogate end points in triaging patients for novel and selective biologic treatments. Up-regulation of several growth factor receptors has been shown to be associated with the biologic progression and response to targeted therapy of several malignancies. To determine the role of growth factor receptors in the biologic stratification of anaplastic thyroid carcinoma, we studied the expression of epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor beta, and HER-2 receptor in a large cohort of anaplastic thyroid carcinomas by immunohistochemical techniques. The percentage of positive cells, staining intensity and localization of staining in the anaplastic component, and coexisting well-differentiated thyroid carcinoma and adjacent nonneoplastic thyroid were evaluated for these markers. EGFR, platelet-derived growth factor receptor beta, and HER-2 were overexpressed in 58%, 16%, and 16% of anaplastic carcinomas, respectively. In tumors with adjacent normal thyroid parenchyma and/or differentiated carcinoma components, overexpression of all 3 markers was noted exclusively in the anaplastic component. Mutational analysis of exons 18, 19, and 21 of the EGFR gene showed no mutations in all anaplastic carcinomas. We conclude that the expression of these markers (1) may play a role in a subset of thyroid tumorigenesis and anaplastic transformation and (2) can be validated for potential use in the stratification of patients for targeted therapy.

Anaplastic Thyroid Carcinoma, Thyroid Lymphoma, and Metastasis to Thyroid

Anaplastic thyroid carcinoma, thyroid lymphoma, and secondary metastasis to the thyroid gland are uncommon thyroid malignancies. They represent significant challenges for the surgeon owing to difficulties in diagnosis, aggressive biology, and the infrequency of their presentation. An awareness and appreciation of multimodality treatment strategies is essential for their management.

Expression of endoderm stem cell markers: evidence for the presence of adult stem cells in human thyroid glands

OBJECTIVE

Adult stem cells have been detected in several human tissues. The object of this study was to investigate whether they also occur in the human thyroid gland.

DESIGN

The expression of the stem cell marker Oct- 4 and the early endodermal markers GATA-4 and HNF4alpha was analyzed in histologic slides and cultured cells derived from goiters, in the FRTL5 cell line, and the HTh74, HTC, C643, and XTC133 thyroid carcinoma cell lines.

MAIN OUTCOME

Stem cell markers were detectable in all primary cultures whereas in the differentiated FRTL5 cell line no expression was observed. Expression of stem cell marker mRNA was not affected by thyrotropin (TSH) stimulation and did not decrease when cells underwent several passages. Immunostaining of cultured cells and of histologic slides of goitrous tissues showed only single cells that were immunoreactive for Oct-4, GATA-4, and HNF4a. Expression of Oct-4 but not of endodermal marker GATA-4 was also detectable in some thyroid carcinoma cell lines. Fluorescence-activated cell sorter (FACS) analysis demonstrated cell populations that were positive for either Oct-4, GATA-4, or HNF4alpha but negative for thyroglobulin. When these putative, FACS-sorted stem cell populations were further analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR), expression of all stem cell markers and of Pax8 but not of thyroglobulin mRNA was detectable.

CONCLUSIONS

These data provide evidence for the presence of adult stem and precursor cells of endodermal origin in the human thyroid gland.

Paneling human thyroid cancer cell lines for candidate proteins for targeted anti-angiogenic therapy

Tumor angiogenesis is believed to result from an imbalance of pro- and anti-angiogenic factors, some of which are candidates for targeted therapy. Such therapy has raised hopes for patients with undifferentiated thyroid carcinomas, who are facing a grave prognosis with a survival of only months. In this study, in vivo growth of xenografted human thyroid carcinomas unexpectedly responded quite differently to neutralizing anti-vascular endothelial growth factor (VEGF) antibody. In particular, lasting inhibition as well as accelerated growth occurred after treatment. Consequently, a panel of anti-angiogenic factors was addressed in a representative sample of thyroid carcinoma lines. VEGF, fibroblast growth factor (FGF-2), and endostatin were demonstrated by Western blotting and EIA, whereas PDGF-A, PDGF-B, and IL-6 were negative. Quantification of VEGF, FGF-2, and endostatin revealed a wide range of concentrations from 500 to 4,200 pg/ml VEGF, 5 to 60 pg/ml FGF-2, and 50 to 300 pg/ml endostatin, not related to a particular histologic thyroid carcinoma background. Angiostatin (kringles 1-3) was detected in all, but one of the cell lines. Finally, aaATIII was confirmed in FTC133 cells. These data highlight the complex regulation of angiogenesis in thyroid carcinoma cell lines and suggest that the array of angiogenic factors differs markedly between individual cell lines. For the first time, angiostatin, endostatin, and possibly also aaATIII are identified as novel candidate regulators of angiogenesis in thyroid carcinoma cells.

