Overexpression of fibroblast growth factor receptor 3 in a human thyroid carcinoma cell line results in overgrowth of the confluent cultures

A novel exosome-related prognostic risk model for thyroid cancer

AIM

The aim was to build an exosome-related gene (ERG) risk model for thyroid cancer (TC) patients.

METHODS

Note that, 510 TC samples from The Cancer Genome Atlas database and 121 ERGs from the ExoBCD database were obtained. Differential gene expression analysis was performed to get ERGs in TC (TERGs). Functional enrichment analyses including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were conducted on the TERGs. Then we constructed a model based on LASSO Cox regression analysis. Kaplan-Meier survival analysis was applied and a Nomogram model was also built. The immune landscape was evaluated by CIBERSORT.

RESULTS

Thirty-eight TERGs were identified and their functions were enriched on 591 GO terms and 30 KEGG pathways. We built a Risk Score model based on FGFR3, ADRA1B, and POSTN. Risk Scores were significantly higher in T4 than in other stages, meanwhile, it didn't significantly differ in genders and TNM N or M classifications. The nomogram model could reliably predict the overall survival of TC patients. The mutation rate of BRAF and expression of cytotoxic T-lymphocyte-associated protein 4 were significantly higher in the high-risk group than in the low-risk group. The risk score was significantly correlated to the immune landscape.

CONCLUSION

We built a Risk Score model using FGFR3, ADRA1B, and POSTN which could reliably predict the prognosis of TC patients.

FGF9/FGFR2 increase cell proliferation by activating ERK1/2, Rb/E2F1, and cell cycle pathways in mouse Leydig tumor cells

Fibroblast growth factor 9 (FGF9) promotes cancer progression; however, its role in cell proliferation related to tumorigenesis remains elusive. We investigated how FGF9 affected MA‐10 mouse Leydig tumor cell proliferation and found that FGF9 significantly induced cell proliferation by activating ERK1/2 and retinoblastoma (Rb) phosphorylations within 15 minutes. Subsequently, the expressions of E2F1 and the cell cycle regulators: cyclin D1, cyclin E1 and cyclin‐dependent kinase 4 (CDK4) in G₁ phase and cyclin A1, CDK2 and CDK1 in S‐G₂/M phases were increased at 12 hours after FGF9 treatment; and cyclin B1 in G₂/M phases were induced at 24 hours after FGF9 stimulation, whereas the phosphorylations of p53, p21 and p27 were not affected by FGF9. Moreover, FGF9‐induced effects were inhibited by MEK inhibitor PD98059, indicating FGF9 activated the Rb/E2F pathway to accelerate MA‐10 cell proliferation by activating ERK1/2. Immunoprecipitation assay and ChIP‐quantitative PCR results showed that FGF9‐induced Rb phosphorylation led to the dissociation of Rb‐E2F1 complexes and thereby enhanced the transactivations of E2F1 target genes, Cyclin D1, Cyclin E1 and Cyclin A1. Silencing of FGF receptor 2 (FGFR2) using lentiviral shRNA inhibited FGF9‐induced ERK1/2 phosphorylation and cell proliferation, indicating that FGFR2 is the obligate receptor for FGF9 to bind and activate the signaling pathway in MA‐10 cells. Furthermore, in a severe combined immunodeficiency mouse xenograft model, FGF9 significantly promoted MA‐10 tumor growth, a consequence of increased cell proliferation and decreased apoptosis. Conclusively, FGF9 interacts with FGFR2 to activate ERK1/2, Rb/E2F1 and cell cycle pathways to induce MA‐10 cell proliferation in vitro and tumor growth in vivo.

Alteration in the serum concentrations of FGF19, FGFR4 and βKlotho in patients with thyroid cancer

INTRODUCTION

βKlotho (βKL) is known to act as co-receptor for fibroblast growth factor receptor 4 (FGFR4) which is the main cognate receptor for fibroblast growth factor 19 (FGF19). Dysregulation of this FGF19/FGFR4/βKL signaling axis has been implicated in the pathogenesis of several cancers. However, its role in the pathogenesis of thyroid cancer has not been determined.

MATERIALS AND METHODS

The aim of this study was to assess FGF19, FGFR4 and βKL concentrations in a group of 36 patients with papillary thyroid cancer (PTC), 11 patients with follicular thyroid cancer (FTC), 9 patients with anaplastic thyroid cancer (ATC) and a group of 19 subjects with multinodular nontoxic goiter (MNG). The control group consisted of 20 healthy volunteers. Serum FGF19, FGFR4 and βKL concentrations were measured using specific ELISA methods.

