Somatostatin receptor subtype expression in human thyroid and thyroid carcinoma cell lines

Molecular Imaging and Theragnostics of Thyroid Cancers

Molecular imaging plays an important role in the evaluation and management of different thyroid cancer histotypes. The existing risk stratification models can be refined, by incorporation of tumor-specific molecular markers that have theranostic power, to optimize patient-specific (individualized) treatment decisions. Molecular imaging with varying radioisotopes of iodine (i.e., 131I, 123I, 124I) is an indispensable component of dynamic and theragnostic risk stratification of differentiated carcinoma (DTC) while [18F]F-fluorodeoxyglucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT) helps in addressing disease aggressiveness, detects distant metastases, and risk-stratifies patients with radioiodine-refractory DTC, poorly differentiated and anaplastic thyroid cancers. For medullary thyroid cancer (MTC), a neuroendocrine tumor derived from thyroid C-cells, [18F]F-dihydroxyphenylalanine (6-[18F]FDOPA) PET/CT and/or [18F]FDG PET/CT can be used dependent on serum markers levels and kinetics. In addition to radioiodine therapy for DTC, some theragnostic approaches are promising for metastatic MTC as well. Moreover, new redifferentiation strategies are now available to restore uptake in radioiodine-refractory DTC while new theragnostic approaches showed promising preliminary results for advanced and aggressive forms of follicular-cell derived thyroid cancers (i.e., peptide receptor radiotherapy). In order to help clinicians put the role of molecular imaging into perspective, the appropriate role and emerging opportunities for molecular imaging and theragnostics in thyroid cancer are discussed in our present review.

Targeting the Sonic Hedgehog Pathway to Suppress the Expression of the Cancer Stem Cell (CSC)-Related Transcription Factors and CSC-Driven Thyroid Tumor Growth

Simple Summary

Poorly differentiated and anaplastic thyroid cancers respond poorly to surgery, radiation, and hormone therapy. Cancer stem cells play an important role in tumor growth, drug resistance, and recurrence. This study focuses on how the sonic hedgehog (Shh) pathway maintains thyroid cancer stem cell self-renewal and whether it can be targeted for anticancer therapy. The authors report that the Shh pathway regulates the expression of BMI1 and SOX2, two genes involved in stem cell self-renewal, and that targeting the Shh pathway has little effect on thyroid tumor xenografts but can inhibit the growth of tumor xenografts derived from thyroid cancer stem cells. This study advances the knowledge on how thyroid cancer stem cells regenerate and highlights the potential therapeutic values of targeting the Shh pathway.

Abstract

The sonic hedgehog (Shh) pathway plays important roles in tumorigenesis, tumor growth, drug resistance, and metastasis. We and others have reported earlier that this pathway is highly activated in thyroid cancer. However, its role in thyroid cancer stem cell (CSC) self-renewal and tumor development remains incompletely understood. B lymphoma Mo-MLV insertion region 1 homolog (BMI1) and SRY-Box Transcription Factor 2 (SOX2) are two CSC-related transcription factors that have been implicated in promoting CSC self-renewal. The objective of our current investigation was to determine the role of the Shh pathway in regulating BMI1 and SOX2 expression in thyroid cancer and promoting thyroid tumor growth and development. Here we report that inhibition of the Shh pathway by Gli1 siRNA or by cyclopamine and GANT61 reduced BMI1 and SOX2 expression in SW1736 and KAT-18 cells, two anaplastic thyroid cancer cell lines. The opposite results were obtained in cells overexpressing Gli1 or its downstream transcription factor Snail. The Shh pathway regulated SOX2 and BMI1 expression at a transcriptional and post-transcriptional level, respectively. GANT61 treatment suppressed the growth of SW1736 CSC-derived tumor xenografts but did not significantly inhibit the growth of tumors grown from bulk tumor cells. Clinicopathological analyses of thyroid tumor specimens by immunohistochemical (IHC) staining revealed that BMI1 and SOX2 were highly expressed in thyroid cancer and correlated with Gli1 expression. Our study provides evidence that activation of the Shh pathway leads to increased BMI1 and SOX2 expression in thyroid cancer and promotes thyroid CSC-driven tumor initiation. Targeting the Shh pathway may have therapeutic value for treating thyroid cancer and preventing recurrence.

Comparative distribution of somatostatin and somatostatin receptors in PTU-induced hypothyroidism

PURPOSE

Propylthiouracil (PTU)-induced hypothyroidism is a well-established model for assessing hormonal and morphological changes in thyroid as well as other central and peripheral tissues. Somatostatin (SST) is known to regulate hormonal secretion and synthesis in endocrine tissues; however, nothing is currently known about the distribution of SST and its receptor in hypothyroidism.

