Search PubMed⌕ Search

Biomedical subjects

S Bader

Publications and source records attributed to S Bader.

At least 19 recordsLinked to original sources
PubMed2001

Epigenetic inactivation of RASSF1A in lung and breast cancers and malignant phenotype suppression.

BACKGROUND: The recently identified RASSF1 locus is located within a 120-kilobase region of chromosome 3p21.3 that frequently undergoes allele loss in lung and breast cancers. We explored the hypothesis that RASSF1 encodes a tumor suppressor gene for lung and breast cancers. METHODS: We assessed expression of two RASSF1 gene products, RASSF1A and RASSF1C, and the methylation status of their respective promoters in 27 non-small-cell lung cancer (NSCLC) cell lines, in 107 resected NSCLCs, in 47 small-cell lung cancer (SCLC) cell lines, in 22 breast cancer cell lines, in 39 resected breast cancers, in 104 nonmalignant lung samples, and in three breast and lung epithelial cultures. We also transfected a lung cancer cell line that lacks RASSF1A expression with vectors containing RASSF1A complementary DNA to determine whether exogenous expression of RASSF1A would affect in vitro growth and in vivo tumorigenicity of this cell line. All statistical tests were two-sided. RESULTS: RASSF1A messenger RNA was expressed in nonmalignant epithelial cultures but not in 100% of the SCLC, in 65% of the NSCLC, or in 60% of the breast cancer lines. By contrast, RASSF1C was expressed in all nonmalignant cell cultures and in nearly all cancer cell lines. RASSF1A promoter hypermethylation was detected in 100% of SCLC, in 63% of NSCLC, in 64% of breast cancer lines, in 30% of primary NSCLCs, and in 49% of primary breast tumors but in none of the nonmalignant lung tissues. RASSF1A promoter hypermethylation in resected NSCLCs was associated with impaired patient survival (P =.046). Exogenous expression of RASSF1A in a cell line lacking expression decreased in vitro colony formation and in vivo tumorigenicity. CONCLUSION: RASSF1A is a potential tumor suppressor gene that undergoes epigenetic inactivation in lung and breast cancers through hypermethylation of its promoter region.

Adult↗
PubMed2000

Most microsatellite unstable sporadic colorectal carcinomas carry MBD4 mutations.

The MBD4 gene is involved in the repair of mutation at methyl-CpG dinucleotides. In microsatellite unstable tumours MBD4 can itself be mutated at an exonic polynucleotide tract. By analysing DNA from microdissected tumour samples we have found that both frequency and pattern of mutation are more significant than originally reported.

Colorectal Neoplasms↗
PubMed1999

Somatic frameshift mutations in the MBD4 gene of sporadic colon cancers with mismatch repair deficiency.

Defects of mismatch repair are thought to be responsible for carcinogenesis in hereditary non-polyposis colorectal cancer and about 15% of sporadic colon cancers. The phenotype is seen as microsatellite instability and is known to be caused either by mutations in mismatch repair genes or by aberrant methylation of these genes stabilizing their downregulation. Lack of repair of microsatellite sequence errors, created during replication, leads to a mutation-prone phenotype. Where mutations occur within mononucleotide tracts within exons they cause translation frameshifts, premature cessation of translation and abnormal protein expression. Such mutations have been observed in the TGFbetaRII, BAX, IGFIIR, MSH3 and MSH6 genes in colon and other cancers. We describe here frameshift mutations affecting the gene for the methyl-CpG binding thymine glycosylase, MBD4, in over 40% of microsatellite unstable sporadic colon cancers. The mutations all appear heterozygous but their location would ensure truncation of the protein between the methyl-CpG binding and glycosylase domains, thus potentially generating a dominant negative effect. It is thus possible that such mutations enhance mutation frequency at other sites in these tumours. A suggestion has been made that MBD4 (MED1) mutations may lead to an increased rate of microsatellite instability but this mechanism appears unlikely due to the nature of mutations we have found.

Base Pair Mismatch↗
PubMed1998

Cloning of a breast cancer homozygous deletion junction narrows the region of search for a 3p21.3 tumor suppressor gene.

