RESUMEN
The main risk factor for skin cancer is ultraviolet (UV) exposure, which causes DNA damage. Cells respond to UV-induced DNA damage by activating the intra-S-phase checkpoint, which prevents replication fork collapse, late origin firing and stabilizes fragile sites. Recently, the 54-kDa multifunctional protein NONO was found to be involved in the non-homologous end-joining DNA repair process and in poly ADP-ribose polymerase 1 activation. Interestingly, NONO is mutated in several tumour types and emerged as a crucial factor underlying both melanoma development and progression. Therefore, we set out to evaluate whether NONO could be involved in the DNA-damage response to UV radiations. We generated NONO-silenced HeLa cell clones and found that lack of NONO decreased cell growth rate. Then, we challenged NONO-silenced cells with exposure to UV radiations and found that NONO-silenced cells, compared with control cells, continued to synthesize DNA, failed to block new origin firing and impaired CHK1S345 phosphorylation showing a defective checkpoint activation. Consistently, NONO is present at the sites of UV-induced DNA damage where it localizes to RAD9 foci. To position NONO in the DNA-damage response cascade, we analysed the loading onto chromatin of various intra-S-phase checkpoint mediators and found that NONO favours the loading of topoisomerase II-binding protein 1 acting upstream of the ATM and Rad3-related kinase activity. Strikingly, re-expression of NONO, through an sh-resistant mRNA, rescued CHK1S345 phosphorylation in NONO-silenced cells. Interestingly, NONO silencing affected cell response to UV radiations also in a melanoma cell line. Overall, our data uncover a new role for NONO in mediating the cellular response to UV-induced DNA damage.
Asunto(s)
Daño del ADN , Proteínas Asociadas a Matriz Nuclear/fisiología , Factores de Transcripción de Octámeros/fisiología , Proteínas de Unión al ARN/fisiología , Puntos de Control de la Fase S del Ciclo Celular/fisiología , Puntos de Control de la Fase S del Ciclo Celular/efectos de la radiación , ADN/metabolismo , Reparación del ADN , Proteínas de Unión al ADN , Células HeLa , Humanos , Proteínas Asociadas a Matriz Nuclear/genética , Proteínas Asociadas a Matriz Nuclear/metabolismo , Factores de Transcripción de Octámeros/genética , Factores de Transcripción de Octámeros/metabolismo , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Puntos de Control de la Fase S del Ciclo Celular/genética , Transfección , Rayos UltravioletaRESUMEN
Malignant mesothelioma (MM) is a highly aggressive tumor of the serous membranes for which there is currently no effective curative modality. Recent data suggest that hyperactivation of the tyrosine kinase SRC has a key role in MM development and therefore this kinase represents an important molecular target for MM therapy. We tested new pyrazolo[3,4-d]pyrimidine SRC inhibitors on a panel of MM cell lines expressing the active form of SRC. These SRC inhibitors exerted a significant proapoptotic effect on MM cells without affecting the normal mesothelial cell line MET-5A, supporting a possible use of these SRC inhibitors for a safe treatment of MM. We also showed that SRC inhibitor-induced apoptosis occurred concomitantly with an increase in the nuclear stability of the cyclin-dependent kinase inhibitor p27. This finding is remarkable considering that loss of nuclear p27 expression is a well-established adverse prognostic factor in MM, and p27 nuclear localization is crucial for its tumor-suppressive function. Consistently, SRC inhibition seems to promote the increase in p27 nuclear level also by inactivating the AKT kinase and downregulating cyclin D1, which would otherwise delay p27 nuclear import and provoke its cytoplasmic accumulation. To determine whether p27 stabilization has a direct role in apoptosis induced by SRC inhibition, we stably silenced the CDKN1B gene, encoding p27, in MSTO-211H and REN mesothelioma cells by transduction with lentiviral vectors expressing short hairpin RNAs against the CDKN1B transcript. Strikingly, p27 silencing was able to suppress the apoptosis induced by these SRC inhibitors in both MM cell lines, suggesting that p27 has a crucial proapoptotic role in MM cells treated with SRC inhibitors. Our findings reveal a new mechanism, dependent on p27 nuclear stabilization, by which SRC inhibition can induce apoptosis in MM cells and provide a new rationale for the use of SRC inhibitors in MM therapy.
