Cytogenetic and molecular genetic studies of follicular and papillary thyroid cancers

Novel thrombospondin-1 transcript exhibits distinctive expression and activity in thyroid tumorigenesis

Thrombospondin 1 (TSP1) is known for its cell-specific functions in cancer progression, such as proliferation and migration. It contains 22 exons that may potentially produce several different transcripts. Here, we identified TSP1V as a novel TSP1-splicing variant produced by intron retention (IR) in human thyroid cancer cells and tissues. We observed that TSP1V functionally inhibited tumorigenesis contrary to TSP1 wild-type, as identified in vivo and in vitro. These activities of TSP1V are caused by inhibiting phospho-Smad and phospho-focal adhesion kinase. Reverse transcription polymerase chain reaction and minigene experiments revealed that some phytochemicals/non-steroidal anti-inflammatory drugs enhanced IR. We further found that RNA-binding motif protein 5 (RBM5) suppressed IR induced by sulindac sulfide treatment. Additionally, sulindac sulfide reduced phospho-RBM5 levels in a time-dependent manner. Furthermore, trans-chalcone demethylated TSP1V, thereby preventing methyl-CpG-binding protein 2 binding to TSP1V gene. In addition, TSP1V levels were significantly lower in patients with differentiated thyroid carcinoma than in those with benign thyroid nodule, indicating its potential application as a diagnostic biomarker in tumor progression.

Quercetin Induces Anticancer Activity by Upregulating Pro-NAG-1/GDF15 in Differentiated Thyroid Cancer Cells

Simple Summary

Thyroid cancer is one of the most common cancers worldwide, and its incidence has increased over the last few decades. It is difficult to diagnose different types of thyroid cancer. Tumor tissues from papillary thyroid cancer patient showed higher expression of mature NAG-1, whereas adjacent normal tissues showed higher expression of pro-NAG-1. Several anti-cancer compounds increased pro-NAG-1 expression in thyroid cancer cell line. Quercetin (3,3’,4’,5,7-pentahydroxyflavone) is a flavonoid that is a major component of various plants, including raspberries, grapes, and onions. Quercetin induced apoptosis by inducing only pro-NAG-1 expression, but not mature NAG-1, mediated by the transcription factor C/EBP. This study indicates that pro-NAG-1 could be used as a useful biomarker for thyroid cancer and also provides a potential therapeutic target for the treatment of thyroid cancer with quercetin.

Abstract

Although the treatment of thyroid cancer has improved, unnecessary surgeries are performed due to a lack of specific diagnostic and prognostic markers. Therefore, the identification of novel biomarkers should be considered in the diagnosis and treatment of thyroid cancer. In this study, antibody arrays were performed using tumor and adjacent normal tissues of patients with papillary thyroid cancer, and several potential biomarkers were identified. Among the candidate proteins chosen based on the antibody array data, mature NAG-1 exhibited increased expression in tumor tissues compared to adjacent normal tissues. In contrast, pro-NAG-1 expression increased in normal tissues, as assessed by western blot analysis. Furthermore, pro-NAG-1 expression was increased when the thyroid cancer cells were treated with phytochemicals and nonsteroidal anti-inflammatory drugs in a dose-dependent manner. In particular, quercetin highly induced the expression of pro-NAG-1 but not that of mature NAG-1, with enhanced anticancer activity, including apoptosis induction and cell cycle arrest. Examination of the NAG-1 promoter activity showed that p53, C/EBPα, or C/EBPδ played a role in quercetin-induced NAG-1 expression. Overall, our study indicated that NAG-1 may serve as a novel biomarker for thyroid cancer prognosis and may be used as a therapeutic target for thyroid cancers.

DNA FISH Diagnostic Assay on Cytological Samples of Thyroid Follicular Neoplasms

Simple Summary

Cytopathology cannot distinguish benign from malignant follicular lesions in 20–30% of cases. These indeterminate cases includes the so-called follicular neoplasms (FNs) according to The Bethesda System for Reporting Thyroid Cytopathology. Frozen samples from 66 classic follicular adenomas (cFAs) and carcinomas (cFTCs) studied by array-comparative genomic hybridization identified three specific alterations of cFTCs (losses of 1p36.33-35.1 and 22q13.2-13.31, and gain of whole chromosome X) confirmed by fluorescent in situ hybridization (FISH) in a second independent series of 60 touch preparations from frozen samples of cFAs and cFTCs. In a third independent set of 27 cases of already stained pre-operative fine-needle aspiration cytology samples diagnosed as FNs and histologically verified, FISH analysis using these three markers identified half of cFTCs. Specificity of our assay for identifying cFTCs is higher than 98% which might be comparable with BRAF^600E testing in cases of suspicion of classic papillary thyroid carcinomas.

Abstract

Although fine-needle aspiration cytology (FNAC) is helpful in determining whether thyroid nodules are benign or malignant, this distinction remains a cytological challenge in follicular neoplasms. Identification of genomic alterations in cytological specimens with direct and routine techniques would therefore have great clinical value. A series of 153 cases consisting of 72 and 81 histopathologically confirmed classic follicular adenomas (cFAs) and classic follicular thyroid carcinomas (cFTCs), respectively, was studied by means of different molecular techniques in three different cohorts of patients (pts). In the first cohort (training set) of 66 pts, three specific alterations characterized by array comparative genomic hybridization (aCGH) were exclusively found in half of cFTCs. These structural abnormalities corresponded to losses of 1p36.33-35.1 and 22q13.2-13.31, and gain of whole chromosome X. The second independent cohort (validation set) of 60 pts confirmed these data on touch preparations of frozen follicular neoplasms by triple DNA fluorescent in situ hybridization using selected commercially available probes. The third cohort, consisting of 27 archived cytological samples from an equal number of pts that had been obtained for preoperative FNAC and morphologically classified as and histologically verified to be follicular neoplasms, confirmed our previous findings and showed the feasibility of the DNA FISH (DNA fluorescent in situ hybridization) assay. All together, these data suggest that our triple DNA FISH diagnostic assay may detect 50% of cFTCs with a specificity higher than 98% and be useful as a low-cost adjunct to cytomorphology to help further classify follicular neoplasms on already routinely stained cytological specimens.

Molecular pathology of thyroid tumours of follicular cells: a review of genetic alterations and their clinicopathological relevance

Thyroid cancer is the most common endocrine malignancy. Knowledge of the molecular pathology of thyroid tumours originating from follicular cells has greatly advanced in the past several years. Common molecular alterations, such as BRAF p.V600E, RAS point mutations, and fusion oncogenes (RET-PTC being the prototypical example), have been, respectively, associated with conventional papillary carcinoma, follicular-patterned tumours (follicular adenoma, follicular carcinoma, and the follicular variant of papillary carcinoma/non-invasive follicular thyroid neoplasm with papillary-like nuclear features), and with papillary carcinomas from young patients and arising after exposure to ionising radiation, respectively. The remarkable correlation between genotype and phenotype shows how specific, mutually exclusive molecular changes can promote tumour development and initiate a multistep tumorigenic process that is characterised by aberrant activation of mitogen-activated protein kinase and phosphoinositide 3-kinase-PTEN-AKT signalling. Molecular alterations are becoming useful biomarkers for diagnosis and risk stratification, and as potential treatment targets for aggressive forms of thyroid carcinoma. What follows is a review of the principal genetic alterations of thyroid tumours originating from follicular cells and of their clinicopathological relevance.

