Transforming growth factor-beta expression in mouse lung carcinogenesis

Transforming growth factor-β3 (TGF-β3) knock-in ameliorates inflammation due to TGF-β1 deficiency while promoting glucose tolerance

Three homologues of TGF-β exist in mammals as follows: TGF-β1, TGF-β2, and TGF-β3. All three proteins share high homology in their amino acid sequence, yet each TGF-β isoform has unique heterologous motifs that are highly conserved during evolution. Although these TGF-β proteins share similar properties in vitro, isoform-specific properties have been suggested through in vivo studies and by the unique phenotypes for each TGF-β knock-out mouse. To test our hypothesis that each of these homologues has nonredundant functions, and to identify such isoform-specific roles, we genetically exchanged the coding sequence of the mature TGF-β1 ligand with a sequence from TGF-β3 using targeted recombination to create chimeric TGF-β1/3 knock-in mice (TGF-β1(Lβ3/Lβ3)). In the TGF-β1(Lβ3/Lβ3) mouse, localization and activation still occur through the TGF-β1 latent associated peptide, but cell signaling is triggered through the TGF-β3 ligand that binds to TGF-β receptors. Unlike TGF-β1(-/-) mice, the TGF-β1(Lβ3/Lβ3) mice show neither embryonic lethality nor signs of multifocal inflammation, demonstrating that knock-in of the TGF-β3 ligand can prevent the vasculogenesis defects and autoimmunity associated with TGF-β1 deficiency. However, the TGF-β1(Lβ3/Lβ3) mice have a shortened life span and display tooth and bone defects, indicating that the TGF-β homologues are not completely interchangeable. Remarkably, the TGF-β1(Lβ3/Lβ3) mice display an improved metabolic phenotype with reduced body weight gain and enhanced glucose tolerance by induction of beneficial changes to the white adipose tissue compartment. These findings reveal both redundant and unique nonoverlapping functional diversity in TGF-β isoform signaling that has relevance to the design of therapeutics aimed at targeting the TGF-β pathway in human disease.

Thymosin alpha1 as a chemopreventive agent in lung and breast cancer

The ability of thymosin alpha1 (Talpha1) to prevent lung and breast cancer was investigated. Lung adenomas developed in A/J mice injected with carcinogens, such as urethane. The lung adenoma number was reduced by 15-45% if animals were daily treated subcutaneously (s.c.) with Talpha1 (0.4 mg/kg). Talpha1 (1 microM) directly inhibited the growth of mouse lung cell lines. These results suggest that Talpha1 may prevent mouse lung carcinogenesis because it directly inhibits the growth of lung cancer cells. Talpha1 prevented mammary carcinogenesis in two animal models. In the Fisher rat, an animal model of mammary cancer that is estrogen receptor dependent, tumors were initiated by the injection of N-methylurea (NMU). The rat survival was significantly increased by the daily injection of Talpha1. In the SV40T antigen mouse, a transgenic female mouse that spontaneously gets mammary cancer in an estrogen receptor-independent manner, survival was increased and tumor burden was significantly decreased by daily injection of Talpha1. These results indicate that Talpha1 is a chemopreventive agent in animal models for lung and breast carcinogenesis.

Transforming growth factor-beta in cancer and metastasis

Transforming growth factor-beta (TGF-beta) is a multifunctional regulatory polypeptide that is the prototypical member of a large family of cytokines that controls many aspects of cellular function, including cellular proliferation, differentiation, migration, apoptosis, adhesion, angiogenesis, immune surveillance, and survival. The actions of TGF-beta are dependent on several factors including cell type, growth conditions, and the presence of other polypeptide growth factors. One of the biological effects of TGF-beta is the inhibition of proliferation of most normal epithelial cells using an autocrine mechanism of action, and this suggests a tumor suppressor role for TGF-beta. Loss of autocrine TGF-beta activity and/or responsiveness to exogenous TGF-beta appears to provide some epithelial cells with a growth advantage leading to malignant progression. This suggests a pro-oncogenic role for TGF-beta in addition to its tumor suppressor role. During the early phase of epithelial tumorigenesis, TGF-beta inhibits primary tumor development and growth by inducing cell cycle arrest and apoptosis. In late stages of tumor progression when tumor cells become resistant to growth inhibition by TGF-beta due to inactivation of the TGF-beta signaling pathway or aberrant regulation of the cell cycle, the role of TGF-beta becomes one of tumor promotion. Resistance to TGF-beta-mediated inhibition of proliferation is frequently observed in multiple human cancers, as are various alterations in the complex TGF-beta signaling and cell cycle pathways. TGF-beta can exert effects on tumor and stromal cells as well as alter the responsiveness of tumor cells to TGF-beta to stimulate invasion, angiogenesis, and metastasis, and to inhibit immune surveillance. Because of the dual role of TGF-beta as a tumor suppressor and pro-oncogenic factor, members of the TGF-beta signaling pathway are being considered as predictive biomarkers for progressive tumorigenesis, as well as molecular targets for prevention and treatment of cancer and metastasis.