METHOD

In the present study, the comparative immunohistochemical distribution of SST and somatostatin receptors (SSTRs) were analyzed in PTU-induced hypothyroid rats. Rats were treated with PTU for 15 days followed by a co-administration of levothyroxine (LVT) for 15 days. After PTU and LVT treatments (day 30), rats were further administered LVT alone for 15 more days (day 45). The subcellular distribution of SST and SSTR subtypes was determined by peroxidase immunohistochemistry in the thyroid gland collected from control and treated rats.

RESULTS

SST and SSTR subtypes were found to be moderately expressed in control thyroid tissues. SST and SSTR subtypes like immunoreactivity increased significantly in follicular and parafollicular epithelial cells in the thyroid of PTU-treated rats. The PTU-induced changes in the expression of SST and SSTR subtypes were suppressed by the administration of the LVT. In addition to thyroid tissues, SST and SSTRs expression was also changed in non-follicular tissues including blood vessels, smooth muscle cells, and connective tissue following treatments.

CONCLUSION

The present study revealed a distinct subcellular distribution of SST and SSTR subtypes in the thyroid and provides a new insight for the role of SST and SSTR subtypes in hypothyroidism in addition to its well-established role in negative regulation of hormonal secretion.

Differentiated thyroid cancer theranostics: radioiodine and beyond

The term theranostics is the combination of a diagnostic tool that helps to define the right therapeutic tool for specific disease. It signifies the "we know which sites require treatment (diagnostic scan) and confirm that those sites have been treated (post-therapy scan)" demonstrating the achievable tumor dose concept. This term was first used by John Funkhouser at the beginning of the 90s, at the same time the concept of personalized medicine appeared. In nuclear medicine, theranostics is easy to apply and understand because of an easy switch from diagnosis to therapy with the same vector. It helps in maximizing tumor dose and sparing normal tissue with high specific and rapid uptake in metastasis. The oldest application of this concept is radioactive iodine I-131 (RAI). The first treatment based on the theranostic concept was performed on thyroid cancer patients with RAI in 1946. From then on management of differentiated thyroid cancer (DTC) has evolved on the multimodality concept. We now use the term "our" patient instead of "my" patient to signify this. However, the initial surgical management followed by RAI as per the theranostics has remained the mainstay in achieving a cure in most of DTC patients. The normal thyroid cells metabolise iodine, the principle of which is utilized in imaging of the thyroid gland with isotopes of iodine. RAI treatment of DTC is based on the principle of sodium iodide symporter (NIS) expressing thyroid cells with DTC cells having the ability of trapping circulating RAI successfully helping in treatment of residual and metastatic disease. NIS is usually negative in poorly differentiated cells and is inversely proportional to Glucose transporter receptor Type 1 expression. Both positive and negative NIS are the key components of the theranostic approach in treatment of DTC. Presence or absence of NIS is documented by either whole body iodine scintigraphy (WBS) or 2-deoxy-2(18F) fludeoxyglucose (FDG) positron emission tomography computed tomography (PET-CT). Currently, single photon emission CT and CT (SPECT-CT) has significantly improved the precision and sensitivity of whole body iodine scintigraphy with its capability of accurate localization of disease foci whether iodine avid or non-avid. This has helped in a more personalized approach in treatment. This review will give an overview of the role of NIS in the theranostic approach to management with RAI, its current status and also the molecular approach to treatment in RAI refractory disease.

Combined effects of octreotide and cisplatin on the proliferation of side population cells from anaplastic thyroid cancer cell lines

Anaplastic thyroid cancer (ATC) represents the most aggressive subtype of thyroid cancer and has a poor prognosis. In addition to surgery, chemotherapy is an important treatment for ATC; however, the therapeutic effects of current chemotherapies for ATC are not particularly promising. There is a high proportion of side population (SP) cells in ATC, which may be a reason for its drug resistance. In the present study, the antitumor activities of combined octreotide (OCT) and cisplatin (DDP) on the proliferation and apoptosis of ATC SP cells were evaluated. First, SP cells from 8305C and BHT101 cell lines were detected and sorted. Following in vitro culture for 1 week, cluster of differentiation (CD)44, CD133, ATP-binding cassette (ABC) subfamily B member 1 (ABCB1), ABC subfamily G member 2 (ABCG2) and somatostatin receptor expression was detected to characterize the SP cells. An MTT assay was performed to investigate the combined effects on 8305C-SP cell proliferation in vitro, and a mouse model was used to investigate the combined effects on 8305C-SP cell proliferation in vivo. Annexin V/propidium iodide staining was used to investigate the combined effects on 8305C-SP cell apoptosis. Chemotherapeutic drug resistance-associated protein expression and apoptosis-associated protein expression were also detected following combined treatment. As a result, SP cells were identified in 8305C and BHT101 cells, and the proportion of 8305C-SP cells was increased compared with that of BTH101-SP cells. SP cells have enhanced proliferation, tumorigenicity and drug resistance compared with main population cells. The combined treatment of OCT with DDP suppressed the proliferation of 8305C-SP cells in vitro and in vivo, and induced 8305C-SP cell apoptosis. Combined treatment decreased the ABCB1 and ABCG2 expression by SP cells and activated mitochondrial apoptotic signaling, resulting in cell apoptosis. In conclusion, these data support the hypothesis that combined treatment with OCT and DDP induces ATC cell apoptosis and suppresses cell proliferation. These data provide a theoretical basis for further combined chemotherapy clinical applications.

