Expression of TGFα in Meningiomas

The objective of this study was to examine the expression of transforming growth factor (TGF), a mitogen for many cell types, and its receptor in basic subtypes of meningiomas as well as in meningiomas of varying grade. Formalin-fixed tissues from 26 meningiomas including 15 benign (5 meningothelial, 5 transitional, and 5 fibrous variants), 6 atypical, and 5 malignant examples were immunohistochemically examined for both TGF protein and EGF/TGF receptor protein. In addition, in situ hybridization (ISH) was used to detect TGF mRNA expression. Immunostaining for TGF was strongest in fibrous and atypical meningiomas, followed closely by transitional and malignant tumors. Only weak reactivity was observed in the meningothelial variant. In all but 4 tumors (2 fibrous, 2 atypical), ISH showed TGF mRNA to be present, the signal being stronger in malignant than in conventional or atypical tumors. Lastly, immunostaining for EGF/TGF receptor was positive in all tumors studied. Strong TGF protein expression in meningiomas is commonly associated with fibrous morphology. Although the frequent detection of both TGF protein and its mRNA, as well as of EGF/TGF receptor within tumors of all type and grades, suggests that TGF serves to promote tumor growth, its possible role in tumorigenesis or malignant progression is uncertain.In summary, demonstration of these substances is of no utility in the classification or grading of this common tumor because the differences in their expression among the various meningioma subtypes were not statistically significant.     

Transforming growth factor-β in breast cancer: A working hypothesis

Transforming Growth Factor- (TGF) is the most potent knowninhibitor of the progression of normal mammary epithelial cells through thecell cycle. During the early stages of breast cancer development, thetransformed epithelial cells appear to still be sensitive toTGF-mediated growth arrest, and TGF can act as an anti-tumorpromoter. In contrast, advanced breast cancers are mostly refractory toTGF-mediated growth inhibition and produce large amounts of TGF,which may enhance tumor cell invasion and metastasis by its effects onextracellular matrix. We postulate that this seemingly paradoxical switch inthe responsiveness of tumor cells to TGF during progression is theconsequence of the activation of the latent TGF that is produced anddeposited into the tumor microenvironment, thereby driving the clonalexpansion of TGF-resistant tumor cells. While tumor cells themselvesmay activate TGF, recent observations suggest that environmental tumorpromoters or carcinogens, such as ionizing radiation, can cause stromalfibroblasts to activate TGF by epigenetic mechanisms. As thebiological effects of the anti-estrogen tamoxifen may well be mediated byTGF, this model has a number of important implications for the clinicaluses of tamoxifen in the prevention and treatment of breast cancer. Inaddition, it suggests a number of novel approaches to the treatment ofadvanced breast cancer.     

Escape from negative regulation of growth by transforming growth factor β and from the induction of apoptosis by the dietary agent sodium butyrate may be important in colorectal carcinogenesis

There are a number of lines of evidence suggesting that transforming growth factor (TGF) has an important role in the control of intestinal growth and differentiation.In vivo localization studies show that TGF expression occurs predominantly in the differentiated non proliferating cells of the intestinal epithelium. The use of an antisense expression vector for TGF resulted in an increased tumorigenicity in an antisense-transfected cancer cell line.In vitro proliferation studies showed colorectal premalignant adenoma cells to be more sensitive to the growth inhibitory effects of TGF than colorectal cancer cells. Furthermore the conversion of an adenoma to a carcinoma was accompanied by a reduced response to the inhibitory effects of TGF. The acquisition of partial or complete resistance to the inhibitory effects of TGF may be an important late event in colorectal carcinogenesis.Of further interest is the possibility that clonal selection could occur even more rapidly in colorectal tumour cells which not only had lost response to TGF inhibition but produced TGF and were growth stimulated by it. This could have the advantage of not only inhibiting the growth of surrounding less malignantly advanced cells but of also escaping from their potential growth suppressive influence. Carcinogenesis is not, however, simply losing response to negative regulators of growth; the fully malignant cell has to acquire new characteristics of invasiveness and metastatic potential. Growth factors including TGF may have a role in the complex cascade of events leading to the activation of proteolytic enzymes which are involved in progression to an invasive phenotype.Cell proliferation in the large bowel, as well as being under the control of endogenous growth factors, is also under the influence of dietary components in the lumen such as the naturally occurring fatty acid sodium butyrate. Sodium butyrate at physiological concentrations induces apoptosis (programmed cell death) in colonic tumour cell lines. Since sodium butyrate occurs naturally in the colorectum, being produced by bacterial fermentation of dietary fibre, it may be involved in the control of cell death in human colorectal epithelium. This could, in part, explain the apparent protective effects of dietary fibre. Clonal evolution and tumour progression in colorectal carcinogenesis could therefore involve loss of response to endogenous growth factors such as TGF and an escape from the induction of programmed cell death by dietary factors.     