Lipoprotein receptors--an evolutionarily ancient multifunctional receptor family

The evolutionarily ancient low-density lipoprotein (LDL) receptor gene family represents a class of widely expressed cell surface receptors. Since the dawn of the first primitive multicellular organisms, several structurally and functionally distinct families of lipoprotein receptors have evolved. In accordance with the now obsolete 'one-gene-one-function' hypothesis, these cell surface receptors were originally perceived as mere transporters of lipoproteins, lipids, and nutrients or as scavenger receptors, which remove other kinds of macromolecules, such as proteases and protease inhibitors from the extracellular environment and the cell surface. This picture has since undergone a fundamental change. Experimental evidence has replaced the perception that these receptors serve merely as cargo transporters. Instead it is now clear that the transport of macromolecules is inseparably intertwined with the molecular machinery by which cells communicate with each other. Lipoprotein receptors are essentially sensors of the extracellular environment that participate in a wide range of physiological processes by physically interacting and coevolving with primary signal transducers as co-regulators. Furthermore, lipoprotein receptors modulate cellular trafficking and localization of the amyloid precursor protein (APP) and the β-amyloid peptide (Aβ), suggesting a role in the pathogenesis of Alzheimer's disease. Moreover, compelling evidence shows that LDL receptor family members are involved in tumor development and progression.

Distinct genetic changes characterise multifocality and diverse histological subtypes in papillary thyroid carcinoma

AIMS

This study was undertaken to investigate the genetic factors underlying the development of multifocality and phenotypic diversity in multifocal papillary thyroid carcinoma (mPTC).

METHODS

Loss of heterozygosity (LOH) and BRAF(V600E) mutation status were analysed in a total of 55 individual tumour foci from 18 cases of mPTC. The genetic findings and morphology of tumour foci were then compared.

RESULTS

Multifocal PTC LOH rates were higher than observed previously in solitary PTC. Different patterns of LOH and BRAF(V600E) positivity separated follicular variant tumours and tumour foci from other PTC histological subtypes. In five cases, genetic alterations were detected in morphologically normal thyroid epithelium.

CONCLUSIONS

These findings support the concept that multifocal PTCs develop through clonal selection from a field of pre-neoplastic cells, with morphotype differentiation correlating with specific tumour-genetic alterations. The relatively high genetic disarray in multifocal PTC may underlie their ability to spread throughout the thyroid gland.

Cytogenetic and molecular events in adenoma and well-differentiated thyroid follicular-cell neoplasia

In spite of its simple organization, the thyroid gland can give rise to a wide spectrum of neoplasms, ranging from innocuous to highly malignant lesions. Approximately 94% of the malignancies is represented by well-differentiated thyroid carcinoma originating from follicular cells. These neoplasms are divided into two main categories, papillary thyroid carcinoma and follicular thyroid carcinoma. Despite their origin from the same type of cells, the two neoplasias show different biological behavior and a different set of genetic features, including specific cytogenetic patterns. Thyroid adenoma is the benign counterpart of follicular carcinoma. No benign counterpart of papillary carcinoma has yet been identified. The chromosomes of thyroid nodules have been investigated since 1965, and different cytogenetic subgroups have been recognized, some of which show structural chromosomal rearrangements. These structural changes lead to the formation of fusion genes RET-PTC, TRK(-T), and BRAF-AKAP9, which originate as a result of intrachromosomal or interchromosomal rearrangements and are found in papillary thyroid carcinoma. Fusion genes involving PPARγ are caused mainly by translocations and are characteristic of follicular neoplastic tissue. Radiation exposure and the particular architectural arrangement of chromatin regions in which the affected genes lie during interphase are thought to favor the formation of fusion genes in papillary thyroid carcinoma and possibly also in follicular thyroid carcinoma.

Chromosomal aberrations in thyroid follicular-cell neoplasia: in the search of novel oncogenes and tumour suppressor genes

Thyroid cancer derived from the follicular cell is characterised by specific gene alterations that are closely linked to the various pathological types comprising papillary, follicular and anaplastic thyroid cancer. However, the correlation between molecular biology and pathology is not absolute, since about 30% of cases do not harbour the typical gene alterations. This situation, coupled with the demonstration of genetic heterogeneity in thyroid cancer, is a strong motivation for the search of novel gene alterations. Chromosomal aberrations are a good starting point to initiate this search and therefore the current knowledge on chromosomal alterations in thyroid follicular-cell neoplasia is reviewed in this article. An overview on molecular cytogenetic approaches for this strategy is also provided. The identification of novel genetic markers in thyroid cancer will be further improved by integrative approaches combining data from genomic and expression analyses with clinical data. This approach is powerful to identify genetic markers as well as new therapeutic targets in follicular-cell thyroid cancer.

Genetic markers differentiating follicular thyroid carcinoma from benign lesions

Thyroid nodules are commonly encountered during routine medical care. The main problem established by a discovery of a thyroid nodule is to discriminate between a benign and malignant lesion. Fine-needle aspiration (FNA) is the most widely used and cost-effective preoperative test for initial evaluation of a thyroid nodule. While the overall accuracy of FNA for classical papillary thyroid carcinoma (PTC) approaches 100%, it has limited accuracy with follicular lesions. Patients with a cytological report of indeterminate or follicular lesions are referred to surgery for a more accurate diagnosis. A more acute molecular-based test for thyroid nodules is needed not only to improve treatment decisions, but also to potentially reduce the long-term health costs. Several studies have looked into biologic markers that could be used as an adjuvant to distinguish the benign from malignant nodules. This review will focus on those biomarkers that are potentially useful in the diagnosis of thyroid lesions commonly classified as indeterminate.

DNA probe pooling for rapid delineation of chromosomal breakpoints

Structural chromosome aberrations are hallmarks of many human genetic diseases. The precise mapping of translocation breakpoints in tumors is important for identification of genes with altered levels of expression, prediction of tumor progression, therapy response, or length of disease-free survival, as well as the preparation of probes for detection of tumor cells in peripheral blood. Similarly, in vitro fertilization (IVF) and preimplantation genetic diagnosis (PGD) for carriers of balanced, reciprocal translocations benefit from accurate breakpoint maps in the preparation of patient-specific DNA probes followed by a selection of normal or balanced oocytes or embryos. We expedited the process of breakpoint mapping and preparation of case-specific probes by utilizing physically mapped bacterial artificial chromosome clones. Historically, breakpoint mapping is based on the definition of the smallest interval between proximal and distal probes. Thus, many of the DNA probes prepared for multiclone and multicolor mapping experiments do not generate additional information. Our pooling protocol, described here with examples from thyroid cancer research and PGD, accelerates the delineation of translocation breakpoints without sacrificing resolution. The turnaround time from clone selection to mapping results using tumor or IVF patient samples can be as short as 3 to 4 days.

BAC-FISH assays delineate complex chromosomal rearrangements in a case of post-Chernobyl childhood thyroid cancer

Structural chromosome aberrations are known hallmarks of many solid tumors. In the papillary form of thyroid cancer (PTC), for example, activation of the receptor tyrosine kinase (RTK) genes, RET and neurotrophic tyrosine kinase receptor type I (NTRK1) by intra- and interchromosomal rearrangements has been suggested as a cause of the disease. However, many phenotypically similar tumors do not carry an activated RET or NTRK-1 gene or express abnormal ret or NTRK-1 transcripts. Thus, we hypothesize that other cellular RTK-type genes are aberrantly expressed in these tumors. Using fluorescence in situ hybridization-based methods, we are studying karyotype changes in a relatively rare subgroup of PTCs, i.e., tumors that arose in children following the 1986 nuclear accident in Chernobyl, Ukraine. Here, we report our technical developments and progress in deciphering complex chromosome aberrations in case S48TK, an aggressively growing PTC cell line, which shows an unusual high number of unbalanced translocations.

The Role of the PAX8/PPARgamma Fusion Oncogene in Thyroid Cancer

Thyroid cancer is uncommon and exhibits relatively low mortality rates. However, a subset of patients experience inexorable growth, metastatic spread, and mortality. Unfortunately, for these patients, there have been few significant advances in treatment during the last 50 years. While substantial advances have been made in recent years about the molecular genetic events underlying papillary thyroid cancer, the more aggressive follicular thyroid cancer remains poorly understood. The recent discovery of the PAX8/PPARγ translocation in follicular thyroid carcinoma has promoted progress in the role of PPARγ as a tumor suppressor and potential therapeutic target. The PAX8/PPARγ fusion gene appears to be an oncogene. It is most often expressed in follicular carcinomas and exerts a dominant-negative effect on wild-type PPARγ, and stimulates transcription of PAX8-responsive promoters. PPARγ agonists have shown promising results in vitro, although very few studies have been conducted to assess the clinical impact of these agents.