RESULTS

Significantly lower concentrations of βKL and higher concentrations of FGF19 were found in patients with PTC, FTC and ATC as compared with MNG group and controls. An elevation of FGFR4 serum concentration was observed in all thyroid cancer groups in comparison to MNG group and controls; however, in FTC group it was statistically insignificant. A positive correlation was found between βKL and FGFR4 concentrations in PTC patients. The levels of βKL, FGF19 and FGFR4 did not differ significantly between MNG group and healthy controls.

CONCLUSIONS

Our results indicate that a disrupted FGF19/FGFR4/βKL signaling pathway may play a role in the development of thyroid cancers. However, further studies are needed to elucidate the molecular mechanism of the neoplastic transition of thyroid epithelial cells.

Primary Benign and Malignant Thyroid Neoplasms With Signet Ring Cells: Cytologic, Histologic, and Molecular Features

OBJECTIVES

Signet ring cells (SRCs) can be seen in a variety of thyroid tumors and can pose a diagnostic pitfall on cytology. This study describes the cytologic, histomorphologic, and molecular aspects of a cohort of primary thyroid tumors with SRCs.

METHODS

A search was performed of the Massachusetts General Hospital and Brigham and Women's Hospital (Boston, MA) pathology archives for the keywords thyroid, signet, and signet ring features between 2000 and 2014. Seven thyroidectomy specimens with corresponding thyroid fine-needle aspiration (FNA) were obtained. Cytology and histopathology slides were evaluated. Molecular analysis was performed using anchored multiplex polymerase chain reaction (AMP).

RESULTS

The cohort consisted of four follicular adenomas (FAs), two noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTPs), and one secretory carcinoma (SC). The FNA diagnoses were atypia of undetermined significance (n = 3), suspicious for follicular neoplasm (n = 3), and suspicious for malignancy (n = 1). Molecular analyses revealed PTEN and FGFR3 mutations in an FA and NIFTP, respectively, and an ETV6-NTRK3 fusion in a case of primary thyroid gland SC.

CONCLUSIONS

Our study demonstrates the range of thyroid tumors with SRCs. While most thyroid tumors with SRCs are benign, primary thyroid SC should also be considered in the differential diagnosis.

Spotlight on lenvatinib in the treatment of thyroid cancer: patient selection and perspectives

Thyroid cancer is the most common endocrine malignancy, with over 60,000 cases reported per year in the US alone. The incidence of thyroid cancer has increased in the last several years. Patients with metastatic differentiated thyroid cancer (DTC) generally have a good prognosis. Metastatic DTC can often be treated in a targeted manner with radioactive iodine, but the ability to accumulate iodine is lost with decreasing differentiation. Until recently, chemotherapy was the only treatment in patients with advanced thyroid cancer, which is no longer amenable to therapy with radioactive iodine. The modest efficacy and significant toxicity of chemotherapy necessitated the need for urgent advances in the medical field. New insights in thyroid cancer biology propelled the development of targeted therapies for this disease, including the tyrosine kinase inhibitor sorafenib as salvage treatment for DTC. In 2015, the US Food and Drug Administration approved a second tyrosine kinase inhibitor, lenvatinib, for the treatment of radioiodine-refractory thyroid cancer. Although associated with a significant progression-free survival improvement as compared to placebo in a large Phase III study (median progression-free survival 18.2 vs 3.6 months; hazard ratio 0.21; 99% confidence interval 0.14-0.31; P<0.001), the benefit of lenvatinib needs to be proved in the context of associated moderate to severe toxicities that require frequent dose reduction and delays. This article reviews the evidence supporting the use of lenvatinib as salvage therapy for radioactive iodine-refractory thyroid cancer, with a focus on the toxicity profile of this new therapy.