Methodology, Criteria, and Characterization of Patient-Matched Thyroid Cell Lines and Patient-Derived Tumor Xenografts

OBJECTIVE

To investigate the molecular underpinnings of thyroid cancer, preclinical cell line models are crucial; however, ∼40% of these have been proven to be either duplicates of existing thyroid lines or even nonthyroid-derived lines or are not derived from humans at all. Therefore, we set out to establish procedures and guidelines that should proactively avoid these problems, which facilitated the creation of criteria to make valid preclinical models for thyroid cancer research.

DESIGN

Based on our recommendations, we systematically characterized all new cell lines that we generated by a standardized approach that included (1) determination of human origin, (2) exclusion of lymphoma, (3) DNA fingerprinting and histological comparisons to establish linkage to presumed tissue of origin, (4) examining thyroid differentiation by screening two to three thyroid markers, (5) examination of biological behavior (growth rate, tumorigenicity), and (6) presence of common thyroid cancer genetic changes (TP53, BRAF, PTEN, PIK3CA, RAS, TERT promoter, RET/PTC, PAX8/PPARγ, NF1, and EIF1AX).

RESULTS

We established seven new thyroid cell lines (LAM136, EAM306, SDAR1, SDAR2, JEM493, THJ529, and THJ560) out of 294 primary culture attempts, and 10 patient-derived tumor xenografts (PDTXs; MC-Th-95, MC-Th-374, MC-Th-467, MC-Th-491, MC-Th-493, MC-Th-504, MC-Th-524, MC-Th-529, MC-Th-560, and MC-Th-562) out of 67 attempts. All were successfully validated by our protocols.

CONCLUSIONS

This standardized approach for cell line and PDTX characterization should prevent (or detect) future cross-contamination and ensure that only valid preclinical models are used for thyroid cancer research.

Refractory thyroid carcinoma: which systemic treatment to use?

The incidence of thyroid cancer has increased markedly in recent decades, but has been stable in terms of mortality rates. For the most part, these cancers are treated with surgery, which may or may not be followed by radioactive iodine depending on the tumor subtype. Still, many of these cancers will recur and may be treated with radioactive iodine or another surgery. It is unclear what treatment is best for cases of locally advanced or metastatic thyroid cancer that are refractory to radioactive iodine. Chemotherapy has a very low response rate. However, in the past few years, several systemic therapies, primarily targeted, have emerged to improve the overall survival of these patients. Alternative treatments are also of interest, namely peptide receptor radionuclide therapy or immunotherapy.

Effects of roniciclib in preclinical models of anaplastic thyroid cancer

Many human cancers have altered cyclin-dependent kinase activity. Inhibition of cyclin-dependent kinases may arrest cell cycle progression and represents an important strategy in the treatment of malignancies. We evaluated the therapeutic effects of roniciclib, a cyclin-dependent kinase inhibitor, as a treatment for anaplastic thyroid cancer. Roniciclib inhibited anaplastic thyroid cancer cell proliferation in a dose-dependent manner. Roniciclib activated caspase-3 activity and induced apoptosis. Cell cycle progression was arrested in G2/M phase. In vivo, the growth of anaplastic thyroid cancer xenograft tumors was retarded by roniciclib treatment without evidence of toxicity. These data provide a rationale for further clinical evaluation using roniciclib in the treatment of patients with anaplastic thyroid cancer.

Incidentally Detected Thyroid Follicular Neoplasm on Somatostatin Receptor Imaging and Post-therapy Scan

Peptide receptor radionuclide therapy (PRRT) either using Lu-177 or Y-90 peptide radiopharmaceuticals has emerged as promising treatment modality in patients with inoperable metastatic neuroendocrine tumour (NET) including medullary thyroid cancer, because of overexpression of somatostatin receptor 2 (sstr-2) on these cells. The several investigators have used PRRT in non-iodine avid differentiated thyroid cancer patients with limited success, where other treatment modalities have failed, probably due to faint sstr-2 expression in these lesions. However Hurthle cell neoplasms being predominantly non-iodine avid lesions have shown sstr-2 over-expression. The present case of inoperable NET patient imaged and treated with radiolabelled somatostatin analogue showed incidentally detected thyroid lesion highlighting the its importance in imaging and treatment in these type of thyroid malignancies.

The sonic hedgehog signaling pathway maintains the cancer stem cell self-renewal of anaplastic thyroid cancer by inducing snail expression

CONTEXT

Cancer stem cells (CSCs) have been recently identified in thyroid neoplasm. Anaplastic thyroid cancer (ATC) contains a higher percentage of CSCs than well-differentiated thyroid cancer. The signaling pathways and the transcription factors that regulate thyroid CSC self-renewal remain poorly understood.