Nódulos com diagnóstico de padrão folicular: marcadores biológicos são o futuro?

Com o uso da ultra-sonografia de alta resolução, a prevalência de nódulos tem aumentado e, conseqüentemente, o número de punção aspirativa por agulha fina (PAAF), que é o método de escolha para diagnóstico inicial. Um dos maiores dilemas clínicos para o citologista é o diagnóstico diferencial das lesões foliculares comumente agrupadas na classe padrão folicular. Neste artigo de revisão, discutiremos quais são as lesões que podem ser assim classificadas e os marcadores moleculares, identificados por nós ou por outros grupos, que são capazes de distinguir as lesões benignas das malignas.

Low-level genomic instability is a feature of papillary thyroid carcinoma: an array comparative genomic hybridization study of laser capture microdissected papillary thyroid carcinoma tumors and clonal cell lines

CONTEXT

Previous chromosomal comparative genomic hybridization (CGH) studies of papillary thyroid carcinoma (PTC) have demonstrated a low prevalence of aberrations, with the majority of tumors showing no evidence of chromosomal instability. The technique of CGH can be optimized, however, using array CGH and laser capture microdissection to ensure pure cell populations for analysis.

OBJECTIVE

To assess PTC using array CGH applied to laser capture microdissected tumor cells and pure cell cultures.

DESIGN

Well-characterized PTC (known ret/PTC and BRAF mutation status), including samples from 5 tumors with classic morphology, 3 follicular variant tumors, and 3 clonal PTC cell lines, were analyzed.

RESULTS

Copy gain and loss occurred in all of the tumor cases and cell lines examined. The most common recurrent aberrations involved gains on chromosomes 1, 5, 7, 11, 15, 17, and 22, with recurrent deletions occurring on chromosomes 4, 18, and 19. Analysis of the data from the 8 tumor samples showed that amplifications of TP73 (1p36.33), SNRPN (15q12), and PDGFB (22q13.1) occurred exclusively in tumors with a wild type BRAF.

CONCLUSIONS

This study shows a higher prevalence of aberrations detected using array CGH allied to laser capture microdissection than previously described in the literature, and it appears that the combination of laser capture microdissection and arrayed clones optimizes studies utilizing CGH. Copy gain of PDGFB occurs in a subset of tumors showing no evidence of mutated BRAF or rearranged ret, suggesting that copy gain of PDGFB may underlie the increased expression of platelet-derived growth factor described recently in the literature.

Molecular cytogenetic characterization of chromosome 9-derived material in a human thyroid cancer cell line

The incidence of papillary thyroid carcinoma (PTC) increases significantly after exposure of the head and neck region to ionizing radiation, yet we know neither the steps involved in malignant transformation of thyroid epithelium nor the specific carcinogenic mode of action of radiation. Such increased tumor frequency became most evident in children after the 1986 nuclear accident in Chernobyl, Ukraine. In the eight years following the accident, the average incidence of childhood PTCs (chPTC) increased 70-fold in Belarus, 200-fold in Gomel, 10-fold in the Ukraine and 50-fold in Tschnigov, Kiev, Rovno, Shitomyr and Tscherkassy compared to the rate of about 1 tumor incidence per 106 children per year prior to 1986 (Likhtarev et al., 1995; Sobolev et al., 1997; Jacob et al., 1998). To study the etiology of radiation-induced thyroid cancer, we formed an international consortium to investigate chromosomal changes and altered gene expression in cases of post-Chernobyl chPTC. Our approach is based on karyotyping of primary cultures established from chPTC specimens, establishment of cell lines and studies of genotype-phenotype relationships through high resolution chromosome analysis, DNA/cDNA micro-array studies, and mouse xenografts that test for tumorigenicity. Here, we report the application of fluorescence in situ hybridization (FISH)-based techniques for the molecular cytogenetic characterization of a highly tumorigenic chPTC cell line, S48TK, and its subclones. Using chromosome 9 rearrangements as an example, we describe a new approach termed 'BAC-FISH' to rapidly delineate chromosomal breakpoints, an important step towards a better understanding of the formation of translocations and their functional consequences.

Promising molecular techniques for discriminating among follicular thyroid neoplasms

To guide the extent of thyroidectomy for indeterminate follicular neoplasm (FN), clinicians have long sought ways to differentiate follicular adenoma from carcinoma pre- or intraoperatively. Several promising molecular techniques have recently appeared including loss of heterozygosity analysis and molecular profiling microarray analysis. These new tools may also prove useful in determining prognosis, thus and allow a paradigm change in current management of the thyroid nodule.

So-called "inflammatory leiomyosarcoma'': a series of 3 cases providing additional insights into a rare entity

Inflammatory leiomyosarcoma, a rare entity first described in 1995, has been characterized by smooth muscle differentiation, a near-haploid karyotype, and a surprisingly good prognosis. The morphology is similar to that of conventional leiomyosarcoma admixed with a chronic inflammatory infiltrate. Thus far, only 15 cases have been reported in the English language literature. We report the clinical and pathological features of 3 additional cases of inflammatory leiomyosarcoma. Two women (ages 64 and 25, respectively) and 1 man (age 32) presented with a thigh, ovary, and lung mass, respectively. Inflammatory symptoms, such as anorexia, fever, night sweats, abdominal pain, and diarrhea, coincided with the thigh and ovarian primaries. Immunohistochemical studies revealed diffuse positivity for desmin and poor expression for other smooth muscle and skeletal muscle markers (muscle-specific actin [0/3], alpha-smooth muscle actin 1/3 [focal], calponin [1/3], caldesmon [0/3], and myogenin [0/3]). CD68 was diffusely positive in both the histiocytes and spindle cell component in all cases. Ultrastructural evaluation of 1 case (lung primary) lacked definitive smooth muscle differentiation. Cytogenetic analysis in 1 of 2 cases that were karyotyped, identified a near-haploid karyotype, which has been reported in other cases of inflammatory leiomyosarcoma. The other case showed 2 clonal populations of cells with interstitial deletions of the short arm of chromosome 8 and the long arm of chromosome 9, respectively. The case without cytogenetic data was intimately associated with an ovarian mature teratoma. These data also suggest that inflammatory leiomyosarcoma may lack smooth muscle differentiation, characterized by diffuse immunoreactivity for desmin but lack of immunoreactivity for alpha-smooth muscle actin, calponin, and caldesmon. In addition, 2 of the 3 cases developed distant metastases to the lungs, which suggests that these lesions may have a worse prognosis than previously believed.

Early occurrence of RASSF1A hypermethylation and its mutual exclusion with BRAF mutation in thyroid tumorigenesis

Follicular epithelial cell-derived thyroid tumors are common neoplasms comprised mainly of benign thyroid adenomas, follicular thyroid cancers, and papillary thyroid cancers (PTCs). Hypermethylation of the tumor suppressor gene RASSF1A and activating mutation of BRAF gene have been reported recently in thyroid cancers. To additionally investigate the roles of these two epigenetic/genetic alterations in thyroid tumor progression, we examined their occurrences and relationship in both benign and malignant thyroid neoplasms. With real-time quantitative methylation-specific PCR, we found that 4 of 9 (44%) benign adenomas, 9 of 12 (75%) follicular thyroid cancers tumors, and 6 of 30 (20%) of PTC tumors harbored promoter methylation in > or = 25% of RASSF1A alleles. Additional quantitative analysis revealed RASSF1A methylation only in BRAF mutation-negative PTCs. A similar inverse correlation of RASSF1A methylation with BRAF mutation was seen in thyroid tumor cell lines. Our results, therefore, suggest that epigenetic inactivation of RASSF1A through aberrant methylation is an early step in thyroid tumorigenesis. Like the previously reported mutually exclusive relationship between BRAF mutation and other Ras pathway components such as RET/PTC rearrangement, a mutually exclusive relationship also exists between BRAF mutation and RASSF1A methylation in thyroid tumorigenesis.

