A Deletion in the Gene for Transforming Growth Factor β Type I Receptor Abolishes Growth Regulation by Transforming Growth Factor β in a Cutaneous T-Cell Lymphoma

Transforming growth factor-beta (TGF-beta)-resistant B cells from chronic lymphocytic leukemia patients contain recurrent mutations in the signal sequence of the type I TGF-beta receptor

B cell chronic lymphocytic leukemia (B-CLL) is the most common leukemia in western societies, and is currently incurable. B cells of some B-CLL patients are resistant to the anti-proliferative effects of transforming growth factor-beta (TGF-beta). Herein, we identified two mutations within the putative signal sequence of TGF-beta type I receptor (TbetaR-I) gene of TGF-beta-resistant B-CLL patients (i.e., a Leu12Gln substitution together with an in-frame single Ala deletion). Although TbetaR-I mutants were expressed to the cell surface and interacted normally with TGF-beta-bound TbetaR-II, their expression significantly reduced gene transcription stimulated by TGF-beta, suggesting a causal relationship in the development of TGF-beta-resistant B-CLL. Screening of additional B-CLL patients solely for the presence of TbetaR-I signal sequence mutations showed that these mutations correlated with and predicted for B-CLL patient insensitivity to TGF-beta. Our results demonstrate that TGF-beta-resistant B-CLL is linked to signal sequence mutations within the TbetaR-I gene, and may eventually be employed as a prognostic indicator in B-CLL.

Secretion of cytokines and growth factors as a general cause of constitutive NFkappaB activation in cancer

The constitutive activation of nuclear factor kappaB (NFkappaB) helps a variety of tumors to resist apoptosis and desensitizes them to chemotherapy, but the causes are still largely unknown. We have analysed this phenomenon in eight mutant cell lines derived from human 293 cells, selected for NFkappaB-dependent expression of a marker gene, and also in seven tumor-derived cell lines. Conditioned media from all of these cells stimulated the activation of NFkappaB (up to 30-fold) in indicator cells carrying an NFkappaB-responsive reporter. Therefore, secretion of extracellular factors as the cause of constitutive activation seems to be general. The mRNAs encoding several different cytokines and growth factors were greatly overexpressed in the tumor and mutant cells. The pattern of overexpression was distinct in each cell line, indicating that the phenomenon is complex. Two secreted factors whose roles in the constitutive activation of NFkappaB are not well defined were investigated further as pure proteins: transforming growth factor beta2 (TGFbeta2) and fibroblast growth factor 5 (FGF5) were both highly expressed in some mutant clones and tumor cell lines, each activated NFkappaB alone, and the combination was synergistic. Our data indicate that a group of different factors, expressed at abnormally high levels, can contribute singly and synergistically to the constitutive activation of NFkappaB in all of the mutant and tumor cell lines we studied. Since several NFkappaB target genes encode secreted proteins that induce NFkappaB, autocrine loops are likely to be ubiquitously important in the constitutive activation of NFkappaB in cancer. We provide the first evidence of the general, complex, and synergistic activation of NFkappaB in tumor and mutant cell lines through the action of secreted factors and suggest that the same explanation is likely for the constitutive activation of NFkappaB in cancers.

Cystatin C Antagonizes Transforming Growth Factor β Signaling in Normal and Cancer Cells

Cystatin C (CystC) is a secreted cysteine protease inhibitor that regulates bone resorption, neutrophil chemotaxis, and tissue inflammation, as well as resistance to bacterial and viral infections. CystC is ubiquitously expressed and present in most bodily fluids where it inhibits the activities of cathepsins, a family of cysteine proteases that can promote cancer cell invasion and metastasis. Transforming growth factor β (TGF-β) is a multifunctional cytokine endowed with both tumor-suppressing and tumor-promoting activities. We show herein that TGF-β treatment up-regulated CystC transcript and protein in murine 3T3-L1 fibroblasts. Moreover, CystC mRNA expression was down-regulated in ∼50% of human malignancies, particularly cancers of the stomach, uterus, colon, and kidney. Overexpression of CystC in human HT1080 fibrosarcoma cells antagonized their invasion through synthetic basement membranes in part via a cathepsin-dependent pathway. Independent of effects on cathepsin activity, CystC also reduced HT1080 cell gene expression stimulated by TGF-β. Invasion of 3T3-L1 cells occurred through both cathepsin- and TGF-β-dependent pathways. Both pathways were blocked by CystC, but only the TGF-β-dependent pathway was blocked by a CystC mutant (i.e., Δ14CystC) that is impaired in its ability to inhibit cathepsin activity. Moreover, CystC and Δ14CystC both inhibited 3T3-L1 cell gene expression stimulated by TGF-β. We further show that CystC antagonized TGF-β binding to its cell surface receptors, doing so by interacting physically with the TGF-β type II receptor and antagonizing its binding of TGF-β. Collectively, our findings have identified CystC as a novel TGF-β receptor antagonist, as well as a novel CystC-mediated feedback loop that inhibits TGF-β signaling.

