Transforming growth factor-beta pathway in human renal cell carcinoma and surrounding normal-appearing renal parenchyma.

OBJECTIVE: To analyze the role of the transforming growth factor (TGF)-beta pathway in renal tumors and to verify whether alterations in TGF-beta 1 pathway expression are associated with the grade of tumor differentiation and pathologic stage in renal cell carcinomas. STUDY DESIGN: The expression of TGF-beta 1 and TGF-beta receptors (T beta RI and T beta RII), SMAD-2 and SMAD-4 was investigated by immunohistochemistry in normal peritumoral and tumoral tissue from 53 renal cell carcinomas (clear cell type). The gene expression of SMAD-2 and SMAD-4 was also studied by reverse transcription polymerase chain reaction (RT-PCR) in normal peritumoral and tumoral tissue from 6 of 56 primary tumors. RESULTS: TGF-beta 1, T beta RI and T beta RII immunoreactivity was more frequent in tumoral than in normal peritumoral renal tissue (96.22%, 79.25% and 75.41% vs. 88.37%, 69.76% and 62.69%), whereas SMAD-2 and SMAD-4 immunoreactivity was more frequent in normal peritumoral than in tumoral tissue (23.25% and 30.23% vs. 15.09% and 7.54%). In tumor areas, immunohistochemical scores were lower for T beta RII than for T beta RI and TGF-beta 1 and higher than SMAD-4 and SMAD-2 scores. TGF-beta 1, T beta RI, T beta RII and SMAD-4 histologic scores correlated with neither the histologic grade of malignancy nor TNM clinical stage, whereas SMAD-2 protein levels were significantly lower in grade 3 than in grade 1 tumors. In the samples of normal kidney and carcinoma studied, RT-PCR detected the correct transcripts for SMAD-2 and SMAD-4, indicating that the RNA of the samples analyzed contained RNA sequences coding for these genes. CONCLUSION: Our data support the concept that the reduction of T beta RII and SMAD proteins in renal cell carcinomas is involved in tumor development and suggest an altered TGF-beta/SMAD signaling pathway in kidney neoplasia.

Increased type II transforming growth factor-beta receptor expression in liver cells during cholesterol challenge.

A large body of evidences implicates transforming growth factor-beta (TGF-beta) in the pathogenesis of atherosclerosis. In this context, TGF-beta receptor dysfunction has been suggested to be relevant. We tested the effect of hypercholesterolemia, a well-known risk factor for atherosclerosis, on liver type II TGF-beta receptor (TbetaR-II) expression in atherosclerosis-susceptible C57BL/6 mouse strain fed atherogenic diet. In addition, the relationship between cholesterol and TbetaR-II expression was verified by cholesterol challenge on human hepatoma cell (HepG2) cultures. The susceptible C57BL/6 mice fed atherogenic diet exhibited significant mRNA and immunohistochemical TbetaR-II liver expression at 2, 5, 9 and 15 weeks as compared to animals fed a regular diet. The TbetaR-II profile on HepG2 resulted in a time-dependent increased expression when the cells were incubated with soluble free cholesterol, associated with an increased TGF-beta-dependent biological activity as detected by luciferase assay of reporter gene. These data provide evidence for a cholesterol-dependent TbetaR-II induction that may play a potentially relevant role in the development of hypercholesterolemia and atherogenesis.

Transforming growth factor-beta1 down-regulation of major histocompatibility complex class I in thyrocytes: coordinate regulation of two separate elements by thyroid-specific as well as ubiquitous transcription factors.