Molecular events in follicular thyroid tumors

Knowledge of the molecular events that govern human thyroid tumorigenesis has grown considerably in the past ten years. Key genetic alterations and new oncogenic pathways have been identified. Molecular genetic aberrations in thyroid carcinomas bear noteworthy resemblance to those in acute myelogenous leukemias. Thyroid carcinomas and myeloid leukemias both possess transcription factor gene rearrangements-PPARgamma-related translocations in thyroid carcinoma and RARalpha-related and CBF-related translocations (amongst others) in myeloid leukemia. PPARgamma and RARalpha are closely related members ofthe same nuclear receptor subfamily, and the PML-RARalpha and PAX8-PPARgamma fusion proteins both function as dominant negative inhibitors of their wild-type parent proteins. Thyroid carcinomas and myeloid leukemias also both harbor NRAS mutations (15-25% of both cancers) and receptor tyrosine kinase mutations--RET mutations in thyroid carcinomas and FLT3 mutations in myeloid leukemias. The NRAS and tyrosine receptor kinase mutations are not observed in the same thyroid carcinoma or leukemia patients, suggesting that multiple initiating pathways exist in both. Lastly, thyroid carcinomas and myeloid leukemias possess p53 mutations at relatively low frequency (10-15%) in patients who tend to be older and have more aggressive, therapy resistant disease. Such parallels are unlikely to occur by chance alone and argue that common mechanisms underlie these diverse epithelial and hematologic cancers. The comparison of thyroid carcinomas and myeloid leukemias may highlight areas of thyroid cancer investigation worthy of further focus. For example, few collaborating mutations have been defined in thyroid carcinomas even though they play a clear role in myeloid leukemias, as exemplified by RARalpha rearrangements and FLT3 mutations that together dictate the promyleocytic leukemia phenotype. Functional interactions between collaborating mutations are possible at multiple levels, and it is tempting to speculate that some thyroid carcinomas might develop through an unique combination or co-activation of RET and RAS and/or RET and PPARgamma (and/or other) signaling systems. In fact, the ELE1-RET (PTC3) fusion protein contains the ELE1 nuclear receptor co-activator domain and it appears to physically associate with and inhibit wild-type PPARgamma in some papillary carcinomas. The similarities of the fusion proteins in thyroid carcinoma and myeloid leukemia suggest that a more directed search for fusion genes in non-thyroid carcinomas is warranted. In fact, novel fusion genes have been identified recently in aggressive midline, secretory breast, and renal cell carcinomas, although the epithelial nature of the latter is not well-documented. Interestingly, these cancers all tend to present more frequently in adolescence and young adulthood in a manner similar to thyroid and myeloid malignancies that have fusion genes. The analyses of cancers that present earlier in life may enhance fusion gene recognition in other carcinoma types. Definition and biologic characterization of the precursor cells that give rise to thyroid carcinoma will also be important. Myeloid leukemias are thought to arise from stem/progenitor cells that acquire disturbed self-renewal and differentiation capacities but retain characteristics of the myeloid lineages. Although the presence of comparable stem/progenitor cells in the thyroid are not defined, distinct thyroid cancer lineages and patterns of differentiation exist and candidate stem/progenitor cells such as the p63-immunoreactive solid cell nests are apparent. A last important area is development of molecular-based therapies for thyroid carcinoma patients resistant to standard radio-iodine treatment. Treatments for such cancers are limited and pathways defined by thyroid cancer mutations are prime targets for pharmacologic interventions with molecular inhibitors. Tyrosine kinase inhibitors and nuclear receptor ligands have proven dramatically effective in some myeloid leukemia patients. Various molecular inhibitors are being investigated now in thyroid cancer models. Such developments predict that the thyroid cancer model will continue to provide biologic insights into human carcinoma biology and that improved pathologic diagnosis and treatment for thyroid cancer patients sit on the not too distant horizon.

Chromosome imbalances in thyroid follicular neoplasms: a comparison between follicular adenomas and carcinomas

The underlying genetic events associated with follicular thyroid tumorigenesis are still ill defined. In this study, we performed a screening for chromosome imbalances by comparative genomic hybridization (CGH) in a group of 12 follicular adenomas (FAs) and 20 follicular carcinomas (FTCs) previously characterized by conventional cytogenetics and flow cytometry analysis. In general, a great similarity was observed between the CGH profiles of the FAs and FTCs. In both benign and malignant tumors, a combination of gains affecting 5, 7, 12, 17, 19, and 20 was observed. Chromosome 7 was the most frequently affected chromosome, with three regions of consensus gains: 7p11-12, 7q11.3-q21, and 7q31. Recurrent gains of chromosomes 5 and 12 involved 5p11, 5p15, 5q13-q22, 5q21-q23, 12p11, and 12q11-q12. DNA sequence losses were also observed in both tumor groups. Chromosomal arms deleted in at least five of the neoplasms were (in order of frequency): in adenomas, 15q, 2p/2q, 3q, 6p/6q, 11q, and 22q; and in FTCs, 3p, 2p, 8q, 1p, 2q, 3q, 6q, 8p, 9p, 11q, 13q, 6p, and 18q. The statistical evaluation of the CGH data demonstrated that 15q loss was significantly associated with FA. Two regions of minimal common loss were defined by CGH at 15: 15q11-q21 and 15q26-qter. The identification of these regions provides a basis for further molecular studies.

Loss of heterozygosity in follicular and papillary thyroid carcinomas

In this study we aimed at investigating the incidence and the role of 3p deletions, particularly at the 3p25 approximately pter region, in follicle cell-derived thyroid neoplasms, by using loss of heterozygosity (LOH) analysis. We analyzed 12 follicular adenomas (FA), 13 follicular thyroid carcinomas (FTC), and 15 papillary thyroid carcinomas (PTC) with 11 microsatellite markers for chromosome 3. One additional marker on 3q25.2 was also investigated for assessment of deletion extent on 3q. Microsatellite instability was detected at one locus in 1 of 15 PTC (7%) and at four loci in 1 of 13 FTC (8%). Loss of heterozygosity was found in 8 of 12 cases of FTC (67%), in 6 of 15 cases of PTC (40%), and in 2 of 12 FA (17%). We identified three minimal common deleted regions (CDR) involving significant sites of LOH: two in FTC (a new terminal region, of approximately 8 cM distal to D3S1620 at 3p25.3 approximately pter and the D3S1573-D3S1595 region at 3p21.2 approximately p12) and one in PTC (D3S1304-D3S1263 region at 3p25.3 approximately p24.2). The newly identified 3p25.3 approximately pter CDR seems to be specific for FTC. Our results suggest the existence of at least three distinct regions on 3p that might harbor tumor suppressor genes involved in the carcinogenesis processes of FTC and PTC.

Expression of PAX8-PPAR gamma 1 rearrangements in both follicular thyroid carcinomas and adenomas

Recently, a translocation t(2;3)(q13;p25), leading to the formation of a chimeric PAX8-peroxisome proliferator-activated receptor (PPAR)gamma 1 oncogene, was detected in follicular thyroid carcinomas (FTC), but not in follicular thyroid adenomas (FTA), papillary thyroid carcinomas (PTC), or multinodular hyperplasias. However, previous cytogenetic studies have identified the t(2;3)(q13;p25) translocation also in some cases of FTA. In this study, we have combined RT-PCR with primers in exons 4-8 of PAX8 and in exon 1 of PPAR gamma 1 with PPAR gamma immunohistochemistry to study PAX8-PPAR gamma 1 oncogene activation in FTC (n = 9), FTA (n = 16), PTC (n = 9), anaplastic thyroid carcinomas (n = 4), and multinodular hyperplasias (n = 2). PAX8-PPAR gamma 1 rearrangements were detected by RT-PCR in 5 of 9 (56%) FTC and in 2 of 16 (13%) FTA. By contrast, all cases of PTC, anaplastic thyroid carcinomas, and multinodular hyperplasia were RT-PCR-negative. Diffuse nuclear immunoreactivity for PPAR gamma was observed in 7 of 9 (78%) FTC, 5 of 16 FTA (31%), and 1 of 9 PTC (11%). Positivity was focal in 3 cases (1 FTC, 1 PTC, and 1 multinodular hyperplasia). Diffuse nuclear staining for PPAR gamma was present in RT-PCR- negative cases of FTC (n = 3), FTA (n = 3), and PTC (n = 1), suggesting that a different PAX8-PPAR gamma 1 breakpoint, a rearrangement between PPAR gamma 1 and a non-PAX8 partner, or overexpression of the native protein might be present. Our findings that PAX8-PPAR gamma 1 rearrangements are present in both follicular carcinomas and adenomas suggest that this oncogene is not a reliable marker to differentiate between FTC and FTA in fine-needle aspiration biopsies of follicular neoplasms of the thyroid.