Nkx2.1 transcription factor in lung cells and a transforming growth factor-beta1 heterozygous mouse model of lung carcinogenesis

The Nkx2.1 homeobox gene and transforming growth factor-beta1 (TGF-beta1) are essential for organogenesis and differentiation of the mouse lung. NKX2.1 is a marker of human lung carcinomas, but it is not known whether this gene participates in early tumorigenesis. Addition of TGF-beta1 to TGF-beta1-responsive nontumorigenic mouse lung cells cotransfected with a NKX2.1Luc luciferase reporter and either a Sp1 or Sp3 plasmid showed a significant increase or decrease, respectively, in NKX2.1Luc transcription. Cotransfection of Sp3 and dominant-negative TGF-beta type II receptor plasmids negated the effect of Sp1. Cotransfected Sp1 plasmid with either dominant-negative Smad2 or Smad3 or Smad4 plasmids significantly decreased NKX2.1Luc transcription. Electrophoretic mobility shift assays revealed binding of Sp1 and Smad4 to the NKX2.1 promoter. With a TGF-beta1 heterozygous mouse model, Nkx2.1 mRNA and protein in lungs of TGF-beta1 heterozygous mice were significantly lower compared to wildtype (WT) littermates. Competitive reverse transcription (RT)-polymerase chain reaction (PCR) and immunostaining showed that Nkx2.1 mRNA and protein decreased significantly in adenomas and adenocarcinomas compared to normal lung tissue. Our in vitro data showed that regulation of Nkx2.1 by TGF-beta1 occurs through TGF-beta type II receptor and Smad signaling, with Sp1 and Sp3 in lung cells. Our in vivo data showed reduced Nkx2.1 in lungs of TGF-beta1 heterozygous mice compared to WT mice, that is detectable in adenomas, and that is further reduced in carcinogenesis, and that correlates with reduction of Sp1, Sp3, and Smads in lung adenocarcinomas. Our findings suggest that reduced Nkx2.1 and TGF-beta1 signaling components may contribute to tumorigenesis in the lungs of TGF-beta1 heterozygous mice.

Integrin alphavbeta8-mediated activation of transforming growth factor-beta inhibits human airway epithelial proliferation in intact bronchial tissue

Transforming growth factor (TGF)-beta is a potent multifunctional cytokine that is an essential regulator of epithelial proliferation. Because TGF-beta is expressed almost entirely in a latent state in vivo, a major source of regulation of TGF-beta function is its activation. A subset of integrins, alphavbeta8 and alphavbeta6, which are expressed in the human airway, has recently been shown to activate latent TGF-beta in vitro, suggesting a regulatory role for integrins in TGF-beta function in vivo. Here we have developed a novel, biologically relevant experimental model of human airway epithelium using intact human bronchial tissue. We have used this model to determine the function of integrin-mediated activation of TGF-beta in the airway. In human bronchial fragments cultured in vitro, authentic epithelial-stromal interactions were maintained and integrin and TGF-beta expression profiles correlated with profiles found in normal lung. In addition, in this model, we found that either the integrin alphavbeta8 or TGF-beta could inhibit airway epithelial cell proliferation. Furthermore, we found that one mechanism of integrin-alphavbeta8-dependent inhibition of cell proliferation was through activation of TGF-beta because anti-beta8 antibody blocked the majority (76%) of active TGF-beta released from bronchial fragments. These data provide compelling evidence for a functional role for integrin-mediated activation of TGF-beta in control of human airway epithelial proliferation in vivo.

Peripheral blood mononuclear cell proliferation to heat shock protein-70 derived from autologous lung carcinoma

In animals, tumor-derived heat shock proteins (HSP) induce immune-mediated protection against autologous cancer. We investigated whether HSP-70 derived from human lung carcinoma are also complexed to tumor-specific antigens. Peripheral blood mononuclear cells collected 10 days after surgery from patients with lung cancer were stimulated with HSP-70 purified from autologous and heterologous tumors. The stimulation index (SI) obtained when stimulating cells with autologous tumor-derived HSP-70 averaged 3.07 +/- 0.75 in patients with lung cancer and 1.57 +/- 0.33 in control subjects (p < 0.001 by analysis of variance). No significant stimulation was observed with HSP-70 derived either from the majority of heterologous tumors or from autologous tumor-free lung tissue. SI decreased from 3.59 +/- 0.65 to 1.65 +/- 0.38 in six patients tested again 3 months after surgery (p = 0.02 by Wilcoxon test for paired data). HSP-70 derived from lung carcinoma are shown to be associated with T cell antigens. The T cell reactivity appears transient and restricted to antigens complexed to HSP-70 derived from autologous tumors only. This suggests that the antigenicity of human lung tumors is unique, which may be crucial for the design of new vaccines.