Differential expression of alphaB-crystallin and Hsp27-1 in anaplastic thyroid carcinomas because of tumor-specific alphaB-crystallin gene (CRYAB) silencing

Expression of the small heat shock protein alphaB-crystallin in differentiated thyroid tumors has been described recently. In this study, we investigated the molecular mechanisms that affect the expression of alphaB-crystallin in benign goiters (n = 7) and highly malignant anaplastic thyroid carcinomas (ATCs) (n = 3). AlphaB-crystallin expression was compared with that of Hsp27-1. Immunoblot and quantitative real-time (RT) polymerase chain reaction revealed marked downregulation of alphaB-crystallin in all the tested ATCs and the ATC-derived cell line C-643 . In contrast, considerable expression of Hsp27-1 in benign and malignant thyroid tissue was demonstrated. Immunofluorescence analysis revealed no relevant topological differences between benign and malignant thyrocytes in the cytoplasmic staining of both proteins. Consistent and marked downregulation of TFCP2L1 was identified as one of the main mechanisms contributing to CRYAB gene silencing in ATCs. In addition, CRYAB gene promoter methylation seems to occur in distinct ATCs. In silico analysis revealed that the differential expression of alphaB-crystallin and Hsp27-1 results from differences between the alphaB-crystallin and Hsp27-1 promoter fragments (712 bp upstream from the transcriptional start site). Biological activity of the analyzed promoter element is confirmed by its heat shock inducibility. In conclusion, we demonstrate downregulation of alphaB-crystallin expression in highly dedifferentiated ATCs because of a tumor-specific transcription factor pattern. The differential expression of alphaB-crystallin and Hsp27-1 indicates functional differences between both proteins.

Differential pattern of integrin receptor expression in differentiated and anaplastic thyroid cancer cell lines

Adhesion of tumor cells to the extracellular matrix (ECM) is a crucial step for the development of metastatic disease and is mediated by specific integrin receptor molecules (IRM). The pattern of metastatic spread differs substantially among the various histotypes of thyroid cancer (TC). However, IRM have only occasionally been characterized in TC until now. IRM expression was investigated in 10 differentiated (FTC133, 236, 238, HTC, HTC TSHr, XTC, PTC4.0/4.2, TPC1, Kat5) and two anaplastic TC cell lines (ATC, C643, Hth74), primary cultures of normal thyroid tissue (Thy1,3), and thyroid cancer specimens (TCS). Expression of 16 IRM (beta1-4, beta7, alpha1-6, alphaV, alphaIIb, alphaL, alphaM, alphaX) and of four IRM heterodimers (alpha2beta1, alpha5beta1, alphaVbeta3, alphaVbeta5), was analyzed by fluorescent-activated cell sorter (FACS) and immunohistochemical staining. Thyroid tumor cell adhesion to ECM proteins and their IRM expression in response to thyrotropin (TSH) was assessed. Follicular TC cell lines presented high levels of integrins alpha2, alpha3, alpha5, beta1, beta3 and low levels of alpha1, whereas papillary lines expressed a heterogenous pattern of IRM, dominated by alpha5 and beta1. ATC mainly displayed integrins alpha2, alpha3, alpha5, alpha6, beta1 and low levels of alpha1, alpha4 and alphaV. Integrin heterodimers correlated with monomer expression. Evaluation of TCS largely confirmed these results with few exceptions, namely alpha4, alpha6, and beta3. The ability of TC cell lines to adhere to purified ECM proteins correlated with IRM expression. TSH induced TC cell adhesion in a dose-dependent fashion, despite an unchanged array of IRM expression or level of a particular IRM. Thyroid carcinoma cell lines of different histogenetic background display profoundly different patterns of IRM expression that appear to correlate with tumor aggressiveness. In vitro adhesion to ECM proteins and IRM expression concur. Finally, TSH-stimulated adhesion of thyroid tumor cell lines to ECM may not be associated with altered IRM expression.

An aberrant autocrine activation of the platelet-derived growth factor alpha-receptor in follicular and papillary thyroid carcinoma cell lines

Platelet-derived growth factor receptor (PDGFR) can bind to its ligand and consequently possess a kinase activity, and which is associated with the carcinogenesis of different cell types, including astrocytomas, oligodendrogliomas, and glioblastoma. In a cDNA microarray analysis, we observe the over-expressed mRNA of both PDGF-A and PDGF-alpha receptor in thyroid carcinoma cells. And the elevated protein expressions of PDGF-A and PDGF-alpha receptor in thyroid carcinoma cells were also confirmed by a Western blot analysis. The phosphorylation of PDGF-alpha receptor evaluated by an antibody against Tyr 720-phosphate was found in thyroid carcinoma cells. The tyrosine kinase activity of PDGF-alpha receptor was inhibited by tyrphostin AG1295 and showed a dose-dependent inhibition for the proliferation of thyroid carcinoma cells. These findings imply that autocrine activation of PDGF-alpha receptor plays a crucial role in the carcinogenesis of thyroid cells.