Asunto(s)
Apoptosis/efectos de los fármacos , Inhibidor p27 de las Quinasas Dependientes de la Ciclina/metabolismo , Pirazoles/farmacología , Pirimidinas/farmacología , Familia-src Quinasas/antagonistas & inhibidores , Antineoplásicos/química , Antineoplásicos/farmacología , Western Blotting , Ciclo Celular/efectos de los fármacos , Línea Celular , Línea Celular Tumoral , Núcleo Celular/metabolismo , Supervivencia Celular/efectos de los fármacos , Ciclina D1/metabolismo , Inhibidor p27 de las Quinasas Dependientes de la Ciclina/genética , Relación Dosis-Respuesta a Droga , Estabilidad de Enzimas/efectos de los fármacos , Citometría de Flujo , Humanos , Mesotelioma/genética , Mesotelioma/metabolismo , Mesotelioma/patología , Estructura Molecular , Proteínas Proto-Oncogénicas c-akt/metabolismo , Pirazoles/química , Pirimidinas/química , Interferencia de ARNRESUMEN
Cell cycle regulation involves processes crucial to the survival of a cell, including the detection and repair of genetic damage as well as the prevention of uncontrolled cell division. The molecular events that control cell cycle are ordered and directional. Cyclins and cyclin-dependent kinases (CDKs), determine cell progression through the cycle ensuring the orderly coordination of cellular events. Alterations of cell cycle controllers are among the main causes of cancer onset. In the past decades many efforts have been made to develop kinase inhibitors that are able to modulate cyclin and CDK complexes, either by mimicking the function of natural CDK inhibitors, such as p21, p16 and p27, or by modulating the cyclin-CDK complexes or their targets directly. The great debate is whether to use peptides or small molecules. Peptides are more selective being derived by the linear protein sequences, indeed they should mimic the catalytic or the regulatory subunits of the cell cycle controller complexes, but on the other side they usually present poorer pharmacokinetic characteristics. In contrast, small molecules have better pharmacokinetic features but lower specificity because many protein kinases show high sequence similarity within the active site. The purpose of this review article is to provide an overview of the main classes of CDK inhibitors focusing on structure-activity relationship (SAR) studies and discussing the pharmacological and therapeutic implications.
Asunto(s)
Quinasas Ciclina-Dependientes/antagonistas & inhibidores , Péptidos/química , Péptidos/farmacología , Inhibidores de Proteínas Quinasas/química , Inhibidores de Proteínas Quinasas/farmacología , Bibliotecas de Moléculas Pequeñas/química , Bibliotecas de Moléculas Pequeñas/farmacología , Secuencia de Aminoácidos , Animales , Ciclo Celular/efectos de los fármacos , Quinasas Ciclina-Dependientes/química , Quinasas Ciclina-Dependientes/metabolismo , Humanos , Modelos Moleculares , Datos de Secuencia Molecular , Péptidos/uso terapéutico , Inhibidores de Proteínas Quinasas/uso terapéutico , Bibliotecas de Moléculas Pequeñas/uso terapéutico , Relación Estructura-ActividadRESUMEN
H4(D10S170) gene has been identified upon its frequent rearrangement with RET in papillary thyroid tumours (RET/PTC1). The kinase ataxia telangectasia mutated (ATM) phosphorylates a limited number of downstream protein targets in response to DNA damage. We investigated the potential role of H4(D10S170) in DNA damage signaling pathways. We found that in cells treated with etoposide or ionizing radiation (IR), H4(D10S170) underwent ATM-mediated phosphorylation at Thr 434, stabilizing nuclear H4. In ataxia telangectasia cells (A-T), endogenous H4(D10S170) was localized to cytoplasm and was excluded from the nucleus. Moreover, H4(D10S170) was not phosphorylated in ATM-deficient lymphoblasts after ionizing irradiation. Inhibition of ATM kinase interfered with H4(D10S170) apoptotic activity, and expression of H4 with threonine 434 mutated in Alanine, H4(T434A), protected the cells from genotoxic stress-induced apoptosis. Most importantly, after exposure to IR we found that silencing of H4(D10S170) in mammalian cells increased cell survival, as shown by clonogenic assay, allows for DNA synthesis as evaluated by bromodeoxyuridine incorporation and permits cells to progress into mitosis as demonstrated by phosphorylation on Histone H3. Our results suggest that H4(D10S170) is involved in cellular response to DNA damage ATM-mediated, and that the impairment of H4(D10S170) gene function might have a role in thyroid carcinogenesis.
