Tif1γ is essential for the terminal differentiation of mammary alveolar epithelial cells and for lactation through SMAD4 inhibition

Murine models of idiopathic inflammatory myopathies

Idiopathic inflammatory myopathies (IIMs) are divided into polymyositis and dermatomyositis (DM) with specific cutaneous manifestation. Several myositis-specific autoantibodies (MSAs) have been identified in IIMs and were found to be associated with distinct clinical features, including anti-synthetase syndrome (ASyS) and immune-mediated necrotizing myopathy (IMNM). Moreover, MSA-related clinical features have been identified even within DM. Although MSAs are valuable for the diagnosis of IIMs, the pathogenic roles of these antibodies remain unknown. To investigate the pathogenesis of IIMs, classical murine models of autoimmune myositis, experimental autoimmune myositis, and C protein-induced myositis have been established by immunization with muscle-specific antigens, myosin, and myosin-binding skeletal C protein, respectively. To according to MSA-related autoimmunity, a murine model of ASyS was generated by immunization with a murine recombinant histidyl-transfer RNA (tRNA) synthetase, Jo-1, in which muscle and lung inflammation are induced depending on acquired immunity. Furthermore, it was found that the transfer of human Immunoglobulin G (IgGs) from patients with IMNM, comprising anti-signal recognition particles and anti-3-hydroxy-3-methylglutaryl coenzyme A reductase antibodies, induced complement-mediated myositis in recipient mice. We found that CD8+ T cell-mediated myositis can be established depending on autoimmunity against transcriptional intermediary factor 1γ (TIF1γ), an autoantigen for MSAs induced by recombinant human TIF1γ immunization. These new murine models reflecting MSA-associated IIMs will reveal the immunological mechanisms underlying IIMs.

TIF1γ and SMAD4 regulation in colorectal cancer: impact on cell proliferation and liver metastasis

We investigated the effects of transcriptional intermediary factor 1γ (TIF1γ) and SMAD4 on the proliferation and liver metastasis of colorectal cancer (CRC) cells through knockdown of TIF1γ and/or SMAD4 and knockdown of TIF1γ and/or restoration of SMAD4 expression. Furthermore, we examined TIF1γ and SMAD4 expression in human primary CRC and corresponding liver metastatic CRC specimens. TIF1γ promoted but SMAD4 inhibited the proliferation of CRC cells by competitively binding to activated SMAD2/SMAD3 complexes and then reversely regulating c-Myc, p21, p27, and cyclinA2 levels. Surprisingly, both TIF1γ and SMAD4 reduced the liver metastasis of all studied CRC cell lines via inhibition of MEK/ERK pathway-mediated COX-2, Nm23, uPA, and MMP9 expression. In patients with advanced CRC, reduced TIF1γ or SMAD4 expression was correlated with increased invasion and liver metastasis and was a significant, independent risk factor for recurrence and survival after radical resection. Patients with advanced CRC with reduced TIF1γ or SAMD4 expression had higher recurrence rates and shorter overall survival. TIF1γ and SMAD4 competitively exert contrasting effects on cell proliferation but act complementarily to suppress the liver metastasis of CRC via MEK/ERK pathway inhibition. Thus, reduced TIF1γ or SMAD4 expression in advanced CRC predicts earlier liver metastasis and poor prognosis.

Murine models of idiopathic inflammatory myopathy

Idiopathic inflammatory myopathies (IIMs) are characterized by inflammation of muscles and other organs. Several myositis-specific autoantibodies (MSAs) have been identified in IIMs and were found to be associated with distinct clinical features. Although MSAs are valuable for the diagnosis of IIMs, the pathogenic roles of these antibodies remain unknown. To investigate the pathogenesis of IIMs, several animal models of experimental myositis have been established. Classical murine models of autoimmune myositis, experimental autoimmune myositis, and C protein-induced myositis are established by immunization with muscle-specific antigens, myosin, and skeletal C protein, respectively. Furthermore, a murine model of experimental myositis was generated by immunization with a murine recombinant histidyl-tRNA synthetase, Jo-1, in which muscle and lung inflammation reflecting anti-synthetase syndrome are induced depending on acquired immunity. Recently, the transfer of human IgGs from patients with immune-mediated necrotizing myopathy, comprising anti-signal recognition particles and anti-3-hydroxy-3-methylglutaryl coenzyme A reductase antibodies, was found to induce complement-mediated myositis in recipient mice. CD8⁺ T cell-mediated myositis can be established depending on autoimmunity against transcriptional intermediary factor 1γ (TIF1γ), an autoantigen for MSAs induced by recombinant human TIF1γ immunization. These new murine models reflecting MSA-related IIMs are useful tools for accurately understanding the pathological mechanisms underlying IIMs.

