RESUMO
The hypothalamic-pituitary-gonadal axis is central to normal reproductive function. This pathway begins with the release of gonadotropin-releasing hormone in systematic pulses by the hypothalamus. Gonadotropin-releasing hormone is bound by receptors on gonadotroph cells in the anterior pituitary gland and stimulates the synthesis and secretion of luteinizing hormone and, to some extent, follicle-stimulating hormone. Once stimulated by these glycoprotein hormones, the gonads begin gametogenesis and the synthesis of sex hormones. In humans, mutations of the forkhead transcription factor, FOXP3, lead to an autoimmune disorder known as immunodysregulation, polyendocrinopathy, and enteropathy, X-linked syndrome. Mice with a mutation in the Foxp3 gene have a similar autoimmune syndrome and are infertile. To understand why FOXP3 is required for reproductive function, we are investigating the reproductive phenotype of Foxp3 mutant mice (Foxp3(sf/Y)). Although the gonadotroph cells appear to be intact in Foxp3(sf/Y) mice, luteinizing hormone beta (Lhb) and follicle-stimulating hormone beta (Fshb) expression are significantly decreased, demonstrating that these mice exhibit a hypogonadotropic hypogonadism. Hypothalamic expression of gonadotropin-releasing hormone is not significantly decreased in Foxp3(sf/Y) males. Treatment of Foxp3(sf/Y) males with a gonadotropin-releasing hormone receptor agonist does not rescue expression of Lhb or Fshb. Interestingly, we do not detect Foxp3 expression in the pituitary or hypothalamus, suggesting that the infertility seen in Foxp3(sf/Y) males is a secondary effect, possibly due to loss of FOXP3 in immune cells. Pituitary expression of glycoprotein hormone alpha (Cga) and prolactin (Prl) are significantly reduced in Foxp3(sf/Y) males, whereas the precursor for adrenocorticotropic hormone, pro-opiomelanocortin (Pomc), is increased. Human patients diagnosed with IPEX often exhibit thyroiditis due to destruction of the thyroid gland by autoimmune cells. We find that Foxp3(sf/Y) mice have elevated expression of thyroid-stimulating hormone beta (Tshb), suggesting that they may suffer from thyroiditis as well. Expression of the pituitary transcription factors, Pitx1, Pitx2, Lhx3, and Egr1, is normal; however, expression of Foxl2 and Gata2 is elevated. These data are the first to demonstrate a defect at the pituitary level in the absence of FOXP3, which contributes to the infertility observed in mice with Foxp3 loss of function mutations.
Assuntos
Subunidade beta do Hormônio Folículoestimulante/biossíntese , Fatores de Transcrição Forkhead/metabolismo , Hormônio Luteinizante Subunidade beta/biossíntese , Hipófise/metabolismo , Animais , Fatores de Transcrição Forkhead/genética , Hormônio Liberador de Gonadotropina/biossíntese , Hipogonadismo/tratamento farmacológico , Hipogonadismo/metabolismo , Hipotálamo/efeitos dos fármacos , Hipotálamo/metabolismo , Infertilidade Masculina/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Hipófise/efeitos dos fármacos , Pró-Opiomelanocortina/biossíntese , Prolactina/biossíntese , Receptores LHRH/agonistas , Tireotropina Subunidade beta/biossíntese , Fatores de Transcrição/biossínteseRESUMO
Many transcription factors have important roles in the function and differentiation of the human pituitary adenomas. Forkhead box gene transcription factor L2, Foxl2, is expressed during mouse pituitary development and co-localizes with the expression of α-glycoprotein hormone subunit (αGSU). In addition, Foxl2 regulates expression of the αGSU gene (Cga) in cell culture. To elucidate the functional role of FOXL2 in the human pituitary, we examined the expression and localization of FOXL2 in normal human pituitaries and various types of pituitary adenomas. Human pituitary adenomas were obtained by trans-sphenoidal surgery from 67 patients. Three normal adult pituitaries were obtained from autopsies of non-endocrine cases. The localization of FOXL2 and pituitary hormones in these pituitary patients was examined by immunohistochemical staining and RT-PCR. Quantitative analysis of FOXL2 protein was performed by immunoblotting. FOXL2 was localized in the nuclei of â¼20% of normal pituitary cells that also co-expressed gonadotropins including follicule-stimulating hormone ß (FSHß), luteinizing hormone ß (LHß), and αGSU, whereas it was observed in minor proportion of thyroid-stimulating hormone (TSH)-producing cells, prolactin (PRL)-producing cells, and precursor of adrenocorticotropic hormone (ACTH)-producing cells. FOXL2 immunoreactivity was not detected in growth hormone (GH)-producing cells or S100-positive folliculo-stellate cells. In human pituitary adenomas, FOXL2 was expressed in the nuclei of the adenoma cells. FOXL2 was detected in 13 of 15 gonadotropin-subunit-producing adenoma (Gn-oma) cases and 8 of 11 null cell adenoma cases, but its incidence was reduced or not detected in the other types of adenomas. The results of this study suggest that FOXL2 contributes to the human-specific functional expression and the differentiation of gonadotroph cells and adenomas.