Investigations on four host response factors whose expression is enhanced in X4 SHIV encephalitis

HIV encephalopathy, one of the major complications of HIV infection, involves productive virus replication in macrophages in the brain in association with heightened expression of several host response factors. One or more of these factors are thought to be the cause of the degenerative changes in neurons in the brain. Macaques infected with SIV and SHIV viruses have provided excellent working models for studying mechanisms of the human disease. Although HIV encephalopathy is primarily associated with CCR5-utilizing viruses, our findings have shown that CXCR4-utilizing SHIVs were also capable of causing the syndrome in rhesus macaques. In SHIV-infected macaques, approximately 30% of the animals developed encephalitis. In order to understand the factors leading to end-stage encephalitis, we performed microarray analyses on brains of encephalitic and non-encephalitic-infected macaques, and found pronounced enhancement of expression of interleukin-4, platelet-derived growth factor-B chain, monocyte chemoattractant protein-1 and CXCL10 in the brains of the encephalitic animals. This review discusses the role of each of these factors in mediating SHIV encephalitis.

Hyaluronan content in experimental carcinoma is not correlated to interstitial fluid pressure

Mechanism(s) for generation of the high tumor interstitial fluid pressure (TIFP) that is characteristic of carcinoma is not known. We investigated the role of hyaluronan, the major water-binding polysaccharide of the extracellular matrix, for the generation of a high TIFP. A human anaplastic thyroid carcinoma (KAT-4) xenografted to athymic mice and a syngeneic rat colon carcinoma (PROb) were used. Neither KAT-4 nor PROb cells produced hyaluronan (HA) in culture, however, both cell lines produced factors that stimulated HA-synthesis by cultured fibroblasts. Modulating hyaluronan levels by transfection of PROb carcinoma cells with hyaluronan synthase-2 revealed no correlation between hyaluronan content and TIFP. Furthermore, lowering of TIFP by treating KAT-4 tumors with a specific inhibitor of TGF-beta 1 and -beta 3 did not change the concentration of hyaluronan in the tumors. In summary, our results suggest that a modulation of hyaluronan content is not a major pathogenetic mechanism for the generation of the characteristically high TIFP in malignant carcinomas.

Collagen type I expression in experimental anaplastic thyroid carcinoma: regulation and relevance for tumorigenicity

Fibrosis in solid malignancies plays a significant role in tumor pathophysiology. Potential mechanisms for collagen type I deposition in anaplastic thyroid carcinoma (ATC) were investigated using 6 characterized ATC cell lines. Three of these cell lines, which produced collagen type I, had, as a group, a poor tumorigenicity when inoculated in athymic mice. This group of cells generated tumors in 4 of 24 injected animals (17%). Pro-alpha 1(I) collagen mRNA-expressing carcinoma and stromal cells were interdispersed in the tumors generated by these ATC cells. By contrast, the 3 noncollagen-producing ATC cell lines were all tumorigenic with a tumor take of 60% in the whole group. In the latter tumors, pro-alpha 1(I) collagen mRNA-expressing cells were confined to the stromal compartment, well delineated from carcinoma cell islets. To study the influence of ATC cells on collagen type I synthesis by fibroblasts, we used AG 1518 diploid human fibroblasts cultured on poly-(2-hydroxyethyl methacrylate) (poly[HEMA])-coated plates. This culture condition allows the study of the effect of collagen mRNA translation in the regulation of collagen type I synthesis. Conditioned media from the 6 ATC cell lines did not influence collagen synthesis. The ATC cell line KAT-4 stimulated fibroblast synthesis of collagen type I when the two cell types were cocultured on poly[HEMA]-coated substrates. Specific inhibitors of PDGF and TGF-beta reduced the KAT 4 carcinoma cell-induced stimulation of collagen type I synthesis. Our data suggest that collagen type I production by carcinoma cells correlates negatively with tumorigenicity and that the formation of a well-defined stroma is of importance for tumor growth. Furthermore, our data suggest that tumor cells are able to stimulate collagen mRNA translation in stromal fibroblasts in direct cell-cell contact by, at least in part, transferring PDGF or TGF-beta.