Multistep carcinogenesis in anaplastic thyroid carcinoma: a case report

We previously established an anaplastic thyroid carcinoma cell line (KOA2) that had double mutations: an N-ras mutation and a p53 gene mutation. To clarify multistep carcinogenesis, we analysed surgical material from the patient from whom KOA2 was derived for abnormalities in the N-ras and p53 genes. The resected material had two histologically different lesions: a follicular neoplasm and an anaplastic carcinoma. The N-ras mutation was observed in both lesions, but the p53 gene mutation only in the anaplastic lesion. These facts indicate that an N-ras mutation may induce follicular neoplasm and a subsequent p53 mutation may have caused the follicular neoplasm to transform to anaplastic carcinoma in this patient. This report suggests direct evidence for multistep carcinogenesis in anaplastic thyroid carcinoma.

Karyotypic characterization of papillary thyroid carcinomas

BACKGROUND

Cytogenetic studies performed in papillary thyroid carcinoma (PTC) identified chromosome 10q rearrangements with breakpoints at 10q11.2 as the most frequent aberrations in these tumors. In the current study, the authors aimed to identify other chromosomal abnormalities nonrandomly associated with papillary thyroid carcinomas.

METHODS

Cytogenetic analysis was performed on 94 papillary thyroid carcinomas after short-term culture of the tumors sterile fragments.

RESULTS

Clonal chromosomal changes were found in 37 tumors (40%). Structural cytogenetic abnormalities were observed in 18 carcinomas. Chromosomes 1, 3, 7, and 10 were the most frequently involved in rearrangements. Pooled results of the breakpoints detected in these tumors, as well as those described in the literature, allowed the authors to verify as the most common breakpoint loci 1p32-36, 1p11-13, 1q, 3p25-26, 7q34-36, and 10q11.2. The correlation between the karyotype features of the 94 PTCs and the histologic data revealed that some PTC follicular variants were characterized by chromosomal aberrations commonly found in thyroid follicular adenomas: a del(11)(q13q13), a t(2;3)(q13;p35), and gains of chromosomes 3, 5, 7, 9, 12, 14, 17, and 20. In the tall cell PTC variant group, 4 of the 7 tumors presented clonal cytogenetic changes, 3 (75%) of which were characterized by anomalies of chromosome 2 that lead to a overrepresentation of the long arm of this chromosome. Noted also in these series was an association between complex karyotypes and tumors with poorly differentiated histiotypes.

CONCLUSIONS

In this study, the authors report chromosome 1p32-36, 1p11-13, 3p25-26, and 7q32-36 as novel breakpoint cluster regions in PTC, and they suggest that there are cytogenetic changes preferentially associated with the follicular and tall cell PTC variants.

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

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

Gain of 1q and loss of 9q21.3-q32 are associated with a less favorable prognosis in papillary thyroid carcinoma

In order to approach the genetic mechanisms behind initiation and progression of papillary thyroid carcinoma (PTC) tumorigenesis, we characterized numerical chromosomal imbalances in a panel of 25 PTCs with varying histopathological and clinical features using comparative genomic hybridization (CGH). The most frequently detected imbalance was gain of 9q33-qter, which was seen in close to 30% of the cases. The commonly occurring regions of loss were assigned to 22q (12%) and 9q21.3-q32 (12%), while gains preferentially involved the entire X chromosome (20%), 1q (16%), 17q (16%), and 22q (12%). The distribution of CGH alterations supports the idea of a progression of genetic events in the development of PTC, where gain of 9q33-qter would represent a relatively early event that is followed by loss of 22q and gain of X, 1q, 17q, and 22q. When the detected CGH alterations were compared with the clinical outcome and the histopathological features of the 25 PTC cases, several statistically significant correlations were revealed. The total number of genetic alterations was higher in tumors from patients with aggressive disease as compared to those without signs of aggressiveness. Gain of 1q and loss of 9q21.3-q32 were exclusively seen in tumors from patients with aggressive disease, and the presence of distant metastases was associated with gain of 1q. A sex-dependent distribution was also evident for one of the common alterations, with gain of X exclusively seen in male cases. Taken together, the findings identify several candidate locations for tumor suppressor genes and oncogenes that are potentially involved in the establishment and progression of papillary thyroid carcinogenesis.

Deletion at 3p25.3-p23 is frequently encountered in endocrine pancreatic tumours and is associated with metastatic progression

For several reasons, chromosome 3p is thought to be involved in the pathogenesis of sporadic endocrine pancreatic tumours (EPTs): von Hippel-Lindau's disease (VHL gene at 3p25.5) is associated with EPTs; 3p is frequently involved in solid human tumours; and comparative genomic hybridization has identified frequent losses at 3p in EPTs. This study investigated 99 benign and malignant tumours, including 20 metastases, from 82 patients, by microsatellite loss of heterozygosity (LOH) analysis and fluorescence in situ hybridization (FISH) in order to evaluate the importance of chromosome 3p deletions in the molecular pathogenesis and biological behaviour of EPTs, to elaborate a common region of deletion, and to narrow down putative tumour suppressor gene loci. Allelic losses of 3p were found in 58/99 (58.6%) of tumours in 45/82 (54.9%) patients; analysis of seven microsatellite markers (3p26-p21) revealed a common region of LOH at 3p25.3-p23. The LOH frequency was significantly higher in malignant than in benign neoplasms (70.2% versus 28.0%; p=0.001). In addition, a strong correlation was found between the loss of alleles on chromosome 3p and clinically metastatic disease (LOH of 73.7% in metastasizing versus 41.5% in non-metastasizing tumours; p=0.008). EPTs from these patients showed a tendency towards losing large parts or the entire short arm of chromosome 3 with tumour progression. Furthermore, FISH analysis revealed complete loss of chromosome 3 in ten out of 37 EPTs (27%). These results indicate that a putative tumour suppressor gene at 3p25.3-p23 may play a role in the oncogenesis of sporadic EPTs and that losses of larger centromeric regions are associated with metastatic progression.

Fra-1 expression in malignant and benign thyroid tumor

BACKGROUND

The differential diagnosis of thyroid nodules is very important in deciding the treatment modality and the fine needle aspiration is the best diagnostic method. But, there are some limitations in use because of inadequate test materials and difficulty in interpreting. According to the study of oncogene and tumor suppressor gene about the origin of thyroid tumor, expression of Fra-1, one of AP-1 complex, is increased in thyroid neoplasm, though not present in the normal tissue. So, there is a possibility that it will be used as a method for the differential diagnosis of thyroid nodules. We tried to know whether presence or absence of Fra-1 expression can be used as a diagnostic method in differential diagnosis of thyroid nodules using the immunohistochemical (IHC) staining method.

METHODS

In 4 types of thyroid tumor that were confirmed by histologic diagnosis after operation (18 cases of adenomatous goiter, 16 cases of follicular adenoma, 30 cases of papillary cancer, 10 cases of follicular cancer), IHC staining method was performed to evaluate the expression of Fra-1.

RESULTS

In papillary and follicular thyroid cancers, the expression of Fra-1 was stronger than in benign thyroid tumor, but there was no difference in Fra-1 expression between the two types of carcinoma. Weak expression of Fra-1 was observed in all cases of follicular adenoma, though it was weaker than in carcinoma, and it was also weakly expressed only in some cases (33%) of adenomatous goiter.