Fibroblast growth factor receptor-2 expression in thyroid tumor progression: potential diagnostic application

Fibroblast growth factor receptor-2 (FGFR-2) plays an important role in tumorigenesis. In thyroid cancer it has been observed a FGFR-2 down-modulation, but the role of this receptor has not been yet clarified. Therefore, we decided to examine the expression of both FGFR-2 isoform, FGFR-2-IIIb and FGFR-2-IIIc, in different histological thyroid variants such as hyperplasia, follicular adenoma and papillary carcinoma. Immunohistochemistry and quantitative Real-Time PCR analyses were performed on samples of hyperplasia, follicular adenoma and papillary carcinoma, compared with normal thyroid tissue. Thyroid hyperplasia did not show statistically significant reduction in FGFR-2 protein and mRNA levels. Interestingly, in both follicular adenoma and papillary carcinoma samples we observed a strongly reduced expression of both FGFR-2 isoforms. We speculate that FGFR-2 down-modulation might be an early event in thyroid carcinogenesis. Furthermore, we suggest the potential use of FGFR-2 as an early marker for thyroid cancer diagnosis.

Fibroblast growth factor receptor-3 expression in meningiomas with stimulation of proliferation by the phosphoinositide 3 kinase-Akt pathway

OBJECT

Fibroblast growth factor receptors (FGFRs)-1, -2, and -3 are expressed in the developing brain and may participate in CNS neoplasia. Fibroblast growth receptor-3 has not been demonstrated in the human CNS or its tumors. Nonetheless, it has been implicated in the pathogenesis of several other forms of neoplasia.

METHODS

Twenty-four human meningiomas were evaluated using Western blot analysis for expression of FGFR3, its ligand acidic FGF, and concomitant phosphorylation/activation of p44/42 mitogen-activated protein kinase (MAPK), Akt, and STAT3. Mutations in exons 7 and 10 of the FGFR3 gene were analyzed by polymerase chain reaction in 10 meningiomas. Primary meningioma cells cultured from 10 human meningiomas were also treated with acidic FGF and evaluated for cell proliferation or activation/phosphorylation of p44/42 MAPK, Akt, and STAT3.

RESULTS

Immunoblotting demonstrated the presence of FGFR3 in 12 (71%) of 17 primarily fibroblastic and transitional WHO Grade I meningiomas. The FGFR3 was detected in 4 (80%) of 5 WHO Grade II, and 2 of 2 Grade III tumors. Acidic FGF was detected in 3 (18%) of 17 Grade I, 1 (20%) of 5 Grade II, and 1 (50%) of 2 Grade III meningiomas. In WHO Grade I meningiomas, 3 of 6 tumors with no detectable FGFR3 had no detectable p-STAT3. In WHO Grades II and III meningiomas, FGFR3 expression was associated with p-STAT3, p-Akt, and p-p44/42 MAPK expression. No mutations were demonstrated in exons 7 or 10 by polymerase chain reaction in any meningioma. Treatment with acidic FGF, a ligand for FGFR3, stimulated meningioma cell proliferation and activation of Akt and STAT3 in primary meningioma cell cultures.

CONCLUSIONS

These findings suggest that FGFR3 and acidic FGF are expressed in adult human leptomeninges as well as WHO Grades I and II meningiomas. Fibroblast growth factor receptor-3 activation stimulates meningioma cell proliferation by activation of the phosphoinositide 3 kinase-Akt-PRAS40-mTOR and STAT3 pathways.

Tumour formation by single fibroblast growth factor receptor 3-positive rhabdomyosarcoma-initiating cells

Background:

The hypothesis that malignant tumours are generated by rare populations of cancer stem cells that are more tumourigenic than other cancer cells has gained increasing credence. The objective of this study was to identify and characterise a subpopulation of human sarcoma-initiating cells.

Methods:

We examined established rhabdomyosarcoma cell lines by flow cytometry. Tumourigenesis was examined by xenograft models. Real-time PCR and immunohistochemistry were performed to examine the gene expression using cell lines and biopsy specimens.

Results:

Rhabdomyosarcoma cell lines included small populations of fibroblast growth factor receptor 3 (FGFR3)-positive cells. FGFR3-positive KYM-1 and RD cells were more strongly tumourigenic than FGFR3-negative cells. In addition, xenoengraftment of 33% of single FGFR3-positive KYM-1 cells yielded tumour formation. Stem cell properties of FGFR3-positive cells were further established by real-time PCR, which demonstrated upregulation of undifferentiated cell markers and downregulation of differentiation markers. We showed that in the absence of serum, addition of basic fibroblast growth factor maintained and enriched FGFR3-positive cells. On the other hand, ciliary neurotrophic factor reduced the proportion of FGFR3-positive cells. Real-time PCR and immunohistochemical examination revealed that embryonal rhabdomyosarcoma patient biopsy specimens were found to over-express FGFR3.

