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

Spectrum of EGFR mutation and its relation with high-risk predictors in thyroid cancer in Kashmiri population: 2 years prospective study at a tertiary care hospital

Background

EGFR mutation has not been extensively studied in thyroid cancer. This study was conducted to study spectrum of EGFR mutation in thyroid cancer in Kashmiri population for possible therapeutic purpose.

Methods

It was 2 years prospective cross-sectional study conducted at a tertiary care center in which histologically confirmed, untreated thyroid cancers were included. These specimens were subjected to EGFR mutation analysis by AS-PCR method.

Results

There were a total 60 patients with preponderance of females [44(73%) vs 16(27%)]. Most were in the age group of less than 45 years (75%). Most of these patients were non-smokers [50(83.3%) vs 10 (17.3%)]. Papillary thyroid carcinoma (PTC) was the commonest type 48(80%), rest was follicular type (FTC) 12(20%). Well-differentiated carcinoma (WDC) was common than poorly differentiated (PDC) [41(68.4%) vs 19 (31.6%)]. Lymph node metastasis and vascular invasion were present in 32 (53.4%) and 17 (28.4%) respectively. Thirty-two (53.3%) patients were having 15 bp deletion in exon 19 of EGFR. These deletions were common in PTC than FTC, 29(60.5%) vs 3(25%) which was statistically significant (p = 0.04, CI = 0.2). The total mutational rate of T790M in EGFR tyrosine kinase domain (exon 20) was found to be only 8.4% (5 of 60). Only 4 (8.3%) of these mutations were detected in PTC and rest in FTC (1 of 12). Twenty-six (43.3%) of exon 21 were positive for L858R mutation in EGFR tyrosine kinase domain. Married persons and PDC were significant predictors of L858R mutation in EGFR tyrosine kinase domain in thyroid cancer as this was statistically significant in them with p = 0.04, 0.03 respectively.

Conclusion

In our population, PTC is common in females with half of population harboring EGFR mutation and it is statistically significant in poorly differentiated carcinoma and in married individuals.

It implies that EGFR may be used in thyroid cancer as a possible therapeutic agent in our set of population.

TROP-2, Nectin-4, GPNMB, and B7-H3 Are Potentially Therapeutic Targets for Anaplastic Thyroid Carcinoma

Simple Summary

Anaplastic thyroid carcinoma is a highly aggressive thyroid tumor with a poor prognosis. There are limited choices for the effective treatment of this type of carcinoma. Whether the targets of antibody–drug conjugates are expressed in anaplastic thyroid carcinoma remains unclear. Therefore, we examined expression rates of the following antibody–drug conjugate targets using the tissue microarrays of anaplastic thyroid carcinomas: human epidermal growth factor receptor 2, nectin-4, trophoblast cell surface antigen 2, glycoprotein non-metastatic B, and B7-H3. We found that glycoprotein non-metastatic B and B7-H3 were expressed in most anaplastic thyroid carcinoma tissues. Trophoblast cell surface antigen 2 and nectin-4 were expressed in 65% and 59% of anaplastic thyroid carcinoma tissues, respectively. Trophoblast cell surface antigen 2 was high expressed in anaplastic thyroid carcinoma undifferentiated from papillary thyroid carcinoma. In contrast, nectin-4 expression was high in patients with de novo anaplastic thyroid carcinoma. These cell membrane proteins are potential therapeutic targets for anaplastic thyroid carcinoma.

Abstract

Background: Anaplastic thyroid carcinoma (ATC) is a highly aggressive thyroid tumor with a poor prognosis. However, there are limited choices for ATC treatment. Recently, the effectiveness of antibody–drug conjugates has been demonstrated in various carcinomas. Whether the targets of antibody–drug conjugates are expressed in anaplastic thyroid carcinoma remains unclear. Methods: Fifty-four patients with ATC were enrolled in this study. Tissue microarrays were constructed using the archives of formalin-fixed paraffin-embedded tissue blocks. All sections were stained with the following antibody–drug conjugate targets: human epidermal growth factor receptor 2 (HER2), nectin-4, trophoblast cell surface antigen 2 (TROP-2), glycoprotein non-metastatic B (GPNMB), and B7-H3. Results: HER2 was negative in all tissues, whereas GPNMB and B7-H3 were expressed in most ATC tissues. TROP-2 and nectin-4 were expressed in 65% and 59% of ATC tissues, respectively. TROP-2 was expressed at significantly higher levels in ATC undifferentiated from papillary thyroid carcinoma than in ATC undifferentiated from follicular thyroid carcinoma and de novo ATC. In contrast, nectin-4 expression was markedly higher in patients with de novo ATC than in those with papillary and follicular thyroid carcinoma. Conclusions: TROP-2 and nectin-4 are potential therapeutic targets for ATC undifferentiated from papillary thyroid carcinoma and de novo ATC, respectively. GPNMB and B7-H3 potential for treating all types of ATC.