CONCLUSION

The expression of Fra-1 was stronger in thyroid cancer than in benign thyroid tumor, but it was impossible to differentiate thyroid cancer from benign thyroid tumor by presence or absence of Fra-1 expression using IHC staining method.

Loss of heterogeneous ribonucleoprotein A(2)/B(1) expression in thyroid neoplasms

OBJECTIVE

To determine whether a difference exists in the immunohistochemical expression of heterogeneous ribonucleoprotein (hnRNP) A(2)/B(1) between benign and malignant thyroid lesions and to assess whether a gradient of expression could be found in normal thyroid, adenomas, and thyroid malignant tumors.

METHODS

Formalin-fixed, paraffin-embedded archival tissues from 32 cases (8 nodular goiters, 8 follicular adenomas, 8 follicular carcinomas, and 8 papillary carcinomas) were immunostained with monoclonal antibody 703D4, directed against hnRNP A(2)/B(1), applied at a concentration of 10 microg/mL. The streptavidin-biotin peroxidase method was used to label bound monoclonal antibody. Positivity was independently scored by two pathologists, who used a three-tiered scale.

RESULTS

The benign thyroid tissues, including the hyperplastic and adenomatous lesions, demonstrated 3+ granular cytoplasmic staining for hnRNP A(2)/B(1), except in two cases (one nodular goiter and one follicular adenoma) in which 2+ staining intensity was noted. In contrast, the papillary and follicular carcinomas failed to stain with the antibody, except in two cases that showed weak (1+) staining.

CONCLUSION

hnRNP A(2)/B(1) immunostaining appears to distinguish benign from malignant thyroid lesions. Loss of hnRNP A(2)/B(1) expression seems to be a characteristic feature of thyroid malignant lesions.

A clinicopathologic study of minimally invasive follicular carcinoma of the thyroid gland with a review of the English literature

BACKGROUND

The criteria for minimally invasive (low grade) follicular carcinoma of the thyroid (MI) remain controversial, often resulting in unnecessary treatment.

METHODS

The records of 130 patients with minimally invasive (MI) follicular thyroid carcinoma were retrieved from the files of the Endocrine Tumor Registry of the Armed Forces Institute of Pathology.

RESULTS

Ninety-five patients were confirmed to have MI based on the authors' criteria of small-to-medium vessel invasion, capsular invasion of up to full thickness, no parenchymal tumor extension, and no tumor necrosis (patients with oxyphilic tumors were excluded). The remaining 35 patients had tumors that were reclassified as "not low grade" based on large vessel invasion, extension into parenchyma, and tumor necrosis (oxyphilic cases excluded). The MI patients included 67 women and 28 men, ages 20-95 years (average, 42.0 years). Nearly all patients presented with a thyroid mass (n = 90 patients). The mean tumor size was 2.8 cm. Histologic features examined for tumor classification included cellularity, capsule nature, capsular invasion, vascular invasion, extension into parenchyma, cytoplasmic oxyphilia, mitotic activity, and necrosis. All patients were treated with surgical excision. Adjuvant radioactive iodine therapy was performed in 24 patients. Five patients developed recurrent disease: four were alive or had died without evidence of disease after additional treatment (mean, 18.1 years), and one patient died with disease (MI tumor) at 15.1 years. All of the remaining patients were disease free (mean follow-up, 16.5 years).

CONCLUSIONS

There are reproducible histologic criteria to diagnose patients with MI follicular carcinoma. The overall excellent long term prognosis and a good patient outcome suggests that no additional surgery is necessary.

Molecular pathogenesis of thyroid nodules and cancer

Tumours derived from the thyroid follicular epithelium represent an informative model for understanding the molecular pathogenesis of multistage tumourigenesis, which is the prevailing theory on cancer development and progression nowadays. The early stages of thyroid tumour development appear to be the consequence of the activation or 'de novo' expression of several proto-oncogenes or growth factor receptors, such as ras, ret, NTRK, met, gsp and the thyrotropin (TSH) receptor. Alterations in the expression pattern of these genes are associated with the development of differentiated neoplasms, ranging from benign toxic adenomas (gsp and TSH receptor), to follicular (ras) and papillary (ret/PTC, NTRK, met) carcinomas. They may all be considered to be early events of thyroid cell transformation and, for some, experimental evidence derived from gene transfer studies supports this hypothesis. Alterations in tumour suppressor genes (p53, Rb) are associated instead with the most aggressive and poorly differentiated forms of thyroid cancer, indicating that, in the thyroid tumourigenic process, they represent late genetic events. Specific environmental factors (iodine deficiency, ionizing radiations) have been shown to play a crucial role in promoting the development of thyroid cancer, influencing both its genotypic and phenotypic features. Interestingly, a high percentage of genetic lesions causing thyroid cancer originate from gene rearrangements and chromosomal translocations (ret/PTC, NTRK, Pax-8/PPARgamma) a finding which, being a rare event in most epithelial tumours, makes the molecular pathogenesis of thyroid cancer unique. The uninterrupted flow of information on the molecular genetics of thyroid nodules and cancer will broaden the correlation between genotype and phenotype and will also provide important information for the development of more accurate preoperative diagnostic tools and more efficient treatment choices for the different forms of thyroid cancer.

Near-haploidy and subsequent polyploidization characterize the progression of peripheral chondrosarcoma

Chondrosarcomas are malignant cartilaginous tumors arising centrally in bone (central chondrosarcoma), or secondarily within the cartilaginous cap of osteochondroma (peripheral chondrosarcoma). We previously used DNA flow cytometry to demonstrate that near-haploidy is relatively frequent in peripheral chondrosarcomas. We performed fluorescence in situ hybridization (FISH) to interphase nuclei using centromeric probes, a genome wide loss of heterozygosity (LOH) analysis, and comparative genomic hybridization on five peripheral chondrosarcomas. We demonstrated near-haploidy in two low-grade tumors with only one copy and LOH of most chromosomes. Few chromosomes are disomic, with retention of heterozygosity and overrepresentation at comparative genomic hybridization. One tumor contains both a near-haploid clone with chromosomes in monosomic and disomic state, and an exactly duplicated clone. Two high-grade tumors clearly demonstrate polyploidization because most chromosomes show LOH and two copies at FISH, whereas few chromosomes have four copies with retention of heterozygosity. Using DNA from a relative, we demonstrate that chromosome loss is random regardless of parental origin. Using FISH on paraffin slides, we exclude near-haploidy to result from meiosis-like division in binucleated cells, characteristic for chondrosarcoma. In conclusion, our results indicate that near-haploidy characterizes the progression from osteochondroma toward low-grade chondrosarcoma. Moreover, further progression toward high-grade chondrosarcoma is characterized by polyploidization.

Structural and numerical aberrations of chromosome 22 in a case of follicular variant of papillary thyroid carcinoma revealed by conventional and molecular cytogenetics

This study reports a case of papillary carcinoma with vesicular components showing multiclonal aberrations of chromosome 22 as revealed by RHG-banding cytogenetics and by fluorescence in situ hybridization (FISH; whole chromosome 22 and BCR-ABL-specific locus probes, multi-FISH). Four clones with chromosome 22 changes as the sole abnormality were seen. The main abnormal clone lacked the whole chromosome 22. A del(22)(q11) was observed in a second group of cells. The third clone had an idic(22). Finally, FISH revealed a fourth abnormal cell population with a der(17)t(?17;22). Some of these chromosome 22 alterations have been described in other solid tumors such as meningiomas and neurinomas, suggesting a common genetic pathway of tumor progression occurring in a multistep process. Chromosome 22 changes do not seem to be involved in pure papillary thyroid tumors and therefore could be related to the maintenance of a follicular-type histological pattern.

Balanced translocation (3;7)(p25;q34): another mechanism of tumorigenesis in follicular thyroid carcinoma?