Critical Review on Physiological and Molecular Features during Bovine Mammary Gland Development: Recent Advances

The mammary gland is a unique organ with the ability to undergo repeated cyclic changes throughout the life of mammals. Among domesticated livestock species, ruminants (cattle and buffalo) constitute a distinct class of livestock species that are known milk producers. Cattle and buffalo contribute to 51 and 13% of the total milk supply in the world, respectively. They also play an essential role in the development of the economy for farming communities by providing milk, meat, and draft power. The development of the ruminant mammary gland is highly dynamic and multiphase in nature. There are six developmental stages: embryonic, prepubertal, pubertal, pregnancy, lactation, and involution. There has been substantial advancement in our understanding of the development of the mammary gland in both mouse and human models. Until now, there has not been a thorough investigation into the molecular processes that underlie the various stages of cow udder development. The current review sheds light on the morphological and molecular changes that occur during various developmental phases in diverse species, with a particular focus on the cow udder. It aims to explain the physiological differences between cattle and non-ruminant mammalian species such as humans, mice, and monkeys. Understanding the developmental biology of the mammary gland in molecular detail, as well as species-specific variations, will facilitate the researchers working in this area in further studies on cellular proliferation, differentiation, apoptosis, organogenesis, and carcinogenesis. Additionally, in-depth knowledge of the mammary gland will promote its use as a model organ for research work and promote enhanced milk yield in livestock animals without affecting their health and welfare.

Clinical and Serological Features and Pregnancy Outcomes in Women with Polymyositis/Dermatomyositis: A Case-based Review

We encountered a 30-year-old woman who developed dermatomyositis during pregnancy and was positive for anti-Mi-2 antibodies. She was successfully treated with prednisolone and tacrolimus and delivered a healthy child. We reviewed the cases of idiopathic inflammatory myositis (IIM) that developed during pregnancy that were published after the year 2000 to elucidate the profile of myositis-specific antibodies (MSAs) in them and to evaluate their obstetric outcomes. In cases with IIM that developed during pregnancy, anti-Mi-2, anti-TIF1-g, anti-Jo-1, and anti-EJ antibodies was detected in one case each. The obstetric outcomes of the IIM-complicated pregnancies were poor, especially when complicated with active maternal myositis. Further studies focusing on the possible causal relationships between MSAs and cases with IIM that developed during pregnancy are needed. For better obstetric outcomes, appropriate suppression of the maternal disease activity using immunosuppressants and vigilance regarding the patient's requirement of Caesarean section is important.

Presence of anti-TIF-1γ, anti-Ro52, anti-SSA/Ro60 and anti-Su/Ago2 antibodies in breast cancer: a cross-sectional study

OBJECTIVES

The presence of myositis-specific antibodies (MSA), was recently reported in healthy individuals, cancer patients without myopathy and paraneoplastic rheumatic syndromes. We sought to analyze the frequency of MSA, myositis-associated antibodies (MAA) and autoantibodies related to systemic autoimmune rheumatic diseases (SARD) in breast cancer patients.

METHODS

One hundred fifty-two breast cancer patients were enrolled in a cross-sectional study. Clinical information was collected, and autoantibodies tested by immunoprecipitation of an ³⁵S-methionine-labeled K562 cell extract, enzyme-linked immunosorbent assay (ELISA) and Western blot when indicated. All statistical tests were performed using the software statistical package for the social science (SPSS) ver. 19.0 (IBM Inc., NYSE, USA).