Assuntos
Adenoma/genética , Adenoma/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Hipófise/metabolismo , Neoplasias Hipofisárias/genética , Neoplasias Hipofisárias/metabolismo , Adenoma/patologia , Adulto , Idoso , Feminino , Proteína Forkhead Box L2 , Fatores de Transcrição Forkhead/genética , Regulação Neoplásica da Expressão Gênica , Humanos , Masculino , Pessoa de Meia-Idade , Hipófise/patologia , Hormônios Hipofisários/metabolismo , Neoplasias Hipofisárias/patologia , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Adulto JovemRESUMO
BACKGROUND: Pancreatic cancer is one of the most aggressive human malignancies, with a very poor prognosis. To evaluate the effect of angiotensin II (Ang II) type 2 receptor (AT2) expression in the host's body on the growth of pancreatic carcinoma, we have investigated the growth of mouse pancreatic ductal carcinoma grafts in syngeneic wild type and AT2 receptor-deficient (AT2-KO) mice. METHODS: The role of AT2 receptor-signaling in stromal cells on the growth of murine pancreatic carcinoma cells (PAN02) was studied using various in vitro and in vivo assays. In vivo cell proliferation, apoptosis, and vasculature in tumors were monitored by Ki-67 immunostaining, TUNEL assay, and von Willebrand factor immunostaining, respectively. In the co-culture study, cell proliferation was measured by MTT cell viability assay. All the data were analyzed using t-test and data were treated as significant when p < 0.05. RESULTS: Our results show that the growth of subcutaneously transplanted syngeneic xenografts of PAN02 cells, mouse pancreatic ductal carcinoma cells derived from the C57/BL6 strain, was significantly faster in AT2-KO mice compared to control wild type mice. Immunohistochemical analysis of tumor tissue revealed significantly more Ki-67 positive cells in xenografts grown in AT2-KO mice than in wild type mice. The index of apoptosis is slightly higher in wild type mice than in AT2-KO mice as evaluated by TUNEL assay. Tumor vasculature number was significantly higher in AT2-KO mice than in wild type mice. In vitro co-culture studies revealed that the growth of PAN02 cells was significantly decreased when grown with AT2 receptor gene transfected wild type and AT2-KO mouse-derived fibroblasts. Faster tumor growth in AT2-KO mice may be associated with higher VEGF production in stromal cells. CONCLUSIONS: These results suggest that Ang II regulates the growth of pancreatic carcinoma cells through modulating functions of host stromal cells; Moreover, Ang II AT2 receptor signaling is a negative regulator in the growth of pancreatic carcinoma cells. These findings indicate that the AT2 receptor in stromal fibroblasts is a potentially important target for chemotherapy for pancreatic cancer.