Clonally related but phenotypically divergent human cancer cell lines derived from a single follicular thyroid cancer recurrence (TT2609)

Starting from different regional samples taken from a heterogeneous follicular thyroid cancer recurrence in a male patient, a series of cell cultures was initiated. Three stable cancer cell lines were successfully established (TT2609-A02, TT2609-B02, and TT2609-C02) and kept in continuous culture for more than 3 years. The lines are each characterized by a unique set of biological parameters such as morphology, ploidy state, cell proliferation rate, ultrastructure, thyroid marker expression, p53 expression, karyogram, agar clonogenic capacity and tumorigenicity as xenografts in nude mice. These characterization studies point to a marked heterogeneity at the level of the clinical tumor recurrence. Karyotype analysis of the cell lines showed a pattern of aberrations indicating that the lines are clonally related and that the A02 and C02 lines are subsequently derived from the more "original" tumor cell type B02 after a tetraploidization event. It is concluded that the obtained cell lines represent an in vitro/in vivo model for human follicular thyroid cancer. The availability of a series of cell lines for human follicular thyroid cancer, mimicking the biological heterogeneity observed in patient tumors, enables both detailed fundamental investigation of thyroid cancer cell biology and the experimental exploration of new treatment approaches.

Tyrosine kinase inhibitor STI571 enhances thyroid cancer cell motile response to Hepatocyte Growth Factor

The Hepatocyte Growth Factor (HGF) and its receptor Met are physiological regulators of cell migration. HGF and Met have also been implicated in tumor progression and metastasis. We show here that the tyrosine kinase inhibitor STI571 has a stimulatory effect on HGF-induced migration and branching morphogenesis in thyroid cancer but not in primary or immortalized thyroid epithelial cells. These stimulatory effects of STI571 are observed at a concentration that is clinically relevant. The STI571-enhanced motile response can be correlated with an increase in the Met receptor tyrosine phosphorylation as well as ERK and Akt activation by HGF. Interestingly, one of the targets of STI571, namely the c-Abl tyrosine kinase, is activated by HGF and is recruited at the migrating edge of thyroid cancer cells. These data suggests that c-Abl and/or STI571-inhibited tyrosine kinases can negatively regulate the Met receptor to restrain the motile response in thyroid cancer cells.

Epidermal growth factor receptor signaling activates met in human anaplastic thyroid carcinoma cells

Overexpression of Met is a common finding in thyroid carcinomas. Recently, we reported on overexpression and ligand-independent constitutive activation of Met in anaplastic thyroid carcinoma cells. In the present study we have investigated a putative mechanism for this phenomenon. Cell lines with constitutively activated Met expressed both TGF-alpha mRNA and protein. Western blot analysis revealed expression of receptors for epidermal growth factor (EGFR) in all carcinoma cell lines; in tumor cells with elevated levels of TGF-alpha mRNA there was a constitutive tyrosine phosphorylation of the EGFRs. Preincubation of carcinoma cells with suramin decreased EGFR activation and downregulated Met expression as well as the ligand-independent phosphorylation of Met. Similar results were obtained with a EGFR tyrosine kinase inhibitor, AG 1478. The MEK inhibitor U0126 had an even more pronounced effect compared to AG 1478, indicating a Ras/MAPK-mediated signal in the regulation of Met expression and activation. Inhibition of EGFR signaling also decreased proliferation of the anaplastic thyroid carcinoma cells. Thus, aberrant activation of EGFRs may lead to an overexpression and activation of Met, which may be of importance for the malignant phenotype of anaplastic thyroid carcinomas.

Fibrosis in undifferentiated (anaplastic) thyroid carcinomas: evidence for a dual action of tumour cells in collagen type I synthesis

The mechanisms involved in stromal reactions and fibrosis in solid malignant tumours are incompletely understood. In the present study, collagen type I production was investigated in tissues and cell lines derived from human undifferentiated (anaplastic) thyroid carcinomas, a highly aggressive, often fibrotic malignancy with mesenchymal phenotype. In situ hybridization showed the expression of pro-alpha1(I) collagen mRNA throughout the stromal part of the tumours. However, immunofluorescence staining using an anti-pro-collagen type I antibody revealed the synthesis of pro-collagen type I protein mainly in stromal cells juxtaposed to nests of tumour cells. In one out of five tissue samples from human undifferentiated thyroid carcinomas, pro-alpha1(I) collagen mRNA expression was also found in a small number of tumour cells. Several well-characterized cell lines established from undifferentiated thyroid carcinomas, two from tumours included in the present study, expressed both pro-alpha1(I) collagen and prolyl 4-hydroxylase mRNA, and three of these cell lines also synthesized native triple-helical collagen type I. Taken together, these data suggest that stromal fibroblasts are the main producers of collagen type I in anaplastic thyroid tumours. The carcinoma cells seem to play a regulatory role, stimulating the synthesis of collagen type I protein in the surrounding stroma by increasing pro-alpha1(I) collagen mRNA translation. However, collagen type I production by the carcinoma cells might also contribute to the marked desmoplasia commonly seen in these tumours.