Transforming growth factor (TGF)-beta1-decreased major histocompatibility complex (MHC) class I gene expression in thyrocytes is transcriptional; it involves trans factors and cis elements important for hormone- as well as iodide-regulated thyroid growth and function. Thus, in rat FRTL-5 thyrocytes, TGF-beta1 regulates two elements within -203 bp of the transcription start site of the MHC class I 5'-flanking region: Enhancer A, -180 to -170 bp, and a downstream regulatory element (DRE), -127 to -90 bp, that contains a cAMP response element (CRE)-like sequence. TGF-beta1 reduces the interaction of a NF-kappaB p50/fra-2 heterodimer (MOD-1) with Enhancer A while increasing its interaction with a NF-kappaB p50/p65 heterodimer. Both reduced MOD-1 and increased p50/p65 suppresses class I expression. Decreased MOD-1 and increased p50/p65 have been separately associated with the ability of autoregulatory (high) concentrations of iodide to suppress thyrocyte growth and function, as well as MHC class I expression. TGF-beta1 has two effects on the downstream regulatory element (DRE). It increases DRE binding of a ubiquitously expressed Y-box protein, termed TSEP-1 (TSHR suppressor element binding protein-1) in rat thyroid cells; TSEP-1 has been shown separately to be an important suppressor of the TSH receptor (TSHR) in addition to MHC class I and class II expression. It also decreases the binding of a thyroid-specific trans factor, thyroid transcription factor-1 (TTF-1), to the DRE, reflecting the ability of TGF-beta1 to decrease TTF-1 RNA levels. TGF-beta1-decreased TTF-1 expression accounts in part for TGF-beta1-decreased thyroid growth and function, since decreased TTF-1 has been shown to decrease thyroglobulin, thyroperoxidase, sodium iodide symporter, and TSHR gene expression, coincident with decreased MHC class I. Finally, we show that TGF-beta1 increases c-jun RNA levels and induces the formation of new complexes involving c-jun, fra-2, ATF-1, and c-fos, which react with Enhancer A and the DRE. TGF-beta1 effects on c-jun may be a pivotal fulcrum in the hitherto unrecognized coordinate regulation of Enhancer A and the DRE.

Increased TGFbeta type II receptor expression suppresses the malignant phenotype and induces differentiation of human neuroblastoma cells.

TGFbeta can modulate neuroblastoma (NB) cell proliferation and differentiation in vitro. In this study we used a NB cell line (LAN-5) which has been shown to partially respond to TGFbeta and to present high levels of TGFbeta receptor type I and low levels of receptor type II (TbetaRII) on the cell surface. To evaluate the role of TbetaRII in mediating TGFbeta effects, LAN-5 cells were transfected with an expression vector containing the human full-length TbetaRII cDNA or with the empty vector pcDNA3. Compared to control CLV3 cells (transfected with empty plasmid) and parental LAN-5 cells, isolated neomycin-resistant clones (CL1 and CL3) expressed higher levels of TbetaRII, had reduced cell growth rate in vitro, and were unable to form tumors in vivo. Furthermore, isolated clones modified their morphology, assuming a terminally differentiated neuronal phenotype. Immunocytochemical staining demonstrated a basal increased expression of neural-specific markers, such as axonal growth-associated protein (GAP43) and neurofilaments (NF200). TGFbeta treatment further increased the synthesis of NF200 and GAP43 in the transfected clones as revealed by Western blot analysis. These data indicate that TbetaRII overexpression potentiates the TGFbeta signal transduction pathway, reverting NB cell neoplastic phenotype with the reduction of proliferation rate and the induction of terminal maturation.

Overexpression of transforming growth factor beta-type II receptor reduces tumorigenicity and metastastic potential of K-ras-transformed thyroid cells.

Expression of type II receptor of transforming growth factor beta (TbetaRII) is necessary for this factor to inhibit the growth of thyroid epithelial cells. In rat thyroid transformed cells, the resistance to transforming growth factor beta (TGFbeta) is associated with a decreased expression of TbetaRII mRNA and protein. Reduced TbetaRII expression has also been found in human thyroid differentiated and undifferentiated carcinomas. To investigate the role of TbetaRII in modulating the tumorigenic potential of k-ras-transformed thyroid cells, we transfected these cells with an expression vector carrying the human TbetaRII gene, regulated by an inducible promoter. Isolated clones, overexpressing TbetaRII, showed a reduction in the anchorage-dependent and -independent cell growth, compared with control k-ras-transformed cells. When transplanted in athymic nude mice, the transfected clones presented a decrease in tumorigenicity with respect to the highly malignant parental cells. Moreover, the diminished tumorigenic ability of the clones studied was accompanied by a statistically significant reduction in spontaneous and lung artificial metastases. Taken together, our data demonstrate that TbetaRII acts as a potent tumor suppressor gene when overexpressed in malignant thyroid cells.

Microsatellite instability in thyroid tumours and tumour-like lesions.