Asunto(s)
Proteínas de Ciclo Celular/fisiología , Proteínas del Citoesqueleto/metabolismo , Daño del ADN/genética , Proteínas de Unión al ADN/fisiología , Proteínas Serina-Treonina Quinasas/fisiología , Proteínas Supresoras de Tumor/fisiología , Secuencia de Aminoácidos , Proteínas de la Ataxia Telangiectasia Mutada , Línea Celular Tumoral , Proteínas del Citoesqueleto/antagonistas & inhibidores , Silenciador del Gen , Células HeLa , Humanos , Datos de Secuencia Molecular , Fosforilación , Neoplasias de la Tiroides/genéticaRESUMEN
Translocations involving chromosomal region 19q13 are a frequent finding in follicular adenomas of the thyroid and might represent the most frequent type of structural aberration in human epithelial tumors. By positional cloning, a putative candidate gene, ZNF331 (formerly RITA) located close to the breakpoint was identified. Recently, aberrant expression of ZNF331 has been described in two cell lines of follicular thyroid adenomas with aberrations in 19q13 indicating an involvement of ZNF331 in tumorigenesis. Nevertheless, knowledge about structure and expression of ZNF331 is limited. We performed RACE-PCR and genomic sequence analyses to gain a deeper insight into its molecular structure. To elucidate ZNF331 expression patterns we performed Northern blot analyses on various normal tissues as well as on thyroid carcinoma and adenoma cell lines. Herein, unique expression of a 3.4-kbp transcript is described in thyroid adenoma cell lines with 19q13 aberrations, which was not detected either in normal tissues or in thyroid carcinoma cell lines.
Asunto(s)
Adenoma/genética , Proteínas de Unión al ADN/genética , Proteínas de Neoplasias/genética , Neoplasias de la Tiroides/genética , Adenoma/metabolismo , Northern Blotting , Línea Celular Tumoral , Aberraciones Cromosómicas , Cromosomas Humanos Par 18 , Proteínas de Unión al ADN/metabolismo , Humanos , Proteínas de Neoplasias/metabolismo , Reacción en Cadena de la Polimerasa , Empalme del ARN , Neoplasias de la Tiroides/metabolismo , Distribución Tisular , Sitio de Iniciación de la Transcripción , Transcripción GenéticaRESUMEN
Both external and internal exposure to radiation have been linked to the development of papillary thyroid cancer. Rearrangement of the gene for RET tyrosine kinase and subsequent expression of this protein has also been found to occur in many papillary thyroid cancers, and with increased frequency in radiation-related cancers following the Chernobyl accident. However, little has been reported on the frequency of RET rearrangements in cancers after exposure to external radiation. We here report on RET protein immunoreactivity in paraffin-embedded thyroid samples from 30 patients with papillary thyroid cancer who received radiation treatment during childhood for benign conditions at Michael Reese Hospital in Chicago, and in 34 patients identified from the tumor registry as having papillary thyroid cancer with no history of therapeutic radiation. The subjects were characterized by sex, age at surgery, and the following attributes of tumor pathology: size, number of lobes involved, number of foci, lymph node metastases, and soft tissue invasion. Representative tissue samples were reacted with an antibody against the RET tyrosine kinase domain whose expression has been shown to correlate highly with RET/PTC rearrangements. A greater percentage of cancers positive for RET immunoreactivity was found in the radiation-exposed group (86.7% vs. 52.9%, P = 0.006). Although the mean age at surgery of the exposed group was lower than the control group, there was no correlation of positive RET immunoreactivity with the age at surgery. No characteristics of the tumors were associated with positive RET immunoreactivity. In summary, the greater incidence of RET-immunopositives in the irradiated group indicates that the expression of RET immunoreactivity is strongly associated with radiation exposure, but the prognostic significance of this is not yet clear.