Concerted effect of transforming growth factor-β, cyclin inhibitor p21, and c-mycon smooth muscle cell proliferation

Increased aortic smooth muscle cell (SMC) proliferation is a key event in the pathogenesis of atherosclerosis. Transforming growth factor-β (TGF-β) is one of the potent inhibitors of SMC proliferation. The purpose of this study was 1) to explore the effect of TGF-β inhibition on proliferation of SMC and expression of growth regulatory molecules like p21 and c- myc and 2) to determine whether restoration of cell cycle regulatory molecules normalizes the altered proliferation. To test the role of TGF-β in SMC proliferation, using antisense plasmid DNA, we inhibited TGF-β gene from aortic SMC, which resulted in a significant increase ( P < 0.03) in proliferation (studied by quantifying new DNA synthesis with [3H]thymidine uptake assay). In TGF-β-altered SMC (TASMC), the mRNA expression (studied by RT-PCR) of c- myc was increased whereas that of the cyclin inhibitor p21 was completely inhibited. Using p21 sense plasmid DNA, we transfected p21 gene in TASMC, which restored p21 mRNA and protein expression and decreased proliferation ( P < 0.002) in TASMC. Similar treatment with c- myc antisense oligonucleotides significantly ( P < 0.001) decreased the proliferation of TASMC. TASMC also exhibited alteration in morphological changes in SMC but returned to normal with treatment of p21 and TGF-β sense plasmid DNA. Two-dimensional gel electrophoresis analysis of SMC and TASMC demonstrated differential expression of proteins relevant to cellular proliferation and atherosclerosis. This study uniquely analyzes the effect of TGF-β at the molecular level on proliferation of SMC and on cell cycle regulatory molecules, implicating their potential role in the pathogenesis of atherosclerosis.

Cutaneous T-cell lymphomas: a review with emphasis on new treatment approaches

Primary cutaneous T-cell lymphomas represent a wide variety of non-Hodgkin lymphomas that are characterized by a distinct clinical presentation. Advanced molecular and biological techniques have enhanced the recognition of cutaneous T-cell lymphomas. The most common subtypes of cutaneous T-cell lymphomas are the epidermotropic variants mycosis fungoides and Sézary syndrome. At present, a stage-adjusted therapy is the best concept available, since early aggressive treatment options did not improve the prognosis of patients with cutaneous T-cell lymphomas. Accurate diagnostic and clinical assessment as well as identification of prognostic factors provides a helpful basis for treatment strategies. Current medical literature on diagnosis, prognosis, and treatment is reviewed with emphasis on new biologic response-modifying treatment options.

Primary cutaneous CD30-positive lymphoproliferative disorders

Primary cutaneous CD30-positive (anaplastic) large T-cell lymphoma and lymphomatoid papulosis have many overlapping clinical, histologic, and immunophenotypic features. These entities are currently considered as parts of a spectrum of primary cutaneous CD30-positive lymphoproliferative disorders. We provide the clinician with practical guidelines for the diagnosis, management, and treatment of patients within this spectrum of primary cutaneous CD30-positive lymphoproliferative disorders. Most patients within this spectrum of disease have an excellent prognosis. Multi-agent chemotherapy should be reserved for patients who have extracutaneous disease.

Primary cutaneous lymphomas: a review with current treatment options

Primary cutaneous T- and B-cell lymphomas are a heterogenous group of diseases with varied clinical presentations and prognosis. The use of new molecular, histological, and clinical criteria have enhanced the recognition of primary cutaneous T- and B-cell lymphomas. Compared to their nodal counterpart they have a different clinical behavior and therefore require a different treatment approach. Independent predictive factors identified clinically, histologically, and by immunopheno- and immunogenotyping are essential to assess the appropriate treatment for each subtype. The European Organization for Research and Treatment of Cancer (EORTC) Cutaneous Lymphoma Study Group provide a classification of cutaneous lymphomas taking into account of the histological and molecular features. Based on this classification we will provide a summary of the current medical literature in diagnosis, treatment, and prognosis for primary cutaneous lymphomas with emphasis on new treatment strategies.

Transforming growth factor-beta signaling in normal and malignant hematopoiesis

Transforming growth factor-beta (TGF-beta) is perhaps the most potent endogenous negative regulator of hematopoiesis. The intracellular signaling events mediating the effects of TGF-beta are multiple, involving extensive crosstalk between Smad-dependent and MAP-kinase-dependent pathways. We are only beginning to understand the importance of the balance between these cascades as a determinant of the response to TGF-beta, and have yet to determine the roles that disruption in TGF-beta signaling pathways might play in leukemogenesis. This review summarizes current knowledge regarding the function of TGF-beta in normal and malignant hematopoiesis. The principal observations made by gene targeting studies in mice are reviewed, with an emphasis on how a disruption of this pathway in vivo can affect blood cell development and immune homeostasis. We overview genetic alterations that lead to impaired TGF-beta signaling in hematopoietic neoplasms, including the suppression of Smad-dependent transcriptional responses by oncoproteins such as Tax and Evi-1, and fusion proteins such as AML1/ETO. We also consider mutations in genes encoding components of the core cell cycle machinery, such as p27(Kip1) and p15(INK4A), and emphasize their impact on the ability of TGF-beta to induce G1 arrest. The implications of these observations are discussed, and opinions regarding important directions for future research on TGF-beta in hematopoiesis are provided.

