Relationship between invasiveness of pituitary somatotrophinomas and structural abnormalities of protein kinase C gene in human

The potential role of the protein kinase C (PKC) transduction system in controlling proliferation of human pituitary somatotrophinomas was investigated. Twenty somatotrophinomas were studied using PCR and direct sequencing methods. No point mutation within the alpha PKC gene, previously thought to be associated with invasive pituitary tumors, was found in any of the 20 somatotrophinomas. It is concluded that PKC transduction system may play an important role in controlling pituitary somatotrophinoma proliferation, but there is no correlation between invasiveness and the previously reported alpha PKC gene mutation.

Expression of CuZn- and Mn-superoxide dismutase in human colorectal neoplasms

Decreased intracellular SOD protein levels and activity have been related with malignancy in the past. To investigate their relevance in the carcinogenetic process in the colon, we determined quantitatively CuZn-SOD and Mn-SOD levels and total SOD activity by histochemical means in human normal colorectal mucosa, adenomas, and carcinomas. Protein levels and activity were significantly decreased in carcinomas. CuZn-SOD protein levels, but not Mn-SOD levels or total SOD activity were related with differentiation grade and to a lesser extent with Dukes stage. Moderately differentiated carcinomas and Dukes stage A carcinomas showed lowest levels. Some carcinomas expressed elevated levels of CuZn-SOD and this was an indication of poor survival. It is concluded that decreased SOD expression is not a prognostic marker and seems to be a secondary phenomenon rather than directly linked with the carcinogenetic process.

Elevated expression of fatty acid synthase and fatty acid synthetic activity in colorectal neoplasia

Expression of the primary enzyme catalyzing the synthesis of fatty acids, ie, fatty acid synthase (FAS), and ex vivo fatty acid synthetic activity were examined in colorectal epithelium and neoplasms, including the relationship to tumor progression and prognosis. Immunohistochemistry for FAS showed only faint staining of native colorectal mucosa, but increased expression was found in all sporadic adenomas (n = 18), adenomas associated with familial adenomatous polyposis (n = 7), hyperplastic polyps (n = 3), dysplasias arising in ulcerative colitis (n = 17), and colorectal carcinomas (n = 130) including 11 with contiguous adenomas. The intensity of staining was strong in 53% of carcinomas, intermediate in 38%, and weak in 9%. Activity of the fatty acid synthetic pathway measured by labeling of six surgical specimens with [U-14C]acetate was 2- to 7-fold higher in colorectal carcinomas than adjacent native mucosa (P = 0.006) and 6- to 16-fold higher than serosal fat (P = 0.01). Activity correlated with immunohistochemical expression (Spearman's rank correlation coefficient = 0.85; P < 0.001). There was no statistically significant association between patient survival and FAS staining intensity of carcinomas. Our study shows that FAS is expressed in all colorectal neoplasms and there is a concomitant increase in fatty acid synthesis. FAS may therefore represent a potential therapeutic target.

In situ stromal expression of the urokinase/plasmin system correlates with epithelial dysplasia in colorectal adenomas

An increase of urokinase-type plasminogen activator (uPA) and a decrease of tissue-type PA (tPA) have been associated with the transition from normal to adenomatous colorectal mucosa. Serial sections from 25 adenomas were used to identify PA-related caseinolytic activities by in situ zymography, blocking selectively uPA or tPA. The distribution of uPA, tPA, and type 1 PA inhibitor mRNAs was investigated by nonradioactive in situ hybridization, and the receptor for uPA was detected by immunostaining. Low- and high-grade epithelial cell dysplasia was mapped histologically. Results show that 23 of 25 adenomas expressed uPA-related lytic activity located predominantly in the periphery whereas tPA-related activity was mainly in central areas of adenomas. In 15 of 25 adenomas, uPA mRNA was expressed in stromal cells clustered in foci that coincided with areas of uPA lytic activity. The probability of finding uPA mRNA-reactive cells was significantly higher in areas with high-grade epithelial dysplasia. uPA receptor was mainly stromal and expressed at the periphery. Type 1 PA inhibitor mRNA cellular expression was diffuse in the stroma, in endothelial cells, and in a subpopulation of alpha-smooth muscle cell actin-reactive cells. These results show that a stromal up-regulation of the uPA/plasmin system is associated with foci of severe dysplasia in a subset of colorectal adenomas.