Lack of responsiveness to TGF-beta1 in a thyroid carcinoma cell line with functional type I and type II TGF-beta receptors and Smad proteins, suggests a novel mechanism for TGF-beta insensitivity in carcinoma cells

Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine. In the present study we have investigated the expression of TGF-beta receptors (TbetaR's) and SMAD proteins in non-neoplastic and neoplastic thyroid follicle cells. We found expression of all TbetaR's (type I, II and III) and SMAD proteins analysed (Smad2, Smad3, Smad4, Smad6 and Smad7). Five out of six human anaplastic thyroid carcinoma cell lines were growth inhibited by addition of TGF-beta1, and therefore considered to be TGF-responsive. One cell line however, HTh 7, did not respond to TGF-beta1 with growth inhibition, induction of the extracellular matrix protein fibronectin or immediate early genes junB, Smad6 and Smad7 mRNA. Analysis of the TGF-beta intracellular signalling pathway in HTh 7 cells showed that receptors were capable of signalling, e.g. Smad2 phosphorylation and SMAD nuclear translocation. In summary, our data shows abundant expression of TGF-beta signalling components in thyroid follicle cells, and the escape from TGF-beta sensitivity in one anaplastic thyroid carcinoma despite an apparently functional TGF-beta/SMAD-signalling pathway, indicating a novel mechanism for TGF-beta insensitivity.

Non-autocrine, constitutive activation of Met in human anaplastic thyroid carcinoma cells in culture

Activation of Met by its ligand HGF has been shown to elicit both mitogenic and motogenic responses in thyrocytes in vitro. In the present study we have investigated the expression of Met in human anaplastic thyroid carcinoma cells in culture. There was a variation in expression level and size of Met in the different cell lines; high Met expression was found in four cell lines, compared to non-neoplastic human thyrocytes. Treatment with glucoproteinase F showed that the size differences observed were due to variances in the degree of glycosylation. Interestingly, in cell lines with high expression of Met, the receptor proteins were found to be constitutively tyrosine phosphorylated. None of these cell lines expressed HGF mRNA, and addition of suramin did not affect the level of tyrosine phosphorylation of Met in unstimulated cells, suggesting the absence of autocrine stimulatory pathways. Furthermore, we did not observe MET gene amplification, activating mutations or phosphatase defects. The tyrosine phosphorylated receptors appeared functionally active since the receptors associated with the adaptor molecule Shc. In summary, we have found ligand-independent constitutively activated Met in four out of six anaplastic thyroid carcinoma cell lines.

Anaplastic thyroid carcinoma: behavior, biology, and therapeutic approaches

Anaplastic thyroid carcinoma (ATC), although exceedingly rare, is the most aggressive solid tumor known. Early studies on the effects of different therapies may be biased by the inclusion of responsive "small cell" ATC patients, which are now known to be mostly lymphoma patients. Local control of disease with surgery and/or external beam radiotherapy (XRT) is of fundamental importance to enhance survival. Ultimately, nearly all ATC patients die from their disease, which is widely metastatic. Development of effective systemic chemotherapy agents would provide the best chance for long-term survival of patients. Early preliminary data suggest that paclitaxel may be helpful, although no agent has yet been identified to result in dramatic improvements in survival. Select patients may benefit from aggressive multimodal therapy, although it is important to provide appropriate palliative care when desired.

Retinoic acid increases sodium/iodide symporter mRNA levels in human thyroid cancer cell lines and suppresses expression of functional symporter in nontransformed FRTL-5 rat thyroid cells

Decreased iodide uptake in de-differentiated thyroid carcinomas impedes radioiodide therapy. RTPCR analysis revealed reduced expression of Na+/I- symporter (NIS) mRNA in human thyroid carcinomas as compared to normal thyroid. However, in follicular thyroid carcinoma cell lines FTC-133 and FTC-238, treatment with 1 microM all-trans retinoic acid (RA) markedly increased NIS mRNA levels. Anaplastic thyroid carcinoma cell lines HTh74 and C643 showed basal expression of NIS mRNA, but no RA-stimulation. All four cell lines contained the approximately 80 kD NIS protein as judged by Western blot, although they did not accumulate iodide. In contrast, in nontransformed rat FRTL-5 cells, 1 microM RA downregulated NIS mRNA levels, inhibited the TSH- or forskolin-triggered induction of NIS message after TSH-depletion, and reduced iodide uptake to 38% after 5 d. This divergent RA-responsivity of NIS may provide the means to target radioiodide to thyroid carcinomas by upregulating iodide transport into tumor tissue while simultaneously inhibiting iodide accumulation in normal thyrocytes and may thus re-establish the potential for radioiodide therapy.