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

Heregulin-dependent autocrine loop regulates growth of K-ras but not erbB-2 transformed rat thyroid epithelial cells.

The EGF-like family of proteins, such as epidermal growth factor (EGF), transforming growth factor alpha (TGFalpha), amphiregulin (AR), betacellulin (BTC), cripto-1 (CR-1), and heregulin (HRG), plays an important role in the pathogenesis of several human carcinomas as autocrine growth factors. Differentiation and proliferation of rat thyroid cells in culture (FRTL-5 cells) are regulated by thyrotropin (TSH); withdrawal of TSH from culture medium produces growth arrest, whereas its addition to quiescent cells stimulates cell entry into S phase. Instead, transformed thyroid cell lines as FRTL-5H2 cell line, overexpressing erbB-2, Kimol cells, transformed by the wild-type K-ras and A6 clone, transformed by a temperature sensitive K-ras mutant, can grow without addition of TSH to the culture medium. In order to identify whether EGF-like growth factors and corresponding receptors (erbB-2, erbB-3, and erbB-4) could be involved in the autonomous growth of these transformed rat thyroid epithelial cells, Northern blot for mRNA analysis and Western blot for protein expression were performed. In contrast to normal control FRTL-5 cells, both K-ras and erbB-2-transformed cells expressed elevated levels of erbB-2 receptor. Moreover, both K-ras transformed cells, Kimol and A6 cells, but no FRTL-5H2 cells, were found able to express also high levels of erbB-4 receptor and HRG/NDF ligand. Treatment of K-ras transformed thyroid cells with neutralizing antibody against HRG/NDF reduced by 50% cell proliferation. These data indicate that unlike the erbB-2 overexpressing FRTL-5 cells, in K-ras rat thyroid epithelial cells, the growth factor heregulin signals through the heterodimer erbB-2/erbB-4 receptors in an autocrine fashion.

Cyclin D1 and Cyclin E expression in malignant thyroid cells and in human thyroid carcinomas.

Evidence of the involvement of cyclin gene alterations in human cancer is growing. In this study, we sought to determine the pattern of expression of cyclin D1 and cyclin E in normal and malignant thyroid cells. Quiescent rat thyroid cells in culture, induced to synthesize DNA by thyrotropin (TSH), expressed cyclin D1 gene after 6 hr and cyclin E gene with a peak at 18 hr from the stimulus; K-ras-transformed rat thyroid cells, which grew without addition of hormones necessary for normal cell proliferation, expressed elevated levels of cyclin D1 and cyclin E, compared with normal differentiated thyroid cells. Human benign and malignant thyroid tumors and their relative normal tissues were then analyzed. Neither major genetic alterations nor amplifications for cyclin D1 and cyclin E genes were found by Southern blot analysis in genomic DNAs extracted from all types of thyroid tumors. Moreover, statistical analyses of densitometric values from Northern blots did not show increased levels of cyclin D1 and E mRNAs in the tumor samples, compared with normal thyroid. Immunohistochemical analyses of formalin-fixed paraffin-embedded sections of tissues with specific antibodies revealed a prevalent cytoplasmic cyclin E staining in the thyroid tissues analyzed. Cyclin D1, instead, was present in the cytoplasm of normal thyroids and adenomas, but in 31% of thyroid papillary carcinomas analysed, it was overexpressed, with a localization in the nucleus. Our in vivo observations suggest that unlike cyclin E, elevated nuclear cyclin D1 expression defines a subset of thyroid papillary carcinomas, and might be a contributory factor to thyroid tumorigenesis.

Transforming growth factor-beta1 enhances the invasiveness of human MDA-MB-231 breast cancer cells by up-regulating urokinase activity.