Tobacco, colorectal cancer, and adenomas: a review of the evidence

Although tobacco has been clearly implicated as a cause of a number of cancers, earlier studies had not generally found cigarette smokers to be at higher risk for cancers of the large bowel. Unlike the earlier studies, more recent studies have tended to find cigarette smokers to be at higher risk of colorectal cancer. In addition, cigarette smoking has been consistently associated with a higher risk of colorectal adenomas, precursors of cancers. We hypothesize that smoking is an initiator of colorectal carcinogenesis. The consistent finding of a positive association between smoking and risk of adenomas may reflect the presumably shorter induction period for these lesions. Recent studies indicate that an increased risk for large-bowel cancer emerges only after about four decades after one begins smoking, perhaps accounting for the null studies that were conducted earlier during the smoking epidemic. Most studies had not taken into account an induction period between timing of smoking and risk for cancer. The increasing male-to-female mortality ratio from colorectal cancer over the latter half of this century in the United States may have been a result of tobacco use by men earlier in the century. If the associations observed with colorectal adenomas and cancers in recent studies are causal, approximately 20% of the large-bowel cancers in men would be attributable to smoking. On the basis of the strength of the available evidence, intensified effort to prevent smoking among young people is warranted.

Cathepsin B in the growth of colorectal cancer: increased activity of cathepsin B in human colorectal cancer

Cathepsin B, a thiol protease, is involved in cancer metastasis. To clarify the role of cathepsin B in tumor progression in human colorectal cancer, the relationship between its activity, immunohistochemical staining, and clinical tumor progression was investigated. Cathepsin B activity in adenocarcinomas was significantly elevated compared with that in the tumor-bearing tissue. Furthermore, the tumor/tumor-bearing tissue (T/Tb) ratio of the activity was significantly higher than that of colorectal adenoma. Immunohistochemical studies demonstrated intense staining in the cancerous tissue. With respect to the clinical stage of tumors, the activity tended to be higher in tumors that had invaded the serosa or subserosa than in those that invaded the proper muscle. The results suggest that cathepsin B participates in the progression of human colorectal cancer, and its increased expression is a sensitive marker of the differentiation between colorectal adenoma and adenocarcinoma.

Oestrogen producing adrenocortical adenoma: clinical, biochemical and immunohistochemical studies

Oestrogen producing adrenocortical tumours are extremely rare. We report a 65-year-old woman who presented with abnormal vaginal bleeding, with no significant abnormalities in her uterus or ovaries, who was found to have a right adrenal mass by radiological examination. Excessive secretion of oestrogens from the tumour was demonstrated by adrenal venous sampling. Basal levels of corticosteroids were within normal limits. Adrenalectomy was performed and pathological examination revealed an adrenocortical adenoma measuring 5.5 cm in its greatest dimension, in which both clear and compact tumour cells were observed. Oestrogen levels normalized following the removal of the adrenal mass. Tissue concentrations of oestrone and oestradiol in the tumour were 6.9 (69.5 pmol/g wet tissue weight) and 34.6 (93.6 pmol/g wet tissue weight)-fold greater respectively than those of adjacent non-neoplastic adrenal cortex. Aromatase activity in the tumour tissue determined by the 3H-water method was 118.6 pmol/h/mg protein, equivalent to that of a full-term human placenta. Immunohistochemical analysis of aromatase demonstrated immunoreactivity in the tumour cells, especially in compact cells, but not in adjacent non-neoplastic adrenal cells. This is the first reported case of an oestrogen producing adrenocortical adenoma in which aromatase in the tumour cells was documented.

Matrix metalloproteinases and tissue inhibitors of metalloproteinases in colonic adenomas-adenocarcinomas

Colonic adenocarcinomas evolve through a multistep process from tubular adenomas to invasive adenocarcinomas. Matrix metalloproteinases (MMPs) have been implicated in proteolysis of basement membrane for initiation of metastatic cascade.