The effects of TGF-α and 17β-estradiol on polyphosphoinositide metabolism in MCF-7 breast cancer cells

Summary The mechanism by which transforming growth factor-alpha (TGF-) stimulates breast cancer cell proliferation is largely unknown. Furthermore, its potential role as an autocrine effector of estradiol-17 (E₂)-stimulated growth of hormone-dependent mammary tumors remains controversial. Transient changes in phosphatidylinositol (PI) turnover have been demonstrated in several tissues in response to growth factors. In these experiments, we tested the effects of TGF- and E₂ on PI metabolism in three MCF-7 breast cancer cell sublines (MCF-7B, MCF-7I, and MCF-7J). Although TGF- was mitogenic in MCF-7I and MCF-7J cells, PI hydrolysis was stimulated by the growth factor only in the MCF-7I cells. In addition, the TGF- effect was relatively modest, ranging from 23% to 42%. E₂ effects on PI turnover were tested in the MCF-7B cells, which were the most sensitive to the proliferative effect of the hormone. E₂ did not stimulate PI hydrolysis, whether or not the cells were labelled in the presence of the hormone. On the other hand, E₂ did seem to stimulatede novo synthesis of phosphatidylinositol and induce activation of PI kinases. These results demonstrate that TGF--stimulated PI hydrolysis is modest and cell type dependent. At least under certain conditions, PI metabolism is not involved in the proliferative effects of TGF- (MCF-7J) or E₂ (MCF-7B). The role of increased PI synthesis in E₂-stimulated MCF-7 cell growth remains to be established.This work is supported by a grant from the National Cancer Institute, POI CA40011.     

Additive effect of mifepristone and tamoxifen on apoptotic pathways in MCF-7 human breast cancer cells

MCF-7 cells growing in culture were used to study the mechanism of the antiproliferative activity of the antiprogestin mifepristone, as compared with the antiestrogen 4-hydroxytamoxifen or the combination of both. These steroid antagonists induced a significant time- and dose-dependent cell growth inhibition (cytotoxicity). This inhibition of cell survival was associated with a significant increase in DNA fragmentation (apoptosis), downregulation of bcl2, and induction of TGF1 protein. Abrogation of the mifepristone- and/or 4-hydroxytamoxifen-induced cytotoxicity by TGF1 neutralizing antibody confirms the correlation between induction of active TGF1 and subsequent cell death. The effect of a combination of mifepristone and 4-hydroxytamoxifen on cell growth inhibition, on the increase in DNA fragmentation, bcl2 downregulation, and induction of TGF1 protein was additive and significantly different (P < 0.05) from the effect of monotherapy. A translocation of protein kinase C (PKC) activity from the soluble to the particulate and/or nuclear fraction appeared to be also additive in cells treated with a combination of both 4-hydroxytamoxifen and mifepristone. These results suggest that the mechanism of the additive antiproliferative activity of mifepristone and tamoxifen could be explained at least in part by an additive induction of apoptosis in both estrogen and progesterone receptor positive MCF-7 breast cancer cells. A bcl2 downregulation, the PKC transduction pathway, and TGF1 expression seem to be involved in this additive mechanism of action. Our data further suggest that a combination of an antiprogestin with tamoxifen may be more effective than tamoxifen monotherapy in the management of human breast cancer.     