Transforming growth factor-beta (TGFbeta1) enhances human MDA-MB-231 breast tumour cell invasion of reconstituted basement membrane in vitro but does not inhibit proliferation of this cell line. In contrast to basal invasion, which is plasmin-, urokinase (uPA)-, tissue-type plasminogen activator (t-PA)-, matrix metalloproteinase (MMP)-9- and TIMP-1-inhibitable MMP-dependent, TGFbeta1 enhanced-invasion is dependent upon plasmin and uPA activity but does not appear to involve t-PA-, MMP9- or TIMP-1-inhibitable MMPs, as judged by inhibitor studies. Enhanced invasion is associated with increased u-PA, UPAR, PAI-1, MT-MMP-1, MMP-9 and TIMP-1 expression; with reduced t-PA, MMP-1 and MMP-3 expression; and with the induction of membrane MMP-9 association. The net result of these changes includes increased secreted, but not membrane-associated, uPA levels and activity and reduced secreted levels of plasmin and APMA-activatable gelatinolytic, collagenolytic and caseinolytic MMP activity but no change in membrane-associated gelatinolytic activity, despite increased MT-MMP-1 expression and MMP-9 membrane association. TGFbeta1 does not induce MMP-2 expression. Our data indicate that TGFbeta1 can promote the malignant behaviour of MDA-MB-231 cells refractory to TGFbeta1-mediated proliferation control by enhancing their invasive capacity. We suggest that this results from the action of a uPA/plasmin-dependent mechanism resulting from stimulation of uPA expression, secretion and subsequent activity, despite elevated PAI-1 inhibitor levels.

Oncogenes and antioncogenes involved in human thyroid carcinogenesis.

The development of cancer is due to the accumulation of multiple somatic mutations, in some cases following germline mutations, which occur in hereditary malignancies such as retinoblastomas or multiple endocrine neoplasia (MEN 2A and B). Genetic alterations or changes in the expression of growth regulatory genes can lead to the initiation of malignant transformation and to eventual tumor progression. Cells that have undergone these cumulative alterations in either the structure or expression of these regulatory genes generally possess a selective growth and/or metastatic advantage over other normal non-transformed cells. Thus, activation of dominantly transforming oncogenes by point mutations, gene amplification, chromosomal translocation or insertional mutagenesis can lead to uncontrolled cellular growth or to a disruption in normal differentiation or apoptosis. Equally contributory to the process of malignant progression is the inactivation of recessive tumor suppressor genes due to point mutations and/or loss of heterozygosity in one allele, which can ultimately lead to a reduction of homozygosity in both alleles. Thyroid tumors in humans represent a particularly suitable multistage model of epithelial tumorigenesis. In fact, even though most thyroid neoplasms originate from a single cell type, i.e. the thyroid follicular cell, they include a broad spectrum of tumors with different phenotypic characteristics and variable biological and clinical behaviour. Multiple degrees of malignancies have been defined: from the benign colloid adenomas through the slowly progressive differentiated papillary and follicular carcinomas to the invariably fatal anaplastic carcinomas, although these histological changes are not necessarily sequential. In this review an effort has been made to summarize and integrate new data published on genetic lesions and altered expression of genes involved in the tumorigenesis of the follicular type of thyroid cancer. We have focused our interest only on gene alterations inducing gain or loss of function, that have been studied in vivo in human thyroid tumor specimens by the use of different techniques, such as PCR mediated DNA analyses, sequencing, mRNA level evaluation and protein expression by immunohistochemical staining.

Restored expression of transforming growth factor beta type II receptor in k-ras-transformed thyroid cells, TGF beta-resistant, reverts their malignant phenotype.

Transforming growth factor beta 1 (TGF beta 1) inhibits the growth of normal rat epithelial thyroid cells (FRTL-5 strain) by counteracting thyrotropin (TSH)-stimulated DNA synthesis and by slowing the cells in the G1 phase of the cell cycle. Here, we have studied two clones of FRTL-5 thyroid cell line transformed by the wild type (wt) v-k-ras oncogene (K.M.A1, K.M.A2) and one clone (A6) transformed by a temperature-sensitive (ts) v-k-ras mutant. Anchorage-dependent as well as anchorage-independent growth of these k-ras-transformed cells was not inhibited by TGF beta 1. TGF beta 1 resistance appeared to be dependent by a functional p21 k-ras, because A6 cell growth was partially inhibited at the nonpermissive temperature (39 degrees C). To determine the basis for TGF beta 1 resistance in k-ras-transformed thyroid cells, we looked for possible defects in the expression of type I (T beta R-I/ALK5) and type II TGF beta receptors (T beta R-II). Lower levels of type II receptors were present in all of the k-ras-transformed clones, as revealed by both Northern blot and cross-linking experiments. A partial reversion of the malignant phenotype of the wt k-ras-transformed clone was obtained in two clones isolated after transfection of the malignant thyroid cells (K.M.A1) with a T beta R-II expression vector. These two clones also showed restored levels of exogenous T beta R-II mRNA and protein, and both clones showed a partially reacquired sensitivity to TGF beta 1. Similarly, the reversion of the malignant phenotype of the A6 clone grown at the nonpermissive temperature was accompanied by a restored expression of the T beta R-II receptors. These data indicate that active k-ras oncogene can induce TGF beta 1 resistance in rat thyroid cells and suggest that one of the possible mechanisms of escape from TGF beta 1 growth control in k-ras-induced thyroid carcinogenesis involves a reduced expression of T beta R-II receptors.