Gold-Based Nanoplataform for the Treatment of Anaplastic Thyroid Carcinoma: A Step Forward

Anaplastic thyroid carcinoma (ATC) is a very rare subtype of thyroid carcinoma and one of the most lethal malignancies. Poor prognosis is mainly associated with its undifferentiated nature, inoperability, and failing to respond to the typically used therapies for thyroid cancer. Photothermal Therapy (PTT) entails using light to increase tissues' temperature, leading to hyperthermia-mediated cell death. Tumours are more susceptible to heat as they are unable to dissipate it. By using functionalized gold nanoparticles (AuNPs) that transform light energy into heat, it is possible to target the heat to the tumour. This study aims to formulate ATC-targeted AuNPs able to convert near-infrared light into heat, for PTT of ATC. Different AuNPs were synthetized and coated. Size, morphology, and surface plasmon resonances band were determined. The optimized coated-AuNPs were then functionalized with ligands to assess ATC's specificity. Safety, efficacy, and selectivity were assessed in vitro. The formulations were deemed safe when not irradiated (>70% cell viability) and selective for ATC. However, when irradiated, holo-transferrin-AuNPs were the most cytotoxic (22% of cell viability). The biodistribution and safety of this formulation was assessed in vivo. Overall, this novel formulation appears to be a highly promising approach to evaluate in a very near future.

EGFR Polysomy in Squamous Cell Carcinoma of the Thyroid. Report of Two Cases and Review of the Literature

Aims and background

Primary squamous cell carcinoma of the thyroid gland (PSCCT) is an uncommon malignancy characterized by a poor prognosis. A radical surgical approach combined with radiotherapy or chemotherapy is the generally accepted treatment for this tumor. The epidermal growth factor receptor (EGFR) is a transmembrane tyrosine kinase receptor modulating the cell proliferation and biological progression of many human epithelial tumors. The EGFR overexpression in PSCCT suggests an additional therapeutic option for the treatment of this tumor.

Methods and study design

The clinicopathological features and immunohistochemical profiles of two cases of primary squamous cell carcinoma of the thyroid in a 66-year-old and an 83-year-old woman are presented. EGFR status was valued in both cases.

Results

Overexpression of EGFR protein was detected in 50% and 75% of the tumor cell membranes. EGRF gene polysomy was detected in both tumors.

Conclusions

Pharmaceuticals targeting EGFR may help to provide the rationale for an additional, novel therapeutic option for this rare tumor, especially when other therapeutic options have been exhausted.

Carfilzomib potentiates CUDC-101-induced apoptosis in anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is one of the most aggressive human malignancies, with no effective treatment currently available. Previously, we identified agents active against ATC cells, both in vitro and in vivo, using quantitative high-throughput screening of 3282 clinically approved drugs and small molecules. Here, we report that combining two of these active agents, carfilzomib, a second-generation proteasome inhibitor, and CUDC-101, a histone deacetylase and multi-kinase inhibitor, results in increased, synergistic activity in ATC cells. The combination of carfilzomib and CUDC-101 synergistically inhibited cellular proliferation and caused cell death in multiple ATC cell lines harboring various driver mutations observed in human ATC tumors. This increased anti-ATC effect was associated with a synergistically enhanced G2/M cell cycle arrest and increased caspase 3/7 activity induced by the drug combination. Mechanistically, treatment with carfilzomib and CUDC-101 increased p21 expression and poly (ADP-ribose) polymerase protein cleavage. Our results suggest that combining carfilzomib and CUDC-101 would offer an effective therapeutic strategy to treat ATC.

