metallothionein and Adenoma

Metallothioneins (MTs) are involved in numerous cell processes such as binding and transport of zinc and copper ions, differentiation, proliferation and apoptosis, therefore contributing to carcinogenesis. Scarce data exist on their expression in benign and malignant lesions of the thyroid.. mRNA expression of functional isoforms of MT genes (MT1A, MT1B, MT1E, MT1F, MT1G, MT1H, MT1X, MT2A, MT4) was studied in 17 nodular goiters (NG), 12 follicular adenomas (FA) and 26 papillary thyroid carcinomas (PTC).. One-way ANOVA revealed significant differences in mRNA expression levels of MT1A (p<0.05), MT1E (p<0.005), MT1F (p<0.0001), MT1G (p<0.005), MT1X (p<0.0005) and MT2A (p<0.005) in the analyzed samples. Post hoc analysis confirmed a significantly lower expression of MT1A mRNA in PTC compared to NG (p<0.05). Significant down-regulation was also noted for other MT isoforms in PTC in comparison to NG: MT1E (p<0.05), MT1F (p<0.0001), MT1G (p<0.005), MT1X (p<0.0005) and MT2A (p<0.05). In addition, significant down-regulation of MT1F and MT1G in FA compared to NG was observed (p<0.005 and p<0.05, respectively).. Expression of functional MT isoforms may contribute to thyroid carcinogenesis and potentially serve as a diagnostic marker in distinguishing benign and malignant lesions.

Topics: Adenoma; Adult; Aged; Aged, 80 and over; Carcinoma; Carcinoma, Papillary; Female; Gene Expression Regulation, Neoplastic; Goiter, Nodular; Humans; Male; Metallothionein; Middle Aged; Protein Isoforms; RNA, Messenger; Thyroid Cancer, Papillary; Thyroid Neoplasms; Young Adult

Metallothioneins are a family of small, cysteine-rich proteins with many functions. Immunohistochemical evaluation of all metallothionein 1 + 2 isoforms in colorectal tumors has demonstrated an important down-regulation compared with normal tissue, although its prognostic significance is unclear. Moreover, the contribution of individual isoforms to overall metallothionein down-regulation is not known. To address these important issues, we analyzed the messenger RNA expression levels of all functional metallothionein 1 + 2 isoforms by quantitative reverse transcription polymerase chain reaction in 22 pairs of normal and tumor-microdissected epithelia and correlated these to the overall immunohistochemical protein expression. Our results showed that 5 isoforms (MT1G, 1E, 1F, 1H, and 1M) were lost during the transition from normal mucosa to tumor, whereas MT1X and MT2A were less down-regulated, and their expression was correlated with overall protein positivity. Second, we showed that MT1G hypermethylation occurred in cell lines and in 29% of tumor samples, whereas histone deacetylase inhibitors are able to induce most isoforms. Furthermore, we analyzed by immunohistochemistry 107 normal mucosae, 25 adenomas, 81 carcinomas, and 19 lymph node metastases to evaluate metallothionein expression during different stages of cancer development and to assess its relationship to patient survival. A lower immunohistochemical expression was associated with poorer survival, although it was not an independent predictor. Overall, this study identifies for the first time the relevant metallothionein isoforms for colorectal cancer progression, supports the concept that their loss is associated with worse prognosis, and suggests 2 mechanisms for epigenetic repression of metallothionein expression in colorectal tumors.

Topics: Adenocarcinoma; Adenoma; Aged; Aged, 80 and over; Argentina; Biomarkers, Tumor; Colorectal Neoplasms; Disease Progression; DNA Methylation; Female; Gene Expression Regulation, Neoplastic; Gene Silencing; Humans; Male; Metallothionein; Middle Aged; Protein Isoforms; RNA, Messenger; Survival Rate

Thyroid carcinomas are the most frequently occurring tumours in the endocrine system. Metallothioneins (MT) and Ki-67 proteins are present in intensely proliferating cells, and their expression has been observed in numerous tumours, including thyroid tumours. The purpose of this study was to analyse the relationship between intensity of MT expression and Ki-67 antigen on one hand and histological features of the examined thyroid tumours on the other. The investigated material included 186 archival paraffin blocks with samples of various thyroid tissues, obtained from the Chair and Department of Pathomorphology, Medical University of Wroclaw. In paraffin sections, immunohistochemical reactions were performed with the use of monoclonal anti-MT (I/II) and anti-Ki-67 antibodies. Intensity of MT and Ki-67 antigen expression was evaluated using a light microscope using the semi-quantitative method of Remmele. A significant difference in MT expression was noted between different tumours of the thyroid: the highest expression was detected in follicular carcinoma and the lowest was detected in medullary carcinoma. Expression of MT was also significantly elevated in follicular carcinoma as compared to follicular adenoma. On the other hand, no significant differences were seen between expression of Ki-67 antigen in follicular adenoma and follicular carcinoma. Moreover, these investigations detected no correlation between the expression of MT and Ki-67 antigen in follicular adenoma and follicular carcinoma. In view of the obtained results, the expression of MT can be considered as a potential marker of differentiation between the two types of thyroid tumours, which are otherwise difficult to differentiate.