Alterations of 3p are the most frequently observed changes in follicular thyroid carcinomas. Loss of 3p25-pter has been speculated to be a critical event in the malignant transformation of a subset of thyroid follicular neoplasms. The present report describes a minimally invasive follicular thyroid carcinoma (FTC) with a balanced t(3;7)(p25;q34) and dic(15;22)(p11;p11) as the only abnormalities. The alterations were present in all metaphases analyzed and were demonstrated by G-banding, spectral karyotyping (SKY), and fluorescence in situ hybridization (FISH). This study represents the second case of FTC where 3p25 is involved in a balanced translocation. The findings support the existence of a gene locus in this region which is involved in the tumorigenesis of thyroid carcinoma.

The Chernobyl accident and its consequences: update at the millennium

A marked increase in the incidence of papillary thyroid cancer in children has been documented in regions of the former Soviet Union most heavily contaminated by radioactive fallout from the Chernobyl nuclear power plant accident in April 1986. Accumulation of radioactive iodines by normal iodine trapping mechanisms resulted in significant radiation doses to the thyroid gland. Although it has long been known that thyroidal radiation resulted in nuclear and chromosomal abnormalities visible by light microscopy, modern molecular biology techniques are beginning to identify much smaller alterations in chromosomal coding sequences that are associated with malignant transformation. Although stable chromosomal abnormalities can be detected in Chernobyl-associated thyroid cancers, they are much less prevalent than in thyroid cancers developing after external beam irradiation. However, several unique chromosomal breakpoints have been described in radiation-associated thyroid cancers that are not commonly found in spontaneously occurring thyroid cancer. Furthermore, activation of specific subtypes of the ret/PTC tyrosine kinase oncogene appears to be more common in radiation-associated thyroid cancers than in spontaneous thyroid cancers. In summary, thyroid cancers developing in the aftermath of the Chernobyl accident provide a unique opportunity to search for chromosomal abnormalities that may be specific for radiation-induced thyroid cancer.

Comparison of losses of heterozygosity and replication errors in primary colorectal carcinomas and corresponding liver metastases

In order to investigate genetic alterations specific to liver metastases of colorectal carcinomas, losses of heterozygosity and replication errors have been compared in 15 cases of primary colorectal carcinoma and in the corresponding metastatic liver tumours. Fifteen microsatellite markers located on 13 different chromosomal arms were used in the study. The LOH patterns of the primary and the metastatic tumours were identical in eight cases and showed differences in seven cases. Areas of deletion predominantly or completely common to the colorectal and the metastatic tumour were detected on chromosomes 5q, 8p, 17p, 18q, and 22q. Preferential loss in metastatic tumours was observed on chromosomal arm 3p. Replication errors were found in four primary tumours and in three of the corresponding secondaries. A replication error phenotype specific to a metastasis was not observed.

DNA copy number changes in thyroid carcinoma

The genetic changes leading to thyroid cancer are poorly characterized. We studied DNA copy number changes by comparative genomic hybridization (CGH) in 69 primary thyroid carcinomas. In papillary carcinoma, DNA copy number changes were rare (3 of 26, 12%). The changes were all gains, and they were associated with old age (P = 0.01) and the presence of cervical lymph node metastases at presentation (P = 0.08). DNA copy number changes were much more frequent in follicular carcinoma (16 of 20, 80%) than in papillary carcinoma (P < 0.0001), and follicular carcinomas had more often deletions (13/20 versus 0/26, P < 0.0001). Loss of chromosome 22 was common in follicular carcinoma (n = 7, 35%), it was more often seen in widely invasive than in minimally invasive follicular carcinoma (54% versus 0%, P = 0.04), and it was associated with old age at presentation (P = 0.01). In three of the four patients with follicular carcinoma who died of cancer, the tumor had loss of chromosome 22. DNA copy number changes were found in 5 (50%) of the 10 medullary carcinomas studied. Four of these five carcinomas had deletions, and in two of them there was deletion of chromosome 22. Eleven (85%) of the thirteen anaplastic carcinomas investigated had DNA copy number changes, of which five had deletions, and one had deletion of chromosome 22. The most common gains in anaplastic carcinoma were in chromosomes 7p (p22-pter, 31%), 8q (q22-qter, 23%), and 9q (q34-qter, 23%). We conclude that DNA copy number changes are frequent in follicular, medullary, and anaplastic thyroid carcinoma but rare in papillary carcinoma when studied by CGH. Loss of chromosome 22 is particularly common in follicular carcinoma, and it is associated with the widely invasive type.

FHIT gene abnormalities in both benign and malignant thyroid tumours

FHIT, a candidate tumour suppressor gene, has recently been identified at chromosomal region 3p14.2, and deletions of the gene have been reported in many types of human cancers. Loss of heterozygosity (LOH) at this region has also been found frequently in follicular thyroid carcinoma (FTC). To investigate the potential role of FHIT in thyroid tumorigenesis, we examined 57 thyroid tumour specimens (eight benign adenomas, 40 papillary, four follicular and five anaplastic carcinomas), and two thyroid carcinoma cell lines (NPA, SW579) for genetic alterations by using reverse transcription-polymerase chain reaction (RT-PCR), PCR product sequencing, single-strand conformation polymorphism (SSCP) and Southern blot analysis. Two cervical carcinoma cell lines (C-33A, HeLa) were included as positive controls. We detected truncated FHIT transcripts in three of eight (38%) benign adenomas, nine of 40 (23%) papillary, and two of five (40%) anaplastic carcinomas, and in three cell lines (SW579, C-33A, HeLa). Most of the truncated transcripts lacked exons 4 or 5 to 7 or 8 of the gene and were presumably non-functional as the translation start site is located in exon 5. SSCP analysis of the coding exons failed to detect any point mutations among the samples without abnormal FHIT transcripts. Southern blot analysis demonstrated either loss or reduced intensity of major Bam HI restriction fragments in the three cell lines found to have abnormal FHIT transcripts, indicating, respectively, either intragenic homozygous or heterozygous deletions of the FHIT gene. Intragenic homozygous deletions were also found in two papillary thyroid carcinoma specimens: one was missing a 13 kb Bam HI fragment which contains exon 4, the other had deletions of 15.5, 13 and 4.2 kb fragments which contain exons 2 and 9, 4, and 5, respectively. The absence of a defective FHIT gene in FTC indicates that an additional tumour suppressor gene may reside in this region and be involved in the development of FTC. Given that defective FHIT genes were found in both benign and malignant thyroid tumours, the inactivation of this putative tumour suppressor gene is likely to be an early event in the pathogenesis of some forms of thyroid neoplasms.

Microsatellite instability in thyroid tumours and tumour-like lesions

Fifty-one thyroid tumours and tumour-like lesions were analysed for instability at ten dinucleotide microsatellite loci and at two coding mononucleotide repeats within the transforming growth factor beta (TGF-beta) type II receptor (TbetaRII) and insulin-like growth factor II (IGF-II) receptor (IGFIIR) genes respectively. Microsatellite instability (MI) was detected in 11 out of 51 cases (21.5%), including six (11.7%) with MI at one or two loci and five (9.8%) with MI at three or more loci (RER+ phenotype). No mutations in the TbetaRII and IGFIIR repeats were observed. The overall frequency of MI did not significantly vary in relation to age, gender, benign versus malignant status and tumour size. However, widespread MI was significantly more frequent in follicular adenomas and carcinomas than in papillary and Hürthle cell tumours: three out of nine tumours of follicular type (33.3%) resulted in replication error positive (RER+), versus 1 out of 29 papillary carcinomas (3.4%, P = 0.01), and zero out of eight Hürthle cell neoplasms. Regional lymph node metastases were present in five MI-negative primary cancers and resulted in MI-positive in two cases.