Chromosome 3p abnormalities and allele loss are frequent in lung and breast cancers, and several lung cancer cell lines exhibit homozygous deletions of 3p indicating potential sites of tumor suppressor genes at regions 3p21.3, 3p14.2 and 3p12. We have identified and characterized a new 3p21.3 homozygous deletion in a breast cancer cell line and the primary tumor that overlaps those previously described in small cell lung cancer (SCLC). This homozygous deletion is approximately 220 kb in length and represents a somatically acquired change in the primary breast cancer. Cloning and sequencing of the breakpoint demonstrated that this resulted from an interstitial deletion and precisely pinpoints this deletion within the three SCLC homozygous deletions previously reported. This deletion significantly narrows the minimum common deleted region to 120 kb and is distinct from the previously reported region that suppresses tumor formation of the murine A9 fibrosarcoma cells. These findings suggest that a common homozygous deletion region on 3p21.3 is important in both lung and breast cancers. It is likely that this very well characterized region either contains one tumor suppressor gene common to both tumor types or two closely linked tumor suppressor genes specific for each tumor.

Adult↗
PubMed1998

Pulmonary tuberculosis presenting as mass lesions and simulating neoplasms in adults.

In a review of the chest X-rays and medical records of 597 cases of culture- or biopsy-proven pulmonary tuberculosis (PTB; age range 1.5-72 years), seen over a period of 6 years (1991-97), 26 patients had radiographic patterns unusual for PTB. These patterns were mass-like densities simulating neoplasms, chronic lower lobe airspace opacities without adenopathy, mediastinal adenopathy without parenchymal airspace opacities and bronchopleural fistula without other radiographic abnormalities. The most common of these unusual radiographic patterns was mass-like densities, most of which were initially and mistakenly diagnosed as neoplasms. These masses, seen in 11 adult patients, form the basis of this report. Two children aged 1.5 and 2 years also had tuberculous mass densities initially diagnosed as neurogenic tumour and round pneumonia, respectively. They have been excluded from the present series, and form the subject of another report. The masses were lower lobe predominant and were not usually associated with fibro-productive satellite lesions or with calcification or cavitation. In view of the recent resurgence of PTB and the importance of chest X-rays in its diagnosis and management, this rare radiographic pattern needs to be emphasized.

Adult↗
PubMed1997

Immune suppression by lysosomotropic amines and cyclosporine on T-cell responses to minor and major histocompatibility antigens: does synergy exist?

BACKGROUND: Using murine models, we have shown that the lysosomotropic amine, chloroquine, is effective in the prevention of graft-versus-host disease (GVHD) mediated by donor T cells reactive with recipient minor histocompatibility antigens (MiHCs). Because lysosomotropic amines can suppress major histocompatibility complex (MHC) class II antigen presentation, their mechanism of action is potentially different from current immune suppressant drugs used to control GVHD such as cyclosporine. METHODS: We investigated the use of cyclosporine and the lysosomotropic amines chloroquine and hydroxychloroquine in combination for additive or synergistic immunosuppression on T-cell responses in vitro to MiHC and MHC in mice. RESULTS: We found that similar concentrations of chloroquine and hydroxychloroquine suppress the T-cell response to MiHC in mice (C57BL/6 anti-BALB.B) and that lysosomotropic amines in combination with cyclosporine result in synergistic suppression of a proliferative response to MiHC. Similar suppression and synergy appear to be present in an alloreactive response (C57BL/6 anti-BALB/c). Direct inhibition by chloroquine of T-cell proliferative responses induced by anti-CD3epsilon in the absence of antigen-presenting cells is present at higher concentrations than that required to suppress responses to MiHC or MHC. Chloroquine appears to induce decreased T-cell viability at high concentrations. This effect does not appear to be due to decreased T-cell production of interleukin-2 or interferon-gamma. At lower concentrations (<25 microg/ml), chloroquine can also decrease the ability of antigen-presenting cells to stimulate an a C57BL/6 anti-BALB/c T-cell response and can inhibit MHC class II expression after activation with lipopolysaccharide. CONCLUSIONS: Lysosomotropic amines in combination with cyclosporine appear to be synergistic in the suppression of T-cell proliferation to MiHC and MHC. Use of chloroquine in combination with cyclosporine may result in improved control of GVHD.