Asunto(s)
Carcinoma Papilar/química , Proteínas de Drosophila , Neoplasias Inducidas por Radiación/química , Proteínas Proto-Oncogénicas/genética , Proteínas Tirosina Quinasas Receptoras/genética , Neoplasias de la Tiroides/química , Adulto , Carcinoma Papilar/epidemiología , Carcinoma Papilar/etiología , Preescolar , Femenino , Humanos , Inmunohistoquímica , Incidencia , Lactante , Masculino , Persona de Mediana Edad , Neoplasias Inducidas por Radiación/epidemiología , Prevalencia , Pronóstico , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-ret , Liberación de Radiactividad Peligrosa , Proteínas Tirosina Quinasas Receptoras/metabolismo , Enfermedades de la Tiroides/radioterapia , Neoplasias de la Tiroides/epidemiología , Neoplasias de la Tiroides/etiologíaRESUMEN
The HMGI proteins (HMGI, HMGY and HMGI-C) have an important role in the chromatin organization and interact with different transcriptional factors. The HMGI genes are expressed at very low levels in normal adult tissues, whereas they are very abundant during embryonic development and in several experimental and human tumours. In order to isolate proteins interacting with the HMGI(Y) proteins, a yeast two-hybrid screening was performed using the HMGI(Y) protein as bait. This analysis led to the isolation of homeodomain-interacting protein kinase-2 (HIPK2), a serine/threonine nuclear kinase. HIPK2 co-immunoprecipitates with the HMGI(Y) protein in 293T cells. The interaction between HIPK2 and HMGI(Y) occurs through the PEST domain of HIPK2 and it is direct because in vitro translated HIPK2 binds HMGI(Y). We also show that HIPK2 is able to phosphorylate the HMGI(Y) protein by an in vitro kinase assay. In order to understand a possible role of HIPK2 gene in cell growth we performed a colony assay which showed an impressive HIPK2 inhibitory effect on normal thyroid cells. Flow cytometric analysis would indicate the block of cell growth at the G2/M phase of the cell cycle. Since normal thyroid cells do not express detectable HMGI(Y) protein levels, we assume that the HIPK2 inhibitory effect is independent from the interaction with the HMGI(Y) protein.
Asunto(s)
Proteínas Portadoras/metabolismo , Proteínas del Grupo de Alta Movilidad/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Factores de Transcripción/metabolismo , Sitios de Unión , Bromodesoxiuridina/metabolismo , Proteínas Portadoras/química , Proteínas Portadoras/genética , Catálisis , División Celular/efectos de los fármacos , Línea Celular , Núcleo Celular/enzimología , ADN Complementario/metabolismo , Citometría de Flujo , Biblioteca de Genes , Proteína HMGA1a , Proteínas del Grupo de Alta Movilidad/química , Proteínas del Grupo de Alta Movilidad/genética , Humanos , Modelos Genéticos , Fosforilación , Plásmidos/metabolismo , Pruebas de Precipitina , Unión Proteica , Biosíntesis de Proteínas , Proteínas Serina-Treonina Quinasas/química , Proteínas Serina-Treonina Quinasas/genética , Estructura Terciaria de Proteína , Proteínas Recombinantes de Fusión/metabolismo , Factores de Transcripción/química , Factores de Transcripción/genética , Transfección , Técnicas del Sistema de Dos HíbridosRESUMEN
HMGI(Y) proteins are overexpressed in experimental and human malignancies, including colon, prostate and thyroid carcinomas. To determine at which step of the carcinogenic process HMGI(Y) induction occurs, we analysed the expression of the HMGI(Y) proteins in hyperplastic, preneoplastic and neoplastic tissues of colorectal origin by immunohistochemistry. All the colorectal carcinomas were HMGI(Y)-positive, whereas no expression was detected in normal colon mucosa tissue. HMGI(Y) expression in adenomas was closely correlated with the degree of cellular atypia. Only 2 of the 18 non-neoplastic polyps tested were HMGI(Y)-positive. These data indicate that HMGI(Y) protein induction is associated with the early stages of neoplastic transformation of colon cells and only rarely with colon cell hyperproliferation.