Loss of sorting nexin 5 stabilizes internalized growth factor receptors to promote thyroid cancer progression

Thyroid carcinoma is the most common endocrine malignancy and its prevalence has recently been increasing worldwide. We previously reported that the level of sorting nexin 5 (Snx5), an endosomal translocator, is preferentially decreased during the progression of well-differentiated thyroid carcinoma into poorly differentiated carcinoma. To address the functional role of Snx5 in the development and progression of thyroid carcinoma, we established Snx5-deficient (Snx5^-/- ) mice. In comparison to wild-type (Snx5^+/+ ) mice, Snx5^-/- mice showed enlarged thyroid glands that consisted of thyrocytes with large irregular-shaped vacuoles. Snx5^-/- thyrocytes exhibited a higher growth potential and higher sensitivity to thyroid-stimulating hormone (TSH). A high content of early endosomes enriched with TSH receptors was found in Snx5^-/- thyrocytes, suggesting that loss of Snx5 caused retention of the TSH receptor (TSHR) in response to TSH. Similar data were found for internalized EGF in primary thyrocytes. The increased TSH sensitivities in Snx5^-/- thyrocytes were also confirmed by results showing that Snx5^-/- mice steadily developed thyroid tumors with high metastatic potential under high TSH. Furthermore, a thyroid cancer model using carcinogen and an anti-thyroidal agent revealed that Snx5^-/- mice developed metastasizing thyroid tumors with activation of MAP kinase and AKT pathways, which are postulated to be major pathways of malignant progression of human thyroid carcinoma. Our results suggest that thyrocytes require Snx5 to lessen tumorigenic signaling driven by TSH, which is a major risk factor for thyroid carcinoma. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

HER2 Analysis in Sporadic Thyroid Cancer of Follicular Cell Origin

The Epidermal Growth Factor Receoptor (EGFR) family member human epidermal growth factor receptor 2 (HER2) is overexpressed in many human epithelial malignancies, representing a molecular target for specific anti-neoplastic drugs. Few data are available on HER2 status in differentiated thyroid cancer (DTC). The present study was aimed to investigate HER2 status in sporadic cancers of follicular cell origin to better clarify the role of this receptor in the stratification of thyroid cancer. By immunohistochemistry and fluorescence in-situ hybridization, HER2 expression was investigated in formalin-fixed paraffin-embedded surgical specimens from 90 DTC patients, 45 follicular (FTC) and 45 papillary (PTC) histotypes. No HER2 immunostaining was recorded in background thyroid tissue. By contrast, overall HER2 overexpression was found in 20/45 (44%) FTC and 8/45 (18%) PTC, with a significant difference between the two histotypes (p = 0.046). Five of the six patients who developed metastatic disease during a median nine-year follow-up had a HER2-positive tumor. Therefore, we suggest that HER2 expression may represent an additional aid to identify a subset of patients who are characterized by a worse prognosis and are potentially eligible for targeted therapy.

Dual inhibition of HDAC and EGFR signaling with CUDC-101 induces potent suppression of tumor growth and metastasis in anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is one of the most lethal human malignancies that currently has no effective therapy. We performed quantitative high-throughput screening (qHTS) in three ATC cell lines using 3,282 clinically approved drugs and drug candidates, and identified 100 active agents. Enrichment analysis of active compounds showed that inhibitors of EGFR and histone deacetylase (HDAC) were most active. Of these, the first-in-class dual inhibitor of EGFR, HER2 and HDACs, CUDC-101, had the highest efficacy and lower IC₅₀ than established drugs. We validated that CUDC-101 inhibited cellular proliferation and resulted in cell death by inducing cell cycle arrest and caspase-dependent apoptosis. CUDC-101 also inhibited cellular migration in vitro. Mechanistically, CUDC-101 inhibited MAPK signaling and histone deacetylation in ATC cell lines with multiple driver mutations present in human ATC. The anticancer effect of CUDC-101 was associated with increased expression of p21 and E-cadherin, and reduced expression of survivin, XIAP, β-catenin, N-cadherin, and Vimentin. In an in vivo mouse model of metastatic ATC, CUDC-101 inhibited tumor growth and metastases, and significantly prolonged survival. Response to CUDC-101 treatment in vivo was associated with increased histone 3 acetylation and reduced survivin expression. Our findings provide a preclinical basis to evaluate CUDC-101 therapy in ATC.