Tamoxifen and fenretinide in women with metastatic breast cancer

Background: Tamoxifen and fenretinide combination therapy has been shown to be an active treatment regimen in metastatic breast cancer patients. This pilot study sought to determine whether the addition of fenretinide to tamoxifen would be associated with antitumor activity in metastatic breast cancer patients who had been previously treated with tamoxifen or who had hormone receptor negative disease. The effect of this therapy on circulating plasma transforming growth factorbeta (TGF) levels and serum lipids was also examined.Patientsand Methods: Thirtyone patients were treated with tamoxifen (20mg po daily), and fenretinide (400mg po daily with a 3day drug holiday each month). Plasma TGF testing was performed using isoform specific sandwich ELISA.Results: Twenty four of the 31 patients were evaluable for an antitumor response including 14 estrogen receptor (ER) positive patients who had failed prior tamoxifen therapy, seven ERnegative patients, and three hormone therapy naive ERpositive patients. There were no objective antitumor responses; three patients had stable disease for 8, 8, and 24 months. Five patients (16%) discontinued therapy for toxicity (one for grade 3 skin rash and four for abnormal dark adaptation). There was a statistically significant decrease in total cholesterol (median change per patient of –13.5mg/dl; p=0.049, a 6.5% decrease), and an increase in HDL levels (median change per patient of +18mg/dl, p=0.0001, a 35% increase) with tamoxifen and fenretinide therapy.TGF-1 plasma levels were normal in 26 of 28 patients, and no changes in these levels post-treatment were demonstrated.Conclusions: Tamoxifen and fenretinide therapy is not an active combination in ER negative metastatic breast cancer or in patients whose disease has progressed on tamoxifen. This combination had a beneficial effect on total serum cholesterol and HDL levels with no associated rise in serum triglyceride levels. The 400mg dose of fenretinide was associated with symptomatic nyctalopia in one-third of patients making it an unsuitable dose for use in breast cancer prevention studies.     

The role of transforming growth factor Β in glioma progression

This review examines the apparently paradoxical conversion of transforming growth factor 's (TGF) regulatory role as a growth inhibitor among normal glial cells to that of a progression factor among glioblastomas (GM). In vitro, TGF functions as an autocrine growth inhibitor of near-diploid gliomas of any grade. In contrast, hyperdiploid glioblastoma multiforme (HD-GM) cultures proliferate in response to TGF, which is mediated by induction of platelet-derived growth factor B chain (PDGF-BB). The dominant hypothesis of TGF's pathogenetic association with malignant transformation has been predicated upon acquisition of resistance to its growth inhibitory effects. However, the lack of obvious correlation with TGF receptor (TR) expression (or loss) between the HD-GM and the TGF-inhibited GM cultures suggests the existence of intrinsically opposed regulatory mechanisms influenced by TGF. The mechanism of conversion might be explained either by the loss of a putative tumor suppressor gene (TSG) which mediates TGF's inhibition of growth or by enhancement of an active oncogenic pathway among the HD-GM. The frequency of mutations within glioma-associated TSG, such as TP53 and RB, suggests that defects in TGF's inhibitory signaling pathway may have analogous effects in the progression to HD-GM, and TGF's conversion to a mitogen. Alternative sites of inactivation which might explain the loss of TGF's inhibitory effect include inactivating mutation/loss of the TR type II, alterations in post-receptor signal transmission or the cyclin/cyclin dependent kinase system which regulates the phosphorylation of pRB. Loss or inactivation of a glial TSG with a consequent failure of inhibition appears to allow TGF's other constitutive effects, such as induction of c-sis, to become functionally dominant. Mechanistically, TGF's conversion from autocrine inhibitor to mitogen promotes 'clonal dominance' by conferring a Darwinian advantage to the hyperdiploid subpopulations through qualitative and quantitative differences in its modulation of PDGF-A and c-sis, with concomitant paracrine inhibition of competing, near-diploid elements. Abbreviations: transforming growth factor (TGF) and receptor (TR); retinoblastoma gene (RB) and protein (pRB); platelet-derived growth factor (PDGF) and receptor (PDGFR); epidermal growth factor (EGF) and receptor (EGFR); fibroblast growth factor (FGF); malignant glioma (MG), astrocytoma (AST), anaplastic astrocytoma (AAST), glioblastoma (GM); hyperdiploid glioblastoma (HD-GM); glioblastoma multiforme (GM); normal rat kidney (NRK); tumor suppressor gene (TSG); loss of heterozygosity (LOH); TP53 wild type (TP53wt); TP53 mutant (TP53m)     

Expression of a Soluble Transforming Growth Factor-β (TGFβ) receptor reduces tumorigenicity by regulating natural killer (NK) cell activity against 9L gliosarcoma in vivo