METHODS

By immunocytochemical staining, hyperplastic polyps, tubular adenomas, tubovillous adenomas, villous adenomas to adenocarcinomas were systematically examined for the presence of MMP-2 (gelatinase A) and MMP-9 (gelatinase B) and tissue inhibitor of MMP (TIMP)-1 and TIMP-2, respectively.

RESULTS

MMP-2 and MMP-9, and TIMP-1 and TIMP-2 were immunolocalized in scattered stromal cells, whereas epithelial cells of normal mucosa and hyperplastic polyps were weakly stained. From tubular adenomas to villous adenomas, immunolocalization of gelatinases and TIMPs showed increasing gradually, and in situ carcinomas showed a definite positive, immunolocalization of gelatinases and TIMPs.

CONCLUSION

Increasing immunolocalization of gelatinases and TIMPs from tubular adenomas to adenocarcinomas coincides with a multistep process of colonic tumorigenesis.

Optimization of a classical aromatase activity assay and application in normal, adenomatous and malignant breast parenchyma

The tritium water release assay, originally described for the analysis of aromatase activity in placental tissue, was used to estimate aromatase activity in breast tissue samples. The lower activity in this tissue necessitates longer incubation times and thus optimization of the assay conditions. To prevent oxidative and proteolytic inactivation of aromatase, dithiothreitol and albumin were added to the incubation mixture. Extra NADPH, cofactor in the aromatase reaction, also improved reaction rate in placental incubations, but after approximately 120 min activity rapidly decreased. Inhibitors gradually produced during the incubation could explain this phenomenon. Quantitative gas chromatography-mass spectrometry (GC-MS) analyses of testosterone, oestradiol, oestrone and androstenedione after incubation with non-labelled androstenedione proved that a substantial amount of the substrate is converted into testosterone. Qualitative GC-MS steroid profiling of the incubation mixture demonstrated the presence of hydroxylated oestradiol and hydroxylated testosterone, produced during incubation, which could have caused partial aromatase inhibition. The adjusted assay was used to analyse 84 breast tissue samples, histologically classified as normal, adenoma or carcinoma. Aromatase activity was found in 56% of all samples and ranged from 0.6 to 26 pmol oestrogen/g protein per hour. Aromatase positivity was found in 80% of the normal samples, 56% of the adenoma samples and 48% of the carcinoma samples. Although carcinoma samples were less often aromatase positive than normal tissue samples (chi2 = 4.80; P < 0.050) there was no difference in absolute aromatase activity. Because no less than approximately 50% of the carcinomas contained aromatase activity and because of the non-routine character of the assay we conclude that it is justified to start aromatase inhibition therapy without previous knowledge of the aromatase status.

Matrilysin is associated with progression of colorectal tumor

Matrilysin and gelatinase A, B mRNA expressions were examined in colorectal tumors. Matrilysin mRNA was observed exclusively in tumors, while the others were also found in normal mucosa surrounding tumors. Further analysis revealed that colorectal adenomas with severe dysplasia, not with mild dysplasia, expressed matrilysin with lower levels than cancers. The level of matrilysin mRNA expression increased with the advancement of stages of colorectal cancers, consequently a relatively higher expression was observed in liver metastatic tumors than primary tumors. These results suggest that matrilysin mRNA expression was correlated with the progression of colorectal tumors, and this enzyme may also play a role in developing metastatic tumors in liver.

Elevated cyclooxygenase-2 levels in Min mouse adenomas

BACKGROUND & AIMS

Mutations in the APC gene result in an increased propensity to develop intestinal neoplasia; however, a complete understanding of the mechanisms resulting in tumor formation has remained elusive. Min mice possess a mutation in the APC gene and display a neoplastic phenotype similar to that observed in familial adenomatous polyposis coli in humans. Cyclooxygenase (COX) inhibitors decrease tumor multiplicity in the Min mouse intestine. The present study was designed to determine if there was an increase in COX-2 in adenomas harvested from Min mouse intestine.

METHODS

COX-2 messenger RNA levels were determined by Northern blots and reverse-transcription polymerase chain reactions of B6Min x 129 mouse-derived tumors. Protein levels and localization were determined by Western blots and immunohistochemical staining.