RESULTS

Autoantibodies associated with SARD: anti-52 kD ribonucleoprotein/tripartite motif-containing 21 (anti-Ro52/TRIM21) was found in 5.9% (9/152), anti-Sjögren syndrome-related antigen A/60 kD ribonucleoprotein antibody (anti-SSA/Ro60) in 3.9% (6/152) and anti-Su antigen/Argonaute 2 antibody (anti-Su/Ago2) in 2.6% (4/152). Meanwhile, anti-transcription intermediary factor-1γ (anti-TIF-1γ, p155/140) antibody was positive in 2 cases and anti-polymyositis/scleroderma antibody was detected in one case. As a whole, 14.47% (22/152) of breast cancer patients showed autoantibodies associated with SARD. These specific autoantibodies were not associated with the presence of rheumatic diseases except one rheumatoid arthritis patient positive for anti-Ro52/TRIM21.

CONCLUSIONS

Autoantibodies to TIF-1γ were found in two patients with breast cancer without dermatomyositis (DM). More common specificities were autoantibodies anti-SSA/Ro60, anti-Ro52/TRIM21 and anti-Su/Ago2. More studies are needed in order to establish the biological meaning of the presence of SARD-associated autoantibodies in breast cancer.

Immune response to dermatomyositis-specific autoantigen, transcriptional intermediary factor 1γ can result in experimental myositis

OBJECTIVES

To investigate whether autoimmunity to transcriptional intermediary factor 1 (TIF1)γ, a ubiquitous nuclear autoantigen for myositis-specific autoantibodies detected in patients with dermatomyositis (DM) is pathogenetic for inflammatory myopathy.

METHODS

Wild-type, β₂-microglobulin-null, perforin-null, Igμ-null and interferon α/β receptor (IFNAR)-null mice were immunised with recombinant human TIF1γ whole protein. A thymidine incorporation assay was performed using lymph node T cells from TIF1γ-immunised mice. Plasma was analysed using immunoprecipitation followed by western blot analysis and enzyme-linked immunosorbent assays. Femoral muscles were histologically and immunohistochemically evaluated. CD8⁺ or CD4⁺ T cells isolated from lymph node T cells or IgG purified from plasma were adoptively transferred to naïve mice. TIF1γ-immunised mice were treated with anti-CD8 depleting antibody and a Janus kinase inhibitor, tofacitinib.

RESULTS

Immunisation with TIF1γ-induced experimental myositis presenting with necrosis/atrophy of muscle fibres accompanied by CD8⁺ T cell infiltration successfully in wild-type mice, in which TIF1γ-specific T cells and antihuman and murine TIF1γ IgG antibodies were detected. The incidence and severity of myositis were significantly lower in β₂-microglobulin-null, perforin-null, CD8-depleted or IFNAR-null mice, while Igμ-null mice developed myositis normally. Adoptive transfer of CD8⁺ T cells induced myositis in recipients, while transfer of CD4⁺ T cells or IgG did not. Treatment with tofacitinib inhibited TIF1γ-induced myositis.

CONCLUSIONS

Here we show that TIF1γ is immunogenic enough to cause experimental myositis, in which CD8⁺ T cells and type I interferons, but not CD4⁺ T cells, B cells or antibodies, are required. This murine model would be a tool for understanding the pathologies of DM.

Anti-TIF1-γ autoantibodies: warning lights of a tumour autoantigen

Anti-transcription intermediary factor 1 (TIF1)-γ autoantibodies are robustly linked with cancer-associated DM in adults. This review aims to give an overview of the physiological context of TIF1-γ and to determine whether there is a pathophysiological link between anti-TIF1-γ autoantibodies and the occurrence of cancer. Detection of anti-TIF1-γ autoantibodies has a high sensitivity and specificity for cancer-associated DM in adults and is therefore useful for both diagnosis and cancer risk stratification. The function of the autoantigen, TIF1-γ, may provide insight into the mechanism behind this association. TIF1-γ is a ubiquitously present protein involved in various biological pathways, including TGF-β signalling. In cancer, it can act either as a tumour suppressor or promoter, depending on the cellular context and cancer stage. Evolving data provide pathophysiological insights, linking anti-TIF1-γ autoantibodies to both the anti-tumour response and to muscle and skin damage. TIF1-γ expression is increased in muscle and skin tissue of patients with DM. Mutations or loss-of-heterozygosity in TIF1-γ alleles in malignant tissue may result in the expression of tumour-specific neo-antigens stimulating autoantibody production. The newly formed autoantibodies are hypothesized to cross-react with antigens in muscle and skin, driving the development of DM. Based on the current evidence, anti-TIF1-γ autoantibodies should be considered warning lights of a potential tumour autoantigen and should alert the physician to the possibility of an underlying cancer.