Assuntos
Carcinoma/patologia , Regulação Neoplásica da Expressão Gênica , Neoplasias Pancreáticas/patologia , Receptor Tipo 2 de Angiotensina/metabolismo , Animais , Linhagem Celular Tumoral , Proliferação de Células , Sobrevivência Celular , Técnicas de Cocultura , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Transdução de Sinais , Sais de Tetrazólio/farmacologia , Tiazóis/farmacologia , Fator de von Willebrand/metabolismoRESUMO
Epitope retrieval (ER) using heating causes a dramatic improvement in the sensitivity of immunohistochemistry for formalin-fixed paraffin-embedded (FFPE) tissue sections. Here, the relationship between the pH of the retrieval buffer used for heat-induced epitope retrieval (HIER) and the isoelectric points (pI) of the antigen recognized by antibodies against nuclear proteins (mainly human pituitary transcription factors in this study) was investigated using FFPE tissue sections. A universal buffer, with a buffering capacity over a wide pH range from 2.0 to 12.0, was used for HIER. We found that the intensity of staining for most nuclear proteins after HIER depended simply on the pH of the buffer. Importantly, for efficient HIER, antigens with acidic pI required basic pH buffer conditions, while antigens with alkaline pI required acidic conditions. This implies that the electrostatic charge of the antigens contributed significantly to the efficiency of HIER. We conclude that appropriate selection of the pH of the buffer based on the pI of the individual antigens is of great importance for efficient ER. It is concluded that the mechanism of HEIR may, therefore, depend to a large extent on the pI of the antigen under investigation.
Assuntos
Epitopos/análise , Imuno-Histoquímica/métodos , Anticorpos , Antígenos , Soluções Tampão , Formaldeído , Temperatura Alta , Humanos , Concentração de Íons de Hidrogênio , Imuno-Histoquímica/normas , Ponto Isoelétrico , Proteínas Nucleares/análise , Proteínas Nucleares/imunologia , Inclusão em Parafina , Fixação de TecidosRESUMO
Genetic cases of congenital pituitary hormone deficiency are common and many are caused by transcription factor defects. Mouse models with orthologous mutations are invaluable for uncovering the molecular mechanisms that lead to problems in organ development and typical patient characteristics. We are using mutant mice defective in the transcription factors PROP1 and POU1F1 for gene expression profiling to identify target genes for these critical transcription factors and candidates for cases of pituitary hormone deficiency of unknown aetiology. These studies reveal critical roles for Wnt signalling pathways, including the TCF/LEF transcription factors and interacting proteins of the groucho family, bone morphogenetic protein antagonists and targets of notch signalling. Current studies are investigating the roles of novel homeobox genes and pathways that regulate the transition from proliferation to differentiation, cell adhesion and cell migration. Pituitary adenomas are a common human health problem, yet most cases are sporadic, necessitating alternative approaches to traditional Mendelian genetic studies. Mouse models of adenoma formation offer the opportunity for gene expression profiling during progressive stages of hyperplasia, adenoma and tumorigenesis. This approach holds promise for the identification of relevant pathways and candidate genes as risk factors for adenoma formation, understanding mechanisms of progression, and identifying drug targets and clinically relevant biomarkers.