OBJECTIVE

The objective of this study is to use two ATC cell lines (KAT-18 and SW1736) as a model to study the role of the sonic hedgehog (Shh) pathway in maintaining thyroid CSC self-renewal and to understand its underlying molecular mechanisms.

DESIGN

The expression and activity of aldehyde dehydrogenase (ALDH), a marker for thyroid CSCs, was analyzed by Western blot and ALDEFLUOR assay, respectively. The effect of three Shh pathway inhibitors (cyclopamine, HhAntag, GANT61), Shh, Gli1, Snail knockdown, and Gli1 overexpression on thyroid CSC self-renewal was analyzed by ALDEFLUOR assay and thyrosphere formation. The sensitivity of transfected KAT-18 cells to radiation was evaluated by a colony survival assay.

RESULTS

Western blot analysis revealed that ALDH protein levels in five thyroid cancer cell lines (WRO82, a follicular thyroid cancer cell line; BCPAP and TPC1, two papillary thyroid cancer cell lines; KAT-18 and SW1736, two ATC cell lines) correlated with the percentage of the ALDH(High) cells as well as Gli1 and Snail expression. The Shh pathway inhibitors, Shh and Gli1 knockdown, in KAT-18 cells decreased thyroid CSC self-renewal and increased radiation sensitivity. In contrast, Gli1 overexpression led to increased thyrosphere formation, an increased percentage of ALDH(High) cells, and increased radiation resistance in KAT-18 cells. Inhibition of the Shh pathway by three specific inhibitors led to decreased Snail expression and a decreased number of ALDH(High) cells in KAT-18 and SW1736. Snail gene knockdown decreased the number of ALDH(High) cells in KAT-18 and SW1736 cells.

CONCLUSIONS

The Shh pathway promotes the CSC self-renewal in ATC cell lines by Gli1-induced Snail expression.

The truncated isoform of somatostatin receptor5 (sst5TMD4) is associated with poorly differentiated thyroid cancer

Somatostatin receptors (ssts) are expressed in thyroid cancer cells, but their biological significance is not well understood. The aim of this study was to assess ssts in well differentiated (WDTC) and poorly differentiated thyroid cancer (PDTC) by means of imaging and molecular tools and its relationship with the efficacy of somatostatin analog treatment. Thirty-nine cases of thyroid carcinoma were evaluated (20 PDTC and 19 WDTC). Depreotide scintigraphy and mRNA levels of sst-subtypes, including the truncated variant sst5TMD4, were carried out. Depreotide scans were positive in the recurrent tumor in the neck in 6 of 11 (54%) PDTC, and in those with lung metastases in 5/11 cases (45.4%); sst5TMD4 was present in 18/20 (90%) of PDTC, being the most densely expressed sst-subtype, with a 20-fold increase in relation to sst2. In WDTC, sst2 was the most represented, while sst5TMD4 was not found; sst2 was significantly increased in PDTC in comparison to WDTC. Five depreotide positive PDTC received octreotide for 3–6 months in a pilot study with no changes in the size of the lesions in 3 of them, and a significant increase in the pulmonary and cervical lesions in the other 2. All PDTC patients treated with octreotide showed high expression of sst5TMD4. ROC curve analysis demonstrated that only sst5TMD4 discriminates between PDTC and WDTC. We conclude that sst5TMD4 is overexpressed in PDTC and may be involved in the lack of response to somatostatin analogue treatment.

Somatostatin receptor expression in thyroid disease

Somatostatin analogues are commercially available and used for the management of acromegaly and neuroendocrine tumours, but the expression of the receptors as a target in thyroid disease has not been explored. To assess somatostatin (SST) and somatostatin receptor (SSTR1-5) expression in both normal and thyroid disorders, as a potential target for somatostatin analogue therapy, 67 thyroid tissue specimens were reviewed: 12 differentiated thyroid carcinomas, 14 follicular adenomas, 17 multinodular goitres, 14 Graves disease, 10 Hashimotos thyroiditis specimens and five normal thyroids. Tissue was immunostained for SST and SSTR1-5. Positivity and the degree of positivity were recorded by double-blinded observers. Somatostatin receptor expression was highly expressed in normal tissue for SSTR1, 3, 4 and 5 (5 of 5, 4 of 5, 4 of 5 and 5 of 5 respectively) whilst SST and SSTR 2a and b were not expressed at all. The commonest receptor expressed for all pathological subtypes grouped together was SSTR2b (63 specimens). The commonest receptors expressed in differentiated thyroid cancer were SSTR5 (11 of 12 specimens) and SSTR2b (10 of 12 specimens). The commonest receptor expressed in benign disease was SSTR2b (53 of 55 specimens). SSTR5 was significantly under-expressed in Graves disease (P < 0.05). This study illustrates that SSTR 1, 3, 4 and 5 are highly expressed in normal, benign and malignant thyroid tissue. SSTR 2a and 2b appear absent in normal tissue and present in benign and malignant thyroid tissue (P < 0.02). This suggests that focussed SSTR2 treatment may be a potential therapeutic target.