Trim33 (Tif1γ) is not required for skeletal muscle development or regeneration but suppresses cholecystokinin expression

The expression of Trim33 (Tif1γ) increases in skeletal muscles during regeneration and decreases upon maturation. Although Trim33 is required for the normal development of other tissues, its role in skeletal muscle is unknown. The current study aimed to define the role of Trim33 in muscle development and regeneration. We generated mice with muscle-specific conditional knockout of Trim33 by combining floxed Trim33 and Cre recombinase under the Pax7 promoter. Muscle regeneration was induced by injuring mouse muscles with cardiotoxin. We studied the consequences of Trim33 knockdown on viability, body weight, skeletal muscle histology, muscle regeneration, and gene expression. We also studied the effect of Trim33 silencing in satellite cells and the C2C12 mouse muscle cell line. Although Trim33 knockdown mice weighed less than control mice, their skeletal muscles were histologically unremarkable and regenerated normally following injury. Unexpectedly, RNAseq analysis revealed dramatically increased expression of cholecystokinin (CCK) in regenerating muscle from Trim33 knockout mice, satellite cells from Trim33 knockout mice, and C2C12 cells treated with Trim33 siRNA. Trim33 knockdown had no demonstrable effect on muscle differentiation or regeneration. However, Trim33 knockdown induced CCK expression in muscle, suggesting that suppression of CCK expression requires Trim33.

The Roles of TIF1γ in Cancer

Transcriptional intermediary factor 1 γ (TIF1γ), also known as TRIM33, RFG7, PTC7, or Ectodermin, is an E3 ubiquitin-ligase family member with a ring-box-coiled-coil region. It can regulate TGF-β/Smad signaling in two different ways in different cellular contexts. On one hand, TIF1γ can monoubiquitinate Smad4 to inhibit the formation of Smad2/3/4 nuclear complexes. On the other hand, TIF1γ can function as a cofactor of phosphorylated (p)-Smad2/3, competing with Smad4 to inhibit the formation of the Smad2/3/4 complex. In addition, TIF1γ has been reported to play a role in transcription elongation, cellular differentiation, embryonic development, and mitosis. As transforming growth factor-β (TGF-β) superfamily signaling plays an important role in the occurrence and development of cancer, and TIF1γ was reported to be involved in the regulation of TGF-β superfamily signaling, studies on TIF1γ during the last decade have focused on its role in the development of cancer. However, TIF1γ can function either as a tumor suppressor or promoter in different cellular contexts, yet there are few reviews focusing on the roles of TIF1γ in cancer. Hence, in this paper we systematically review and discuss the roles of TIF1γ in cancer. Firstly, we review the biological features, the regulatory mechanisms and the related signaling pathways of TIF1γ. Next, we illustrate the roles of TIF1γ in different tumors. We then provide a tentative hypothesis that explains the dual roles of TIF1 γ in cancer. Finally, we provide our viewpoint regarding the future developments of cancer research focusing on TIF1γ, especially in relation to the effects of TIF1γ on tumoral immunity.