Comparison of benign and malignant follicular thyroid tumours by comparative genomic hybridization

DNA copy number changes were compared in 29 histologically benign follicular adenomas, of which five were atypical, and 13 follicular carcinomas of the thyroid by comparative genomic hybridization. DNA copy number changes were frequent in adenomas (14 out of 29, 48%). Most changes were gains, and they always involved a gain of the entire chromosome 7 (10 out of 29, 34%); other common gains involved chromosomes 5 (28%), 9 (10%), 12 (24%), 14 (21%), 17 (17%), 18 (14%) and X (17%). Losses were found only in four (14%) adenomas. Two of the five atypical adenomas had DNA copy number losses, and none had gains. Unlike adenomas, gains were rare and losses were frequent in carcinomas. A loss of chromosome 22 or 22q was particularly common in carcinomas (6 out of 13, 46%), whereas a loss of chromosome 22 was found in only two (7%) adenomas, one of which was atypical (P = 0.002). A loss of 1p was also frequent in carcinomas (31%), but gains of chromosomes 5, 7, 12, 14 or X that were common in adenomas were not found. Loss of chromosome 22 or 22q was present in six of the eight widely invasive follicular carcinomas, but in only one of the five minimally invasive carcinomas. We conclude that large DNA copy number changes are common in thyroid adenomas. These changes are strikingly different from those found in follicular carcinomas consisting of few losses and frequent gains, especially those of chromosome 7. A loss of chromosome 22 is common in widely invasive follicular carcinoma.

Recent developments in the investigation of thyroid regulation and thyroid carcinogenesis

This review covers new mechanistic information spanning the past 10 years relevant to normal and abnormal thyroid growth and function that may assist in the risk assessment of chemicals inducing thyroid follicular cell neoplasia. Recent studies have shown that thyroid regulation occurs via a complex interactive network mediated through several different messenger systems. Increased thyroid-stimulating hormone (TSH) levels activate the signal transduction pathways to stimulate growth and differentiation of the follicular cell. The important role of TSH in growth as well as in function helps to explain how disruptions in the thyroid-pituitary axis may influence thyroid neoplasia in rodents. New investigations that couple mechanistic studies with information from animal cancer bioassays (e. g., sulfamethazine studies) confirm the linkage between prolonged disruption of the thyroid-pituitary axis and thyroid neoplasia. New initiation/promotion studies in rodents also support the concept that chronic stimulation of the thyroid induced by goitrogens can result in thyroid tumors. Some of these studies confirm previous suggestions regarding the importance of chemically induced thyroid peroxidase inhibition and the inhibition of 3,3',5, 5'-tetraiodothyronine (T4, thyroxine) deiodinases on disruption of the thyroid-pituitary axis leading to thyroid neoplasia. Some comparative physiologic and mechanistic data highlight certain differences between rodents and humans that could be expected to confer an increased vulnerability of rodents to chronic hypersecretion of TSH. New data from epidemiologic and molecular genetic studies in humans contribute further to an understanding of thyroid neoplasia. Acute exposure to ionizing radiation, especially in childhood, remains the only verified cause of thyroid carcinogenesis in humans. Iodine deficiency studies as a whole remain inconclusive, even though several new studies in humans examine the role of dietary iodine deficiency in thyroid cancer. Specific alterations in gene expression have been identified in human thyroid neoplasia, linked to tumor phenotype, and thus oncogene activation and tumor-suppressor gene inactivation may also be factors in the development and progression of thyroid cancer in humans. An analysis by the U.S. EPA Risk Assessment Forum, prepared as a draft report in 1988 and completed in 1997, focused on the use of a threshold for risk assessment of thyroid follicular tumors. New studies, involving several chemicals, provide further support that there will be no antithyroid activity until critical intracellular concentrations are reached. Thus, for chemically induced thyroid neoplasia linked to disruptions in the thyroid-pituitary axis, a practical threshold for thyroid cancer would be expected. More information on thyroid autoregulation, the role of oncogene mutations and growth factors, and studies directly linking persistently high TSH levels with the sequential cellular development of thyroid follicular cell neoplasia would provide further confirmation.

Polymerase chain reaction-based microsatellite polymorphism analysis of follicular and Hürthle cell neoplasms of the thyroid

Follicular and Hürthle cell carcinomas of the thyroid cannot be differentiated from adenomas by either preoperative fine needle aspiration or intraoperative frozen section examination, and yet there exist potentially significant differences in the recommended surgical management. We examined, by PCR-based microsatellite polymorphism analysis, DNA obtained from 83 thyroid neoplasms [22 follicular adenomas, 29 follicular carcinomas, 20 Hürthle cell adenomas (HA), and 12 Hürthle cell carcinomas (HC)] to determine whether a pattern of allelic alteration exists that could help distinguish benign from malignant lesions. Alterations were found in only 7.5% of informative PCR reactions from follicular neoplasms, whereas they were found in 23.3% of reactions from Hürthle cell neoplasms. Although there were no significant differences between follicular adenoma and follicular carcinoma, HC demonstrated a significantly greater percentage of allelic alteration than HA on chromosomal arms 1q (P < 0.001) and 2p (P < 0.05) by Fisher's exact test. The documentation of an alteration on either 1q or 2p was 100% sensitive and 65% specific in the detection of HC (P < 0.0005, by McNemar's test). In conclusion, PCR-based microsatellite polymorphism analysis may be a useful technique in distinguishing HC from HA. Potentially, the application of this technique to aspirated material may allow this distinction preoperatively and thus facilitate more optimal surgical management. Consistent regions of allelic alteration may also indicate the locations of critical genes, such as tumor suppressor genes or oncogenes, that are important in the progression from adenoma to carcinoma. Finally, this study demonstrates that Hürthle cell neoplasms, now considered variants of follicular neoplasms, differ significantly from follicular neoplasms on a molecular level.

Differentiated thyroid cancer: determinants of disease progression in patients <21 years of age at diagnosis: a report from the Surgical Discipline Committee of the Children's Cancer Group

OBJECTIVE

This study was done to define the extent of disease and evaluate the effect of staging and treatment variables on progression-free survival in patients with differentiated thyroid carcinoma who were less than 21 years of age at diagnosis.

SUMMARY BACKGROUND DATA

Differentiated thyroid cancer in young patients is associated with early regional lymph node involvement and distant parenchymal metastases. Despite this, the overall long-term survival rate is greater than 90%, which suggests that biologic rather than treatment factors have a greater effect on outcome.

METHODS

Variables analyzed for their impact on progression-free survival in a multi-institutional cohort of 329 patients included age, antecedent thyroid irradiation, extrathyroidal tumor extension, size, nodal involvement, distant metastases, technique of thyroid surgery and lymphatic dissection, initial treatment with 131Iodine, residual cervical disease, and histopathologic subtype. Surgical complications were correlated with the specific procedures completed on the thyroid gland or cervical lymphatics.

RESULTS

The overall progression-free survival rate was 67% (95%, CI: 61%-73%) at 10 years with 2 disease-related deaths. Regional lymph node and distant metastases were present in 74% and 25% of patients, respectively. Progression-free survival was less in younger patients (p = 0.009) and those with residual cervical disease after thyroid surgery (p = 0.001). Permanent hypocalcemia was more frequent after total or subtotal thyroidectomy (p = 0.001) while wound complications increased after radical neck dissections (p < 0.00001).

CONCLUSIONS

The progression-free survival rate was better after a complete resection and in older patients. Progression-free survival rate was the same after lobectomy or more extensive thyroid procedures, but comparison was confounded by the increased use of total or subtotal thyroidectomy in patients with advanced disease. The risk of permanent hypocalcemia increased when total or subtotal thyroidectomy was done. Thyroid lobectomy alone may be appropriate for patients with small localized lesions while total or subtotal thyroidectomy should be considered for more extensive tumors.

Near haploidy in breast cancer: a particular pathway of chromosome evolution

In a series of 260 cytologically abnormal breast cancers studied in our laboratory, we observed a single case of near-haploid karyotype: 27,X, +der(1;16)(q10;p10), +7, +14, +15. A review of published cases of near-haploid malignancies suggests that near haploidy belongs to a process of chromosome evolution distinct from that of most epithelial cancers in which hypodiploidy is strongly associated with the occurrence of unbalanced structural rearrangements. In near-haploid tumors, chromosome loss is independent from chromosome rearrangements and may not be associated with an adverse prognosis.