Linkage localization of TGFB2 and the human homeobox gene HLX1 to chromosome 1q

Transforming growth factor-β in tumour development

Transforming growth factor-β (TGFβ) is a ubiquitous cytokine essential for embryonic development and postnatal tissue homeostasis. TGFβ signalling regulates several biological processes including cell growth, proliferation, apoptosis, immune function, and tissue repair following injury. Aberrant TGFβ signalling has been implicated in tumour progression and metastasis. Tumour cells, in conjunction with their microenvironment, may augment tumourigenesis using TGFβ to induce epithelial-mesenchymal transition, angiogenesis, lymphangiogenesis, immune suppression, and autophagy. Therapies that target TGFβ synthesis, TGFβ-TGFβ receptor complexes or TGFβ receptor kinase activity have proven successful in tissue culture and in animal models, yet, due to limited understanding of TGFβ biology, the outcomes of clinical trials are poor. Here, we review TGFβ signalling pathways, the biology of TGFβ during tumourigenesis, and how protein quality control pathways contribute to the tumour-promoting outcomes of TGFβ signalling.

Prognostic factors and genetic markers in thymoma

In this literature review prognostic factors and genetic markers that play a role in the staging of thymomas are discussed. The effect on prognosis of different factors, such as paraneoplastic syndromes, age, gender, classification, capsular invasion and surgical treatment, is evaluated. There is no generally accepted pathological classification of thymomas. More recently developed surgical techniques such as video-assisted or robotic thoracic surgery require longer follow-up times to determine whether they have equal long-term results compared to the classical surgical techniques. Many genetic markers have been described but at the present time no definite guidelines can be provided regarding screening and staging of thymomas.

Cellular and functional characterization of immunoresistant human glioma cell clones selected with alloreactive cytotoxic T lymphocytes reveals their up-regulated synthesis of biologically active TGF-beta

Two immunoresistant (IR) glioma cell variants, 13-06-IR29 and 13-06-IR30, were cloned from 13-06-MG glioma cell populations after receiving continuous immunoselective pressure from multiple alloreactive cytotoxic T lymphocyte (aCTL) preparations. Reapplication of aCTL immunoselective pressure to the IR clones, displaying a partial regain in sensitivity to aCTL after removal of the selective pressure, restored the resistance. The IR variants exhibited cross-resistance to non-human leukocyte antigen (HLA)-restricted effector cells and gamma-irradiation, but not to carmustine. The IR clones were characterized for factors that might contribute to the immunoresistance. The aCTL adhesion to extracellular matrix extracts derived from either the IR clones or the parental cells was similar and not impaired. Furthermore, aCTL binding to parental cells and IR clones was equal. Down-regulation of the cell recognition molecules, class I HLA or intercellular adhesion molecule-1 (ICAM-1), that would inhibit their recognition by aCTL was not observed on the IR clones. The down-regulation of Fas by the IR clones correlated with their resistance to FasL-induced apoptosis. HLA-G or FasL that might provide an immunotolerant environment or provide a means of counterattack to aCTL, respectively, were not associated with the IR phenotype. The aCTL, coincubated with the IR clones and parental cells, displayed up-regulation of multiple secreted cytokines. A significant up-regulation of bioactive transforming growth factor (TGF)-beta was observed in the IR clones compared with the parental cells. These data suggest that increased secretion of bioactive TGF-beta may inhibit aCTL lysis of the IR clones. Disruption of the TGF-beta signaling pathway may circumvent the resistance.

Recurrent genetic aberrations in thymoma and thymic carcinoma

Apart from single reported aberrant karyotypes, genetic alterations in thymic epithelial neoplasms have not been investigated so far. In this study, 12 World Health Organization classification type A thymomas (medullary thymomas), 16 type B3 thymomas (well-differentiated thymic carcinomas), and nine type C thymomas, all of them primary thymic squamous cell carcinomas, were analyzed by comparative genomic hybridization and fluorescence in situ hybridization. With the exception of one single case, type A thymomas did not reveal chromosomal gains or losses in comparative genomic hybridization. In contrast, all type B3 thymomas showed chromosomal imbalances, with gain of 1q, loss of chromosome 6, and loss of 13q occurring in 11 (69%), six (38%), and five (31%) of 16 cases, respectively. In primary thymic squamous cell carcinoma, the most frequent chromosomal losses were observed for 16q (six of nine cases, 67%), 6 (4 of 9, 44%), and 3p and 17p (three of nine each, 33%), whereas recurrent gains of chromosomal material were gains of 1q (5 of 9, 56%), 17q, and 18 (three of nine each, 33%). This study shows that the distinct histological thymoma types A and B3 exhibit distinct genetic phenotypes, whereas type B3 thymoma and primary thymic squamous cell carcinoma partially share genetic aberrations. In addition to the possible tumorigenic role, the deletion in type B3 thymoma of chromosome 6, harboring the HLA locus, might play a role in the pathogenesis of paraneoplastic autoimmunity characteristic of thymoma.

Lack of association of transforming growth factor (TGF)-beta 1 and beta 2 gene polymorphisms with multiple sclerosis (MS) in Northern Ireland

OBJECTIVE

To examine the influence of TGF-beta genes on MS susceptibility.