Trim33 is required for appropriate development of pre-cardiogenic mesoderm

Congenital cardiac malformations are among the most common birth defects in humans. Here we show that Trim33, a member of the Tif1 subfamily of tripartite domain containing transcriptional cofactors, is required for appropriate differentiation of the pre-cardiogenic mesoderm during a narrow time window in late gastrulation. While mesoderm-specific Trim33 mutants did not display noticeable phenotypes, epiblast-specific Trim33 mutant embryos developed ventricular septal defects, showed sparse trabeculation and abnormally thin compact myocardium, and died as a result of cardiac failure during late gestation. Differentiating embryoid bodies deficient in Trim33 showed an enrichment of gene sets associated with cardiac differentiation and contractility, while the total number of cardiac precursor cells was reduced. Concordantly, cardiac progenitor cell proliferation was reduced in Trim33-deficient embryos. ChIP-Seq performed using antibodies against Trim33 in differentiating embryoid bodies revealed more than 4000 peaks, which were significantly enriched close to genes implicated in stem cell maintenance and mesoderm development. Nearly half of the Trim33 peaks overlapped with binding sites of the Ctcf insulator protein. Our results suggest that Trim33 is required for appropriate differentiation of precardiogenic mesoderm during late gastrulation and that it will likely mediate some of its functions via multi-protein complexes, many of which include the chromatin architectural and insulator protein Ctcf.

Prognostic role of Tif1γ expression and circulating tumor cells in patients with breast cancer

Transcription intermediary factor 1γ (Tif1γ), a ubiquitous nuclear protein, is a regulator of transforming growth factor-β (TGF-β)/Smad signaling. Tif1γ can function as an oncogene and as a tumor suppressor. In the present study, Tif1γ levels were measured in the plasma of patients with breast cancer in order to investigate the association of Tif1γ with overall survival (OS). The results indicated that Tif1γ is an independent prognostic and predictive factor in breast cancer, and thus, a promising target protein for use in diagnostics and patient follow-up. Plasma levels of Tif1γ were measured in samples obtained from 110 patients with operable breast cancer and in 110 healthy volunteers at the Breast Cancer Department of Yangpu Hospital between 2008 and 2016. The association between Tif1γ levels and clinicopathologic parameters, and the OS in a follow-up period of 98 months was evaluated. The prognostic significance was assessed using the Kaplan-Meier method. The levels of Tif1γ were significantly lower in patients with breast cancer compared with healthy controls. The average concentration of 18.40 ng/ml was used to discriminate between Tif1γ-positive (52) and Tif1γ-negative patients (58). Tif1γ-positive patients had a significantly improved OS compared with Tif1γ-negative patients. In the multivariate analysis, Tif1γ was an independent predictor of a favorable OS in a prospective follow-up setting; thus, Tif1γ plasma levels are an independent prognostic factor for patients with breast cancer. These findings support the potential of using measurements of Tif1γ plasma levels to guide breast cancer therapy and monitoring. Further studies are required to validate Tif1γ as an easily detectable, non-invasive prognostic biomarker for breast cancer.

TGF-β Family Signaling in Ductal Differentiation and Branching Morphogenesis

Epithelial cells contribute to the development of various vital organs by generating tubular and/or glandular architectures. The fully developed forms of ductal organs depend on processes of branching morphogenesis, whereby frequency, total number, and complexity of the branching tissue define the final architecture in the organ. Some ductal tissues, like the mammary gland during pregnancy and lactation, disintegrate and regenerate through periodic cycles. Differentiation of branched epithelia is driven by antagonistic actions of parallel growth factor systems that mediate epithelial-mesenchymal communication. Transforming growth factor-β (TGF-β) family members and their extracellular antagonists are prominently involved in both normal and disease-associated (e.g., malignant or fibrotic) ductal tissue patterning. Here, we discuss collective knowledge that permeates the roles of TGF-β family members in the control of the ductal tissues in the vertebrate body.

Trim33 regulates early maturation of mouse embryoid bodies in vitro

Embryonic stem cells (ESCs) are an established model for investigating developmental processes, disease conditions, tissue regeneration and therapeutic targets. Previous studies have shown that tripartite motif-containing 33 protein (Trim33) functions as a chromatin reader during Nodal-induced mesoderm induction. Here we report that despite reduced proliferation, mouse ESCs deficient in Trim33 remained pluripotent when cultured under non-differentiating conditions. However, when induced to differentiate to embryoid bodies (EBs), the mutant cultures showed increased cell shedding and apoptosis at day 3 of differentiation. Gene set enrichment analysis (GSEA) indicated that several molecular functions associated with cell survival, transcriptional/translational activity and growth factor signaling were affected already by the second day of differentiation in Trim33-deficient EBs. Consistent with increased apoptosis, expression of Rac1, a critical factor for EB cell survival, was reduced in Trim33 mutant EBs. In addition, a set of genes involved in regulation of pluripotency was upregulated in mutant EBs. Our results suggest that Trim33 regulates early maturation of mouse embryoid bodies in vitro.