Immunotherapy of gliomas has been forwarded as an attractive alternative to standard therapeutic modalities. Numerous observations indicate some therapeutic efficacy with this approach, but it is not curative in most reports. It is well established that gliomas suppress immune reactivity via a number of mechanisms, including expression CD95 ligand (CD95L), which induces apoptosis of immune effector cells, and secretion of immunosuppressive factors such as transforming growth factor-beta (TGF). It has been hypothesized that abrogation of production or function of TGF would improve immune reactivity to gliomas. To investigate this in a fashion that is translatable into clinical practice, we utilized a retroviral vector encoding a truncated, soluble form of the Type II receptor for TGF (TFGsr) and expressed it in the rat 9L gliosarcoma line (9L-TGFsr). We then determined whether expression of TGFsr affected in vitro sensitivity of 9L to lysis by immune effector cells, whether expression of TGFsr affected tumorigenesis of 9L in vivo, and whether TGFsr affected expression of immunity to 9L. In these experiments, we determined that 9L-TGFsr was more susceptible than sham transfected 9L (9L-neo) to lysis by natural killer (NK) cells. We also determined that subcutaneously implanted 9L-TGFsr was less tumorigenic than 9L-neo in syngeneic rats. Similarly, survival was extended by 40% in rats given intracranial 9L-TGFsr compared to 9L-neo. Finally, we determined that elimination of CD161⁺ cells resulted in comparable growth of 9L-neo and 9L-TGFsr in vivo, indicating that NK or NK-like cells were responsible for the anti-tumor effects in this model.     

Transforming growth factor b as a potential tumor progression factor among hyperdiploid glioblastoma cultures: Evidence for the role of platelet-derived growth factor

Among early-passage, near-diploid gliomas in vitro, transforming growth factor type (TGF) has been previously shown to be an autocrine growth inhibitor. In contrast, hyperdiploid ( 57chromosomes/metaphase) glioblastoma multiforme (HD-GM) cultures were autocrinely stimulated by the TGF. The mechanism of this conversion from autocrine inhibitor to mitogen is not understood; previous studies have suggested that platelet-derived growth factor (PDGF) might be modulated by TGF. The similar expression of TGF types 1—3, PDGF-AA, — BB, as well as the PDGF receptor and subunits (a/PDGFR) between biopsies of the HD-GM and near-diploid, TGF-inhibited glioblastomas (GM) by immunohistochemistry did not explain the discrepancy in their regulatory responses. Flowcytometry demonstrated that TGF's mitogenic effect was selective for the aneuploid subpopulations of two of three selected HD-GM cultures,while the diploid cells were inhibited. Among the HD-GM, TGF1 induced the RNA of PDGF-A, c-sis and TGF1. The amount of PDGF-AA secreted following TGF treatment was sufficient to stimulate the proliferation of a HD-GM culture. Antibodies against PDGF-AA, -BB, -AB,PDGFR and/or PDGFR subunits effectively neutralized TGF's induction of DNA synthesis among the HD-GM cell lines, indicating that PDGF served as the principal mediator of TGF's growth stimulatory effect. By comparison, TGF induced only the RNA of PDGF-A and TGF1 among the near-diploid GM; c-sis was not expressed at all. However, the amount of PDGF-A which was secreted in response to TGF1 was insufficient to prevent TGF's arrest of the near-diploid cultures in G₁ phase. Thus, the emergence of hyperdiploidy was associated with qualitative and quantitative differences in TGF's modulation of PDGF-A and c-sis, which provided a mechanism by which the aneuploid glioma cellsmight achieve clonal dominance. We hypothesize that TGF may serve as an autocrine promoter of GM progression by providing a selective advantage to the hyperdiploid subpopulation through the loss of a tumor suppressor gene which mediates TGF's inhibitory effect.     