RESULTS

The Northern blots revealed an approximately threefold increase in the level of COX-2 messenger RNA in Min mouse adenoma compared with normal mucosa. COX-2 protein levels in adenomatous tissues were also approximately threefold higher compared with normal mucosa from the same mouse. Immunohistochemical staining with a monospecific COX-2 antibody confirmed that increases in COX-2 immunoreactivity were restricted to dysplastic and neoplastic foci within intestinal mucosa.

CONCLUSIONS

These data show that COX-2 levels may be increased at an early stage in colorectal neoplasia during polyp formation and before invasion.

Immunohistochemical study of DNA topoisomerase II in human gastric disorders

Topoisomerase II (topo II) separates chromosomes at the end of mitosis and is also the target for various chemotherapeutic agents. Expression of this enzyme has been demonstrated to increase rapidly at the end of the S to G2/M phase and decrease after the completion of mitosis. We immunolocalized topo II in specimens of both normal and neoplastic human gastric mucosas to evaluate expression of this enzyme. Three different antibodies were used for the immunostaining of topo II (anti-topo II alpha isoform, anti-topo II beta isoform and anti-topo II alpha and -beta isoforms). There were no significant differences in topo II labeling index (LI) between frozen and paraffin-embedded tissue sections obtained from the same cases. Topo II LI was significantly correlated with Ki67 LI in all of the specimens examined. The area of cells positive for Topo II was much narrower than that of Ki67 in the normal gastric glands, and the pattern of Topo II immunolocalization in both adenomas and adenocarcinomas was also essentially the same as that of Ki67. The topo II LI values (positive cells/1000 cells) for normal gastric gland, adenoma, intestinal-type adenocarcinoma, and diffuse-type adenocarcinoma were 114.7 +/- 2.2, 266.7 +/- 18.8, 277.6 +/- 19.2, and 324.5 +/- 5.3, respectively. Significant differences in topo II LI and topo II/Ki67 index were observed between normal and neoplastic mucosas (P < 0.0001) and between adenomas or intestinal-type adenocarcinoma and diffuse-type adenocarcinoma (P < 0.001 and P < 0.01, respectively). Simultaneous measurement of topo II alpha and nuclear DNA content by two-parameter flow cytometry revealed that the Jurkat cell line established from acute lymphocytic leukemia cells expressed the enzyme in cells at other than S and G2/M phases of the cell cycle whereas topo-II alpha-positive cells were predominantly observed in S and G2/M phases of the cell cycle in the cells from normal lymph nodes. These findings suggest that dys-regulation or qualitative changes of topo II alpha expression are associated with malignancy. Topo II immunostaining can thus detect proliferating cells in routinely processed tissue sections and can indicate the altered topo II alpha expression in human cancers, which may be related to the sensitivity to topo-II-targeted chemotherapeutic agents.

Activation of cathepsin B, secreted by a colorectal cancer cell line requires low pH and is mediated by cathepsin D

The aim of our study was to identify changes in secreted procathepsin B levels in a model of the human colorectal adenoma to carcinoma sequence and to determine the factors required for its extracellular activation. Conversion of the non-tumorigenic adenoma-derived cell line PC/AA to a highly tumorigenic phenotype (designated AA/CI/SB10/M) was associated with an 8-fold increase in the presence of the proform of cathepsin B in 24 hr conditioned serum-free medium (SFM). In addition, mature enzyme was only detected in the cell lines of this model with increased malignant potential. This is in agreement with the findings of a previous study, in which mature cathepsin B was only present in the 24 hr conditioned SFM of cancer-derived cell lines and not in SFM from adenoma-derived cell lines. Having demonstrated a reduction in the pH of conditioned medium from cell lines with increased malignant potential, we used a range of specific proteinase inhibitors to show that an aspartyl proteinase was involved in the initial activation of procathepsin B. Consistent with this finding, we subsequently demonstrated an increased secretion of the aspartyl proteinase cathepsin D in the medium of the AA/CI/SB10/M adenocarcinoma cells compared with the non-tumorigenic AA/Cl cell line. Therefore, the presence of mature cathpsin B in the conditioned medium of the more malignant cell lines coincided with a reduction in pH and an increase in the amount of cathepsin D secreted. Data from the human colorectal derived adenoma to carcinoma sequence indicate that an in vivo mechanism may exist that, dependent on the simultaneous presence of both a tumour-generated acidic extracellular environment and an elevated secretion of procathepsin D, could result in the activation of latent procathepsin outside the cell.