Animals↗
PubMed1997

The human homolog of the rodent immediate early response genes, PC4 and TIS7, resides in the lung cancer tumor suppressor gene region on chromosome 3p21.

Recently, human chromosome band 3p21.3 was shown to undergo overlapping homozygous deletions in several small cell lung cancer lines further defining a putative tumor suppressor gene(s) region. We report the cloning and mutational analysis of a novel human gene, SKMc15, from the commonly homozygously deleted region in three small cell lung cancer lines (NCI-H1450, NCI-H740, GLC20). It has 11 exons ranging in size from 50 to 541 bp with an open reading frame of 442 amino acids. The gene covers 7 to 10 kb of genomic DNA; the message of 1.8 to 2 kb is expressed in all analyzed fetal and adult human and mouse tissues including heart, brain, placenta, lung liver, skeletal muscle, kidney, testis and pancreas and in small cell and non-small cell cancer lines. The intron/exon boundaries were used to analyze the gene for mutations by exon PCR-SSCP sequencing in 60 small cell lung cancer cell lines. No loss-of-function mutations were detected. The cDNA sequence has high homology, 75% at the protein level, to the rat early response gene PC4 and its murine homolog TIS7. In addition, the known partial sequence of the putative mouse interferon beta2 (64 amino acids) gene is highly conserved in PC4/TIS7 (94%) and in SKMc15 (83%) at the amino acid level. The sequence TAAAT, which is thought to be involved in mRNA degradation, is present in the 3' UTR of SKMc15 and in the 3' UTR of PC4 and TIS7 genes.

Amino Acid Sequence↗
PubMed1997

Group practice vs. solo practice--a dentist's view.

The percentage of dentists joining group practices has increased sharply in the past fifteen years. Many advantages to practicing in a group setting including social, clinical, and financial aspects have contributed to this change. Solo practice has become increasingly difficult for new dentists. Market forces as well as insurance changes have accelerated the transition to group practice. Multispecialty groups have particular features that have allowed them to become much more popular. The advent of dental practice management companies has fueled the growth of multispecialty groups and has created new business opportunities for dental practice owners.

Dentists↗
PubMed1996

Human semaphorins A(V) and IV reside in the 3p21.3 small cell lung cancer deletion region and demonstrate distinct expression patterns.

Semaphorins and collapsins make up a family of conserved genes that encode nerve growth cone guidance signals. We have identified two additional members of the human semaphorin family [human semaphorin A(V) and human semaphorin IV] in chromosome region 3p21.3, where several small cell lung cancer (SCLC) cell lines exhibit homozygous deletions indicative of a tumor suppressor gene. Human semaphorin A(V) has 86% amino acid homology with murine semaphorin A, whereas semaphorin IV is most closely related to murine semaphorin E, with 50% homology. These semaphorin genes are approximately 70 kb apart flanking two GTP-binding protein genes, GNAI-2 and GNAT-1. In contrast, other human semaphorin gene sequences (human semaphorin III and homologues of murine semaphorins B and C) are not located on chromosome 3. Human semaphorin A(V) is translated in vitro into a 90-kDa protein, which accumulates at the endoplasmic reticulum. The human semaphorin A(V) (3.4-kb mRNA) and IV (3.9- and 2.9-kb mRNAs) genes are expressed abundantly but differentially in a variety of human neural and nonneural tissues. Human semaphorin A(V) was expressed in only 1 out of 23 SCLCs and 7 out of 16 non-SCLCs, whereas semaphorin IV was expressed in 19 out of 23 SCLCs and 13 out of 16 non-SCLCs. Mutational analysis in semaphorin A(V) revealed mutations (germ line in one case) in 3 of 40 lung cancers. Our data suggest the need to determine the function of human semaphorins A(V) and IV in nonneural tissues and their role in the pathogenesis of lung cancer.