Assuntos
Biomarcadores Tumorais/biossíntese , Biomarcadores Tumorais/genética , Regulação Neoplásica da Expressão Gênica/genética , Proteínas de Neoplasias/biossíntese , Proteínas de Neoplasias/genética , Hipófise/metabolismo , Neoplasias Hipofisárias/genética , Neoplasias Hipofisárias/metabolismo , Animais , Biologia Computacional/métodos , Modelos Animais de Doenças , Perfilação da Expressão Gênica , Camundongos , Camundongos Mutantes , Hipófise/patologia , Hormônios Hipofisários/deficiência , Hormônios Hipofisários/genética , Hormônios Hipofisários/metabolismo , Neoplasias Hipofisárias/patologiaRESUMO
The Wnt signaling pathway has been implicated in the genesis of numerous human cancers. A member of the Wnt family of genes, Wnt4, has been known to regulate proliferation of anterior pituitary cell types in the mouse during embryonic development. In order to elucidate the roles of Wnt signaling in human pituitary adenomas, we examined the expression of Wnt4 and its putative receptor Frizzled6 (Fzd6) by immunohistochemistry in pituitary adenomas and normal pituitaries. Expression of Wnt4 was higher in growth hormone-producing adenomas (GHomas), prolactin-producing adenomas (PRLomas), and thyroid-stimulating hormone-producing adenomas (TSHomas) than in the normal pituitary. Fzd6 was widely expressed in GHomas, PRLomas, TSHomas, and gonadotropin subunit (GnSU)-positive adenomas. In normal pituitary glands, Wnt4 and Fzd6 were colocalized predominantly in follicle-stimulating hormone-, luteinizing hormone-, and alpha-subunits of glycoprotein hormone-positive cells. The canonical Wnt/beta-catenin signaling pathway was analyzed by beta-catenin immunohistochemistry. beta-Catenin was localized at the cell membrane in all pituitary adenomas, but not in the nuclei. On the other hand, Erk1/2 was highly activated in GHomas and TSHomas. These results suggested that activation of Wnt4/Fzd6 signaling through a "beta-catenin-independent" pathway played a role in proliferation and survival of the pituitary adenoma cells. Detailed involvement of transcription factors including Pit-1 remains to be further investigated.
Assuntos
Adenoma/metabolismo , Biomarcadores Tumorais/metabolismo , Neoplasias Hipofisárias/metabolismo , Proteínas Wnt/metabolismo , beta Catenina/metabolismo , Adenoma/genética , Adenoma/patologia , Adolescente , Adulto , Idoso , Feminino , Técnica Indireta de Fluorescência para Anticorpo , Receptores Frizzled/genética , Receptores Frizzled/metabolismo , Perfilação da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Humanos , Técnicas Imunoenzimáticas , Masculino , Pessoa de Meia-Idade , Hipófise/metabolismo , Neoplasias Hipofisárias/genética , Neoplasias Hipofisárias/patologia , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo , Transdução de Sinais/genética , Proteínas Wnt/genética , Proteína Wnt4 , Adulto Jovem , beta Catenina/genéticaRESUMO
We examined whether an enhanced green fluorescent protein (EGFP)-tagged chromogranin A (CgA) gene construct could serve as a marker protein to follow the synthesis of CgA and the process of granulogenesis in non-neuroendocrine (NE) cells. We transfected a CgA-EGFP expression vector into non-NE COS-7 cells and investigated the localization of a chimeric CgA-EGFP protein using confocal laser scanning microscopy (CLSM). The fluorescent signal of CgA-EGFP was distributed granularly in the cytoplasm. An immunocytochemical study using anti-CgA antibody with a quantum dot (Qd)525 shows colocalization of fluorescent signal of chimeric CgA-EGFP and CgA-Qd525 signals in granular structures, particularly at the periphery of the cytoplasm. We interpreted granules that were immunoreactive to CgA in electron micrographs as secretory. Spectral analysis of EGFP fluorescence revealed distinct EGFP signals without CgA colocalization. This is the first report to show that a granular structure can be induced by transfecting the EGFP-tagged human CgA gene into non-NE cells. The EGFP-tagged CgA gene could be a useful tool to investigate processes of the regulatory pathway. A more precise analysis of the fluorescence signal of EGFP by combination with the Qd system or by spectral analysis with CLSM can provide insight into biological phenomena.