When thyroid carcinoma goes bad: a morphological and molecular analysis

Thyroid carcinomas of follicular epithelial derivation are common and generally well-behaved malignancies with excellent cure and survival rates. However, a subset of these carcinomas, whether well-differentiated, poorly differentiated, or anaplastic, is highly aggressive, manifesting with local invasion, recurrence, and distant metastasis. The recognition of dedifferentiation is of paramount importance. In addition, the challenge for Pathologists is to identify the rare aggressive differentiated carcinomas so that treatment may be tailored appropriately. Thus, histological subtyping and documentation of other aggressive features such as widespread invasion and angioinvasion are critical. Mutational analyses in the past decade have delineated the molecular alterations responsible for thyroid carcinogenesis and progression, allowing greater sub-classification and prognostication of thyroid carcinomas. This review article highlights important aggressive morphologic features and molecular mutations associated with thyroid carcinoma.

Anaplastic thyroid cancer: outcome and the mutation/expression profiles of potential targets

Anaplastic thyroid cancer (ATC) is a rare but aggressive malignancy of the thyroid. No effective treatment modalities are currently available. Targeted therapy against protein kinases showed promising results in preclinical studies. Our goal was to assess the mutational status of potential therapeutic targets, as well as the biomarker for immunotherapy in the clinical context. Using allele specific PCR, Sanger sequencing, fragment analysis and immunohistochemistry, we assessed BRAF, KRAS, EGFR mutations and protein overexpression of C-KIT and PDL1 in anaplastic thyroid cancer specimens. Results were compared to clinical information and patient outcome to assess the utility of these biomarkers. There were 13 patients in our study with a median overall survival of 19 weeks. Of the 13 ATC patients, 3 (23 %) had BRAF V600E mutation. C-KIT overexpression was found in 1 (8 %) patient who responded well to a tyrosine kinase inhibitor. PDL1 expression was seen in 3 (23 %) patients, none of them were surgical candidates due to unresectability and poor performance status. KRAS codon 12/13 and EGFR exon 18, 19, 20 and 21 were all wild type in our patients. Protein kinase inhibitors and immunotherapy may be useful adjuvant therapies for ATC.

Epidermal growth factor receptor overexpression is a marker for adverse pathologic features in papillary thyroid carcinoma

BACKGROUND

Epidermal growth factor receptor (EGFR) overexpression (EGFR-H) is implicated in thyroid carcinoma disease progression; however, the clinicopathologic significance of EGFR-H in tumors that harbor EGFR and/or v-Raf murine sarcoma viral oncogene homolog B1 (BRAF)(V600E) mutations is unknown.

METHODS

Tissue microarrays from 81 patients who had undergone thyroidectomy for carcinoma from 2002-2011 were scored for EGFR expression using immunohistochemistry. Somatic mutations in EGFR exons 19 and 21 and BRAF were analyzed. Correlations between the EGFR immunohistochemistry, EGFR, and BRAF(V600E) mutations and the clinicopathologic features were assessed.

RESULTS

EGFR-H was detected in 39.5% of carcinomas (n = 32) from patients with papillary (PTC, 46.2%, n = 18), follicular (29.6%, n = 8), and anaplastic (100.0%, n = 6) but not medullary (0.0%, n = 9) thyroid carcinoma. BRAF(V600E) mutations were identified in 22.2% of the carcinoma cases (n = 18, 15 PTCs and 3 anaplastic thyroid carcinomas). No somatic EGFR mutations were detected in any subtype. On PTC univariate analysis, EGFR-H correlated with increasing stage, extrathyroid extension, tumor capsule invasion, adverse pathologic features (any demonstration of extrathyroid extension, tumor capsule invasion, lymphovascular invasion, lymph node metastasis, and/or distant metastasis), and BRAF(V600E) mutations. On multivariate analysis, EGFR-H correlated with BRAF(V600E) mutations. In BRAF wild-type PTCs, the correlation between EGFR-H and adverse pathologic features approached statistical significance (P = 0.065).

CONCLUSIONS

EGFR-H could be an important biomarker for aggressive PTCs, particularly in BRAF wild-type PTCs. Despite EGFR-H in PTC, follicular thyroid carcinoma, and anaplastic thyroid carcinoma by immunohistochemistry, somatic EGFR mutations were absent. Therefore, future investigations of EGFR should consider histologic and immunohistochemical methods, in addition to molecular profiling of thyroid carcinomas. This multimodal approach is particularly important for future clinical trials testing anti-EGFR therapy.