Conclusions:

Our findings suggest that rhabdomyosarcoma cell lines include a minor subpopulation of FGFR3-positive sarcoma-initiating cells, which can be maintained indefinitely in culture and which is crucial for their malignancy.

FGFR3 mutations in seborrheic keratoses are already present in flat lesions and associated with age and localization

Somatic activating fibroblast growth factor 3 (FGFR3) mutations in human skin can cause seborrheic keratoses, one of the most frequent skin tumors in man. However, details of the involved mechanisms remain elusive. We analyzed 65 acanthotic seborrheic keratoses with varying vertical diameters for FGFR3 mutations using a SNaPshot multiplex assay. Immunohistochemistry was performed for Ki-67, bcl-2 and FGFR3 protein in all seborrheic keratoses and 19 normal skin samples. FGFR3 mutations were detected in 37 of 65 seborrheic keratoses (57%). These mutations were found both in flat (initial) and thick seborrheic keratoses. FGFR3 mutations were significantly associated with increased age and localization on the head and neck (P<0.01). Ki-67 expression was significantly higher in seborrheic keratoses than in normal epidermis independent of the FGFR3 status (P<0.001). Furthermore, FGFR3 mutations were associated with an increased expression of bcl-2 and FGFR3 protein (P<0.05). Our results indicate that FGFR3 mutations can occur early in the pathogenesis of at least a subset of seborrheic keratoses. Increased age appears to be a risk factor for these mutations. The preferential occurrence of FGFR3 mutations in seborrheic keratoses of the head and neck suggests a causative role for cumulative lifetime ultraviolet light exposure.

Effect of all-trans retinoic acid on sodium/iodide symporter expression, radioiodine uptake and gene expression profiles in a human anaplastic thyroid carcinoma cell line

The plasma membrane glycoprotein sodium/iodide symporter (NIS) is crucial for thyroid hormone biosynthesis and mediates the iodide uptake of thyrocytes. It has been shown that retinoic acid (RA) alters NIS gene expression in thyroid carcinoma lines and stimulates their iodide uptake. Here, we generated an ARO human thyroidal cancer cell line that expresses the NIS gene (ARO-NIS) and found that its baseline 125I uptake was threefold higher than that of its parental ARO cells. However, a 1-microM all-trans retinoic acid (tRA) treatment significantly increased this 125I uptake up to approximately approximately 6.5-fold on Day 3. tRA also elevated NIS mRNA expression in ARO-NIS cells, with peaks of expression being observed on Day 3. To investigate the underlying genomic mechanisms involved in these tRA-induced phenotypic changes, we subjected tRA-treated and untreated ARO-NIS cells to cDNA microarray analysis. Of 1152, genes spotted onto the microarray membrane, 18 were up-regulated (z ratio>2.0) and 33 were down-regulated (z ratio<-2.0) in ARO-NIS cells after 3 days of tRA treatment. More specifically, tRA increased the expression of BCL3, CSRP3, v-fos, and CDK5 genes and decreased the expression of the FGF12 and IGFBP6 genes. Thus, tRA treatment of human anaplastic thyroid carcinoma cells stably expressing the NIS gene significantly elevates their NIS-mediated radioiodine uptake and alters the expression of many genes involved in cell growth and cellular differentiation. Therefore, tRA treatment and NIS gene transfection are potential tools for the diagnosis and treatment of thyroid cancer.

Pathogenetic mechanisms in thyroid follicular-cell neoplasia

Thyroid cancer is one of the few malignancies that are increasing in incidence. Recent advances have improved our understanding of its pathogenesis; these include the identification of genetic alterations that activate a common effector pathway involving the RET-Ras-BRAF signalling cascade, and other unique chromosomal rearrangements. Some of these have been associated with radiation exposure as a pathogenetic mechanism. Defects in transcriptional and post-transcriptional regulation of adhesion molecules and cell-cycle control elements seem to affect tumour progression. This information can provide powerful ancillary diagnostic tools and can also be used to identify new therapeutic targets.

Constitutive activating mutation of the FGFR3b in oral squamous cell carcinomas

A G to T mutation at nucleotide position 2128 in the human FGFR3b coding region resulting in a Cys for Gly substitution (G697C) in the tyrosine kinase domain was observed in 62% (44/71) of oral squamous cell carcinomas (OSCC) examined. Immunostained FGFR3b was found in the cytoplasm of prickle cells in normal epithelia, and FGFR3b was localized in the cytoplasm and nucleus in non-FGFR3b mutant OSCC. Overexpressed FGFR3b protein on plasma membranes was noted in OSCC bearing the FGFR3b mutation. Enhanced tyrosine kinase activity of G697CFGFR3b was confirmed. Our results indicate that G697C is an activating mutation causing constitutive ligand-independent FGFR3b signaling. This mutation may be involved in the progression of OSCC and thus the FGFR3b coding sequence may have diagnostic or prognostic value for OSCC.