Assuntos
Cromogranina A/biossíntese , Grânulos Citoplasmáticos/fisiologia , Proteínas de Fluorescência Verde/biossíntese , Animais , Células COS , Chlorocebus aethiops , Cromogranina A/genética , Grânulos Citoplasmáticos/metabolismo , Proteínas de Fluorescência Verde/genética , Humanos , Immunoblotting , Microscopia Confocal , Proteínas Recombinantes de Fusão/biossíntese , Proteínas Recombinantes de Fusão/genética , TransfecçãoRESUMO
FOXL2 is a forkhead transcription factor expressed in the eye, ovary, and pituitary gland. Loss of function mutations in humans and mice confirm a functional role for FOXL2 in the eye and ovary, but its role in the pituitary is not yet defined. We report that FOXL2 colocalizes with the glycoprotein hormone alpha-subunit (alphaGSU) in quiescent cells of the mouse pituitary from embryonic d 11.5 through adulthood. FOXL2 is expressed in essentially all gonadotropes and thyrotropes and a small fraction of prolactin-containing cells during pregnancy, but not somatotropes or corticotropes. The coincident expression patterns of FOXL2 and alphaGSU suggested that the alphaGSU gene (Cga) is a downstream target of FOXL2. We demonstrate that FOXL2 regulates mouse Cga transcription in gonadotrope-derived (alphaT3-1, LbetaT2), thyrotrope-derived (alphaTSH) and heterologous (CV-1) cells in a context-dependent manner. In addition, a FOXL2-VP16 fusion protein is sufficient to stimulate ectopic Cga expression in transgenic animals. Normal FOXL2 expression requires the transcription factors Lhx3 and Lhx4 but not of Prop1. Thus, FOXL2 expression is affected by mutations in early pituitary developmental regulatory genes, and its expression precedes that of genes necessary for gonadotrope-specific development such as Egr1 and Sf1 (Nr5a1). These data place FOXL2 in the hierarchy of pituitary developmental control and suggest a role in regulation of Cga gene expression.
Assuntos
Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Fatores de Transcrição Forkhead/fisiologia , Hipófise/embriologia , Hipófise/metabolismo , Animais , Embrião de Mamíferos , Proteína Forkhead Box L2 , Regulação da Expressão Gênica no Desenvolvimento , Subunidade alfa de Hormônios Glicoproteicos/metabolismo , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/fisiologia , Proteínas com Homeodomínio LIM , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Modelos Biológicos , Adeno-Hipófise/embriologia , Adeno-Hipófise/crescimento & desenvolvimento , Adeno-Hipófise/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/fisiologiaRESUMO
OBJECTIVE: The aim of this study was to determine the correlation between the expression of somatostatin receptors by immunohistochemistry and the percent suppression of GH levels in the octreotide suppression test. PATIENTS AND METHODS: Twenty-two patients with acromegaly who underwent an octreotide suppression test before surgery were studied. We performed immunohistochemistry for Somatostatin receptor 2A (SSTR2A) and Somatostatin receptor 5 (SSTR5) on the surgical specimens from all patients, which we scored according to the number of tumor cells staining positive at the surface membrane (3+: >50%, 2+: 25-50%, 1+: <25%). We sought correlations of percent suppression in the octreotide suppression test with these immunohistochemistry scores. RESULTS: Somatostatin receptor 2A (SSTR2A) showed the highest frequency of score 3+ (13 of 22, 59.1%) by immunohistochemistry. Subtype 5 showed the highest frequency for score 2+ (9 of 22, 40.9%), and one (4.5%) was immunonegative. For subtype 2A, there was a significant correlation with percent decrease (P = 0.002 < 0.01). In contrast, there was no significant correlation for SSTR5. CONCLUSION: Immunohistochemistry for SSTR2A in pathology specimens from acromegalic patients enabled selection of those experiencing clinical benefit from octreotide. Therefore, performing immunohistochemistry for detection of SSTR2A is recommended for all specimens obtained by surgery.