SPARC inhibits epithelial cell proliferation in part through stimulation of the transforming growth factor-beta-signaling system

Secreted protein, acidic and rich in cysteine (SPARC) is a multifunctional secreted protein that regulates cell-cell and cell-matrix interactions, leading to alterations in cell adhesion, motility, and proliferation. Although SPARC is expressed in epithelial cells, its ability to regulate epithelial cell growth remains largely unknown. We show herein that SPARC strongly inhibited DNA synthesis in transforming growth factor (TGF)-beta-sensitive Mv1Lu cells, whereas moderately inhibiting that in TGF-beta-insensitive Mv1Lu cells (i.e., R1B cells). Overexpression of dominant-negative Smad3 in Mv1Lu cells, which abrogated growth arrest by TGF-beta, also attenuated growth arrest stimulated by SPARC. Moreover, the extracellular calcium-binding domain of SPARC (i.e., SPARC-EC) was sufficient to inhibit Mv1Lu cell proliferation but not that of R1B cells. Similar to TGF-beta and thrombospondin-1, treatment of Mv1Lu cells with SPARC or SPARC-EC stimulated Smad2 phosphorylation and Smad2/3 nuclear translocation: the latter response to all agonists was abrogated in R1B cells or by pretreatment of Mv1Lu cells with neutralizing TGF-beta antibodies. SPARC also stimulated Smad2 phosphorylation in MB114 endothelial cells but had no effect on bone morphogenetic protein-regulated Smad1 phosphorylation in either Mv1Lu or MB114 cells. Finally, SPARC and SPARC-EC stimulated TGF-beta-responsive reporter gene expression through a TGF-beta receptor- and Smad2/3-dependent pathway in Mv1Lu cells. Collectively, our findings identify a novel mechanism whereby SPARC inhibits epithelial cell proliferation by selectively commandeering the TGF-beta signaling system, doing so through coupling of SPARC-EC to a TGF-beta receptor- and Smad2/3-dependent pathway.

Mutational analysis of the transforming growth factor beta receptor type I gene in primary non-small cell lung cancer

Transforming growth factor-beta receptor-dependent signals are critical for cell growth and differentiation and are often disrupted during tumorigenesis. The entire coding region of TGFbetaRI and flanking intron sequences from 53 primary non-small cell lung cancer (NSCLC) tissues were examined for alterations using SSCP and direct sequencing. No somatic point mutations other than two silent mutations and a polymorphism were found in the TGFbetaRI gene. The two silent mutations located at codon 344 (AAT to AAC) and codon 406 (TTA to CTA), respectively, and the polymorphism was at the 24th base of intron 7 (G to A). To investigate whether the presence of this polymorphism is associated with NSCLC, we determined its allele distribution in all the 53 carcinomas and 89 normal controls. Interestingly, we found that the subjects with homozygous genotype A/A displayed more than 3-fold increased risk of developing NSCLC than the common wild genotype G/G. As the first report, the present study showed that TGFbetaRI gene is not a frequent site of spontaneous mutational inactivation while the detected polymorphism is frequent in the pathogenesis of NSCLC.

T cell receptor-gamma gene analysis of CD30+ large atypical individual cells in CD30+ large primary cutaneous T cell lymphomas

The hallmark of primary cutaneous CD30+ large T cell lymphoma are large lymphoid tumor cells, at least 75% of which, by definition, must be positive for CD30. The relatively benign clinical course of this lymphoma type has been explained with CD30-induced apoptosis, on the assumption that expression of CD30 defines the tumor clone; however, this hypothesis has not been tested on the molecular level to date. In this study we analyzed CD30+ cells in four patients with primary cutaneous CD30+ large T cell lymphoma by single cell polymerase chain reaction of T cell receptor-gamma genes followed by sequencing. Here, we demonstrate that most of the large CD30+ atypical cells possessed identical T cell receptor-gamma gene rearrangements, indicative of clonal proliferation. Nevertheless, polyclonally rearranged T cells were present in all CD30+ samples studied. In addition, one patient showed a second clone in a separate biopsy and three of four patients showed chromosomal imbalances as revealed by comparative genomic hybridization. Taken together, our data suggest that the CD30+ population in primary cutaneous CD30+ large T cell lymphoma indeed contains the tumor clone, thus providing molecular support for a link between clinical course and CD30-related signaling. Importantly, however, CD30 expression does not define the tumor clone as bystander T cells, as well as occasional additional clones, are also present in this population.

Decreased expression of TGF-beta type 2 receptor in primary B-cell lymphomas of the stomach

TGF-beta insensitivity has been reported in some malignant lymphomas showing loss of TGF-beta receptor expression. This loss of TGF-beta sensitivity is thought to have removed the immunosuppressive properties of TGF-beta, thus enhancing cell proliferation and resulting in the development of malignant lymphoma. In this study, we performed immunohistochemical stains for TGF-beta1, TGF-beta RI and TGF-beta RII in primary gastric B-cell lymphomas in order to ascertain their possible roles in lymphomagenesis. A total of twenty cases of gastric lymphoma were included. All cases of low- and high-grade lymphomas were negative or weakly positive for TGF-beta1. Reactive lymphoid cells, including the germinal center, were also negative for TGF-beta1. In contrast, reactive germinal centers showed moderate to strong cytoplasmic or membranous staining for TGF-beta RI and TGF-beta RII. In malignant lymphomas, TGF-beta RI expression was maintained in all cases of low- and high-grade lymphomas. In contrast, TGF-beta RII expression was decreased in all low- and high-grade lymphoma cells. These findings suggest that the loss of TGF-beta RII expression may be involved in the lymphomagenesis of the stomach.