Topics: Adenocarcinoma, Follicular; Adenoma; Cell Nucleus; Cytoplasm; Humans; Immunohistochemistry; Ki-67 Antigen; Metallothionein; Paraffin Embedding; Thyroid Neoplasms

Hyperactivation of the GHRH receptor or downstream signaling components is associated with hyperplasia of the pituitary somatotrope population, in which adenomas form relatively late in life, with less than 100% penetrance. Hyperplastic and adenomatous pituitaries of metallothionein promoter-human GHRH transgenic (Tg) mice (4 and > 10 months, respectively) were used to identify mechanisms that may prevent or delay adenoma formation in the presence of excess GHRH. In hyperplastic pituitaries, expression of the late G(1)/G(2) marker Ki67 increased, whereas the proportion of 5-bromo-2'-deoxyuridine-labeled cells (S phase marker) did not differ from age-matched controls. These results indicate cell cycle progression is blocked, with further evidence suggesting that enhanced p27 activity may contribute to this process. For adenomas, formation was associated with loss of p27 activity (nuclear localization and mRNA). Increased endogenous somatostatin (SST) tone may also slow the conversion from hyperplastic to adenomatous state because mRNA levels for SST receptors, sst2 and sst5, were elevated in hyperplastic pituitaries, whereas adenomas were associated with a decline in sst1 and sst5 mRNA. Also, SST-knockout Tg pituitaries were larger and adenomas formed earlier compared with those of SST-intact Tg mice. Unexpectedly, these changes were independent of changes in proliferation rate within the hyperplastic tissue, suggesting that endogenous SST controls GHRH-induced adenoma formation primarily via modulation of apoptotic and/or cellular senescence pathways, consistent with the predicted function of some of the most differentially expressed genes (Casp1, MAP2K1, TNFR2) identified by membrane arrays and confirmed by quantitative real-time RT-PCR.

Topics: Adenoma; Aging; Animals; Cell Proliferation; Female; Growth Hormone-Releasing Hormone; Human Growth Hormone; Humans; Male; Metallothionein; Mice; Mice, Knockout; Organ Size; Pituitary Gland; Pituitary Neoplasms; Proliferating Cell Nuclear Antigen; Proto-Oncogene Proteins; Receptors, Neuropeptide; Receptors, Pituitary Hormone-Regulating Hormone; RNA, Messenger; Somatostatin; Somatotrophs

Previous studies have provided some evidence of a possible association between cancer and metallothioneins. Whether this relates to an exposure to carcinogenic metals remains unclear.. In order to examine the association between the expression of metallothioneins and bladder tumors, and to compare the levels of arsenic, cadmium, chromium, lead and nickel in animals with bladder tumors and animals without bladder tumors, 37 cases of bovine bladder tumors and 17 controls were collected. The detection and quantification of metallothioneins in bladder tissue of both cases and controls was performed by immunohistochemistry. And the quantification of metals in tissue and hair was assessed by inductively coupled plasma - mass spectrometry.. Increased expression of metallothioneins was associated with bladder tumors when compared with non-tumoral bladder tissue (OR = 9.3, 95% CI: 1.0 - 480). The concentrations of cadmium, chromium, lead and nickel in hair of cases were significantly higher than those of controls. However, as for the concentration of metals in bladder tissue, the differences were not significant.. Though the sample size was small, the present study shows an association between bladder tumors and metallothioneins. Moreover, it shows that concentrations of metals such as cadmium, chromium, lead and nickel in hair may be used as a biomarker of exposure.