Assuntos
Adenoma/metabolismo , Antineoplásicos Hormonais/uso terapêutico , Adenoma Hipofisário Secretor de Hormônio do Crescimento/metabolismo , Octreotida/uso terapêutico , Receptores de Somatostatina/biossíntese , Acromegalia/tratamento farmacológico , Acromegalia/etiologia , Adenoma/tratamento farmacológico , Adulto , Idoso , Feminino , Adenoma Hipofisário Secretor de Hormônio do Crescimento/tratamento farmacológico , Humanos , Imuno-Histoquímica , Masculino , Pessoa de Meia-Idade , Terapia NeoadjuvanteRESUMO
The pituitary tumor-transforming gene (PTTG) is a homolog of yeast Securin, which arrests the activation of Separin to induce sister chromatid separation in the transition from metaphase to anaphase. Pituitary tumor-transforming gene is also known to induce angiogenesis during pituitary tumorigenesis. It has not been clarified whether PTTG functions as a cytoplasmic or a nuclear protein. Our immunohistochemical study indicated that PTTG is localized in the cytoplasm of pituitary tumor cells. In the present study, confocal laser scanning microscopy (CLSM) analysis of human pituitary adenomas and immunoelectron microscopy of the mouse pituitary cell line, AtT-20, demonstrated the localization of PTTG in the Golgi apparatus and vesicles. Secreted PTTG was detected by immunoblotting from culture medium of mouse pituitary tumor cell lines. Our results suggested that PTTG is a secretory protein produced by pituitary tumor cells. In addition, PTTG may exert autocrine and/or paracrine functions as a newly proposed important pathway for the action of PTTG.
Assuntos
Adenoma/metabolismo , Linhagem Celular Tumoral/metabolismo , Proteínas de Neoplasias/metabolismo , Neoplasias Hipofisárias/metabolismo , Adenoma/patologia , Animais , Biomarcadores Tumorais/metabolismo , Western Blotting , Linhagem Celular Tumoral/patologia , Expressão Gênica , Humanos , Processamento de Imagem Assistida por Computador , Técnicas Imunoenzimáticas , Camundongos , Microscopia Confocal , Microscopia Imunoeletrônica , Proteínas de Neoplasias/genética , Neoplasias Hipofisárias/patologia , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , SecurinaRESUMO
The differentiation of pituitary cells and human pituitary adenomas follow three cell lineages: GH-PRL-TSH, ACTH, and FSH/LH, which are regulated by a combination of various transcription factors and co-factors. We have used RT-PCR and immunohistochemistry to show that immunonegative, "null cell" adenomas are equipped with multiple transcription factors and co-factors. The "null cell" adenomas showed similar frequencies of transcription factors as did the gonadotropin subunit (GnSU)-positive adenomas, with the exception that there were fewer instances of SF1 in the former. We speculate, therefore, that null cell adenomas and GnSU-positive adenomas share common molecular mechanisms in functional differentiation, even though the former do not produce hormones. From the high frequency of various transcription factors, we also speculate that both null cell adenomas and GnSU-positive adenomas are derived from "committed" pituitary progenitor stem cells. The questions, why a certain proportion of these pituitary tumor groups lack hormone production and why they are molecularly more committed to Gn transcription, remain to be further investigated.
Assuntos
Adenoma/metabolismo , Gonadotropinas Hipofisárias/metabolismo , Neoplasias Hipofisárias/metabolismo , Fatores de Transcrição/biossíntese , Adenoma/genética , Adenoma/patologia , Adulto , Idoso , Linhagem da Célula , Transformação Celular Neoplásica , Primers do DNA/química , Feminino , Expressão Gênica , Gonadotropinas Hipofisárias/genética , Hormônios/metabolismo , Humanos , Técnicas Imunoenzimáticas , Masculino , Pessoa de Meia-Idade , Neoplasias Hipofisárias/genética , Neoplasias Hipofisárias/patologia , RNA Mensageiro/metabolismo , RNA Neoplásico/análise , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fatores de Transcrição/genéticaRESUMO
This review article describes functional differentiation of the pituitary cells and pituitary adenomas with special emphasis on transcription factors and co-factors. Human pituitary adenomas generally follow the combination of transcription factors and co-factors, which are similar to those of physiologic anterior pituitary cells. On very rare occasions, the single pituitary adenoma produces two hormones, which belong to different cell lineage 'trans-cell lineage'. Basic mechanism for this was considered to be 'aberrant expression' of transcription factors, i.e. NeuroD1 and Pit-1. This was experimentally supported by the induction of GH (mRNA and protein) in AtT-20 cells by transfecting Pit-1 gene. Various mechanisms have been reported for the experimental pituitary oncogenesis. Among these, GHRH has been emphasized as one of oncogenic factors for both human GHomas as well as in the transgenic animals.