Protein kinase C isoforms in the chemopreventive effects of a novel vitamin D3 analogue in rat colonic tumorigenesis

BACKGROUND & AIMS

We recently showed that dietary supplementation with an analogue of 1alpha,25-dihydroxy-vitamin D3, 1alpha,25-dihydroxy-16-ene-23-yne-26,27 F6-vitamin D3 (RO24-5531), reduced the incidence of colonic tumors in rats treated with azoxymethane (AOM). The aim of this study was to determine whether alterations in specific isoforms of protein kinase C (PKC) are involved in this phenomenon.

METHODS

Protein abundance and subcellular distribution of several PKC isoforms were examined and compared in AOM-induced tumors of rats fed control and RO24-5531-supplemented diets.

RESULTS

In both AOM-induced colonic adenomas and carcinomas, a significant down-regulation of PKC-alpha, -delta, and -zeta and an up-regulation of PKC-beta11 were found compared with control colonocytes. Dietary RO24-5531 preserved the expression of PKC-zeta and increased the abundance of PKC-epsilon in carcinogen-induced adenomas.

CONCLUSIONS

Because identical changes in specific isoforms of PKC were found in AOM-induced adenomas and carcinomas, these alterations may be involved in the early stage(s) of colonic malignant transformation. Moreover, the ability of RO24-5531 to block the changes in PKC-zeta induced by AOM, as well as to up-regulate PKC-epsilon, may underlie its ability to prevent adenomas from progressing to carcinomas.

Protein kinase C tissue localization in human colonic tumors suggests a role for adenoma growth control

BACKGROUND & AIMS

Protein kinase C (PKC) has been implicated as a mediator of growth control during colorectal carcinogenesis, but the mechanisms involved are still a matter of dispute. The aim of this study was to analyze PKC patterns and tissue distribution to gain further insight in PKC function during tumor development in the gut.

METHODS

PKC isoenzymes alpha, beta 1, beta 2, delta, and eta and the proliferation antigen Ki67 were analyzed in formalin-fixed normal, premalignant, and malignant specimens using immunohistochemistry.

RESULTS

In normal colonic mucosa, protein levels of all PKC isoenzymes followed an increasing gradient from the bottom to the top of the crypt, staining mainly terminally differentiated, resting cells. Atypical crypts observed in the normal mucosa adjacent to tumors expressed higher levels of Ca(2+)-dependent isoenzymes than the surrounding tissue. In tumors, the number and abundance of PKC isoenzymes was inversely related to proliferation in 7 adenomas and 9 carcinomas. Areas containing PKC-beta 1 as the only isoenzyme had the highest proliferation rates (50%-82% Ki67-positive cells).

CONCLUSIONS

The data suggest a function of PKCs, especially PKC-beta 1, in colorectal carcinogenesis and tumor growth control.

Bilateral aldosterone-producing adenomas in two patients diagnosed by immunohistochemical analysis of steroidogenic enzymes

Bilateral adrenal aldosterone-producing adenomas (APA) are rare. It is important to distinguish bilateral APA from idiopathic hyperaldosteronism (IHA) which is due to bilateral hyperplasia of the adrenal cortex. We present two patients with bilateral APA in whom the diagnosis was made histochemically by analyzing steroidogenic enzymes. They showed hypokalemia, high plasma aldosterone concentration (PAC) and suppressed plasma renin activity (PRA). Bilateral adrenal tumors were represented by computed tomography, and surgical resection was performed. In both cases, cytochrome P-450 and other enzymes that were involved in aldosterone synthesis were found mainly in tumor, but little in the zona glomerulosa of the adjacent adrenals, which showed paradoxical hyperplasia. Such cases are difficult to distinguish from IHA. The two disorders were differentiated by immunohistochemical analysis of steroidogenic enzymes.