Cellular signaling by fibroblast growth factor receptors

The 22 members of the fibroblast growth factor (FGF) family of growth factors mediate their cellular responses by binding to and activating the different isoforms encoded by the four receptor tyrosine kinases (RTKs) designated FGFR1, FGFR2, FGFR3 and FGFR4. Unlike other growth factors, FGFs act in concert with heparin or heparan sulfate proteoglycan (HSPG) to activate FGFRs and to induce the pleiotropic responses that lead to the variety of cellular responses induced by this large family of growth factors. A variety of human skeletal dysplasias have been linked to specific point mutations in FGFR1, FGFR2 and FGFR3 leading to severe impairment in cranial, digital and skeletal development. Gain of function mutations in FGFRs were also identified in a variety of human cancers such as myeloproliferative syndromes, lymphomas, prostate and breast cancers as well as other malignant diseases. The binding of FGF and HSPG to the extracellular ligand domain of FGFR induces receptor dimerization, activation and autophosphorylation of multiple tyrosine residues in the cytoplasmic domain of the receptor molecule. A variety of signaling proteins are phosphorylated in response to FGF stimulation including Shc, phospholipase-Cgamma, STAT1, Gab1 and FRS2alpha leading to stimulation of intracellular signaling pathways that control cell proliferation, cell differentiation, cell migration, cell survival and cell shape. The docking proteins FRS2alpha and FRS2beta are major mediators of the Ras/MAPK and PI-3 kinase/Akt signaling pathways as well as negative feedback mechanisms that fine-tune the signal that is initiated at the cell surface following FGFR stimulation.

Dual Inhibition of RET and FGFR4 Restrains Medullary Thyroid Cancer Cell Growth

Medullary thyroid cancer is frequently an aggressive form of carcinoma for which there are currently no effective forms of systemic therapy. These carcinomas arise as a result of activating mutations in the RET proto-oncogene transmembrane tyrosine kinase receptor. We, therefore, examined the potential efficacy of the tyrosine kinase inhibitor STI571 on the growth of human TT medullary cancer cells in vitro and in xenografted severe combined immunodeficiency mice. Treatment with STI571 resulted in inhibition of RET phosphorylation, cell proliferation, tumor growth and invasiveness. Based on the profile of expression of fibroblast growth factor receptors (FGFR), we examined the effects of FGFR tyrosine kinase inhibition using the small molecule FGFR inhibitor PD173074. This inhibitor resulted in abrogation of fibroblast growth factor-1-mediated FGFR4 phosphorylation in TT cells, an effect that was accompanied by significant arrest of cell proliferation and tumor growth in vivo. Moreover, the combination of STI571 and PD173074 resulted in greater suppression of cell proliferation in vitro and tumor control in vivo than that achieved with either agent alone. These data highlight RET and FGFR4 as therapeutic targets and suggest a potential role for the combined use of tyrosine kinase inhibitors in the management of inoperable medullary thyroid cancers.

Targeting FGFR3 in multiple myeloma: inhibition of t(4;14)-positive cells by SU5402 and PD173074

The t(4;14)(p16.3;q32), associated with 10-20% of cases of multiple myeloma (MM), deregulates the expression of MMSET and FGFR3. To assess the potential of FGFR3 as a drug target, we evaluated the effects of selective inhibitors on MM and control cell lines. SU5402 and PD173074 specifically inhibited the growth of the two t(4;14)-positive MM lines, KMS-11 and OPM-2. Importantly, inhibition was still observed in the presence of IL-6, a growth factor known to play an important role in MM. Both compounds induced a dose-dependent reduction in cell viability and an increase in apoptosis, accompanied by a decrease in extracellular signal-related kinase phosphorylation. In contrast, no inhibition was seen with either compound against t(4;14)-negative cell lines or NCI-H929, a t(4;14)-positive, FGFR3-negative MM cell line. FGFR3 is thus a plausible candidate for targeted therapy in a subset of MM patients.