Assuntos
Adenoma/metabolismo , Adenoma/patologia , Hipófise/metabolismo , Hipófise/patologia , Neoplasias Hipofisárias/metabolismo , Neoplasias Hipofisárias/patologia , Animais , Diferenciação Celular , Humanos , Hipófise/citologia , Hormônios Hipofisários/metabolismo , Fatores de Transcrição/metabolismoRESUMO
With applications of recent development of molecular techniques, endocrine pathology, as a scientific discipline, has been expanding its field to cover not only the pathologic diagnosis but also molecular mechanisms of hormone production and secretion as well as implementation for appropriate therapeutic approaches. In this review, the discussion includes molecular markers for the diagnosis of neuroendocrine (NE) tumors focusing on various proteins for the transport of secretory granules. MIB-1, proliferative indices, is particularly useful to access biologic activities of NE tumors. The specific hormone production relies on the expression of combination of transcription factors and proteolytic digestion (processing) of prohormones by specific enzymes, prohormone convertases PC1/3 and PC2. Inappropriate processing of prohormones sometimes are related to neoplastic conditions. Endocrine therapeutics have been focusing on the compensation of deficient hormones by transplanting specific hormone producing cells including embryonic stem (ES) cells. The endocrine pathology is expected to play a major role in translational medicine.
Assuntos
Glândulas Endócrinas/patologia , Tumores Neuroendócrinos/genética , Tumores Neuroendócrinos/patologia , Patologia/métodos , Biossíntese de Proteínas , Biomarcadores Tumorais/metabolismo , Glândulas Endócrinas/metabolismo , Hormônios/metabolismo , Humanos , Tumores Neuroendócrinos/terapia , Patologia/tendências , Vesículas Secretórias/metabolismoRESUMO
Growth hormone (GH)-producing adenomas (GHomas) are one of the most frequently-occurring pituitary adenomas. Differentiation of hormone-producing cells in the pituitary gland is regulated by transcription factors and co-factors. The transcription factors include Pit-1, Prop-1, NeuroD1, Tpit, GATA-2, SF-1. Aberrant expression of transcription factors such as Pit-1 results in translineage expression of GH in adrenocorticotropic hormone-producing adenomas (ACTHomas). This situation has been substantiated by GFP-Pit-1 transfection expression in the AtT20 cell line. Experimentally, GHomas have been induced in GH-releasing hormone (GHRH) or Prop-1 transgenic animals. Immunohistochemical detection of somatostatin receptor (SSTR2a) has recently emphasized their role in the response of GHomas to somatostatin analogue therapy. In this review, the advances in technology and their contribution to cell biology and medical practice are discussed.
RESUMO
Transcription factors play specific roles in the development and differentiation of normal pituitary tissues and pituitary adenoma. The transcription factor, muscle segment homeobox 1 (MSX1), which belongs to the homeobox gene family, binds the promoter region of the glycoprotein hormone alpha-subunit (SU) in TSH-producing cells in the mouse pituitary and regulates alpha-SU expression. The present study investigated MSX1 expression in the normal human pituitary. In addition, 50 pituitary adenomas were examined using immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR) to clarify the role of MSX1 in the development and functional differentiation of pituitary adenoma cells. In the normal pituitary, MSX1 was predominantly expressed in the cytoplasm of GH-producing cells. Furthermore, MSX1 immunoreactivity was observed in the cytoplasm of some alpha-SU-producing cells. It is interesting to note that, in the pituitary adenoma, MSX1 was expressed in the nucleus of GH- and TSH-producing adenomas. RT-PCR using RNA extracted and purified from formalin-fixed paraffin-embedded pituitary adenoma specimens revealed MSX1 mRNA expressed in GH- and TSH-producing adenomas. Immunoelectron microscopy demonstrated MSX1 localized at intranuclear heterochromatin and euchromatin, which suggests transcriptional activity. These results suggest that MSX1 plays a specific role in human pituitary adenoma.