Topics: Adenoma; Animals; Carcinoma; Cattle; Cattle Diseases; Gene Expression Regulation, Neoplastic; Hair; Hemangioma; Metallothionein; Metals; Papilloma; Risk Factors; Trace Elements; Urinary Bladder Neoplasms

Excessive GHRH stimulation leads to somatotrope hyperplasia and, ultimately, pituitary adenoma formation in the metallothionein promoter-driven human GHRH (hGHRH) transgenic mouse. This pituitary phenotype is similar to that observed in humans with ectopic production of GHRH. In both mice and man, GHRH hyperstimulation also results in dramatic increases in circulating GH and IGF-I. To determine whether GH/IGF-I modulates the development and growth rate of GHRH-induced pituitary tumors, pituitary growth and histology were evaluated in mice generated from cross-breeding metallothionein promoter-driven hGHRH transgenic mice with GH receptor binding protein (GHR) gene disrupted mice (GHR(-/-)). Expression of the hGHRH transgene in 2-month-old GHR intact (GHR(+)) mice resulted in the doubling of pituitary weight that was largely attributed to an increase in the number of GH-immunopositive cells. Pituitary weight of GHR(+) hGHRH mice did not significantly change between 2 and 6 months of age, whereas at 12 months, weights increased up to 100-fold those of GHR(+) pituitaries, and 70% of the glands contained grossly visible adenomas. All adenomas stained positively for GH, whereas some showed scattered PRL staining. Pituitaries of GHR(-/-) mice were half the size of those of GHR(+) mice. Although reduced in size, the histological features of GHR(-/-) mouse pituitaries were suggestive of somatotrope hyperplasia. Despite evidence of somatotrope hyperplasia, pituitaries from GHR(-/-) mice as old as 28 months of age were similar in size to those of 2-month-old mice and did not show signs of adenoma formation. Expression of the hGHRH transgene in GHR(-/-) mice did not significantly increase pituitary size between 2 and 6 months of age. However, at 12 months the majority of GHR(-/-), hGHRH pituitaries developed adenomas with mean pituitary weight and histological features similar to those of GHR(+), hGHRH mice. These observations demonstrate that intact GH signaling is not required for GHRH tumor formation. Although the majority of GHR(+), hGHRH and GHR(-/-), hGHRH pituitaries developed tumors by 12 months of age, a small subset remained morphologically indistinct from those at 2 months of age. These observations taken together with the fact that overt tumor formation is preceded by a static pituitary growth phase between 2 and 6 months, indicates that protective mechanisms are in place to maintain pituitary mass despite hGHRH hyperstimulation.

Topics: Adenoma; Aging; Animals; Gene Expression; Growth Hormone; Growth Hormone-Releasing Hormone; Humans; Hyperplasia; Male; Metallothionein; Mice; Mice, Inbred Strains; Mice, Knockout; Phenotype; Pituitary Gland; Pituitary Gland, Anterior; Pituitary Neoplasms; Promoter Regions, Genetic; Receptors, Somatotropin; Reference Values; Signal Transduction; Transgenes

Immunocytochemical demonstration of metallothionein (MT) has been reported as a useful prognostic tool in human breast cancer. The aim of this study was to determine the immunohistochemical location of MT in canine mammary tumours and its possible correlation with the morphologic characteristics of these tumours. Surgical specimens from spontaneous malignant (n = 20) and benign mammary neoplasms (n = 20) were processed for routine histological examination and immunohistochemical study. An indirect immunoperoxidase technique, using monoclonal antibody E9 against horse MT was employed. Intensity of the stain, the percentage of immunoreactive tumour cells and immunohistochemical overexpression of MT was estimated for each case. Metallothionein over-expression, defined as those cases with more than 10% immunopositive cells, was detected in both benign and malignant mammary tumours. However, strong immunostaining intensity was seen in benign tumours, whereas in malignant tumours immunopositive cells stained weakly. Positive MT immunostaining occurred in neoplastic epithelial cells, and some chondrocytes present in mixed mammary tumours. However, staining intensity was variable in immunopositive cells. Differences in staining intensity between the primary malignant mammary tumour, tumour emboli and metastatic cells within a lymph node were also noted. Myoepithelial cells and connective tissue did not stain for MT. We concluded that metallothionein immunostaining cannot be used as a diagnostic or prognostic tool in canine mammary neoplasms. However, results of this study support the hypothesis that MT has a role in tumour proliferation and tumour progression.

Topics: Adenocarcinoma; Adenoma; Animals; Biomarkers, Tumor; Carcinoma; Dogs; Female; Immunoenzyme Techniques; Mammary Neoplasms, Animal; Metallothionein; Mixed Tumor, Malignant; Neoplasms, Complex and Mixed; Neoplasms, Glandular and Epithelial