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Trim33-/- ES cells can be normally maintained under non-differentiating conditions.

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Trim33-/- EBs show changes in gene expression during early maturation.

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Trim33 is required for survival and appropriate maturation of EBs in vitro.

Dermatomyositis and Immune-Mediated Necrotizing Myopathies: A Window on Autoimmunity and Cancer

Autoimmune myopathies (myositides) are strongly associated with malignancy. The link between myositis and cancer, originally noticed by Bohan and Peter in their classification in 1975 (1), has been evidenced by large population-based cohort studies and a recent meta-analysis. The numerous reports of cases in which the clinical course of myositis reflects that of cancer and the short delay between myositis and cancer onset support the notion that myositis may be an authentic paraneoplastic disorder. Thus, cancer-associated myositis raises the question of cancer as a cause rather than a consequence of autoimmunity. Among myositides, dermatomyositis and more recently, although to a lesser extent, immune-mediated necrotizing myopathies are the most documented forms associated with cancer. Interestingly, the current diagnostic approach for myositis is based on the identification of specific antibodies where each antibody determines specific clinical features and outcomes. Recent findings have shown that the autoantibodies anti-TIF1γ, anti-NXP2 and anti-HMGCR are associated with cancers in the course of myositis. Herein, we highlight the fact that the targets of these three autoantibodies involve cellular pathways that intervene in tumor promotion and we discuss the role of cancer mutations as autoimmunity triggers in adult myositis.

Trim33 is essential for macrophage and neutrophil mobilization to developmental or inflammatory cues

Macrophages infiltrate and establish in developing organs from an early stage, often before these have become vascularized. Similarly, leukocytes, in general, can quickly migrate through tissues to any site of wounding. This unique capacity is rooted in their characteristic amoeboid motility, the genetic basis of which is poorly understood. Trim33 (also known as Tif1-γ), a nuclear protein that associates with specific DNA-binding transcription factors to modulate gene expression, has been found to be mainly involved in hematopoiesis and gene regulation mediated by TGF-β. Here, we have discovered that in Trim33-deficient zebrafish embryos, primitive macrophages are unable to colonize the central nervous system to become microglia. Moreover, both macrophages and neutrophils of Trim33-deficient embryos display a reduced basal mobility within interstitial tissues, and a profound lack of a response to inflammatory recruitment signals, including local bacterial infections. Correlatively, Trim33-deficient mouse bone marrow-derived macrophages display a strongly reduced three-dimensional amoeboid mobility in fibrous collagen gels. The transcriptional regulator Trim33 is thus revealed as being essential for the navigation of macrophages and neutrophils towards developmental or inflammatory cues within vertebrate tissues.

Zinc Finger Homeodomain Factor Zfhx3 Is Essential for Mammary Lactogenic Differentiation by Maintaining Prolactin Signaling Activity

The zinc finger homeobox 3 (ZFHX3, also named ATBF1 for AT motif binding factor 1) is a transcription factor that suppresses prostatic carcinogenesis and induces neuronal differentiation. It also interacts with estrogen receptor α to inhibit cell proliferation and regulate pubertal mammary gland development in mice. In the present study, we examined whether and how Zfhx3 regulates lactogenic differentiation in mouse mammary glands. At different stages of mammary gland development, Zfhx3 protein was expressed at varying levels, with the highest level at lactation. In the HC11 mouse mammary epithelial cell line, an in vitro model of lactogenesis, knockdown of Zfhx3 attenuated prolactin-induced β-casein expression and morphological changes, indicators of lactogenic differentiation. In mouse mammary tissue, knock-out of Zfhx3 interrupted lactogenesis, resulting in underdeveloped glands with much smaller and fewer alveoli, reduced β-casein expression, accumulation of large cytoplasmic lipid droplets in luminal cells after parturition, and failure in lactation. Mechanistically, Zfhx3 maintained the expression of Prlr (prolactin receptor) and Prlr-Jak2-Stat5 signaling activity, whereas knockdown and knock-out of Zfhx3 in HC11 cells and mammary tissues, respectively, decreased Prlr expression, Stat5 phosphorylation, and the expression of Prlr-Jak2-Stat5 target genes. These findings indicate that Zfhx3 plays an essential role in proper lactogenic development in mammary glands, at least in part by maintaining Prlr expression and Prlr-Jak2-Stat5 signaling activity.