Assuntos
Adenoma/genética , Fator de Transcrição MSX1/genética , Hipófise/fisiologia , Neoplasias Hipofisárias/genética , Adenoma/patologia , Adenoma/ultraestrutura , Animais , Autopsia , Western Blotting , Diferenciação Celular , Primers do DNA , Humanos , Imuno-Histoquímica , Camundongos , Microscopia Imunoeletrônica , Hipófise/citologia , Hipófise/ultraestrutura , Neoplasias Hipofisárias/patologia , Neoplasias Hipofisárias/ultraestrutura , RNA Mensageiro/genética , RNA Neoplásico/genética , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Prophet of Pit-1 (Prop1) is an early transcription factor that delays the appearance of gonadotropin in the developing pituitaries. Prop1 transgenic (Tg) mice have been shown to generate pituitary tumors that either produce TSH or are non-hormone producing. In our series of Prop1 Tg mice, only 5 out of 9 female mice produced pituitary adenomas, and the adenomas were only GH, PRL, GH and PRL, PRL and gonadotropin or TSH producing. The pituitary cells that surrounded these adenomas showed hyperplasia of the corresponding hormone producing cells; i.e. the GH cells were increased in the pituitary that contained GH producing adenoma. In addition, although the adenomas lacked the expression of Prop1, the non-neoplastic pituitary cells showed expression of Prop1. The Prop1 Tg mice also showed vacuolated cells with eccentric nuclei, which are characteristic of "signet-ring hypertrophic cells". Using immunohistochemistry, these signet ring hypertrophic cells were found to be positive for gonadotropin.Taken together, our results suggest a (1) tumorigenic effect of Prop1 in the pituitaries, and (2) causative effects of signet ring-type gonadotropes.
RESUMO
This article describes pertinent aspects of histochemical and molecular changes of the human pituitary adenomas. The article outlines individual tumor groups with general, specific and molecular findings. The discussion further extends to the unusual adenomas or carcinomas. The description in this article are pertinent not only for the practicing pathologists who are in the position of making proper diagnosis, but also for the pituitary research scientists who engage in solving basic problems in pituitary neoplasms by histochemistry and molecular biology.
Assuntos
Neoplasias Hipofisárias/patologia , Animais , Diferenciação Celular , Gonadotropinas/biossíntese , Hormônio do Crescimento/biossíntese , Hormônio do Crescimento/metabolismo , Humanos , Leucemia/metabolismo , Leucemia/patologia , Neoplasias Hipofisárias/classificação , Neoplasias Hipofisárias/metabolismo , Prolactina/biossínteseRESUMO
The functional differentiation of pituitary cells and adenomas follows the combination of transcription factors and co-factors in three cell lineages [growth hormone-prolactin-thyroid-stimulating hormone lineage, adrenocorticotrophic hormone (ACTH)/pro-opiomelanocortin (POMC) lineage, and follicular stimulating hormone (FSH)/luteinizing hormone (LH) lineage], which include Pit-1, GATA-2, SF-1, NeuroD1/beta2, Tpit, ERalpha, and others. Only rarely are hormones from different lineages co-expressed in the same adenoma cells. Most corticotroph cell adenomas belonging to the ACTH/POMC lineage are mono-hormonal. In our study of 89 corticotroph cell adenomas, 5 cases expressed both ACTH and alpha-subunit; these adenomas did not express any other anterior pituitary hormones or subunits. To clarify the mechanism involved, we studied the transcription factors that regulate pituitary cell differentiation. NeuroD1 and T-pit, markers of the ACTH/POMC lineage, and SF-1 and DAX-1, related to the LH/FSH cell lineage were expressed in all cases. GATA2, a synergistic factor in the gonadotroph cell lineage with SF-1, was also expressed in three of five cases. As ACTH and alpha-subunit are the earliest hormones to appear during development, we speculate that these particular adenomas are derived from committed ACTH progenitor cells. The molecular process governing functional differentiation of these adenomas requires further investigation.