Human T-cell lymphotropic virus oncoprotein Tax represses TGF-beta 1 signaling in human T cells via c-Jun activation: a potential mechanism of HTLV-I leukemogenesis

Human T-cell leukemia virus I is the etiologic agent of adult T-cell leukemia (ATL), an aggressive T-cell malignancy. The viral oncoprotein Tax, through the activation of nuclear factorkappaB (NF-kappaB), CCAAT-enhancer binding protein (CREB), and activated protein-1 (AP-1) pathways, is a transcriptional regulator of critical genes for T-cell homeostasis. In ATL cells, activated AP-1 complexes induce the production of transforming growth factor beta1 (TGF-beta1). TGF-beta1 is an inhibitor of T-cell proliferation and cytotoxicity. Here we show that, in contrast to normal peripheral T cells, ATL cells are resistant to TGF-beta1-induced growth inhibition. The retroviral transduction of the Tax protein in peripheral T cells resulted in the loss of TGF-beta1 sensitivity. Transient transfection of Tax in HepG2 cells specifically inhibited Smad/TGF-beta1 signaling in a dose-dependent manner. In the presence of Tax transfection, increasing amounts of Smad3 restored TGF-beta1 signaling. Tax mutants unable to activate NF-kappaB or CREB pathways were also able to repress Smad3 transcriptional activity. Next we have demonstrated that Tax inhibits TGF-beta1 signaling by reducing the Smad3 DNA binding activity. However, Tax did not decrease the expression and the nuclear translocation of Smad3 nor did it interact physically with Smad3. Rather, Tax induced c-Jun N-terminal kinase (JNK) activity and c-Jun phosphorylation, leading to the formation of Smad3/c-Jun complexes. Whereas c-Jun alone abrogates Smad3 DNA binding, cotransfection of Tax and of a dominant-negative form of JNK or a c-Jun antisense-restored Smad3 DNA binding activity and TGF-beta1 responsiveness. In ATL and in normal T cells transduced by Tax, c-Jun was constitutively phosphorylated. Thus, we describe a new function of Tax, as a repressor of TGF-beta1 signaling through JNK/c-Jun constitutive activation, which may play a critical role in ATL leukemogenesis.

Context-specific effects of fibulin-5 (DANCE/EVEC) on cell proliferation, motility, and invasion. Fibulin-5 is induced by transforming growth factor-beta and affects protein kinase cascades

Fibulin-5 (FBLN-5; also known as DANCE or EVEC) is an integrin-binding extracellular matrix protein that mediates endothelial cell adhesion; it is also a calcium-dependent elastin-binding protein that scaffolds cells to elastic fibers, thereby preventing elastinopathy in the skin, lung, and vasculature. Transforming growth factor-beta (TGF-beta) regulates the production of cytokines, growth factors, and extracellular matrix proteins by a variety of cell types and tissues. We show here that TGF-beta stimulates murine 3T3-L1 fibroblasts to synthesize FBLN-5 transcript and protein through a Smad3-independent pathway. Overexpression of FBLN-5 in 3T3-L1 cells increased DNA synthesis and enhanced basal and TGF-beta-stimulated activation of ERK1/ERK2 and p38 mitogen-activated protein kinase (MAPK). FBLN-5 overexpression also augmented the tumorigenicity of human HT1080 fibrosarcoma cells by increasing their DNA synthesis, migration toward fibronectin, and invasion through synthetic basement membranes. In stark contrast, FBLN-5 expression was down-regulated in the majority of metastatic human malignancies, particularly in cancers of the kidney, breast, ovary, and colon. Unlike its proliferative response in fibroblasts, FBLN-5 overexpression in mink lung Mv1Lu epithelial cells resulted in an antiproliferative response, reducing their DNA synthesis and cyclin A expression. Moreover, FBLN-5 synergizes with TGF-beta in stimulating AP-1 activity in Mv1Lu cells, an effect that was abrogated by overexpression of dominant-negative versions of either MKK1 or p38 MAPKalpha. Accordingly, both the stimulation and duration of ERK1/ERK2 and p38 MAPK by TGF-beta was enhanced in Mv1Lu cells expressing FBLN-5. Our findings identify FBLN-5 as a novel TGF-beta-inducible target gene that regulates cell growth and motility in a context-specific manner and affects protein kinase activation by TGF-beta. Our findings also indicate that aberrant FBLN-5 expression likely contributes to tumor development in humans.