TIF1γ interferes with TGFβ1/SMAD4 signaling to promote poor outcome in operable breast cancer patients

BACKGROUND

The Transforming growth factor β (TGFβ) signaling has a paradoxical role in cancer development and outcome. Besides, the prognostic significance of the TGFβ1, SMAD4 in breast cancer patients is an area of many contradictions. The transcriptional intermediary factor 1γ (TIF1γ) is thought to interact with the TGFβ/SMAD signaling through different mechanisms. Our study aims to define the prognostic significance of TGFβ1, SMAD4 and TIF1γ expression in breast cancer patients and to detect possible interactions among those markers that might affect the outcome.

METHODS

Immunohistochemistry was performed on tissue microarray (TMA) blocks prepared from samples of 248 operable breast cancer patients who presented at Centre Léon Bérard (CLB) between 1998 and 2001. The intensity and the percentage of stained tumor cells were integrated into a single score (0-6) and a cutoff was defined for high or low expression for each marker. Correlation was done between TGFβ1, SMAD4 and TIF1γ expression with the clinico-pathologic parameters using Pearson's chi-square test. Kaplan-Meier method was used to estimate distant metastasis free survival (DMFS), disease free survival (DFS) and overall survival (OS) and the difference between the groups was evaluated with log-rank test.

RESULTS

223 cases were assessable for TIF1γ, 204 for TGFβ1 and 173 for SMAD4. Median age at diagnosis was 55.8 years (range: 27 to 89 years). Tumors were larger than 20 mm in 49.2% and 45.2% had axillary lymph node (LN) metastasis (N1a to N3). 19.4% of the patients had SBR grade I tumors, 46.8% grade II tumors and 33.9% grade III tumors. ER was positive in 85.4%, PR in 75.5% and Her2-neu was over-expressed in 10% of the cases. Nuclear TIF1γ, cytoplasmic TGFβ1, nuclear and cytoplasmic SMAD4 stainings were high in 35.9%, 30.4%, 27.7% and 52.6% respectively. TIF1γ expression was associated with younger age (p=0.006), higher SBR grade (p<0.001), more ER negativity (p=0.035), and tumors larger than 2 cm (p=0.081), while TGFβ1 was not associated with any of the traditional prognostic factors. TGFβ1 expression in tumor cells was a marker of poor prognosis regarding DMFS (HR=2.28; 95% CI: 1.4 to 3.8; p=0.002), DFS (HR=2.00; 95% CI: 1.25 to 3.5; p=0.005) and OS (HR=1.89; 95 % CI: 1.04 to 3.43; p=0.037). TIF1γ expression carried a tendency towards poorer DMFS (p=0.091), DFS (p=0.143) and OS (p=0.091). In the multivariate analysis TGFβ1 remained an independent predictor of shorter DMFS, DFS and OS. Moreover, the prognostic significance of TGFβ1 was more obvious in the TIF1γ high patient subgroup than in the patients with TIF1γ low expression. The subgroup expressing both markers had the worst DMFS (HR=3.2; 95% CI: 1.7 to 5.9; p<0.0001), DFS (HR=3.02; 95 % CI: 1.6 to 5.6; p<0.0001) and OS (HR=2.7; 95 % CI: 1.4 to 5.4; p=0.005).

CONCLUSION

There is a crosstalk between the TIF1γ and the TGFβ1/SMAD4 signaling that deteriorates the outcome of operable breast cancer patients and when combined together they can serve as an effective prognostic tool for those patients.