Involvement of nuclear steroid/thyroid/retinoid receptors and of protein kinases in the regulation of growth and of c‐erbB and retinoic acid receptor expression in MCF‐7 breast cancer cells

Nuclear steroid/thyroid/retinoid receptors and cerbB membrane receptor tyrosine kinases control epithelial growth and differentiation. Retinoid receptors can dimerize with the vitamin D receptor, the glucocorticoid receptor or the thyroid receptor. Furthermore, multiple cerbB receptor dimers have been identified. It has been shown that some of these receptor pathways communicate with each other via crossconnected regulatory networks. Molecular interactions between retinoid receptors or estrogen receptors (ER) and cerbB2, and between ER and retinoic acid receptor(RAR) have been reported. Here, we demonstrate the effects of steroids/thyroids/retinoids and of activators of protein kinase A (forskolin, Forsk) and C (12Otetradecanoylphorbol13acetate, TPA), on growth and expression of cerbB and RARs in MCF7 breast cancer cells, which contain high levels of RAR and , and which express significant amounts of cerbB2 and 3. All transretinoic acid (tRA), the antiestrogen ICI 182 780 (ICI), Forsk and TPA reduced, whereas triiodothyronine and 17estradiol (E₂) stimulated cell growth. Flow cytometry revealed that tRA and E₂ reduced cerbB2 and 3, whereas tamoxifen, Forsk and TPA upregulatedcerbB2. cerbB3 was coregulated with cerbB2. Northern analysis demonstrated that RAR was downregulated by dexamethasone, ICI, and TPA, whereas vitamin D₃ and E₂ upregulated RAR. RAR expression was less responsive to such treatment, being reduced only by ICI and Forsk. These data indicate that nuclear receptor and protein kinase signaling communicate with each other and control the expression of RARs and cerbB receptors. Efficient growth control requires the coordinated interplay of both receptor systems.     

Epidermal growth factor-related peptides in the pathogenesis of human breast cancer

Summary A number of different epidermal growth factor (EGF)-related peptides such as EGF, transforming growth factor (TGF), amphiregulin (AR), heregulin (HRG), and cripto-1 (CR-1), are coexpressed to varying degrees in both normal and malignant mammary epithelial cells. However, in general the frequency and level of expression of TGF, AR, and CR-1 are higher in malignant breast epithelial cells than in normal mammary epithelium. In addition, several of these peptides such as TGF and AR can function as autocrine and/or juxtacrine growth factors in mammary epithelial cells, and their expression is stringently regulated by mammotrophic hormones such as estrogens, activated proto-oncogenes that have been implicated in the pathogenesis of breast cancer, and other growth factors. The redundancy of expression that is observed for a number of these structurally related peptides in both normal and malignant mammary epithelial cells suggests that some of these peptides may be involved in regulating other aspects of cellular behavior such as differentiation in addition to proliferation.     

TGFβ Signaling Pathways and Human Diseases

Recent progress in deciphering the TGF pathway has uncovered a new signaling molecule, the Smads, and with this finding now gives us insights into how TGF-like signals are transmitted from outside the cell to the nucleus. As we learn more about how TGF regulates normal development, we also are gaining insights into diseases that are caused by mis-regulation or mutation of various components of the signaling pathways.     

Analyses of microsatellite instability and the transforming growth factor‐β receptor type II gene mutation in sporadic breast cancer and their correlation with clinicopathological features

To determine the incidence of microsatellite instability (MSI) and its relationship with both clinicopathologic parameters and patient survival, 101 cases of breast cancer were investigated. In addition, transforming growth factor (TGF) receptor type II (RII) gene mutation was also examined to clarify the relation to MSI in breast cancer development. MSI and RII gene mutation were screened by single strand conformation polymorphism (SSCP). The mutations of the RII gene were confirmed by a direct sequence. An association between the MSI status and the clinicopathological features was examined to assess the potential of the MSI status as a prognostic indicator in sporadic breast cancer cases. MSI was detected in 12 of 101 (11.9%) breast cancer cases. The positive MSI breast cancer cases showed relatively more advanced disease than negative MSI cases, and also exhibited relatively poorer prognoses. No RII gene mutations were observed in any of the breast cancer cases. Our data suggest that the MSI status may thus be a useful indicator for the prognosis of sporadic breast cancer cases. However, the breast seems to be an infrequent target organ for cancer development through RII gene mutations. As a result, tumor progression through this pathway appears to be related to organ specificity. For positive MSI breast cancers, other target genes therefore still need to be identified.     