Impairment of ATP-induced Ca2+ -signalling in human thyroid cancer cells

Extracellular nucleotides like ATP that activate the Ca2+ -phosphatidylinositol (PI) signalling pathway have been suggested to participate in the regulation of normal human thyroid function. We examined, whether P2y-purinergic receptors are expressed on human thyroid cancer cells and whether post-receptor Ca2+ signalling is altered by malignant transformation. Extracellular ATP caused a biphasic increase in cytosolic free Ca2+ ([Ca2+]i) in normal human thyrocytes and in human follicular (FTC) and papillary (PTC) thyroid carcinoma cells. In FTC and PTC cell lines the dose-response curves for ATP-induced changes in [Ca2+]i were shifted to the right when compared with normal thyrocytes, whereas in undifferentiated thyroid carcinoma (UTC) cells even high concentrations of ATP (500 microM) failed to stimulate a rise in [Ca2+]i. By contrast, ATP stimulated inositol 1,4,5-trisphosphate (IP3) formation and capacitative Ca2+ entry was operational as judged by thapsigargin in normal thyrocytes and all thyroid cancer cells. Thus, P2y-purinergic receptors are expressed on thyroid tumor cells independent of degree of differentiation. In UTC cells, however, impairment in the Ca2+ -phosphatidylinositol (PI) signalling cascade occurs distal to the formation of IP3 and proximal to the activation of capacitative Ca2+ entry. Disturbed ATP-induced Ca2+ -signalling and alterations in the Ca2+ -PI signalling cascade may contribute to decreased expression or loss of specific thyroid functions in thyroid cancer cells.

Pregnancy-stimulated growth of vascular smooth muscle cells: importance of protein kinase C-dependent synergy between estrogen and platelet-derived growth factor

Dramatic smooth muscle cell (SMC) growth occurs in the uterine artery during pregnancy. The potential for pregnancy-associated growth may also exist at other vascular sites. We tested the hypothesis that increased growth of uterine artery SMC isolated from pregnant (vs. nonpregnant) guinea pigs would be detectable in culture, that pregnancy-associated phenotypic changes would also be found in nonuterine vascular cells (aortic SMC), and that the enhanced growth would be dependent on estrogen, peptide growth factors like platelet-derived growth factor (PDGF), and protein kinase C (PKC). Growth responses were measured by [3H]-thymidine incorporation and cell counts. Uterine artery SMC from pregnant guinea pigs grew to a higher plateau density with serum stimulation, had increased spontaneous DNA synthesis and persistent growth following serum with-drawal, and were more responsive to 3-30 ng/ml PDGF-BB than nonpregnant cells. Aortic SMC from pregnant animals also grew to a higher plateau density and had enhanced responsiveness of PDGF-BB. This increased response to PDGF-BB by pregnant uterine artery and aortic SMC (40-233% increase over nonpregnant PDGF result) was reproduced in nonpregnant cells by pretreatment for 1-24 h with 17-beta(beta)-estradiol (30-100 nM). Neither the pregnancy-induced difference nor the estradiol pretreatment was associated with increased PDGF-BB binding activity. The synergistic effect of 17 beta-estradiol was partially (62%) reproduced with 17-alpha(alpha)-estradiol, an isomer which does not bind the estrogen receptor. This suggested that 17 beta-estradiol modulates the PDGF-BB response by both estrogen-receptor- and nonreceptor-mediated mechanisms. To test if the estrogen effects were dependent on PKC, two different antagonist strategies (3 microM dihydrosphingosine and phorbol-ester-induced downregulation) were applied prior to 17 alpha- or beta-estradiol and blocked the enhanced responses to PDGF. The synergistic effect of 17 beta-estradiol on PDGF was then reproduced by 1 h pretreatment with the cell-permeable PKC activator, 10 nM PMA. We conclude that pregnancy stimulates increased growth of uterine and aortic SMC in vitro which is dependent on estrogen, PDGF, and PKC and may be important in vascular remodeling during pregnancy.

Histopathology, classification, and grading of gliomas

Neoplastic transformation occurs in all glial cell types of the human nervous system, producing a wide variety of clinico-pathological entities and morphological variants. Astrocytomas are most common and span an unusually wide spectrum, ranging from the slowly growing juvenile pilocytic astrocytoma to the highly malignant glioblastoma multiforme. Diffusely infiltrating astrocytomas of the cerebral hemispheres show an inherent tendency for progression towards a more malignant phenotype. This change is morphologically categorized in histologic grading schemes (e.g., WHO Grade II to IV) and is associated with the sequential acquisition of genetic alterations, including mutations in the p53 and homozygous deletions of the p16 tumour suppressor genes. Loss of heterozygosity on chromosomes 10 and 19q as well as amplification of the EGF receptor are largely restricted to malignant gliomas and thus considered late events in astrocytoma progression. Gliomas often show phenotypic expression of different glial cell lineages (e.g., oligoastrocytoma). Recent studies suggest that the occurrence of mixed gliomas is not indicative of a polyclonal origin but rather reflects altered gene expression, leading to a change in the balance of growth factors influencing glioma differentiation.