The next generation of positron emission tomography radiopharmaceuticals in oncology

Although (18)F-fluorodeoxyglucose ((18)F-FDG) is still the most widely used positron emission tomography (PET) radiotracer, there are a few well-known limitations to its use. The last decade has seen the development of new PET probes for in vivo visualization of specific molecular targets, along with important technical advances in the production of positron-emitting radionuclides and their related labeling methods. As such, a broad range of new PET tracers are in preclinical development or have recently entered clinical trials. The topics covered in this review include labeling methods, biological targets, and the most recent preclinical or clinical data of some of the next generation of PET radiopharmaceuticals. This review, which is by no means exhaustive, has been separated into sections related to the PET radionuclide used for radiolabeling: fluorine-18, for the labeling of agents such as FACBC, FDHT, choline, and Galacto-RGD; carbon-11, for the labeling of choline; gallium-68, for the labeling of peptides such as DOTATOC and bombesin analogs; and the long-lived radionuclides iodine-124 and zirconium-89 for the labeling of monoclonal antibodies cG250, and J591 and trastuzumab, respectively.

Exploring new frontiers in molecular imaging: Emergence of 68Ga PET/CT

Since US Food and Drug Administration approval of 18-fluorodeoxyglucose as a positron tracer, and the development of hybrid positron emission tomography/computed tomography machines, there has been a great increase in clinical application and progress in the field of nuclear molecular imaging. However, not underestimating the value of ¹⁸F, there are known limitations in the use of this cyclotron-produced positron tracer. We hence turn our focus to an emerging positron tracer, ⁶⁸Ga, and examine the advantages, current clinical uses and potential future applications of this radioisotope.

C cells evolve at the same rhythm as follicular cells when thyroidal status changes in rats

C cells are primarily known for producing calcitonin, a hypocalcemic and hypophosphatemic hormone. Nevertheless, besides their role in calcium homeostasis, C cells may be involved in the intrathyroidal regulation of follicular cells, suggesting a possible interrelationship between the two endocrine populations. If this premise is true, massive changes induced by different agents in the activity of follicular cells may also affect calcitonin-producing cells. To investigate the behaviour of C cells in those circumstances, we have experimentally induced two opposite functional thyroid states. We hyperstimulated the follicular cells using a goitrogen (propylthiouracil), and we suppressed thyroid hormone synthesis by oral administration of thyroxine. In both scenarios, we measured T(4), TSH, calcitonin, and calcium serum levels. We also completely sectioned the thyroid gland, specifically immunostained the C cells, and rigorously quantified this endocrine population. In hypothyroid rats, not only follicular cells but also C cells displayed hyperplastic and hypertrophic changes as well as increased calcitonin levels. When exogenous thyroxine was administered to the rats, the opposite effect was noted as a decrease in the number and size of C cells, as well as decreased calcitonin levels. Additionally, we noted that the two cell types maintain the same numerical relation (10 +/- 2.5 follicular cells per C cell), independent of the functional activity of the thyroid gland. Considering that TSH serum levels are increased in hypothyroid rats and decreased in thyroxine-treated rats, we discuss the potential involvement of thyrotropin in the observed results.

Potential utility and limitations of thyroid cancer cell lines as models for studying thyroid cancer

BACKGROUND

Tumor-derived cell lines are widely used to study the mechanisms involved in thyroid carcinogenesis but recent studies have reported redundancy among thyroid cancer cell lines and identification of some "thyroid cell lines" that are likely not of thyroid origin.

SUMMARY

In this review, we have summarized the uses, the limitations, and the existing problems associated with the available follicular cell-derived thyroid cancer cell lines. There are some limitations to the use of cell lines as a model to "mimic" in vivo tumors. Based on the gene expression profiles of thyroid cell lines originating from tumors of different types it has become apparent that some of the cell lines are closely related to each other and to those of undifferentiated carcinomas. Further, many cell lines have lost the expression of thyroid-specific genes and have altered karyotypes, while they exhibit activation of several oncogenes (BRAF, v-raf murine sarcoma viral oncogene homolog B1; RAS, rat sarcoma; and RET/PTC, rearranged in transformation/papillary thyroid carcinoma) and inactivation of tumor suppressor gene (TP53) which is known to be important for thyroid tumorigenesis.

CONCLUSIONS

A careful selection of thyroid cancer cell lines that reflect the major characteristics of a particular type of thyroid cancer being investigated could be used as a good model system to analyze the signaling pathways that may be important in thyroid carcinogenesis. Further, the review of literature also suggests that some of the limitations can be overcome by using multiple cell lines derived from the same type of tumor.