Morphological changes in a hyperfunctioning thyroid adenoma after percutaneous ethanol injection: histological, enzymatic and sub-microscopical alterations

Ultrasound-guided ethanol injection (PEI) is an effective treatment of autonomously functioning thyroid nodules (AFTN) but little is known about the tissue lesions induced by alcohol. We report morphological changes of an AFTN which was removed after successful PEI treatment. At histological evaluation, the adenoma showed multiple areas of coagulative necrosis with eosinophilic ghost follicles, hemorrhages, small vessel thrombosis and a wedge-shaped hemorrhagic infarction. The peripheral adenomatous tissue and the surrounding thyroid parenchyma were free of regressive changes and/or lympho-monocytic inflammatory reactions. Enzyme histochemistry confirmed the hyperfunctioning character of the lesion and showed reduction of succinic dehydrogenase and cytochrome-c-oxydase activity in the viable tissue surrounding the central necrotic areas. By electron microscopy, the hyperfunctioning follicular epithelium showed submicroscopical alterations of the adenomatous cells surrounding the areas of coagulative necrosis. These results suggest that control of hyperthyroidism, after PEI, is due to: a) directly induced, irreversible damage (coagulative necrosis and vascular thrombosis with hemorrhagic infarction) in the central areas of the lesion; b) potentially reversible damage (reduction of intracellular enzyme activity and ultrastructural changes) in the peripheral areas.

Protein kinase A-catalyzed phosphorylation and its effect on conformation in phytochrome A

Phytochromes are ubiquitous red/far-red wavelength-sensitive photoreceptors in plants. Oat phytochrome A is a phosphoprotein. Phytochrome A (phyA) possesses two spatially different sites for phosphorylation with cAMP-dependent protein kinase (PKA) [McMichael & Lagarias (1990) Biochemistry 29, 3872-3878]. To assess the modulation of protein conformation by phosphorylation/dephosphorylation and its possible implication in phytochrome-mediated signal transduction, the conformations of phytochrome have been probed by PKA catalyzed phosphorylation. The phosphorylated species were purified and analyzed, along with untreated phytochrome, by limited proteolysis, circular dichroism (CD) and fluorescence quenching measurements. No significant changes in secondary structure of the phyA molecule after its phosphorylation were observed by CD. However, a subtle topographic and/or electrostatic effect of the phytochrome phosphorylation was detected by the time-resolved fluorescence quenching of Trp residues with Cs+ ions. N-Terminal phosphorylation at Ser17 was unique to the Pr form, but both Pr and Pfr phytochromes were phosphorylated at the hinge region to some extent. Phosphorylation at the hinge region resulted in noticeable changes in the proteolytic patterns, inhibiting cleavage near the phosphorylation site and favoring tryptic digestion of the Lys536-Asn537 peptide bond. Phosphorylation at the N-terminus did not cause observable changes in the helical structure of this region, but had an inhibitory effect on proteinase V8 accessibility at a site near the chromophore attachment. The functional relevance of protein phosphorylation of phyA is also discussed.

Marked increases in cathepsin B and L activities distinguish papillary carcinoma of the thyroid from normal thyroid or thyroid with non-neoplastic disease

Cathepsin B (CB) and cathepsin L (CL) are cysteine endopeptidases involved in the processing of thyroglobulin (Tg) in the normal thyroid. As thyroglobulin expression is frequently altered in thyroid carcinomas, we have analyzed 42 human thyroid tissues from 40 patients to study the effect of malignant transformation an the expression of these endopeptidases. Our samples included 18 cases of papillary carcinoma (of which 10 also had matched adjacent normal thyroid tissue), 6 cases of normal thyroid from autopsy patients, 1 case of follicular carcinoma, 2 cases of medullary carcinoma, 2 cases of follicular adenoma, 3 cases of Hashimoto's thyroiditis (HT) and 10 samples from 8 patients with multi-nodular goiter (MNG). Enzyme-specific activities were increased 15-fold for CB and 9-fold for CL in papillary carcinoma compared with normal adjacent thyroid tissue or normal thyroid from autopsies. CB mRNA content was also markedly increased in papillary carcinoma compared with normal thyroid, primarily due to elevated levels of the 2.2-kb CB mRNA transcript. In thyroids with nonneoplastic diseases, including MNG and HT, there was no significant increase in either CB or CL enzyme activities nor CB mRNA levels compared with normal thyroids from non-cancer cases. Immunohistochemical studies on papillary carcinomas revealed increased CB staining in papillary carcinoma cells, with prominent staining close to the basement membranes of many of the neoplastic cells. Our observations suggest that CB and CL enzyme activities are potentially useful new biochemical markers for distinguishing papillary carcinoma of the thyroid from non-neoplastic thyroid disease.