Growth hormone (GH) transgenic mice are known to develop hepatocellular adenomas and carcinomas. In order to understand more about hepatocarcinogenesis in the GH-transgenic mouse model we quantitated the rates of hepatocellular proliferation and apoptosis in these mice.. Two lines of GH-transgenic mice and non-transgenic control mice were generated and sacrificed at regular intervals between one and nine months. Hepatocellular replication was measured by in vivo incorporation of bromodeoxyuridine (BrdU) and counting BrdU-positive nuclei in histological liver sections. Serial sections taken from these mouse livers were also assessed for rates of hepatocellular apoptosis using the in situ end-labelling of fragmented DNA (TUNEL) method.. High levels of hepatocellular replication were sustained life-long in this model. Increased rates of hepatocellular proliferation preceded the onset of hepatic inflammation, a prominent feature in the liver pathology of GH-transgenic mice. In tumour tissue, cellular proliferation was up to 17-fold greater than in surrounding non-tumour tissue. Apoptosis rates were also elevated in non-tumour regions of GH-transgenic mouse livers compared to controls. Interestingly, large dysplastic hepatocytes were common in the fraction of cells undergoing apoptosis, especially in older mice with inflamed livers. The increase in the rate of hepatocellular apoptosis in GH-transgenic animals largely balanced the augmented levels of proliferation seen in these mice. In tumour tissue, however, the profound increase in the number of proliferating tumour cells outstripped the increase in apoptosis.. Relatively high and enduring levels of hepatocellular replication and apoptosis precede hepatocarcinogenesis in GH-transgenic mice. Increased cellular proliferation and resistance to apoptosis were evident in tumour growth in older animals.

Topics: Adenoma; Age Factors; Animals; Apoptosis; Body Weight; Carcinoma, Hepatocellular; Cell Division; Female; Growth Hormone; In Situ Nick-End Labeling; Liver; Liver Neoplasms, Experimental; Male; Metallothionein; Mice; Mice, Inbred C57BL; Mice, Transgenic; Mitotic Index; Organ Size

The immunohistochemical distribution pattern of metallothionein, a low molecular weight protein with strong affinity for divalent heavy metal ions, has been investigated in normal and neoplastic conditions of the large bowel. Utilizing a monoclonal mouse antibody the following formalin-fixed paraffin-embedded surgical or biopsy samples were studied: tubulo-villous adenomas (8 cases); adenocarcinomas with various degree of differentiation (85), nine of which were mucinous-type; synchronous tubular or tubulo-villous adenomas separate from carcinomas (30); transitional mucosa (45); metastases in lymph nodes (43); and distant metastases (45). Twenty biopsies from the right and left colon of 10 patients affected by irritable bowel syndrome were also analyzed. Normal colonic mucosa as well as transitional mucosa showed metallothionein immunopositivity in enterocytes at the luminal surface and crypts. Evident nuclear and cytoplasmic staining was encountered in tubulo-villous adenomas; the same reactivity was noted in the basal glandular component of colorectal carcinomas-synchronous adenomas, while less intense staining was noted in the apical villous portions. A variable metallothionein immunostaining was observed in adenocarcinomas (62.3%), in lymph node (55.8%) and distant hepatic (17.2%) and omental (43.8%) metastases, although it was not always concordant with that reported in the corresponding primary tumour. Whether the metallothionein positivity observed in normal and neoplastic cells is the result of expression of a stable form of the protein or an accumulation in the nucleus and cytoplasm remains to be clarified.

Topics: Adenocarcinoma; Adenoma; Colon; Colorectal Neoplasms; Humans; Immunohistochemistry; Intestinal Mucosa; Metallothionein; Rectum

Morphologic changes in the pituitary, liver, and pancreas of mice with the metallothionein-human growth hormone--releasing hormone (MT-hGRH) transgene were analyzed by in situ hybridization histochemistry (ISH). There was progression from somatotroph hyperplasia to neoplasia in pituitaries of transgenic mice. Pituitary neoplasms were present between 9 to 12 months of age in some mice. Magnetic resonance imaging (MRI) readily identified enlarged pituitaries in MT-hGRH transgenic mice. Serum mouse GH and hGRH levels were marked elevated in MT-hGRH transgenic mice. In situ hybridization histochemistry showed mRNA for hGRH in liver, pituitary, pancreas, spleen, and in most other tissues examined. Combined ISH and immunohistochemistry in the pituitary gland showed that some of the GH cells also produced hGRH, and ultrastructural immunohistochemical analysis of pituitaries showed that GH and hGRH were localized in the same cell and within the same secretory granules. Liver cells of MT-hGRH transgenic mice showed evidence of hypertrophy, and the pancreatic islets were hyperplastic with significant increases in the islet cell areas. The morphologic changes in the liver were distinctive enough to separate control littermates from MT-hGRH transgenic mice in all cases. The enlarged pancreatic islets had increased numbers of insulin-producing cells. Immunoreactive hGRH and hGRH mRNA were both localized in islet cells, and an intense hybridization signal of hGRH mRNA, but only weak staining for hGRH protein, were detected in the liver of transgenic mice. These results indicate that excessive hGRH production leads to distinct morphologic changes in various organs in MT-hGRH transgenic mice and that there is temporal progression from hyperplasia to adenomatous somatotrophs in pituitaries with chronic stimulation by hGRH that involves paracrine, endocrine, and autocrine mechanisms.