Amino Acid Sequence↗
PubMed1996

Construction of a 600-kilobase cosmid clone contig and generation of a transcriptional map surrounding the lung cancer tumor suppressor gene (TSG) locus on human chromosome 3p21.3: progress toward the isolation of a lung cancer TSG.

The critical region on human chromosome 3p21.3 harboring a putative lung cancer tumor suppressor gene (TSG) was previously defined by allelotyping and recently refined by overlapping homozygous deletions. We report the construction of a 700-kb (cosmid and one P1 phage) clone contig covering the deletion overlap and its flanks. The minimal set of 23 cosmids comprises 600 kb and is extended by one P1 phage to 700 kb to cover the distal breakpoint of the overlap. The clone contig was extensively characterized by restriction and expression mapping to produce high resolution physical and transcription maps of the cloned region. Potential transcribed fragments were detected by hybridization with PCR-amplified cDNA libraries, direct cDNA selection "zoo" blotting, cDNA screening, and identification of 24 CpG islands. Thus far, 15 new genes represented by partial or full-length cDNAs were isolated, characterized, and precisely positioned on the contig. Two previously cloned genes, namely GNAI-2 and GNAT-1, were also positioned. In addition, the telomeric breakpoint of the NCI H740 deletion and centromeric breakpoint of the overlapping GLC20 deletion were discovered and mapped to define precisely the candidate TSG region. This large cosmid clone contig and high resolution maps will prove crucial in the identification of the lung cancer TSG(s).

Chromosome Mapping↗
PubMed1996

Synergy between lysosomotropic amines and cyclosporin A on human T cell responses to an exogenous protein antigen, tetanus toxoid.

Previously, it has been shown that the lysosomotropic amine, chloroquine, is effective in the prevention of graft-versus-host disease (GVHD) using murine models. Because chloroquine and hydroxychloroquine suppress MHC class II antigen presentation, their mechanism of action is different to other immune suppressant drugs (cyclosporin A) currently used to control GVHD. It is possible that the use of cyclosporin A and chloroquine in combination may have an additive or synergistic effect on T cell responses to antigens presented in the context of MHC class II. We investigated the effects of chloroquine or hydroxychloroquine in combination with cyclosporin A on human T cell responses in vitro to tetanus toxoid, an exogenous protein antigen dependent on MHC class II presentation for proliferative responses. We demonstrate that similar levels of chloroquine and hydroxychloroquine suppress human T cell responses to tetanus toxoid and that the use of either agent in combination with cyclosporin A results in synergistic suppression. Evaluation for a direct effect by the lysosomotropic amines on T cells, in the absence of antigen presenting cells, revealed that there was inhibition of T cell responses but only at high concentrations. No significant decrease or increase was seen in surface MHC II or invariant chain expression or in cytoplasmic invariant chain after exposure to chloroquine. Thus, lysosomotropic amines in combination with cyclosporin A are synergistic in suppression of T cell proliferation. Use of these agents in combination with cyclosporin A may improve control of graft-versus-host disease.

Adult↗
PubMed1995

Chloroquine treatment affects T-cell priming to minor histocompatibility antigens and graft-versus-host disease.

Graft-versus-host disease (GVHD) caused by T-cell recognition of minor histocompatibility (MiHC) antigens is a major complication of bone marrow transplantation. GVHD therapy has focused on removal or suppression of donor T cells, but modulation of MiHC antigen presentation to CD4+ T cells may represent an alternative approach. Chloroquine is known to inhibit major histocompatibility complex (MHC) class II presentation of antigen in vitro by affecting invariant chain dissociation from MHC class II. The goal of this study was to evaluate the role of chloroquine in abrogating T-cell priming to MiHC and GVHD in mice after transplantation of an MiHC incompatible donor. C57BL/6 mice were treated with phosphate-buffered saline or chloroquine at 400 micrograms intraperitoneally every day for 5 days before priming with BALB.B cells (MiHC-incompatible) followed by weekly injections of chloroquine at 400 micrograms for 4 to 8 weeks. Chloroquine treatment decreased the proliferative T-cell response to MiHC by 67% and the cytolytic T-cell activation by greater than 50%. After bone marrow transplantation (LP/J into C57BL/6; MiHC-incompatible), GVHD was significantly decreased in chloroquine-treated mice (17% with GVHD) as compared with that in controls (92% with GVHD). Chloroquine treatment did not have other effects in vivo on the normal T- and B-cell mitogenic responses, T-cell allogeneic responses, and MHC class II and I surface expression. Chloroquine treatment does decrease the ability of C57BL/6 antigen-presenting cells to stimulate C3H.SW T cells reactive with MiHC expressed on C57BL/6 cells, suggesting an effect on MHC class II presentation of MiHC in vivo. Treatment with chloroquine in vivo appears to result in decreased CD4+ T-cell priming to MiHC and GVHD by decreased class II MHC antigen presentation. Thus, chloroquine treatment may represent an alternative approach to control GVHD.