Single-cell analysis of CD30+ cells in lymphomatoid papulosis demonstrates a common clonal T-cell origin

Lymphomatoid papulosis (LyP) represents an intriguing cutaneous T-cell lymphoproliferative disorder with a histologic appearance resembling malignant lymphoma. This finding strongly contrasts with the benign clinical course of the disease. However, in 10% to 20% of cases, LyP can precede, coexist with, or follow malignant lymphoma. In these cases, the same T-cell population has been shown to be present in the LyP as well as in the associated lymphoma. In most LyP cases, there is-despite the sometimes extremely long course of the disease-no evolution of a secondary lymphoma. The investigation of these uncomplicated LyP cases for the presence of clonal T-cell receptor rearrangements has produced heterogeneous results. This might be explained by biologic or technical reasons arising from analyzing whole tissue DNA extracts. To definitively clarify whether the large atypical CD30(+) cells in LyP without associated lymphoma all belong to the same clone or represent individually rearranged T cells, we analyzed the T-cell receptor-gamma rearrangements of single CD30+ as well as of single CD30- cells isolated from 14 LyP lesions of 11 patients. By using this approach we could demonstrate that the CD30+ cells represent members of a single T-cell clone in all LyP cases. Moreover, in 3 patients the same CD30+ cell clone was found in anatomically and temporally separate lesions. In contrast, with only a few exceptions, the CD30- cells were polyclonal in all instances and unrelated to the CD30+ cell clone. Our results demonstrate that LyP unequivocally represents a monoclonal T-cell disorder of CD30+ cells in all instances.

TGF-beta signaling in tumor suppression and cancer progression

Epithelial and hematopoietic cells have a high turnover and their progenitor cells divide continuously, making them prime targets for genetic and epigenetic changes that lead to cell transformation and tumorigenesis. The consequent changes in cell behavior and responsiveness result not only from genetic alterations such as activation of oncogenes or inactivation of tumor suppressor genes, but also from altered production of, or responsiveness to, stimulatory or inhibitory growth and differentiation factors. Among these, transforming growth factor beta (TGF-beta) and its signaling effectors act as key determinants of carcinoma cell behavior. The autocrine and paracrine effects of TGF-beta on tumor cells and the tumor micro-environment exert both positive and negative influences on cancer development. Accordingly, the TGF-beta signaling pathway has been considered as both a tumor suppressor pathway and a promoter of tumor progression and invasion. Here we evaluate the role of TGF-beta in tumor development and attempt to reconcile the positive and negative effects of TGF-beta in carcinogenesis.

Allelic loss on chromosome 4 (Lyr2/TLSR5) is associated with myeloid, B-lympho-myeloid, and lymphoid (B and T) mouse radiation-induced leukemias

The CBA/H mouse model of radiation-induced acute myeloid leukemia (AML) was re-examined using molecular approaches. In addition to the typical promyelocytic AMLs, 34% were reclassified as early pre-B lympho-myeloid leukemias (L-ML) based on leukemic blood cell morphology, immunoglobulin heavy-chain gene re-arrangements (IgH(R)), or expression of both lymphoid (Vpre-B1 and Rag1) and myeloid (myeloperoxidase and lysozyme M) genes. Allelic loss on chromosome 4 was frequently detected in AMLs (53%) and L-MLs (more than 95%), and the preferential loss of the maternally transmitted allele suggests the locus may be imprinted. A minimally deleted region (MDR) maps to a 3.4-cM interval, which is frequently deleted in radiation-induced thymic lymphomas (TLSR5) and contains a recessive, maternally transmitted genetic locus (Lyr2) that confers resistance to spontaneous and radiation-induced pre-B and T cell lymphomas, suggesting they are one and the same. Thus, the Lyr2/TLSR5 locus is frequently implicated in myeloid, lymphoid (B and T), and mixed-lineage mouse leukemias and lymphomas. Epigenetic inactivation of one Lyr2/TLSR5 allele during normal mouse development suggests that only a single hit is required for its inactivation during leukemogenesis, and this may be a significant contributing factor to the efficiency of the leukemogenic process in the mouse.

Novel inactivating mutations of transforming growth factor-beta type I receptor gene in head-and-neck cancer metastases

Carcinoma cell lines are frequently refractory to transforming growth factor-beta (TGF beta)-mediated cell cycle arrest. Whether and how TGF beta signaling is disrupted in the majority of human tumors, however, remains unclear. To investigate whether TGF beta signaling might be disrupted by inactivation of the key signaling molecule, the TGF beta type I (T beta R-I) receptor, and whether or not T beta R-I inactivation is associated with late stage disease, we conducted a comprehensive structural analysis of the T beta R-I gene in fine-needle aspirates of 23 head-&-neck cancer metastases. We encountered 4 different mutations of T beta R-I, 3 of which have not been previously identified. In 1 case, we found a somatic intragenic 4-bp deletion predicting for a truncation of the receptor protein. This is the first example of a true loss-of-function mutation of T beta R-I in a human epithelial neoplasm. In 2 other cases, we identified missense mutations located between the juxtamembrane- and serine-threonine kinase domains. One of these resulted in an alanine-to-threonine substitution (A230T), which disrupts receptor signaling activity by causing rapid protein degradation within the endoplasmatic reticulum. This represents a novel mechanism of inactivation of a TGF beta signaling intermediate. Finally, we identified a serine-to-tyrosine substitution at codon 387 (S387Y) in a metastasis but not in the corresponding primary tumor. We had previously shown this S387Y mutant to be predominantly associated with breast cancer metastases and to have a diminished ability to mediate TGF beta-dependent signaling. In aggregate, these findings provide further support for the hypothesis that inactivation of the TGF beta signaling pathway occurs in a significant subset of human cancers.