Growth inhibition of thyroid follicular cell-derived cancers by the opioid growth factor (OGF) - opioid growth factor receptor (OGFr) axis

BACKGROUND

Carcinoma of the thyroid gland is an uncommon cancer, but the most frequent malignancy of the endocrine system. Most thyroid cancers are derived from the follicular cell. Follicular carcinoma (FTC) is considered more malignant than papillary thyroid carcinoma (PTC), and anaplastic thyroid cancer (ATC) is one of the most lethal human cancers. Opioid Growth Factor (OGF; chemical term - [Met5]-enkephalin) and its receptor, OGFr, form an inhibitory axis regulating cell proliferation. Both the peptide and receptor have been detected in a wide variety of cancers, and OGF is currently used clinically as a biotherapy for some non-thyroid neoplasias. This study addressed the question of whether the OGF-OGFr axis is present and functional in human thyroid follicular cell - derived cancer.

METHODS

Utilizing human ATC (KAT-18), PTC (KTC-1), and FTC (WRO 82-1) cell lines, immunohistochemistry was employed to ascertain the presence and location of OGF and OGFr. The growth characteristics in the presence of OGF or the opioid antagonist naltrexone (NTX), and the specificity of opioid peptides for proliferation of ATC, were established in KAT-18 cells. Dependence on peptide and receptor were investigated using neutralization studies with antibodies and siRNA experiments, respectively. The mechanism of peptide action on DNA synthesis and cell survival was ascertained. The ubiquity of the OGF-OGFr axis in thyroid follicular cell-derived cancer was assessed in KTC-1 (PTC) and WRO 82-1 (FTC) tumor cells.

RESULTS

OGF and OGFr were present in KAT-18 cells. Concentrations of 10-6 M OGF inhibited cell replication up to 30%, whereas NTX increased cell growth up to 35% relative to cultures treated with sterile water. OGF treatment reduced cell number by as much as 38% in KAT-18 ATC in a dose-dependent and receptor-mediated manner. OGF antibodies neutralized the inhibitory effects of OGF, and siRNA knockdown of OGFr negated growth inhibition by OGF. Cell survival was not altered by OGF, but DNA synthesis as recorded by BrdU incorporation was depressed by 28% in OGF-treated cultures compared to those exposed to sterile water. The OGF-OGFr axis was detected and functional in PTC (KTC-1) and FTC (WRO 82-1) cell lines.

CONCLUSION

These data suggest that OGF and OGFr are present in follicular-derived thyroid cancers, and that OGF serves in a tonically active inhibitory manner to maintain homeostasis of cell proliferation. These results may provide a biotherapeutic strategy in the treatment of these cancers.

Functional expression of the thyrotropin receptor in C cells: new insights into their involvement in the hypothalamic-pituitary-thyroid axis

Thyroid C cells, or parafollicular cells, are mainly known for producing calcitonin, a hormone involved in calcium homeostasis with hypocalcemic and hypophosphatemic effects. Classically, the main endocrine activity of this cell population has been believed to be restricted to its roles in serum calcium and bone metabolism. Nonetheless, in the last few years evidence has been accumulating in the literature with regard to local regulatory peptides secreted by C cells, such as somatostatin, ghrelin, thyrotropin releasing hormone or the recently described cocaine- and amphetamine-related transcript, which could modify thyroid function. As thyrotropin is the main hormone controlling the hypothalamic-pituitary-thyroid axis and, accordingly, thyroid function, we have examined the functional expression of the thyrotropin receptor in C-cell lines and in thyroid tissues. We have found that rat and human C-cell lines express the thyrotropin receptor at both mRNA and protein levels. Furthermore, incubation of C cells with thyrotropin resulted in a 10-fold inhibition of thyrotropin-receptor expression, and a concomitant decrease of the steady-state mRNA levels for calcitonin and calcitonin gene-related peptide determined by quantitative real-time PCR was found. Finally, thyrotropin receptor expression by C cells was confirmed at protein level in both normal and pathological thyroid tissues by immunohistochemistry and immunofluorescence. These results confirm that C cells, under regulation by thyrotropin, are involved in the hypothalamic-pituitary-thyroid axis and suggest a putative role in local fine-tuning of follicular cell activity.

Expression of somatostatin receptor subtypes in human thyroid tumors: the immunohistochemical and molecular biology (RT-PCR) investigation

Human endocrine tumors often express the somatostatin receptors SSTR 1-5 with different intensity. It has been widely investigated their distribution in pituitary adenomas, brain tumors, adrenal tumors and neuroendocrine tumors in gastrointestinal tract (NET). Some of studies also concern the expression of SSTRs in thyroid tumors but they are mainly limited to parafollicular C cells - derived medullary thyroid carcinomas (MTC). Results of SSTR 1-5 detection in other thyroid pathologies like follicular adenomas and papillary cancers are still scarce and often controversial, depending of investigation method used. The aim of this study was to report the presence of all the 5 subtypes of SSTR (including 2A and 2B SSTR isoforms) in some surgically treated human thyroid tumors by means of immunohistochemistry and real-time PCR method and to correlate the results obtained with both techniques. SSTR 1 protein was expressed in 88.8% of investigated cases, SSTR 2A and 2B both in 44.4%, SSTR 3 in 55.5%, SSTR 4 in 11.2% and SSTR 5 in 33.3%. SSTR 1 is the dominant form in the thyroid gland tumor and hyperplasia. We found positive confirmation of both methods in 88.8% for SSTR 1, 2A, 3 subtypes, in 22.2% for SSTR 4 and in 100% for SSTR 5. It suggests that somatostatin multiligand analogs or selective SSTR 1 agonists may be used in thyroid tumors treatment.