Tissue inhibitor of metalloprotease (TIMP)‐1 and proliferative behaviour of clonal breast cancer cells

In the present paper, we have examined whether human tissue inhibitor of metalloprotease1 (hTIMP1) is able to exert a growth factorlike effect on two clonal cell lines (BC3A and BC61), isolated from a parental line of human breast carcinoma cells (8701BC), and endowed with different growth and invasive behaviour in vitro and in nude mouse. The data obtained indicate that only the more tumorigenic clonal cell line (BC61) is responsive to hTIMP1 treatment by increasing its proliferative rate in a dosedependent manner. It was also found that BC61 cells selectively express a transmembrane protein of about 80kDa able to bind hTIMP1 in vitro and in vivo with high affinity (K_d of 0.07 ± 0.004 nM), and that treatment of BC61 cells with a proliferationpromoting concentration of hTIMP1 is able to stimulate tyrosinetargeted phosphorylation. The cumulative results obtained strongly support the hypothesis that hTIMP1, classically regarded as a collagenase inhibitor, may be a crucial element of the extracellular signalling network during breast cancer development by controlling cell growth phenotype in autocrine and paracrine manner, and that intratumoural heterogeneity for the biological response to TIMP1 may exist within the composite cell population of the primary tumour site.     

Breast tumor-derived factors stimulate reduction of estrone to estradiol in nonmalignant breast tissue

Summary This study examines the paracrine influence by human breast carcinoma cells (UISO-BCA-1) on nonmalignant breast tissuein vitro. The 17-OH-SDH-mediated reductive pathway (estroneestradiol) was significantly increased in nonmalignant breast tissue coincubated with human breast carcinoma cells, compared to control tissues incubated in the media alone. No influence on the enzyme activity was noticed in coincubated breast cancer cells. Preincubation of breast cancer cells with estradiol (10^–8 M) significantly decreased the enzyme activity in coincubated nonmalignant breast tissue, which was restored to control levels by addition of R5020 (10^–8 M), tamoxifen (10^–6 M), or a combination of both. In nonmalignant tissues incubated in the presence of growth factor TGF, enzyme activity was reduced to between 46% and 76%. No other growth factors (IGF I, IGF II, PDGF) influenced enzyme activity. In nonmalignant tissues incubated with malignant tumor cytosol, enzyme activity was increased in 16% cases, inhibited in 21%, and not significantly changed in 63%.The data from the present study suggest that factors produced by breast carcinoma cells may influence interconversion of estradiol in nonmalignant tissue. In patients, factors produced by malignant tumor mass may have paracrine influence on surrounding nonmalignant breast tissue and, thereby, may influence the estrogen availability to tumor mass.     

Differential regulation of normal and tumoral breast epithelial cell growth by fibroblasts and 1,25‐dihydroxyvitamin D3

Mesenchymalepithelial interactions are of paramount importance during normal and tumoral breast developments. We have investigated the paracrine growth regulation of normal and tumoral breast epithelial cells by fibroblasts derived from normal or pathological breast tissues. In some cases, breast cancer MCF7 cells or normal epithelial cells in primary culture were cocultured with fibroblasts in a Transwell system allowing diffusible factor exchanges. Alternatively, conditioned medium produced by fibroblast cultures was added to epithelial cell cultures. Fibroblasts were shown to stimulate the proliferation of normal and carcinoma cells through paracrine mechanisms. However, the paracrine exchanges appeared to be different in normal versus tumoral breast epithelial cell growth regulation. Moreover, vitamin Drelated compounds that have been proposed as antitumoral drugs were studied for their ability to affect normal and tumoral mammary epithelial cell proliferation and to interfere with the growthregulatory activity of fibroblasts. Whereas vitamin D compounds inhibited MCF7 cell growth, they led to a marked stimulation of the proliferation of normal mammary epithelial cells. Moreover, it was shown that the vitamin D analog EB 1089 can block the mitogenic effect of fibroblastconditioned medium on tumoral but not normal breast epithelial cells. The differential effects of vitamin D compounds on cell proliferation provide further data in favor of the different behaviours of normal and tumoral mammary epithelial cells. The potential therapeutic use of vitamin D derivatives in the treatment of breast cancer is supported by these results but their growthstimulatory properties on normal epithelial cells cannot be overlooked.     