Constitutive activation of the Gs alpha protein-adenylate cyclase pathway may not be sufficient to generate toxic thyroid adenomas

In toxic thyroid adenomas, mutations in the TSH receptor (TSH-R) gene or the gene encoding the alpha-subunit of the stimulatory guanine nucleotide-binding protein (Gs alpha) have been demonstrated to constitutively activate the cAMP cascade, which subsequently stimulates the growth and function of these tumors. However, the widely varying thyroid phenotypes in patients with TSH-R germline mutations, ranging from only slightly enlarged diffuse to multinodular goiters, suggest that additional mechanisms may be effective in the pathogenesis of toxic adenomas. We have investigated the levels of stimulatory and inhibitory G protein alpha-subunits together with basal and TSH-stimulated adenylate cyclase (AC) activity in toxic adenomas with or without activating mutations and in nodular and extranodular tissues of a toxic goiter due to a germline mutation in the TSH-R gene. Augmented expression of Gs alpha protein was detected in all toxic adenomas, independent of the presence of mutations, and in the nodular tissue of the toxic goiter, but not in the nonnodular hyperplastic tissue of the toxic goiter with the mutated TSH-R. Analogously, the expression of the alpha-subunit of the inhibitory G protein (Gi alpha) was also increased in all adenomas and the nodular tissue of the goiter, but, again, not in the hyperplastic goiter tissue. Basal AC activity was high in all tissues with mutations, but was only slightly increased in adenomas without detected mutations. No correlation was detectable between basal or TSH-stimulated AC activity and the levels of Gs alpha and Gi alpha. Our data suggest that mutational activation of the cAMP cascade may not be sufficient to generate toxic nodules and adenomas, but far more complex mechanisms, including alterations of G protein signaling, may be effective in the pathogenesis of these tumors.

Staining for dipeptidyl aminopeptidase IV activity in nodular thyroid diseases

OBJECTIVE

To determine the effectiveness of staining for dipeptidyl aminopeptidase IV (DAP IV) activity in thyroid nodular diseases.

STUDY DESIGN

Imprint smears were made in 76 cases of papillary carcinoma, 10 of follicular carcinoma, 32 of follicular adenoma and 48 of adenomatous goiter after surgery, and staining for DAP IV activity was performed in all cases.

RESULTS

All papillary carcinomas stained positively, and most adenomatous goiter cases were negative. Follicular carcinoma and follicular adenoma cases exhibited various degrees of positivity, though the former tended to be stained more than the latter. Of the total 166 cases of thyroid nodules, 53 showed negative staining; of those 53, all except 1 were benign. Follicular carcinoma cases that had vascular invasion tended to show a high DAP IV staining pattern, but no statistically significant difference between it and follicular carcinoma that did not show vascular invasion was found.

CONCLUSION

DAP IV activity staining might reveal malignant potential and could have some value in the preoperative diagnosis between thyroid nodular diseases. The DAP IV method is a reliable indicator of benign disease if negative results are obtained.

Phospholipase C activation in rat pituitary adenoma (GH) cells

The presence of the pertussis toxin (PTX) insensitive GTP-binding proteins (C-proteins) G(q) alpha and/or G(11) alpha has been demonstrated in three different prolactin (PRL) and growth hormone (GH) producing pituitary adenoma cell lines. Immunoblocking of their coupling to hormone receptors indicates that G(q) and/or G(11) confer throliberin (TRH) responsive phospholipase C (PL-C) activity in these cells. The contention was substantiated by immunoprecipitation analyses showing that anti G(q)/11 alpha-sera coprecipitated PL-C activity. In essence, only G(q)/11 (but neither G(12) G(13) nor G(o)) seems to mediate the TRH-sensitive PL-C activity, while G(o) may be coupled to a basal or constitutive PL-C activity. Immunoblocking studies imply that the B gamma-complex also, to some extent, may stimulate GH(3) pituitary cell line PL-C activity. Finally, the steady state levels of G(q)/(11) alpha mRNA and protein were down regulated upon long term exposure of the GH(3) cells to TRH (but not to vasoactive intestinal peptide = VIP).