Deoxyribonucleic acid profiling analysis of 40 human thyroid cancer cell lines reveals cross-contamination resulting in cell line redundancy and misidentification

CONTEXT

Cell lines derived from human cancers provide critical tools to study disease mechanisms and develop novel therapies. Recent reports indicate that up to 36% of cell lines are cross- contaminated.

OBJECTIVE

We evaluated 40 reported thyroid cancer-derived cell lines using short tandem repeat and single nucleotide polymorphism array analysis.

RESULTS

Only 23 of 40 cell lines tested have unique genetic profiles. The following groups of cell lines are likely derivatives of the same cell line: BHP5-16, BHP17-10, BHP14-9, and NPA87; BHP2-7, BHP10-3, BHP7-13, and TPC1; KAT5, KAT10, KAT4, KAT7, KAT50, KAK1, ARO81-1, and MRO87-1; and K1 and K2. The unique cell lines include BCPAP, KTC1, TT2609-C02, FTC133, ML1, WRO82-1, 8505C, SW1736, Cal-62, T235, T238, Uhth-104, ACT-1, HTh74, KAT18, TTA1, FRO81-2, HTh7, C643, BHT101, and KTC-2. The misidentified cell lines included the DRO90-1, which matched the melanoma-derived cell line, A-375. The ARO81-1 and its derivatives matched the HT-29 colon cancer cell line, and the NPA87 and its derivatives matched the M14/MDA-MB-435S melanoma cell line. TTF-1 and Pax-8 mRNA levels were determined in the unique cell lines.

CONCLUSIONS

Many of these human cell lines have been widely used in the thyroid cancer field for the past 20 yr and are not only redundant, but not of thyroid origin. These results emphasize the importance of cell line integrity, and provide the short tandem repeat profiles for a panel of thyroid cancer cell lines that can be used as a reference for comparison of cell lines from other laboratories.

Regulation of 14-3-3sigma expression in human thyroid carcinoma is epigenetically regulated by aberrant cytosine methylation

Increased 14-3-3sigma expression has been observed by immunohistochemistry in papillary and anaplastic tumors, but not follicular thyroid cancers. 14-3-3sigma mRNA expression and methylation status was examined in tumor cell lines and primary thyroid tissues using real-time RT-PCR, bisulfite sequencing and methylation-specific PCR. Most of the 27 CpG's in the gene's CpG island were methylated in normal thyroid, TPC-1, NPA, FTC-238 and 2-7, which did not express 14-3-3sigma. In contrast, they were unmethylated in KAK-1 and anaplastic lines KAT4 and DRO-90. 14-3-3sigma expression was not increased in thyroid carcinomas, the majority of which had a methylated CpG island. In addition, 5-aza-dC treatment increased 14-3-3sigma expression in the FTC-238 and NPA cell lines, which had low baseline expression. We conclude 14-3-3sigma expression in thyroid carcinomas is regulated by CpG island hypermethylation.

UbcH10 overexpression may represent a marker of anaplastic thyroid carcinomas

The hybridisation of an Affymetrix HG_U95Av2 oligonucleotide array with RNAs extracted from six human thyroid carcinoma cell lines and a normal human thyroid primary cell culture led us to the identification of the UbcH10 gene that was upregulated by 150-fold in all of the carcinoma cell lines in comparison to the primary culture cells of human normal thyroid origin. Immunohistochemical studies performed on paraffin-embedded tissue sections showed abundant UbcH10 levels in thyroid anaplastic carcinoma samples, whereas no detectable UbcH10 expression was observed in normal thyroid tissues, in adenomas and goiters. Papillary and follicular carcinomas were only weakly positive. These results were further confirmed by RT-PCR and Western blot analyses. The block of UbcH10 protein synthesis induced by RNA interference significantly reduced the growth rate of thyroid carcinoma cell lines. Taken together, these results would indicate that UbcH10 overexpression is involved in thyroid cell proliferation, and may represent a marker of thyroid anaplastic carcinomas.