Expression of the dermatomyositis autoantigen transcription intermediary factor 1γ in regenerating muscle

OBJECTIVE

Autoantibodies against transcription intermediary factor 1γ (TIF1γ) are found in many patients with dermatomyositis (DM). Although TIF1γ is known to play a role in the differentiation of other tissues, its functional role in muscle regeneration has not been elucidated. This study was undertaken to explore the regulation and functional role of this protein during muscle differentiation and regeneration.

METHODS

TIF1γ expression was analyzed in human muscle biopsy specimens using immunofluorescence microscopy. Immunofluorescence microscopy and immunoblotting analyses were used to study TIF1γ expression in a mouse model of muscle injury and repair. The effect of premature TIF1γ silencing on muscle differentiation was studied in cultured mouse myoblasts.

RESULTS

In muscle biopsy specimens from DM patients, TIF1γ was expressed at low levels in the nuclei of histologically normal muscle cells but at high levels in the centralized nuclei of atrophic, perifascicular myofibers expressing markers of regeneration. TIF1γ levels were also increased in regenerating myonuclei following muscle injury in mice. Premature silencing of TIF1γ in vitro using small interfering RNA did not accelerate the expression of myogenin, a transcription factor that plays a central role in regulating relatively early stages of muscle differentiation. However, premature silencing of TIF1γ did accelerate myotube fusion and the expression of myosin heavy chain (MyHC), a later marker of muscle differentiation.

CONCLUSION

The DM autoantigen TIF1γ is markedly up-regulated during muscle regeneration in human and mouse muscle cells. Premature silencing of this protein in cultured myoblasts accelerates MyHC expression and myoblast fusion. However, TIF1γ may function independently of, or downstream from, myogenin.

New insights into extracellular and post-translational regulation of TGF-β family signalling pathways

Members of the transforming growth factor-β (TGF-β) family of secreted proteins are present in all multicellular animals. TGF-β proteins are versatile intercellular signalling molecules that orchestrate cell fate decisions during development and maintain homeostasis in adults. The Smad family of signal transducers implements TGF-β signals in responsive cells. Given the ability of TGF-β ligands to induce dramatic responses in target cells, numerous regulatory mechanisms exist to prevent unintended consequences. Here we review new reports of extracellular and post-translational regulation in Drosophila and vertebrates. Extracellular topics include the regulation of TGF-β signalling range and the coordination between tissue morphogenesis and TGF-β signalling. Post-translational topics include the regulation of TGF-β signal transduction by Gsk3-β phosphorylation of Smads and by cycles of Smad mono- and deubiquitylation. Extension of the ubiquitylation data to the Hippo pathway is also discussed.

TIF1γ requires sumoylation to exert its repressive activity on TGFβ signaling

TIF1γ, a new regulator of TGFβ signaling, inhibits the Smad4-mediated TGFβ response by interaction with Smad2/3 or ubiquitylation of Smad4. We have shown that TIF1γ participates in TGFβ signaling as a negative regulator of Smad4 during the TGFβ-induced epithelial-to-mesenchymal transition (EMT) in mammary epithelial cells, and during terminal differentiation of mammary alveolar epithelial cells and lactation. We demonstrate here that TIF1γ is sumoylated and interacts with Ubc9, the only known SUMO-conjugating enzyme. Four functional sumoylation sites lie within the middle domain of TIF1γ, the Smad interaction domain. We show that a sumoylation-defective TIF1γ mutant significantly reduces TIF1γ inhibition of Smad complexes and that of the Smad-mediated TGFβ transcriptional response. Moreover, chromatin immunoprecipitation experiments indicate that TIF1γ sumoylation is required to limit Smad4 binding on the PAI-1 TGFβ target gene promoter. Ectopic expression of TIF1γ in mammary epithelial cells inhibits TGFβ-induced EMT, an effect relieved by expression of non-sumoylated TIF1γ. Taken together, our results identify a new TGFβ regulatory layer, whereby sumoylation strengthens the TIF1γ repressive action on canonical TGFβ signaling.