The myeloma-associated oncogene fibroblast growth factor receptor 3 is transforming in hematopoietic cells

Translocations involving fibroblast growth factor receptor 3 (fgfr3) have been identified in about 25% of patients with myeloma. To directly examine the oncogenic potential of fgfr3, murine bone marrow (BM) cells were transduced with retroviral vectors containing either wild-type fgfr3 or an activated mutant form of the receptor, fgfr3-TD. Mice transplanted with FGFR3-TD-expressing BM developed a marked leukocytosis and lethal hematopoietic cell infiltration of multiple tissues within 6 weeks of transplantation. Secondary and tertiary recipients of spleen or BM from primary fgfr3-TD mice also developed tumors within 6 to 8 weeks. Analysis of the circulating tumor cells revealed a pre-B-cell phenotype in most mice, although immature T-lymphoid or mature myeloid populations also predominated in some animals. Enhanced lymphoid but not myeloid colony formation was observed in the early posttransplantation period and only interleukin 7 and FGF-responsive pre-B-cell lines could be established from tumors. Cell expansions in primary recipients appeared polyclonal, whereas tumors in later passages exhibited either clonal B- or T-cell receptor gene rearrangements. Mice transplanted with wild-type FGFR3-expressing BM developed delayed pro-B-cell lymphoma/leukemias approximately 1 year after transplantation. These studies confirm that FGFR3 is transforming and can produce lymphoid malignancies in mice.

Loss of heterozygosity at 4p16.3 and mutation of FGFR3 in transitional cell carcinoma

4p16.3 has previously been identified as a region of non-random LOH in transitional cell carcinoma, suggesting the presence of a tumour suppressor gene. One candidate within this region is fibroblast growth factor receptor 3 (FGFR3). Germline mutations in FGFR3 are known to cause several autosomal dominant skeletal dysplasias, the severity of which depends on the position and nature of the mutation in the protein. We investigated the frequency and nature of FGFR3 mutations in a panel of transitional cell carcinomas and cell lines and studied the possible link between mutation and loss of heterozygosity (LOH) on 4p16.3. FGFR3 coding sequence from 63 transitional cell carcinomas (TCC) of various stages and grades, and 18 cell lines was analysed by fluorescent SSCP. Samples with abnormal migration patterns were sequenced to identify the mutation or polymorphism. Thirty-one of the 63 tumours had previously been assessed to have LOH at 4p16.3. Twenty-six of the 63 tumours (41%) and 4/18 (22%) of the cell lines had missense mutations in FGFR3. All mutations detected in our panel have been reported in the germline where all apart from one cause lethal conditions. One tumour contained K652Q which has recently been identified in less severe cases of skeletal dysplasia. Tumours with and without LOH at 4p16.3 had mutations in FGFR3 suggesting that these two events are not causally linked. The frequency of FGFR3 mutation indicates that this protein plays an important role in TCC.

A subpopulation of fibroblast growth factor-2-binding heparan sulfate is lost in human papillary thyroid carcinomas

We hypothesized that a change in composition of proteoglycans can regulate the bioactivity of fibroblast growth factor (FGF)-2 in the thyroid. In order to test this hypothesis, we established a simple and sensitive method for detecting FGF-2-binding heparan sulfates and characterized them in papillary thyroid carcinomas and normal thyroids. The thyroid extracts were applied to a Q-Sepharose anion exchange column. After the column was washed with 10 mM of phosphate buffer, 1 microgram of human recombinant FGF-2 was added onto the column. The column was eluted with a gradient of NaCl (0.3-1.5 M). Each fraction was blotted onto nitrocellulose membrane. Immunoreactivity of heparan sulfate and FGF-2 was revealed by the incubation of membranes with the specific antibodies, and quantitatively estimated by measuring the density of the color product. In normal thyroids, immunoreactivity of heparan sulfate was detected as two peaks at 0.7 and 0.9 M of NaCl. Heparan sulfate-containing fractions also showed FGF-2 immunoreactivity, indicating the complex formation of FGF-2 and heparan sulfate. In papillary thyroid carcinomas, immunoreactivity of heparan sulfate showed various elution profiles on Q-Sepharose chromatography, including single peak at 0.7 M of NaCl and the one similar to that of the normal thyroids. However, FGF-2 immunoreactivity was detected only in the fractions eluting at 0.7 M of NaCl. This loss of a subpopulation of FGF-2-binding heparan sulfate in human papillary thyroid carcinomas may lead to the increase of free FGF-2 bioavailable in extracellular matrix.