Revisiting immune-based therapies for aggressive follicular cell-derived thyroid cancers

BACKGROUND

With our growing understanding of the immune system and mechanisms employed by tumors to evade destruction, the field of cancer immunotherapy has been revitalized. Concurrent inflammation has long been associated with follicular cell-derived thyroid cancer (FDTC). In the last decade, much research has focused on characterizing the tumor-associated immune response in patients with FDTC.

SUMMARY

Mast cells, natural killer cells, macrophages, dendritic cells, B cells, and T cells have been identified within FDTC-associated immune infiltrate. Collectively, these findings suggest that the immune response to FDTC is compromised and may even promote tumor progression. A more thorough characterization of the tumor-associated immune response in FDTC may lead to the development of immune-based adjuvant therapies for patients with aggressive disease.

CONCLUSIONS

Immune-based therapies could provide essential alternatives to patients that cannot be treated surgically, those with recurrent or persistent lymph node metastases, and those with anaplastic thyroid cancer.

Approach to the patient with anaplastic thyroid carcinoma

Anaplastic thyroid carcinoma is the least common but most lethal of thyroid cancers. All patients are classified as stage IV, with the primary lesion restricted to the thyroid gland in stage IVA; locoregional lymph nodes may exist in IVA/IVB; and IVC disease is defined by distant metastases. Prognosis is highly dependent on disease extent at presentation, and staging and establishing a plan of care must be accomplished quickly. Although almost all studies are biased due to their retrospective nature, the most important factors associated with longer survival are completeness of surgical resection (achievable in only a minority of patients) and high-dose (>40 Gy) external beam radiotherapy (preferably intensity modulated radiation therapy). Recent reports suggest that a multimodal approach (surgery, radiation, and chemotherapy) is beneficial. Given the high lethality even with apparent local disease, combination systemic therapy (cytotoxics and/or targeted agents) may improve outcomes in stage IVA/IVB patients. Newer, more effective drug combinations are urgently needed for IVC patients who want aggressive therapy. A candid discussion of the prognosis and management options, including palliative care/hospice, should be held with the patient and caregiver as soon as possible after diagnosis to clarify the patient's preference and expectations. Prospective multicenter clinical trials, incorporating molecular analyses of tumors, are required if we are to improve survival in anaplastic thyroid carcinoma.

A comparative study of cell cycle mediator protein expression patterns in anaplastic and papillary thyroid carcinoma

Anaplastic thyroid carcinoma (ATC) is an extremely aggressive and rapidly fatal neoplasm. The aim of this study was to identify a limited cell cycle associated protein expression pattern unique to ATC and to correlate that pattern with clinical outcome. This represents one of the largest tissue micro-array projects comparing the cell cycle protein expression data of ATC to other well-differentiated tumors in the literature. Tissue microarrays were created from 21 patients with ATC and an age and gender matched cohort of patients with papillary thyroid carcinoma (PTC). Expression of epidermal growth factor receptor, cyclin D1, cyclin E, p53, p21, p16, aurora kinase A, opioid growth factor (OGF), OGF-receptor, thyroglobulin and Ki-67 was evaluated in a semi-quantitative fashion. Differences in protein expression between the cohorts were evaluated using chi-square tests with Bonferroni adjustments. Survival time and presence of metastasis at presentation were collected. The ATC cohort showed a statistically significant decrease (p < 0.05) in thyroglobulin expression and statistically significant increases (p < 0.05) in Ki-67 and p53 expression as compared with the PTC cohort. A trend toward loss of p16 and p21 expression was noted in the ATC cohort. A trend toward decreased survival was noted with p21 expression. These data indicate disruption of the normal cell cycle with aberrant expression of multiple protein markers suggesting increased proliferative activity and loss of control of cell cycle progression to G₁ phase. These findings support the assertion that ATC may represent the furthest end of a continuum of thyroid carcinoma dedifferentiation.