Topics: Adenoma; Animals; Growth Hormone-Releasing Hormone; Hormones, Ectopic; Hyperplasia; Immunohistochemistry; In Situ Hybridization; Liver; Metallothionein; Mice; Mice, Transgenic; Pancreas; Pituitary Gland; Pituitary Neoplasms; Recombinant Fusion Proteins

Cu/Zn-containing proteins have recently become of interest with regard to their relation with malignant disorders. Cu Zn-superoxide dismutase (Cu/Zn-SOD) was found increased in chemically induced tumors of the large bowel whereas metallothionein (MT), containing Zn and some Cu, was shown important for the response of tumors to chemotherapy. In the present study, we evaluated the Cu/Zn-SOD and MT content of normal human colonic mucosa and colorectal carcinomas, obtained from 20 resection specimens, and of 47 adenomatous polyps. The Cu/Zn-SOD content of polyps and carcinomas was significantly (p less than 0.01) elevated when compared to normal mucosa. In the adenomatous polyps the Cu/Zn-SOD content increased significantly with increasing grade of epithelial cell dysplasia, diameter, and presence of a villous component. In the carcinomas no relation was noticed between the Cu/Zn-SOD content and the Dukes' stage or the grade of differentiation. The MT content was significantly decreased in both adenomatous polyps and carcinomas when compared to that in normal mucosa. The MT content was not related to the grade of epithelial cell dysplasia of the polyps, and to the Dukes' stage or the differentiation of the carcinomas. In conclusion, neoplasia of the colorectum is accompanied by an increase in Cu/Zn-SOD and a decrease in MT. These findings support the association between changes in Cu/Zn proteins and malignancy.

Topics: Adenocarcinoma; Adenoma; Adult; Aged; Aged, 80 and over; Colonic Neoplasms; Copper; Female; Free Radicals; Humans; Intestinal Mucosa; Intestinal Polyps; Male; Metallothionein; Middle Aged; Superoxide Dismutase; Zinc

Hepatocellular carcinomas developed at a high frequency in the livers of transgenic (C57BL/6 X SJL/J)F1 mice under the influence of growth hormone. Three lines of giant transgenic mice expressing a mouse metallothionein-ovine growth hormone fusion gene were generated. The giant mice weighed twice as much as control littermates. The three lines of giant mice expressing very high levels of growth hormone were bred over several generations. Mice from all three lines developed hepatocellular tumors, including adenoma and carcinoma. The occurrence of tumors was age-dependent, and their incidence increased to 70% of the mice studied after 43 weeks of age. Pathologic changes in the livers resembled those observed in rats in which hepatocellular carcinomas are induced chemically. Transgenic mice carrying the metallothionein-ovine growth hormone fusion gene represent a new model for hepatocellular carcinogenesis. This model exemplifies the oncogenic potential for a sustained proliferative growth stimulus within an organ.

Topics: Adenoma; Animals; Growth Hormone; Hepatitis Antibodies; Hepatitis, Viral, Animal; Liver Neoplasms, Experimental; Metallothionein; Mice; Mice, Transgenic; Murine hepatitis virus; Recombinant Fusion Proteins; Sheep

High levels of metallothionein (MT) are present in the developing mammalian liver; however, a remarkable decrease is observed during postnatal life after weaning. This developmental profile is similar to that of certain oncofetal gene products such as alpha-fetoprotein, which is used as a tumor marker. This study deals with the reexpression of MT genes in thyroid tumors. With an immunohistochemical method, the presence of MT was investigated in tissue sections of normal and neoplastic human thyroid glands. Tissue sections of 34 thyroid tumors and 10 normal human thyroid glands were studied by means of the peroxidase-antiperoxidase method. MT was localized in 31 of the thyroid gland tumors. MT was also present in two of the normal thyroid glands. These findings indicate that although high levels of MT are mainly found in the fetal liver, it may also be expressed actively in certain human thyroid neoplastic tissues, and occasionally in normal thyroid tissue.

Topics: Adenocarcinoma; Adenocarcinoma, Papillary; Adenoma; Adolescent; Adult; Aged; Aged, 80 and over; Cell Nucleus; Cytoplasm; Female; Humans; Immunohistochemistry; Male; Metallothionein; Middle Aged; Thyroid Neoplasms