The phosphatase inhibitor okadaic acid stimulates the TSH-induced G1-S phase transition in thyroid cells.

Protein phosphorylation plays an essential role in regulating many cellular processes in eukaryotes. Signal transduction mechanisms that are reversibly controlled by protein phosphorylation require also protein phosphatases (PPs). Okadaic acid (OA), which is a potent inhibitor of protein phosphatase 2A (PP2A) and protein phosphatase 1, elicits phosphorylation of many proteins in unstimulated cells and induces different cellular responses, including transcriptional activation, shape changes, and pseudomitotic state. In this study, the effects of OA on rat thyroid cells (FRTL-5 strain) were analyzed to evaluate the role of serine/threonine phosphatases in hormone-induced thyroid cell proliferation. OA at a concentration range between 0.1 and 1 nM stimulated thyroid cell growth. Furthermore, 0.25 nM OA increased about 3.5-fold the thyrotropin (TSH)-induced DNA synthesis in quiescent cells. OA treatment also stimulated cell proliferation induced by drugs that mimic TSH effect, such as 8Br-cAMP and cholera toxin, suggesting that PP2A activity was relevant in the cAMP pathway activated by the hormone. Flow cytometry experiments showed that OA significantly increased the fraction of TSH-stimulated quiescent cells entering the S phase. In order to define the mechanisms underlying the observed stimulatory effect of OA on thyroid cell growth, expression of genes relevant in the G1-S phase transition was evaluated. A 2-fold increase in the level of cyclin D1 mRNA expression was found by Northern blot analysis in OA-treated cells. Although cdk2 gene expression was not modulated by the same OA treatment, an increase in Cdk2 protein was revealed by immunoprecipitation experiments. Moreover, OA modifies the phosphorylation pattern of the tumor suppressor retinoblastoma protein, a key event in the G1-S phase transition. Therefore, these experiments reveal that PP2A phosphatases play an important role in thyroid cell growth and can act at multiple sites in the TSH pathways driving cells to S phase.

Increased transforming growth factor-beta production and gene expression by peripheral blood monocytes of hypertensive patients.

Cultured human peripheral blood monocytes are known to secrete and express transforming growth factor-beta (TGF-beta), a multifunctional cytokine that can be involved in myocardial and vascular remodeling. In addition, monocytes/macrophages have been demonstrated to be colocalized with fibrosis of hypertrophied heart and in the vascular wall of hypertensive vessels. In this study, we tested TGF-beta production and mRNA expression in peripheral blood monocytes from hypertensive patients with myocardial hypertrophy and increased carotid myointimal thickness with respect to healthy normotensive control subjects. We found an increased TGF-beta activity in the conditioned medium of monocytes from hypertensive patients compared with control subjects as evaluated by inhibition of [3H]thymidine incorporation by mink lung epithelial cells (-83% and -18% in hypertensive and normotensive subjects; P<.001). Western blot analysis confirmed a significant difference in the amount of TGF-beta protein secreted in the conditioned medium of hypertensive patients compared with that of normotensive subjects. Finally, we also observed a 4.2- and 5.5-fold increase in the amount of TGF-beta1 and TGF-beta2 transcripts, respectively. Our results indicate an upregulation of the TGF-beta system in the peripheral blood monocytes of hypertensive patients with cardiovascular structural changes, suggesting a possible role of TGF-beta monocyte production in hypertensive disease.

Human malignant thyroid tumors displayed reduced levels of transforming growth factor beta receptor type II messenger RNA and protein.