Progression of lymphomatoid papulosis to systemic lymphoma is associated with escape from growth inhibition by transforming growth factor-beta and CD30 ligand

Our objective is to understand the mechanism of progression of lymphomatoid papulosis (LyP) to CD30+ systemic lymphoma. LyP lesions appear in recurrent crops that regress, only to reappear at a later date in the same or different locations. About 10% of patients develop systemic lymphoma. Because transforming growth factor-beta (TGF-beta) and CD30 ligand inhibit the growth of normal lymphocytes and can be detected in regressing lesions of LyP, we tested the effect of these cytokines on cell lines clonally derived from LyP in the progression to systemic lymphoma. TGF-beta failed to inhibit the growth of lymphoma cells from advanced disease due to mutations of the TGF-beta receptor complex that prevented binding of the ligand to tumor cells. A CD30 ligand agonist antibody caused proliferation of tumor cells from one patient and had no effect on tumor cells of another. In contrast, a Fas agonist antibody caused significant growth inhibition of all cell lines. The results suggest that progression of LyP to lymphoma is associated with escape of lymphoma cells from growth regulation by TGF-beta and CD30 ligand.

Analysis of loss of heterozygosity in lymphoma and leukaemia arising in F1 hybrid mice locates a common region of chromosome 4 loss

Previous studies have identified five lymphoma-related tumour suppressor gene regions on murine chromosome 4. Using detailed allelotype analysis on a range of lympho-haematopoietic tumour types arising in F1 hybrid mice, we now show a consistent pattern of loss of heterozygosity (LOH) which identifies a common region of loss delineated by microsatellites D4Mit21 and D4Mit53 on proximal chromosome 4. This critical segment corresponds to the thymic lymphoma tumour suppressor region 5 (TLSR5) identified in an earlier study. Tumours of this type have also been reported as showing allelic loss from the Trp53 and Ikaros regions on chromosome 11. In the present study, only a small fraction of tumours showed LOH in the Ikaros region, while a minority of lymphomas, but not acute myeloid leukaemias, showed allelic loss of the chromosome 11 segment encoding Trp53. These and other data indicate strongly that the genomic regions identified as showing recurrent LOH depend on the genetic background of the mice. Overall, the results indicate a key role for a tumour suppressor gene(s) encoded in an approximately 3 cM segment on proximal chromosome 4 and provide an experimental basis for the further investigation of the functional role of candidate genes which include Pax5 and Tgfbr1.

Transforming growth factor-beta signal transduction in epithelial cells

Transforming growth factor (TGF)-beta is a natural and potent growth inhibitor of a variety of cell types, including epithelial, endothelial, and hematopoietic cells. The ability of TGF-beta to potently inhibit the growth of many solid tumors of epithelial origin, including breast and colon carcinomas, is of particular interest. However, many solid tumor cells become refractory to the growth inhibitory effects of TGF-beta due to defects in TGF-beta signaling pathways. In addition, TGF-beta may stimulate the invasiveness of tumor cells via the paracrine effects of TGF-beta. Accordingly, in order to develop more effective anticancer therapeutics, it is necessary to determine the TGF-beta signal transduction pathways underlying the growth inhibitory effects and other cellular effects of TGF-beta in normal epithelial cells. Thus far, two primary signaling cascades downstream of the TGF-beta receptors have been elucidated, the Sma and mothers against decapentaplegic homologues and the Ras/mitogen-activated protein kinase pathways. The major objective of this review is to summarize TGF-beta signaling in epithelial cells, focusing on recent advances involving the Sma and mothers against decapentaplegic homologues and Ras/mitogen-activated protein kinase pathways. This review is particularly timely in that it provides a comprehensive summary of both signal transduction mechanisms and the cell cycle effects of TGF-beta.

Divergence and convergence of TGF-beta/BMP signaling

The transforming growth factor-beta (TGF-beta) superfamily includes more than 30 members which have a broad array of biological activities. TGF-beta superfamily ligands bind to type II and type I serine/threonine kinase receptors and transduce signals via Smad proteins. Receptor-regulated Smads (R-Smads) can be classified into two subclasses, i.e. those activated by activin and TGF-beta signaling pathways (AR-Smads), and those activated by bone morphogenetic protein (BMP) pathways (BR-Smads). The numbers of type II and type I receptors and Smad proteins are limited. Thus, signaling of the TGF-beta superfamily converges at the receptor and Smad levels. In the intracellular signaling pathways, Smads interact with various partner proteins and thereby exhibit a wide variety of biological activities. Moreover, signaling by Smads is modulated by various other signaling pathways allowing TGF-beta superfamily ligands to elicit diverse effects on target cells. Perturbations of the TGF-beta/BMP signaling pathways result in various clinical disorders including cancers, vascular diseases, and bone disorders.