Towards understanding the molecular basis of thyroid cancer

Cancer is a multistep phenomenon and multiple genetic lesions are involved in the emergence of the cancerous lesion. This has best been demonstrated in colonic cancer. The authors review their work and that of others highlighting what is known about thyroid cancer. They implicate ras mutations predominantly in follicular carcinoma, rearrangement of the ret proto-oncogene in papillary carcinoma and the tumor suppressor genes p53 and retinoblastoma gene product in all stages of thyroid carcinoma. They find a low rate of ret proto-oncogene rearrangement in the Saudi population (>5%) as compared to elsewhere in the world (20%). They find TSH receptor message abundance to be predictive of prognosis in thyroid cancer patients. Lastly, they examine whether the abundance of the anti-metastatic gene nm23 message abundance negatively correlated with the tendency of thyroid tumors to metastasize and find that not to be the case in thyroid carcinoma. The study of oncogenes and tumor suppressor genes in the pathogenesis of thyroid cancer is in its infancy; however, rapid progress is being made in identifying genes participating in malignant thyroid cell transformation.

Expression of growth factors and growth factor receptors in normal and tumorous human thyroid tissues

A number of growth factors have been implicated as stimuli of thyroid cell proliferation; overexpression of these growth factors and/or their receptors may play a role in the growth of thyroid tumors. To determine if immunohistochemical detection of growth factors and/or their receptors correlates with morphological alterations in proliferative lesions of thyroid, we examined the localization of epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha) and their common receptor, EGF-receptor (EGF-R), insulin-like growth factor-1 (IGF-1), IGF-1-receptor (IGF-R) and IGF binding proteins (IGFBP)-1, -2, -3, and -4, nerve growth factor (NGF), and its receptor NGF-receptor (NGF-R), transforming growth factor-beta (TGF-beta), and basic fibroblast growth factor (bFGF), in normal thyroid tissue and various thyroid tumors. We applied the streptavidin-biotin technique to formalin-fixed, paraffin-embedded tissues. We studied 8-16 different cases of each of the following: normal human thyroid, multinodular hyperplasia, follicular adenoma, papillary carcinoma, follicular carcinoma, medullary carcinoma, and anaplastic carcinoma. EGF, TGF-alpha, and their receptor EGF-R were widely expressed in normal thyroid and in all the thyroid lesions examined. IGF-1 and IGFBP-1 were diffusely present in all different thyroid tissues as well. There was no difference in staining intensity or distribution that correlated with the pathological process. IGFBP-4 seemed to have a variable expression. IGFBP-2 and -3 were detected only in medullary carcinomas.(ABSTRACT TRUNCATED AT 250 WORDS)

The association of well-differentiated thyroid carcinoma with insular or anaplastic thyroid carcinoma; evidence for dedifferentiation in tumor progression

The sequence of tumorigenesis in the thyroid is unclear. It has been proposed that anaplastic carcinomas of the thyroid develop by dedifferentiation in pre-existing differentiated carcinomas. We reviewed all anaplastic and insular (poorly differentiated) thyroid carcinomas in a consultation practice of thyroid pathology that included more than 400 thyroid cancers. Sixteen tumors (4%) were classified as anaplastic or insular (poorly differentiated) thyroid carcinomas. We examined these cases to determine whether these carcinomas were associated with well-differentiated neoplasms of follicular cell derivation. Ten patients were women and 6 were men, and ages ranged from 29 to 85 years; 10 patients with anaplastic carcinomas and 2 with insular carcinomas were 56 years or older, whereas 3 of the 6 patients with insular carcinomas were 31 years or younger. Four tumors were composed exclusively of anaplastic carcinoma; all were represented only by incisional biopsies. One insular carcinoma infiltrated and destroyed all underlying thyroid tissue. In the remaining total, subtotal, or hemithyroidectomy specimens, areas of well-differentiated papillary or follicular carcinoma were found. Some differentiated papillary lesions had a wide spectrum of morphologies, including Hurthle cell, tall cell, and columnar cell features. In the literature, simultaneous or previous occurrence of well-differentiated thyroid carcinomas with anaplastic carcinomas is extremely variable, ranging from 7-89% of cases. in experimental animals, serial transplantation of differentiated thyroid tumors has been shown to lead to anaplastic transformation. Our findings suggest that the majority of anaplastic thyroid carcinomas in humans arise from well-differentiated tumors. However, only a very small number of differentiated carcinomas progress to anaplastic lesions; the factors underlying this phenomenon remain to be identified.