Asunto(s)
Adenoma/química , Neoplasias Colorrectales/química , Proteínas del Grupo de Alta Movilidad/análisis , Proteínas de Neoplasias/análisis , Factores de Transcripción/análisis , Colon/patología , Pólipos del Colon/química , Pólipos del Colon/patología , Neoplasias Colorrectales/patología , Proteína HMGA1a , Humanos , Hiperplasia , InmunohistoquímicaRESUMEN
fra-1 gene overexpression has been shown to represent a general event in thyroid cell transformation in vitro and in vivo. Moreover, inhibition of FRA-1 protein synthesis by stable transfection with a fra-1 antisense construct significantly reduces the malignant phenotype of the transformed thyroid cells, indicating a pivotal role of the fra-1 gene product in the process of cellular transformation. In the attempt to define the potential use of FRA-1 protein detection in the diagnosis of thyroid diseases, we analyzed Fra-1 expression by a combination of immunohistochemistry and reverse transcription-PCR (RT-PCR) assay in 174 samples of thyroid nodules (22 nodular hyperplasias, 102 follicular adenomas, 34 papillary carcinomas, 12 follicular carcinomas, and 4 anaplastic carcinomas) representative of the spectrum of thyroid tumor pathology. FRA-1 protein was abundant in all of the carcinoma samples (50/50, 100%), with an intense staining in the nucleus and the cytoplasm. Positive staining was also found in most of the adenomas (90 of 102; 88%), but in this case, the staining was restricted to the nucleus. Similar results were obtained from the analysis of thyroid goiters; however, the number of positive cases is lower than adenomas (8 of 22; 36%); moreover, the staining was not observed in all of the cells. Conversely, no FRA-1 protein was detectable in 12 normal thyroid tissue samples used as controls. RT-PCR analysis confirmed a higher fra-1 expression in papillary and follicular carcinomas compared with goiters and adenomas. fra-1 expression was also analyzed on 10 fine needle aspiration biopsy (FNAB) samples by RT-PCR. fra-1-specific mRNA was detected in seven of the eight FNABs corresponding to thyroid nodules that were eventually diagnosed as adenomas (three of four) and carcinomas (four of four) after surgery. Conversely, no fra-1 gene expression was observed in two FNABs derived from normal thyroid. Further studies are required before suggesting FRA-1 protein detection as a useful tool for the diagnosis of hyperplastic and neoplastic disorders of the thyroid gland.
Asunto(s)
Proteínas Proto-Oncogénicas c-fos/análisis , Proteínas Proto-Oncogénicas c-fos/genética , Glándula Tiroides/patología , Neoplasias de la Tiroides/metabolismo , Nódulo Tiroideo/metabolismo , Biopsia con Aguja , Proteína HMGA1a , Proteínas del Grupo de Alta Movilidad/análisis , Proteínas del Grupo de Alta Movilidad/genética , Humanos , Hiperplasia , Inmunohistoquímica , ARN Mensajero/análisis , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Neoplasias de la Tiroides/patología , Nódulo Tiroideo/patología , Factores de Transcripción/análisis , Factores de Transcripción/genética , Células Tumorales CultivadasRESUMEN
A sharp increase in the incidence of pediatric thyroid papillary cancer was documented after the Chernobyl power plant explosion. An increased prevalence of rearrangements of the RET protooncogene (RET/PTC rearrangements) has been reported in Belarussian post-Chernobyl papillary carcinomas arising between 1990 and 1995. We analyzed 67 post-Chernobyl pediatric papillary carcinomas arising in 1995-1997 for RET/PTC activation: 28 were from Ukraine and 39 were from Belarus. The study, conducted by a combined immunohistochemistry and RT-PCR approach, demonstrated a high frequency (60.7% of the Ukrainian and 51.3% of the Belarussian cases) of RET/PTC activation. A strong correlation was observed between the solid-follicular subtype of papillary carcinoma and the RET/PTC3 isoform: 19 of the 24 RET/PTC-positive solid-follicular carcinomas harbored a RET/PTC3 rearrangement, whereas only 5 had a RET/PTC1 rearrangement. Taken together these results support the concept that RET/PTC activation plays a central role in the pathogenesis of thyroid papillary carcinomas in both Ukraine and Belarus after the Chernobyl accident.