Role of transforming growth factor beta in cancer

Transforming growth factor beta (TGF-beta) is an effective and ubiquitous mediator of cell growth. The significance of this cytokine in cancer susceptibility, cancer development and progression has become apparent over the past few years. TGF-beta plays various roles in the process of malignant progression. It is a potent inhibitor of normal stromal, hematopoietic, and epithelial cell growth. However, at some point during cancer development the majority of transformed cells become either partly or completely resistant to TGF-beta growth inhibition. There is growing evidence that in the later stages of cancer development TGF-beta is actively secreted by tumor cells and not merely acts as a bystander but rather contributes to cell growth, invasion, and metastasis and decreases host-tumor immune responses. Subtle alteration of TGF-beta signaling may also contribute to the development of cancer. These various effects are tissue and tumor dependent. Identifying and understanding TGF-beta signaling pathway abnormalities in various malignancies is a promising avenue of study that may yield new modalities to both prevent and treat cancer. The nature, prevalence, and significance of TGF-beta signaling pathway alterations in various forms of human cancer as well as potential preventive and therapeutic interventions are discussed in this review.

Transforming growth factor-beta signaling in cancer

Transforming growth factor (TGF-beta) is a multifunctional polypeptide implicated in the regulation of a variety of cellular processes including growth, differentiation, apoptosis, adhesion, and motility. Abnormal activation or inhibition of these TGF-beta regulated processes is implicated in many diseases, including cancer. Cancers can develop through selective exploitation of defects in TGF-beta signaling that occur at several different levels in the pathway. The TGF-beta signal transduction cascade is initiated when TGF-beta binds to transmembrane receptors. The TGF-beta receptors then phosphorylate and activate Smad proteins, which transduce the signal from the cytoplasm to the nucleus. In the nucleus, Smads can bind directly to DNA and cooperate with other transcription factors to induce transcription of TGF-beta target genes. Mutations in target genes, Smads, or the TGF-beta receptor are associated with certain human cancers.

Role of transforming growth factor beta in cancer

Transforming growth factor beta (TGF-beta) is an effective and ubiquitous mediator of cell growth. The significance of this cytokine in cancer susceptibility, cancer development and progression has become apparent over the past few years. TGF-beta plays various roles in the process of malignant progression. It is a potent inhibitor of normal stromal, hematopoietic, and epithelial cell growth. However, at some point during cancer development the majority of transformed cells become either partly or completely resistant to TGF-beta growth inhibition. There is growing evidence that in the later stages of cancer development TGF-beta is actively secreted by tumor cells and not merely acts as a bystander but rather contributes to cell growth, invasion, and metastasis and decreases host-tumor immune responses. Subtle alteration of TGF-beta signaling may also contribute to the development of cancer. These various effects are tissue and tumor dependent. Identifying and understanding TGF-beta signaling pathway abnormalities in various malignancies is a promising avenue of study that may yield new modalities to both prevent and treat cancer. The nature, prevalence, and significance of TGF-beta signaling pathway alterations in various forms of human cancer as well as potential preventive and therapeutic interventions are discussed in this review.

Lymphomatoid papulosis and human herpesviruses--A PCR-based evaluation for the presence of human herpesvirus 6, 7 and 8 related herpesviruses

BACKGROUND

Lymphomatoid papulosis (LyP) is a chronic, recurrent lymphoproliferative disorder of the skin that belongs to the group of primary cutaneous CD30-positive T-cell lymphomas. Ultrastructural and clinical features of LyP suggest that it has a viral etiology. Human herpesviruses have been proposed as causative cofactors for LyP because of their oncogenic potential and their association with other lymphomas.

METHODS

LyP skin lesions and a LyP-derived cell line were examined for the presence of the recently discovered oncogenic human herpesvirus 8 (HHV-8) and the two T-lymphotropic human herpesviruses 6 and 7 (HHV-6 and HHV-7) by nested polymerase chain reaction (PCR) using virus-specific oligonucleotide primers. Furthermore, a recently described method involving degenerate PCR primers was applied to detect highly conserved DNA sequences shared by a variety of herpesviruses, especially oncogenic gamma-herpesviruses, in an attempt to identify a yet undiscovered herpesvirus associated with LyP.

RESULTS

HHV-6 and 8 could not be found in 26 archival and 11 snap-frozen LyP lesions and a LyP tumor cell line. HHV-7 DNA sequences were detected in 14% (5 of 37) of LyP samples. HHV-6 was found in 23% (3 of 13) and HHV-7 in 8% (1 of 13) of normal skin samples from healthy individuals, respectively. Using degenerate PCR primers to amplify the highly conserved polymerase region of herpesviruses, no DNA sequences related to human herpesviruses could be detected.

CONCLUSIONS

LyP is not associated with HHV-6, HHV-7 and HHV-8. In addition, the studies using degenerate PCR primers do not indicate the presence of a previously undescribed human herpesvirus in LyP.