BACKGROUND

TGF-beta, of which three homologous isoforms exist (1, 2 and 3), is a strongly immunosuppressive cytokine-inhibiting expression of pro-inflammatory cytokines and blocking cytokine induction of adhesion molecules. TGF-beta delays onset of EAE and TGF-beta 1 gene knockout mice develop fatal multifocal inflammatory disease. High TGF-beta levels exist during MS remission whilst E-selectin, whose expression is inhibited by TGF-beta, is found at higher levels in primary progressive disease (PPMS) and it is postulated that the unremitting course of PPMS may be due to low levels of TGF-beta.

METHODS

Gene association studies using separate polymorphic microsatellite markers for TGF-beta 1 and TGF-beta 2 were performed, incorporating 151 relapsing-remitting or secondary progressive MS (RR/SPMS) patients, 104 PPMS patients and 159 normal controls (Nor). Forward primers were 5' end-labelled with 6-Fam, PCR products were analysed on an Applied Biosystems 373A fluorescent fragment analyser and Genescan 672 software was used for allele sizing.

RESULTS

No significant differences existed in allele frequencies between either MS group and controls regarding the TGF-beta 1 marker: RR/SPMS vs Nor (P = 0.48, df = 8); PPMS vs Nor (P = 0.34, df = 8). Similarly there were no associations demonstrated with the TGF-beta 2 marker: RR/SPMS vs Nor (P = 0.24, df = 2); PPMS vs Nor (P = 0.53, df = 2).

CONCLUSION

These data indicate that TGF-beta 1 and beta 2 genes are not loci influencing MS susceptibility, either RR/SPMS or PPMS, in this population.

Evidence for linkage of a candidate chromosome 1 region to human systemic lupus erythematosus

Genetic susceptibility confers significant risk for systemic lupus erythematosus (SLE). The MHC region and other polymorphic loci have been associated with SLE. Because more compelling evidence for an involvement of a genetic locus includes linkage, we tested a candidate region homologous to a murine SLE susceptibility region in 52 SLE-affected sibpairs from three ethnic groups. We analyzed seven microsatellite markers from the human chromosome 1q31-q42 region corresponding to the telomeric end of mouse chromosome 1, the region where specific manifestations of murine lupus, including glomerulonephritis and IgG antichromatin, have been mapped. Comparing the mean allele sharing in affected sibpairs of each of these seven markers to their expected values of 0.50, only the five markers located at 1q41-q42 showed evidence for linkage (P = 0.0005-0.08). Serum levels of IgG antichromatin also showed evidence for linkage to two of these five markers (P = 0.04), suggesting that this phenotype is conserved between mice and humans. Compared to the expected random distribution, the trend of increased sharing of haplotypes was observed in affected sibpairs from three ethnic groups (P < 0.01). We concluded that this candidate 1q41-q42 region probably contains a susceptibility gene(s) that confers risk for SLE in multiple ethnic groups.

Studies of the candidate genes TGFB2, MSX1, TGFA, and TGFB3 in the etiology of cleft lip and palate in the Philippines

Population-based candidate-gene studies can be an effective strategy for identifying genes involved in the etiology of disorders where family-based linkage studies are compromised by lack of access to affected members, low penetrance, and/or genetic heterogeneity. We evaluated association data for four candidate genes using a population from the Philippines that is genetically separate from previously studied Caucasian populations. Case ascertainment was made possible by collaboration with Operation Smile, a volunteer medical organization, which facilitated identification of a large number of cases for study. A new allelic variant of transforming growth factor-beta 3 was identified to use in these studies. After exclusion of syndromic cases of cleft lip and palate, no evidence for association with previously reported allelic variants of transforming growth factor-beta 2 (TGFB2), homeobox 7 (MSX1), or transforming growth factor-alpha (TGFA), or with the new TGFB3 variant was detected. Previous association studies using Caucasian populations of nonsyndromic cleft lip and/or palate (CL/P) and cleft palate only (CPO) have strongly suggested a role for TGFA in the susceptibility of clefting in humans. Exclusion of significant association in a non-Caucasian population for TGFA suggests that TGFA plays less of a role than it does in Caucasians. This may be due to multiple or different genetic and/or environmental factors contributing to the etiology of this most common cranio-facial anomaly in the Philippine population.

Evolution of the transforming growth factor-beta superfamily

Transforming growth factor beta 1 (TGF-beta 1) is the prototype of an increasingly complex superfamily of growth and differentiation factors. To date, a total of 74 TGF-beta-like sequences have been published, probably representing 23 distinct genes. These sequences were obtained from mammalian, avian, amphibian and insect species, thus emphasising the ancient nature of the TGF-beta superfamily peptides. This article summarises current hypotheses concerning the evolutionary history of this protein superfamily, based on the molecular phylogeny of the published sequences. Comparison of the deduced amino acid sequences leads to the definition of five main groups within the superfamily (TGF-beta, Bone Morphogenetic Proteins [BMP], Anti-Müllerian Hormone [AMH], Inhibin alpha [INH alpha] and GDF-9) and six subgroups within the BMPs (60A, Decapentaplegic [dpp], Vg1, BMP-3, Inhibin beta [INH beta A/B] and nodal). This classification predicts possible phylogenetic and functional relationships among these proteins.