Expression of MMP-1 in the capsule of thyroid cancer--relationship with invasiveness

To investigate the invasive activity of thyroid cancer, an in situ hybridization study was carried out in 19 thyroid tumors, including nine papillary carcinomas, five follicular carcinomas and five follicular adenomas, by using a 35S-labeled MMP-1 (matrix metalloproteinase-1) cDNA probe. The MMP-1 gene was expressed not in the cancer cells but in the fibrous capsules of papillary carcinoma. Thyroid cancer is generally circumscribed by a fibrous capsule. We found that types I and III collagen constitute the fibrous capsule, and that the MMP-1 gene was expressed in the outer border of these sites. These findings suggest that MMP-1 plays an important role in the invasion of thyroid cancer.

Matrix metalloprotease 2 (MMP-2) and matrix metalloprotease 9 (MMP-9) type IV collagenases in colorectal cancer

Using quantitative zymography, we measured activity of the type IV collagenases metalloprotease 2 (MMP-2) and MMP-9 in 192 biopsies from colorectal carcinomas, adenomas, and normal bowel. The median level of MMP-9 in samples from Dukes' stage A (n = 18) or C (n = 48) tumors was significantly higher than in stage B carcinomas (n = 65), adenomas (n = 25), and normals (n = 36; P = 0.0001). The median level of active MMP-2 was significantly higher in stage A or C compared with adenomas (P = 0.0001) and normals (P = 0.0001). The median level of inactive MMP-2 was higher in all Dukes' stages compared with normals and adenomas (P = 0.0001). There was a significant increase in inactive MMP-2 from Jass prognostic groups I-IV (P = 0.006) but no correlation with the active enzyme. MMP activity was not related to tumor differentiation, colon versus rectal location, or disease-free, 5-year survival. All groups expressed mRNA for both enzymes, but there were quantitative and locational differences in MMP-2 mRNA expression between normal, benign, and malignant tissues. Thus MMP-2 is controlled at the level of mRNA and protein production and activation in colorectal cancer, and active MMP-2 and MMP-9 enzymes are associated strongly with Dukes' A and C stages of the disease. Variations in MMP levels with the stage or prognostic group of colorectal cancer reflect their differing stromal content.

Increased plasminogen activator and type IV collagenase activity in invasive follicular thyroid carcinoma cells

BACKGROUND

An essential difference between benign and malignant follicular thyroid tumors is the ability to invade and metastasize. Thyrotropin (TSH) stimulates invasion of cultured human follicular thyroid cancer cells (FTC-133) via a protein kinase C (PKC) dependent mechanism. Tumor invasion depends on degradation of extracellular matrix by proteases.

METHODS

We analyzed protease activity in FTC-133 and its more invasive clone, FTC-238. Cells were treated with TSH or 12-0-tetradecanoyl-phorbol-13-acetate (TPA), a PKC agonist, for 24 hours. Conditioned medium and cellular extract were subjected to substrate gel zymography with either casein-plasminogen or gelatin (collagen). Western blot and immunohistochemistry confirmed protease identity.

RESULTS

We found increased 50 kd urokinase-like plasminogen activator (uPA) and 62 kd gelatinase activity by FTC-238 cells compared with the less invasive FTC-133 cells. There was no effect of TSH on uPA or collagenase activity at concentrations of 0.01 to 10 mU/ml. In both FTC-133 and FTC-238, TPA incubations of 0.1 to 100 ng/ml caused a dose-dependent increase in uPA and a 94 kd type IV collagenase.

CONCLUSIONS

These findings show that TSH-stimulated invasion may be due to PKC-induced activation of uPA and 94 kd type IV collagenase. uPA and basement membrane type IV collagenase warrant investigation as markers for follicular thyroid cancer.