Murine sclerodermatous graft-versus-host disease, a model for human scleroderma: cutaneous cytokines, chemokines, and immune cell activation

Murine sclerodermatous graft-vs-host disease (Scl GVHD) models human scleroderma, with prominent skin thickening, lung fibrosis, and up-regulation of cutaneous collagen mRNA. Fibrosis in Scl GVHD may be driven by infiltrating TGF-beta1-producing mononuclear cells. Here we characterize the origin and types of those cutaneous effector cells, the cytokine and chemokine environments, and the effects of anti-TGF-beta Ab on skin fibrosis, immune cell activation markers, and collagen and cytokine synthesis. Donor cells infiltrating skin in Scl GVHD increase significantly at early time points post-transplantation and are detectable by PCR analysis of Y-chromosome sequences when female mice are transplanted with male cells. Cutaneous monocyte/macrophages and T cells are the most numerous cells in Scl GVHD compared with syngeneic controls. These immune cells up-regulate activation markers (MHC class II I-A(d) molecules and class A scavenger receptors), suggesting Ag presentation by cutaneous macrophages in early fibrosing disease. Early elevated cutaneous mRNA expression of TGF-beta1, but not TGF-beta2 or TGF-beta3, and elevated C-C chemokines macrophage chemoattractant protein-1, macrophage inflammatory protein-1alpha, and RANTES precede subsequent skin and lung fibrosis. Therefore, TGF-beta1-producing donor mononuclear cells may be critical effector cells, and C-C chemokines may play important roles in the initiation of Scl GVHD. Abs to TGF-beta prevent Scl GVHD by effectively blocking the influx of monocyte/macrophages and T cells into skin and by abrogating up-regulation of TGF-beta1, thereby preventing new collagen synthesis. The Scl GVHD model is valuable for testing new interventions in early fibrosing diseases, and chemokines may be new potential targets in scleroderma.

Localisation of transforming growth factor β1 and β3 mRNA transcripts in normal and fibrotic human lung

BACKGROUND

Transforming growth factor β1 is implicated in the pathogenesis of lung fibrosis. It promotes extracellular matrix accumulation by increasing procollagen synthesis and reducing degradation. TGFβ1 gene and protein expression increase in experimental lung fibrosis, and TGFβ1 antibodies attenuate fibrosis in mice. The role of other TGFβ isoforms is unclear. This study aimed to localise TGFβ1 and TGFβ3 gene expression in fibrotic human lung and compare it with that in normal human lung.

METHODS

Lung tissue from patients with cryptogenic fibrosing alveolitis and fibrosis associated with systemic sclerosis was examined by in situ hybridisation. Macroscopically normal lung from carcinoma resections was used as control tissue. Digoxigenin labelled riboprobes were synthesised from TGFβ isoform specific cDNA templates.

RESULTS

The digoxigenin labelled riboprobes were sensitive and permitted precise cellular localisation of mRNA transcripts. TGFβ1 and TGFβ3 mRNA transcripts were widespread in normal lung and localised to alveolar macrophages and bronchiolar epithelium. TGFβ1 but not TGFβ3 mRNA was detected in mesenchymal and endothelial cells. In fibrotic lung tissue mRNA transcripts for both isoforms were also detected in metaplastic type II cells. TGFβ1 gene expression was enhanced in some patients. TGFβ3 was expressed in fibrotic lung but was not consistently altered compared with controls.

CONCLUSION

TGFβ1mRNA transcripts were localised in normal and fibrotic human lung and TGFβ3 gene expression in human lung fibrosis was shown for the first time. The results suggest that TGFβ1 may play the predominant role in pathogenesis. It is suggested that TGFβ1 should be the primary target of anticytokine treatments for pulmonary fibrosis.

Localisation of transforming growth factor beta1 and beta3 mRNA transcripts in normal and fibrotic human lung

BACKGROUND

Transforming growth factor beta1 is implicated in the pathogenesis of lung fibrosis. It promotes extracellular matrix accumulation by increasing procollagen synthesis and reducing degradation. TGFbeta1 gene and protein expression increase in experimental lung fibrosis, and TGFbeta1 antibodies attenuate fibrosis in mice. The role of other TGFbeta isoforms is unclear. This study aimed to localise TGFbeta1 and TGFbeta3 gene expression in fibrotic human lung and compare it with that in normal human lung.

METHODS

Lung tissue from patients with cryptogenic fibrosing alveolitis and fibrosis associated with systemic sclerosis was examined by in situ hybridisation. Macroscopically normal lung from carcinoma resections was used as control tissue. Digoxigenin labelled riboprobes were synthesised from TGFbeta isoform specific cDNA templates.

RESULTS

The digoxigenin labelled riboprobes were sensitive and permitted precise cellular localisation of mRNA transcripts. TGFbeta1 and TGFbeta3 mRNA transcripts were widespread in normal lung and localised to alveolar macrophages and bronchiolar epithelium. TGFbeta1 but not TGFbeta3 mRNA was detected in mesenchymal and endothelial cells. In fibrotic lung tissue mRNA transcripts for both isoforms were also detected in metaplastic type II cells. TGFbeta1 gene expression was enhanced in some patients. TGFbeta3 was expressed in fibrotic lung but was not consistently altered compared with controls.

CONCLUSION

TGFbeta1 mRNA transcripts were localised in normal and fibrotic human lung and TGFbeta3 gene expression in human lung fibrosis was shown for the first time. The results suggest that TGFbeta1 may play the predominant role in pathogenesis. It is suggested that TGFbeta1 should be the primary target of anticytokine treatments for pulmonary fibrosis.