Human Astrocytomas Co-expressing Fas and Fas Ligand also Produce TGFβ2 and Bcl-2

Human astrocytomas frequently co-express Fas (APO-1/CD95) and Fas ligand (FasL), yet do not appear to be overly susceptible to suicidal, fratricidal and immune-mediated elimination. This suggests that these gliomas have acquired mechanisms to prevent Fas-mediated apoptosis from occurring. Candidates for such a role include transforming growth factor-(₂ (TGF2) and B-cell lymphoma/leukemia-2 (Bcl-2). TGF2 effectively functions by hiding tumor cells from the immune system. This may potentially prevent the delivery of FasL from cytolytic T cells to Fas bearing astrocytomas. Bcl-2 works by rendering gliomas resistant to Fas-mediated apoptosis. Using immunohistochemistry, we analyzed seventy-six human astrocytomas (11 World Health Organization (WHO) grade I, 17 grade II, 17 grade III, and 31 grade IV) for the expression of Fas, FasL, (TGF₂) and Bcl-2 in vivo. Positive immunoreactivity was found to significantly increase with increasing tumor grade for Fas (p<0.0002), FasL (p<0.0001), TGF2 (p<0.001) and Bcl-2 (p<0.01). In addition, Fas/FasL co-expression, a counter-intuitive combination of factors in regards to glioma survival, also increased with WHO grade. Forty-five of 76 (59%) astrocytomas co-expressed Fas and FasL. Of those co-expressing Fas and FasL, 44 of 45 (98%) produced TGF2, and 26 of 45 (58%) expressed Bcl-2. We found a significant positive correlation between Fas/FasL co-expression and TGF2 (p<0.002) and Bcl-2 (p<0.005) production. We conclude that Fas and FasL are frequently co-expressed in human astrocytomas and these tumors are likely to produce other immunosuppressive and antiapoptotic factors such as TGF2 and Bcl-2.     

TGFβ and Wnt pathway cross-talk

Transforming growth factor-s (TGF) and Wnts represent two distinct families of secreted molecules each of which utilizes different signaling pathways to elicit their biological effects. These factors regulate numerous developmental events and mutations in components of both pathways have been described in human cancers including colorectal carcinomas. Several studies have demonstrated that TGF and Wnt ligands can cooperate to regulate differentiation and cell fate determination by controlling gene expression patterns. In addition, their cooperation in promoting tumorigenesis in mice has been described. Here, we focus on reviewing our current understanding of the molecular mechanisms that may mediate these cooperative effects.     

Adrenal androgens and human breast cancer: A new appraisal

A clearer picture of the role of adrenal androgens in the etiology of breast cancer is beginning to emerge. Women who develop breast cancer in premenopausal years tend to have subnormal serum levels of adrenal androgens, while subjects who develop the disease in postmenopausal years have supranormal levels of these hormones. Androgens, by acting via the androgen receptor, oppose estrogen-stimulated cell growth in premenopausal years. In postmenopausal women, elevated adrenal androgen levels stimulate cell growth by the action of the unique adrenal androgen 5-androstene-3,17-diol, also termed hermaphrodiol, via its combination with the estrogen receptor in a hormone milieu lacking, or having low concentrations of, the classical estrogen 17-estradiol.     

Ligand-Induced Regulation of ERα and ERβ is Indicative of Human Breast Cancer Cell Proliferation

Two estrogen receptors (ER), ER and ER, are expressed in breast cancer but their role in treatment response is unclear. The overall objective of this study was to determine if the presence of ER protein in breast cancer cell lines is an indicator of a poor prognosis based on cell proliferation. In addition, we determined the effect of estradiol (E2) and selective estrogen receptor modulators (SERMs), such as tamoxifen and genistein, on ER and ER protein regulation, to help in the understanding of the mechanism behind their role in modulating cell proliferation. Using western blot and immunofluorescence analysis, the ER positive cell lines, MCF-7 and T47D, were found to contain both ER and ER, and thus were used as model systems. E2 and genistein, which increased cell proliferation in both cell lines, induced an up regulation of ER in both cell lines. This suggests that an estrogenic response in breast cancer cells is indicated by an increase in ER expression. Tamoxifen decreased cell proliferation in both cell lines, while up regulating ER in both cell lines, suggesting that antiestrogenic response is indicated by an increase in ER expression. Although a change in the ER/ER ratio may play a role in the effect seen in cell proliferation, this study indicates that ER is a poor prognosticator of cell proliferation in breast cancer and that ER is a positive prognosticator of responsiveness to antiestrogen treatment.