RET TKI: potential role in thyroid cancers

The increasing incidence of thyroid cancer is associated with a higher number of advanced disease characterized by the loss of cancer differentiation and metastatic spread. The knowledge of the molecular pathways involved in the pathogenesis of thyroid cancer has made possible the development of new therapeutic drugs able to blockade the oncogenic kinases (RET/PTC) or signaling kinases (vascular endothelial growth factor receptor [VEGFR]) involved in cellular growth and proliferation. Some clinical trials have been conducted showing the ability of targeted therapies able to inhibit RET(sorafenib, imatinib, vandetanib) in stabilizing the course of the disease. The aim of the introduction of these targeted therapies is to extend life duration assuring a good quality of life; however, further studies are needed to reach these goals.

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.

[Management of refractory thyroid cancers]

During the last two decades, the understanding of molecular biology of thyroid cancers has greatly improved, and this has permitted the development of novel therapeutic tools in patients with refractory disease. Kinase inhibitors inhibit kinases of the VEGF receptors, and by doing this inhibit angiogenesis, and some of these agents also inhibit other kinases of the Mitogen-Activated Protein kinases (MAPkinase) pathway. These inhibitors are effective in differentiated and medullary thyroid cancers, and induce a partial response or a long-term stabilisation in more than half of patients.

Anaplastic thyroid carcinoma: pathogenesis and emerging therapies

Anaplastic thyroid carcinoma ranges from 1.3 to 9.8% of all thyroid cancers globally. Mutations, amplifications, activation of oncogenes and silencing of tumour suppressor genes contribute to its aggressive behaviour, and recent studies (e.g. microarrays, microRNAs) have provided further insights into its complex molecular dysregulation. Preclinical studies have identified numerous proteins over- or underexpressed that affect critical cellular processes, including transcription, signalling, mitosis, proliferation, cell cycle, apoptosis and adhesion, and a variety of agents that effectively inhibit these processes and tumour growth. In clinical studies of 1771 patients, 64% were women, the median survival was 5 months, and 1-year survival was 20%. The variables associated with survival in some series included age, tumour size, extent of surgery, higher dose radiotherapy, absence of distant metastases at presentation, co-existence of differentiated thyroid cancer and multimodality therapy. However, considerable bias exists in these non-randomised studies. Although more aggressive radiotherapy has reduced locoregional recurrences, the median overall survival has not improved in over 50 years. Newer systemic therapies are being tried, and more effective combinations are needed to improve patient outcomes.

Targeted therapy of thyroid cancer

Systemic chemotherapies for advanced or metastatic thyroid carcinomas have been of only limited effectiveness. For patients with differentiated or medullary carcinomas unresponsive to conventional treatments, novel therapies are needed to improve disease outcomes. Multiple novel therapies primarily targeting angiogenesis have entered clinical trials for metastatic thyroid carcinoma. Partial response rates up to 30% have been reported in single agent studies, but prolonged disease stabilization is more commonly seen. The most successful agents target the vascular endothelial growth factor receptors, with potential targets including the mutant kinases associated with papillary and medullary oncogenesis. Two drugs approved for other malignancies, sorafenib and sunitinib, have had promising preliminary results reported, and are being used selectively for patients who do not qualify for clinical trials. Additional agents targeting tumor vasculature, nuclear receptors, epigenetic abnormalities, and the immune response to neoplasia have also been investigated. Randomized trials for several agents are underway that may lead to eventual drug approval for thyroid cancer. Treatment for patients with metastatic or advanced thyroid carcinoma now emphasizes clinical trial opportunities for novel agents with considerable promise. Alternative options now exist for use of tyrosine kinase inhibitors that are well tolerated and may prove worthy of regulatory approval for this disease.

Thyroid tumorigenesis and molecular markers in thyroid cancer

PURPOSE OF REVIEW

The purpose of this review is to provide an update on recent advances in the understanding of thyroid cancer tumorigensis and implications in clinical practice.

RECENT FINDINGS

Recent novel and promising findings include additional abnormalities in key pathways associated with thyroid tumorigenesis (RET-Ras-BRAF-MEK; RET-beta-cateinin; TRK-PI3K-AKT; and MDM-p53-PTEN), single-nucleotide polymorphisms associated with thyroid cancer susceptibility, epigenetic silencing, alternative splicing, and gene expression abnormalities. Complex regulatory mechanisms and insights into ways in which molecular aberrancies occur are becoming better understood through this research.

SUMMARY

With ongoing research, clinical problems such as the suspicious thyroid fine needle aspiration, better treatment algorithms for well differentiated thyroid cancer, and more effective treatment for anaplastic cancer will likely be found.