Asunto(s)
Carcinoma Papilar/genética , Proteínas de Drosophila , Reordenamiento Génico , Centrales Eléctricas , Proteínas Proto-Oncogénicas/genética , Liberación de Radiactividad Peligrosa , Proteínas Tirosina Quinasas Receptoras/genética , Neoplasias de la Tiroides/genética , Adolescente , Niño , Femenino , Humanos , Masculino , Proteínas Proto-Oncogénicas c-ret , República de Belarús , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , UcraniaRESUMEN
The majority of thyroid carcinomas maintain the expression of the cell growth suppressor p27, an inhibitor of cyclin-dependent kinase-2 (Cdk2). However, we find that 80% of p27-expressing tumors show an uncommon cytoplasmic localization of p27 protein, associated with high Cdk2 activity. To reproduce such a situation, a mutant p27 devoid of its COOH-terminal nuclear-localization signal was generated (p27-NLS). p27-NLS accumulates in the cytoplasm and fails to induce growth arrest in 2 different cell lines, indicating that cytoplasm-residing p27 is inactive as a growth inhibitor, presumably because it does not interact with nuclear Cdk2. Overexpression of cyclin D3 may account in part for p27 cytoplasmic localization. In thyroid tumors and cell lines, cyclin D3 expression was associated with cytoplasmic localization of p27. Moreover, expression of cyclin D3 in thyroid carcinoma cells induced cytoplasmic retention of cotransfected p27 and rescued p27-imposed growth arrest. Endogenous p27 also localized prevalently to the cytoplasm in normal thyrocytes engineered to stably overexpress cyclin D3 (PC-D3 cells). In these cells, cyclin D3 induced the formation of cytoplasmic p27-cyclin D3-Cdk complexes, which titrated p27 away from intranuclear complexes that contain cyclins A-E and Cdk2. Our results demonstrate a novel mechanism that may contribute to overcoming the p27 inhibitory threshold in transformed thyroid cells.
Asunto(s)
Quinasas CDC2-CDC28 , Proteínas de Ciclo Celular , Ciclinas/metabolismo , Proteínas Asociadas a Microtúbulos/metabolismo , Neoplasias de la Tiroides/metabolismo , Proteínas Supresoras de Tumor , Núcleo Celular/metabolismo , Ciclina D3 , Quinasa 2 Dependiente de la Ciclina , Inhibidor p27 de las Quinasas Dependientes de la Ciclina , Quinasas Ciclina-Dependientes/antagonistas & inhibidores , Quinasas Ciclina-Dependientes/metabolismo , Ciclinas/genética , Citoplasma/metabolismo , Genes Supresores de Tumor , Humanos , Proteínas Asociadas a Microtúbulos/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Transducción de Señal , Especificidad por Sustrato , Neoplasias de la Tiroides/patología , Células Tumorales CultivadasRESUMEN
Hyperplastic or neoplastic proliferative lesions of thyroid follicular epithelium consist of a spectrum, ranging from nodular hyperplasia to undifferentiated (anaplastic) carcinoma, and usually present as palpable thyroid nodules. Thyroid nodules are a common occurrence in the general population, but only a small proportion of them are eventually diagnosed as carcinoma. The difficulty in objectively identifying those thyroid nodules that are malignant to avoid unnecessary surgery, combined with the range and effectiveness of the available therapeutic options in those patients who do, indeed, have thyroid carcinoma, has prompted the search for tumor markers and prognostic indicators. The high mobility group I (HMGI) proteins represent a class of nuclear proteins involved in the regulation of chromatin structure and function. HMGI(Y), one of the members of this class, is expressed at high levels during embryogenesis and in malignant tumors but at generally low levels in normal adult human tissues. Previous work on a limited number of thyroid samples suggested that the detection of the HMGI(Y) proteins may provide a clinically useful diagnostic tool. To verify this assumption, we analyzed HMGI(Y) expression by a combination of immunohistochemistry and reverse transcription-PCR in 358 thyroid tissue samples that were representative of the spectrum of thyroid tumor pathology. HMGI(Y) was detectable in 18 of 19 follicular carcinomas, 92 of 96 papillary carcinomas, and 11 of 11 undifferentiated (anaplastic) carcinomas but in only 1 of 20 hyperplastic nodules, 44 of 200 follicular adenomas, and 0 of 12 normal tissue samples. The correlation between HMGI(Y) expression and a diagnosis of carcinoma was highly significant (P < 0.0001). We also prospectively collected and analyzed for HMGI(Y) expression by immunohistochemistry and reverse transcription-PCR in 12 fine needle aspiration biopsies from 10 patients who subsequently underwent surgical removal of a solitary thyroid nodule. HMGI(Y) was detectable only in the four fine needle aspiration biopsies, corresponding to the thyroid nodules that were definitively diagnosed as carcinomas after surgery (two follicular carcinomas and two papillary carcinomas). The remaining eight samples (six follicular adenomas and two samples consisting of normal follicular cells) were negative. The findings of this study confirm the differential expression of HMGI(Y) in thyroid neoplasia and indicate the HMGI(Y) protein as a potential marker for thyroid carcinoma.