Transforming growth factor beta (TGF-beta) is a physiological regulator of thyroid epithelial cell growth and differentiation. This factor signals through a heteromeric complex composed of type I (TGF-beta receptor type I) and type II [TGF-beta receptor type II (TbetaRII)] receptors. Loss of TbetaRII expression has been related to resistance to TGF-beta inhibition of cell proliferation. In the present work, we analyzed the TbetaRII expression in a series of human thyroid tumors, from benign lesions (adenomas) to neoplastic lesions of increasing aggressiveness (papillary and follicular carcinomas) up to the extremely aggressive anaplastic tumors. Results obtained indicated a clear reduced expression of TbetaRII mRNA only in the group of thyroid carcinomas when compared with their relative normal tissues. Immunohistochemical analyses with specific anti-TbetaRII antibodies confirm these observations. These data indicate that loss of expression of TbetaRII can contribute to thyroid cancer progression, inducing cancer cells to escape the growth-inhibitory effect of TGF-beta.

Transforming growth factor beta regulates differentiation and proliferation of human neuroblastoma.

The effects of transforming growth factor-beta1 (TGFbeta) on two human neuroblastoma cell lines, LAN-5 and SK-N-AS, and one human glioblastoma cell line, GL15, were evaluated. Of the three cultures, only two, SK-N-AS and GL15, had a complete response to TGFbeta, with induction of the following effects: (i) inhibition of cell proliferation; (ii) up-regulation of the extracellular matrix glycoprotein fibronectin, together with down-regulation of the VLA5 integrin receptor; (iii) up-regulation of histotype-specific cytoskeletal intermediate filaments (neurofilaments for neuroblastoma and GFAP for glioblastoma); and (iv) increase in the glycoprotein CD44, only in SK-N-AS. In the third cell line, neuroblastoma LAN-5, the effects exerted by TGFbeta consisted only of (i) neurofilament increase and (ii) morphological differentiation. The TGFbeta receptor pattern was different in each culture: SK-N-AS expressed low rates of type I and type II receptors and high rates of type III receptor; LAN-5 expressed high rates of type I, low rates of type II, and no type III; GL15 expressed high rates of all three receptors. These data suggest that TGFbeta can induce a histotype-specific cell maturation and that the neuroblastoma expressing low type II and at the same time lacking type III receptor responds only partially to TGFbeta, with induction of neural differentiation but without inhibition of cell growth.

Enhanced expression of heregulin in c-erb B-2 and c-Ha-ras transformed mouse and human mammary epithelial cells.

Heregulin beta 1 was found to stimulate the anchorage-dependent, serum-free growth of nontransformed human MCF-10A mammary epithelial cells. Unlike epidermal growth factor, transforming growth factor alpha, or amphiregulin, heregulin beta 1 was also able to induce the anchorage-independent growth of MCF-10A cells. In contrast, the anchorage-independent, serum-free growth of c-Ha-ras or c-erb B-2 transformed MCF-10A cells was unaffected by heregulin beta 1, whereas heregulin beta 1 was able to stimulate the anchorage-independent growth of these cells. c-Ha-ras or c-erb B-2 (c-neu) transformed MCF-10A or mouse NOG-8 mammary epithelial cells express elevated levels of 2.5, 5.0, 6.5, 6.8, and 8.5 kb heregulin mRNA transcripts and/or synthesize cell-associated 25, 29, 50, and 115 kDa isoforms of heregulin. Since the MCF-10A cells and transformants also express c-erb B-3, these data suggest that endogenous heregulin might function as an autocrine growth factor for Ha-ras or erb B-2 transformed mammary epithelial cells.

Expression of messenger RNA for amphiregulin, heregulin, and cripto-1, three new members of the epidermal growth factor family, in human breast carcinomas.

The expression of amphiregulin (AR), heregulin (HRG), and cripto-1 (CR-1) mRNA transcripts was assessed in 60 human primary breast carcinoma. AR and HRG transcripts were expressed respectively in 58% and 25% of the carcinomas as measured by Northern blot analysis. CR-1 mRNA was found in 77% of the carcinomas using Reverse Transcriptase-PCR analysis. Coexpression of two or three of these peptides was observed in several specimens. There was no significant association between AR, HRG, and CR-1 expression and nodal status, EGF receptor, or c-erbB-2 protooncogene expression in these tumors. However, a significant association between AR expression and estrogen receptor positivity was observed.