Beyond RET: potential therapeutic approaches for advanced and metastatic medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) is a rare calcitonin-producing neuroendocrine tumour that originates from the parafollicular C-cells of the thyroid gland. The RET proto-oncogene encodes the RET receptor tyrosine kinase, which has essential roles in cell survival, differentiation and proliferation. Activating mutations of RET are associated with the pathogenesis of MTC and have been demonstrated in nearly all hereditary and in 30-50% of sporadic MTC cases, making this receptor an excellent target for small-molecule inhibitors for this tumour. Clinical trials of small organic inhibitors of tyrosine kinase receptors (TKIs) targeting the RET receptor have shown efficacy for treatment of metastatic MTC with 30-50% of patients responding to these agents. Despite the importance of the RET receptor in MTC, it is clear that other signal transduction pathways, tyrosine kinase receptors, and tumour suppressor genes are involved in MTC tumourigenesis and progression. A better understanding of molecular cross-talk between these signal pathways and the RET receptor may lead to combinatorial therapy that will improve outcomes beyond what is currently possible with RET-directed TKIs. Finally, there is evidence that immunological-based therapy using dendritic cell vaccination strategies have been effective for reducing tumour mass in a small number of patients. The identification of additional MTC-specific tumour antigens and a better understanding of specific epitopes in these tumour antigens may lead to improvement of response rates.

Anaplastic thyroid cancer: molecular pathogenesis and emerging therapies

Anaplastic thyroid cancer (ATC) is a rare malignancy. While external beam radiation therapy has improved locoregional control, the median survival of approximately 4 months has not changed in more than half a century due to uncontrolled systemic metastases. The objective of this study was to review the literature in order to identify potential new strategies for treating this highly lethal cancer. PubMed searches were the principal source of articles reviewed. The molecular pathogenesis of ATC includes mutations in BRAF, RAS, catenin (cadherin-associated protein), beta 1, PIK3CA, TP53, AXIN1, PTEN, and APC genes, and chromosomal abnormalities are common. Several microarray studies have identified genes and pathways preferentially affected, and dysregulated microRNA profiles differ from differentiated thyroid cancers. Numerous proteins involving transcription factors, signaling pathways, mitosis, proliferation, cell cycle, apoptosis, adhesion, migration, epigenetics, and protein degradation are affected. A variety of agents have been successful in controlling ATC cell growth both in vitro and in nude mice xenografts. While many of these new compounds are in cancer clinical trials, there are few studies being conducted in ATC. With the recent increased knowledge of the many critical genes and proteins affected in ATC, and the extensive array of targeted therapies being developed for cancer patients, there are new opportunities to design clinical trials based upon tumor molecular profiling and preclinical studies of potentially synergistic combinatorial novel therapies.

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.

Targeted therapeutic approach for an anaplastic thyroid cancer in vitro and in vivo

Anaplastic thyroid carcinoma (ATC) is among the most aggressive human malignancies, being responsible for the majority of thyroid cancer-related deaths. Despite multimodal therapy including surgery, chemotherapy, and radiotherapy, the outcome of ATC is poor. The human ATC cell line MB1, derived from tumor tissue of a 57-year-old man with thyroid cancer and pronounced neutrophilia, was established from surgically excised tumor tissue. The karyotype of the cell line shows many chromosomal abnormalities. Preclinical investigations have shown antitumor activity and effectiveness of the BRAF kinase inhibitor Sorafenib and the proteasome inhibitor Bortezomib. After establishment of the MB1 cell line these agents were applied in vitro and, showing activity in a cell culture model, were also used for in vivo treatment. Sorafenib had some clinical effect, namely normalization of leucocytosis, but had no sustained impact on subsequent tumor growth and development of distant metastasis. Molecular diagnostics of the tumor demonstrated no BRAF mutations in exons 11 and 15 concordant with a rather modest effect of Sorafenib on MB1 cell growth. Clinical benefit was seen with subsequent bortezomib therapy inducing a temporary halt to lymph node growth and a progression-free interval of 7 weeks. Our observations together with previous data from preclinical models could serve as a rationale for selecting those patients suffering from ATC most likely to benefit from targeted therapy. A prospective controlled randomized trial integrating kinase and proteasome inhibitors into a therapeutic regime for ATC is warranted.