Value of 111In-DOTA-lanreotide and 111In-DOTA-DPhe1-Tyr3-octreotide in differentiated thyroid cancer: results of in vitro binding studies and in vivo comparison with 18F-FDG PET

PURPOSE

Radioiodine-negative thyroid cancer presents diagnostic and therapeutic difficulties, warranting the implementation of new imaging and treatment strategies. The purpose of this study was twofold. First, we investigated in vitro the binding characteristics of 111In-DOTA-lanreotide (111In-DOTA-LAN) and 111In-DOTA-D: Phe1-Tyr3-octreotide (111In-DOTA-TOC) to cells derived from differentiated thyroid cancer (DTC). Second, we evaluated the value of somatostatin receptor (SSTR) scintigraphy with these radioligands, as compared with 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET), for the detection of tumour lesions in DTC patients.

METHODS

Binding of 111In-DOTA-LAN and 111In-DOTA-TOC to cells isolated from surgically removed thyroid tissue was evaluated in vitro by performing saturation and displacement studies. Eighteen DTC patients with elevated thyroglobulin (12 radioiodine-negative, six radioiodine-positive) were investigated with 111In-DOTA-LAN, 111In-DOTA-TOC and 18F-FDG PET scans.

RESULTS

Large numbers of SSTR binding sites for 111In-DOTA-LAN and 111In-DOTA-TOC were found on the cells investigated. Both SSTR radioligands exhibited a high binding affinity for these SSTR binding sites. 111In-DOTA-LAN and 111In-DOTA-TOC scintigraphy detected 37 and 33 lesions, respectively, in 17 (94%) patients each, whereas 18F-FDG PET revealed 30 lesions in 15 (83%) patients. Uptake of both SSTR radioligands was found in several radioiodine-negative sites. No striking differences in lesion imaging by 111In-DOTA-LAN and 111In-DOTA-TOC were found. In both radioiodine-negative and radioiodine-positive patients, more lesions were SSTR-positive/18F-FDG-negative than were 18F-FDG-positive/SSTR-negative.

CONCLUSION

Adding a SSTR scan with these radioligands to the diagnostic work-up increases the diagnostic capacity in DTC, and should be considered particularly in radioiodine-negative patients with elevated thyroglobulin levels.

Antiproliferative effect of octreotide on gastric cancer cells mediated by inhibition of Akt/PKB and telomerase

AIM: To investigate the antiproliferative effect of octreotide, a long-acting analogue of somatostatin, on gastric cancer cell line SGC7901 and its possible molecular mechanisms.

METHODS: Gastric cancer cell line SGC7901 employed in the study was treated with 0.008, 0.04, 0.2, 1, 5 and 25 μg·mL^-1 of octreotide respectively for 24 h to evaluate the antiproliferative effect of somatostatin analog on the tumor cells by MTT assay method. To elucidate the underlying mechanism, the cells were exposed to 1 μg·mL^-1 of octreotide for 0, 12, 24 and 48 h, when their Akt/PKB and telomerase activities were respectively determined using PCR-ELSIA and nonradioactive protein kinase assay protocols. The same experimental procedures were also performed in the control cells that were treated with corresponding vehicles instead of somatostatin analog.

RESULTS: After exposed to octreotide for 24 h at the concentrations of more than 1 μg·mL^-1, SGC7901 cells exhibited a dose-dependent inhibition of growth with the inhibiting rate to be as high as 34.66% when 25 μg·mL^-1 of octreotide was applied. The Akt/PKB and telomerase activity of SGC7901 cells was significantly inhibited when the cells were exposed to 1 μg·mL^-1 of octreotide for 12, 24 and 48 h compared with that of their control counterparts (P < 0.01), both of which exhibited in a time-dependent manner.

CONCLUSION: The antiproliferative effect of octreotide on SGC7901 cells might be mediated by the inhibition of Akt/PKB and telomerase.

Effect of centrally administered somatostatin on pituitary thyrotropes in male rats

The effects of intracerebroventricularly administered somatostatin (SRIH-14 or -28) on growth and function of pituitary thyrotropes (TSH-cells) were examined in adult male Wistar rats. The animals were implanted with an intracerebroventricular cannula and after a recovery period, administered three 1 microg doses of SRIH-14 or -28 dissolved in 5 microl saline every second day. Controls were treated in the same way with the same volume of saline only. TSH-producing cells were studied using the peroxidase-antiperoxidase immunohistochemical procedure. Blood samples were collected for hormone (TSH) analyses 5 days after the last injection. Both SRIH-treatments significantly decreased (p < 0.05) all morphometric parameters obtained for TSH-cells in comparison with controls. The volume of TSH-cells decreased by 27%, nuclei by 44% and volume density by 33% in animals treated with SRIH-14. In animals treated with SRIH-28, these parameters were also significantly decreased (p < 0.05) (22%, 31%, and 25% respectively) compared to control rats. Serum concentrations of TSH were significantly decreased (p < 0.05) by 15% in SRIH-14- and by 12% in SRIH-28-treated animals in comparison with the controls. These observations suggest that centrally administered SRIH- 14 or -28 is specifically involved in the control of growth and secretory activity of TSH cells.