Human neuroblastoma cells express alpha and beta platelet-derived growth factor receptors coupling with neurotrophic and chemotactic signaling

Both platelet-derived growth factor (PDGF) A- and B-chains are expressed in mammalian neurons, but their precise roles still remain to be clarified. In the present studies, we examined the expression of two PDGF receptor genes in human tumor cell lines derived from neural crest. The expression of alpha and/or beta PDGF receptors was detected in a wide variety of neural crest-derived human tumor cell lines such as neuroblastoma, primitive neuroectodermal tumor, and Ewing's sarcoma by RNA blot analysis, and confirmed by immunoblot analysis. We have also demonstrated that PDGF receptors on the human neuroblastoma cell lines were biologically functional. Accordingly, chemotactic and mitogenic activities were induced by either PDGF-AA or PDGF-BB in serum-free medium. PDGF isoforms as well as nerve growth factor induced morphological changes showing neuronal cell maturation. Moreover, PDGF coordinately increased the levels of the transcript of the midsize neurofilament gene. The neuroblastoma cell lines also expressed the transcripts of PDGF A- and B-chains. These findings suggest that PDGF isoforms are involved not only in the promotion of the neuroblastoma cell growth, but also in neuronal cell migration, growth, and differentiation in human brain development.

Establishment of a human anaplastic thyroid cancer cell line secreting granulocyte colony-stimulating factor in response to cytokines

A human anaplastic thyroid cancer cell line K-119, derived from a 77-yr-old woman who had developed marked neutrophilia and underwent surgery for anaplastic thyroid cancer, has been established. The spindlelike and polygonal cells in shape are stably proliferating since the beginning of its culture 2 yr ago. The cells grow rapidly and the population doubling time is 26 h. The chromosomes show many abnormalities and many marker chromosomes have been observed. Heterotransplantation of the cells into nude mice has resulted in the formation of tumors that are histologically interpreted as anaplastic cancer. The most noteworthy characteristics of the cell line are the many Ki-67-positive cells (86.3%) and that the cell line spontaneously secretes granulocyte colony-stimulating factor (G-CSF) and releases increased amounts of G-CSF in response to the stimulation of tumor necrosis factor, interleukin 1 alpha, and interleukin 1 beta. The conditioned medium obtained from K-119 cells contains an autocrine factor stimulating the proliferation of themselves.

Expression of functionally intact PDGF-alpha receptors in highly metastatic 3LL Lewis lung carcinoma cells

The ability of disseminating tumor cells to grow in a target organ is the final limiting step of the metastatic cascade. The growth of a highly lung-metastatic clone, D122, of the murine 3LL Lewis lung carcinoma was induced in vitro with lung-conditioned media (CM) to a greater extent than that of a weakly metastatic clone, A9. With the use of platelet-derived growth factor (PDGF)-alpha-receptor-specific antibodies, the possible paracrine mode of metastatic cell growth was further suggested by demonstrating the presence of these receptors on highly metastatic cells only. Receptors for PDGF have been found almost exclusively on cells of mesenchymal and glial origin. Therefore, the functionality of this receptor in the D122 epithelial cell line was verified by immune complex kinase and ligand-stimulation assays. Moreover, PDGF was shown to specifically induce in vitro growth of D122 highly metastatic cells only and to be abundantly expressed in lung CM but not in kidney or liver CM. Thus, the interaction of PDGF-like factors in the lung with PDGF receptors on the metastatic tumor cell may be important in the development of metastatic lesions in the target organ.

Platelet-derived growth factor. Structure, function and implications in normal and malignant cell growth

Platelet-derived growth factor (PDGF) is a potent mitogen for a variety of cell types. PDGF is made up as dimers of A and B polypeptide chains which are combined to generate the three isoforms of PDGF (AA, AB, BB). These bind with different specificities and affinities to two types of cell surface receptors (the alpha-receptor and the beta-receptor), both being members of the protein tyrosine kinase family of growth factor receptors. A number of human tumor cell lines, particularly those established from glioma and sarcoma, have been shown to produce PDGF and express the cognate receptor type. In these instances, tumor cell growth may be enhanced by an autocrine receptor activation. In other tumor cell types, where PDGF is produced in the absence of receptor expression, the growth factor may act in a paracrine fashion. This view is supported by our recent finding that human melanoma cells that have been stably transfected with a PDGF B-chain cDNA, elicit a stroma response when transplanted to nude mice.