Epithelial rat thyroid cell clones, escaping from transforming growth factor beta negative growth control, are still inhibited by this factor in the ability to trap iodide.

Transforming growth factor beta (TGF beta) acts on epithelial thyroid cells, negatively controlling their proliferation and functions. The effects of TGF beta on epithelial rat thyroid cells (FRTL-5) and on two TGF beta-resistant rat thyroid cell clones (FRTL-5H2 and FRTL-R) were investigated. FRTL-5H2 represents a rat thyroid cell clone overexpressing active erbB-2 oncogene, recently obtained after FRTL-5 cell infection with a retrovirus vector carrying the erbB-2 human oncogene (G. Mincione et al., Cancer Res., 53: 5548-5553, 1993). FRTL-R is a FRTL-5 subclone spontaneously isolated after long term in culture. FRTL-5H2 and FRTL-R cell clones were stimulated by TGF beta at the same concentration of 5 ng/ml that induced 70% inhibition of [3H]thymidine incorporation in control FRTL-5 thyroid cells. Nuclear events regulated by TGF beta, such as cyclin and cyclin-dependent kinase gene expression, were then analyzed. In FRTL-5 cells, TGF beta was found to reduce the expression of cdk2 and cyclin A genes; the same treatment did not modify nuclear gene expression in the resistant cell clones. TGF beta is known to reduce iodide uptake in thyroid cells; in both FRTL-5H2 and FRTL-R cells, TGF beta was found to inhibit the thyrotropin-induced iodide uptake. Thus, thyroid cell clones, resistant to the growth-inhibitory activity of TGF beta, were sensitive to TGF beta inhibition of iodide incorporation, suggesting that TGF beta activates divergent signaling pathways in these cells, separately controlling cell proliferation and differentiation parameters. Studies on TGF beta receptors showed similar amounts of TGF beta-binding species on FRTL-5 cells and TGF beta-resistant clones, while 125I-labeled TGF beta cross-linking experiments revealed differences; thus, the TGF beta-resistant cells showed a 40% decrease in the amount of labeled type II TGF beta receptor on the cell surface. However, this different pattern of TGF beta receptors cannot totally account for the shown TGF beta resistance to growth inhibition that might also be due to perturbation in signaling pathways.

Analysis of adenomatous polyposis coli gene in thyroid tumours.

Familial adenomatous polyposis (FAP) is known to be associated with neoplasia of various tissues, including thyroid carcinoma. Germline mutations of the tumour-suppressor gene APC, responsible for the predisposition to FAP, may therefore be involved in the pathogenesis of these tumours. In this report the structure of the APC gene has been investigated in 26 thyroid tumours, at different stages of dedifferentiation, that were surgically excised from patients with a negative history of FAP. Approximately 35% of the APC gene coding region, where most of the mutations are clustered, has been analysed by a combination of single-strand conformation polymorphism and direct sequencing. No significant alterations could be demonstrated in any sample examined. It is concluded that, at least in patients not affected by FAP, APC gene abnormalities do not seem to play a relevant role in the pathogenesis of thyroid carcinoma.

Transforming growth-factor-alpha modulates replication and differentiation markers on a human neuroblastoma cell-line.

The effects of TGF alpha and EGF on a human neuroblastoma cell line expressing EGF receptor were studied. Both growth factors were mitogenic for neuroblastoma and, at the same time, induced a morphological differentiation. TGF alpha treatment (10 ng/ml) determined an increase in the expression of laminin and neurofilaments, both markers typical of neuronal phenotype. Hovewer, unlike the differentiation induced by retinoic acid treatment, TGF alpha modulation of neuroblastoma neuronal markers was not mediated by an increase in the expression of the ret oncogene. Moreover, TGF alpha appeared to stimulate an autocrine production of TGF alpha itself, as evaluated by an increase in mRNA at three days of treatment. These data suggest a possible involvement of EGF and TGF alpha in a paracrine and autocrine control of neuroblastoma, possibly each accomplishing similar but complementary functions.