Distinct effects of CD30 and Fas signaling in cutaneous anaplastic lymphomas: a possible mechanism for disease progression

Lymphomatoid papulosis is part of a spectrum of CD30+ cutaneous lymphoproliferative disorders characterized by spontaneous tumor regression. The mechanism(s) of regression is unknown. In a recent study, a selective increase in CD30 ligand expression in regressing lesions of lymphomatoid papulosis and cutaneous CD30+ anaplastic large cell lymphoma was shown, suggesting that activation of the CD30 signaling pathway may be responsible for tumor regression, whereas no difference in Fas/Fas ligand expression was found between regressing and nonregressing lesions. Therefore we tested the effects of CD30 and Fas activation on three CD30+ cutaneous lymphoma cell lines (Mac-1, Mac-2 A, JK) derived from nonregressing tumors of two patients who had progressed from lymphomatoid papulosis to systemic anaplastic large cell lymphoma. To evaluate the effects of CD30 signaling, the cell lines were incubated with a CD30 agonistic antibody, HeFi-1. Proliferative responses, mitogen-activated protein kinase, and nuclear factor kappa B activities were determined with and without CD30 activation. Mac-1 and Mac-2 A showed increased proliferative responses to incubation with CD30 activating antibody, HeFi-1. Inhibition of the mitogen-activated protein kinase activity caused growth inhibition of the Mac-1, Mac-2 A, and JK cell lines. Activation of the Fas pathway induced apoptosis in all three cell lines. Taken together, these findings suggest that resistance to CD30-mediated growth inhibition provides a possible mechanism for escape of cutaneous anaplastic large cell lymphoma from tumor regression. Mitogen-activated protein kinase inhibitors are potential therapeutic agents for the treatment of advanced cutaneous anaplastic large cell lymphoma. J Invest Dermatol 115:1034-1040, 2000

Disruption of TGF-beta growth inhibition by oncogenic ras is linked to p27Kip1 mislocalization

Expression of oncogenic Ras in epithelial tumor cells is linked to the loss of transforming growth factor-beta (TGF-beta) anti-proliferative activity, and was proposed to involve inhibition of Smad2/3 nuclear translocation. Here we studied several epithelial cell lines expressing oncogenic N-RasK61 and show that TGF-beta-induced nuclear translocation of and transcriptional activation by Smad2/3 were unaffected. In contrast, oncogenic Ras mediated nuclearto-cytoplasmic mislocalization of p27KiP1 (p27) and of the cyclin-dependent kinase (CDK) CDK6, but not CDK2. Concomitantly, oncogenic Ras abrogated the ability of TGF-beta to release p27 from CDK6, to enhance its binding to CDK2 and to inhibit CDK2 activity. Inactivation of Ras by a specific antagonist restored the growth inhibitory response to TGF-beta with concurrent normalization of p27 and CDK6 localization. Therefore, the disruption of TGF-beta-mediated growth inhibition by oncogenic Ras appears to be due to lack of inhibition of CDK2, caused by the sequestration of p27 and CDK2 in different subcellular compartments and by the loss of TGF-beta-induced partner switching of p27 from CDK6 to CDK2.

Transforming growth factor-β: pleiotropic role in the regulation of hematopoiesis

Hematopoiesis is a remarkable cell-renewal process that leads to the continuous generation of large numbers of multiple mature cell types, starting from a relatively small stem cell compartment. A highly complex but efficient regulatory network is necessary to tightly control this production and to maintain the hematopoietic tissue in homeostasis. During the last 3 decades, constantly growing numbers of molecules involved in this regulation have been identified. They include soluble cytokines and growth factors, cell–cell interaction molecules, and extracellular matrix components, which provide a multifunctional scaffolding specific for each tissue. The cloning of numerous growth factors and their mass production have led to their possible use for both fundamental research and clinical application.

Transforming growth factor-β: pleiotropic role in the regulation of hematopoiesis

Hematopoiesis is a remarkable cell-renewal process that leads to the continuous generation of large numbers of multiple mature cell types, starting from a relatively small stem cell compartment. A highly complex but efficient regulatory network is necessary to tightly control this production and to maintain the hematopoietic tissue in homeostasis. During the last 3 decades, constantly growing numbers of molecules involved in this regulation have been identified. They include soluble cytokines and growth factors, cell–cell interaction molecules, and extracellular matrix components, which provide a multifunctional scaffolding specific for each tissue. The cloning of numerous growth factors and their mass production have led to their possible use for both fundamental research and clinical application.

Primary cutaneous lymphomas

Primary cutaneous lymphomas have a distinct clinical behavior and prognosis, and therefore require a different therapeutic approach, as compared with their primary nodal equivalents. The European Organization for Research and Treatment of Cancer (EORTC) classification for primary cutaneous lymphomas recognizes a limited number of cutaneous T-cell lymphomas and cutaneous B-cell lymphomas and is at present the best guide to optimal management and treatment of these conditions. Herein, the relationship between the EORTC classification and the recently published World Health Organization classification is discussed, and recent developments regarding the main types of cutaneous T-cell lymphomas and cutaneous B-cell lymphomas recognized in the EORTC classification are presented.

Transforming growth factor-beta and breast cancer: Transforming growth factor-beta/SMAD signaling defects and cancer

Transforming growth factor-beta (TGF-beta) is a tumor suppressor, the function of which is compromised in many types of human cancer, including breast cancer. The tumor suppressive effects of TGF-beta are caused by potent inhibition of cell proliferation due to cell cycle arrest in the G1 phase. Such antiproliferative responses are mediated by a signaling system that includes two types of cell surface receptors and intracellular signal transducers, the SMAD proteins. Different molecular mechanisms can lead to loss of antiproliferative TGF-beta responses in tumor cells, including mutations in components of the signaling system and inhibition of the SMAD signaling pathway by aberrant activities of various regulatory molecules. Some of these mechanisms will be discussed, with emphasis on their potential involvement in breast tumorigenesis.