Animals↗
PubMed1995

Neurofibromatosis type 2 (NF2) gene is somatically mutated in mesothelioma but not in lung cancer.

We have found 16 of 28 small cell lung cancers, 17 of 31 non-small cell lung cancers, 2 of 3 carcinoids, and 12 of 14 mesotheliomas that had chromosome 22 cytogenetic abnormalities. To determine whether the neurofibromatosis type 2 (NF2) gene located on chromosome 22 participates in the oncogenesis of these malignancies, we studied DNAs from lung cancer cell lines and mesotheliomas using Southern blot analysis and the single-strand conformation polymorphism (SSCP) technique for mutations covering 8 of the 16 known NF2 exons. We detected 7 mutations in 17 mesotheliomas (41%) within the coding region of NF2 but none in 75 lung cancer cell lines (38 small cell lung cancers, 34 non-small cell lung cancers, and 3 carcinoids). These mutations were found to be somatic when normal tissue was available for testing. Four mesothelioma cell lines had relatively large deletions (approximately 10-50 kilobases) in the NF2 gene detectable by Southern blot analysis. Two mesothelioma cell lines had nonsense mutations at codons 57 and 341, respectively. Another mesothelioma obtained as a specimen directly from a patient, had a 10-base pair microdeletion from nucleotide 1004 to nucleotide 1013 causing a frameshift mutation. These results suggest that the NF2 gene participates in the oncogenesis in a subset of mesotheliomas but not in lung cancers.

Base Sequence↗
PubMed1995

Requirement for B cells in T cell priming to minor histocompatibility antigens and development of graft-versus-host disease.

Increased understanding of minor histocompatibility complex (MiHC) antigen presentation to donor T cells may permit methods to modulate graft-versus-host disease (GVHD), a major complication of allogeneic bone marrow transplantation (BMT). Previously, we described the importance of B cells as antigen presenting cells in T cell responses to a virally induced murine leukemia. Using a B cell deficient mouse model in which mice receive either control rabbit immunoglobulin (RIgG) or rabbit anti-IgM mu chain from birth (B cell deficient), we evaluated whether B cells were necessary for T cell responses to MiHC and the induction of GHVD. Normal and B cell deficient C57BL/6 (H-2b) mice were primed with BALB.B (H-2b; MiHC incompatible) spleen cells and evaluated > 4 weeks later in vitro. While splenic or lymph node T cells obtained from BALB.B primed control C57BL/6 mice demonstrated strong in vitro proliferative responses to MiHC mismatched targets, B cell deficient hosts were markedly reduced to 14-42% of controls. Similarly, a strong MiHC specific cytolytic T cell response was observed in control C57BL/6 mice (53-100% specific cytotoxicity) whereas B cell depleted recipients had no activity (< or = 5% specific lysis). The role of B cells in GVHD was evaluated using a MiHC disparate mouse model (LP/J donor into C57BL/6 recipient). We found that 12% of B cell depleted recipient mice receiving B cell depleted donor cells developed GVHD compared to 50% of RIgG control mice. B cell depletion of donor cells only, resulted in a similar result with 0% of mice receiving B cell depleted donor cells developing GVHD compared to 38% of controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Resistance to fracture of endodontically treated premolars restored with new generation dentine bonding systems.

MOD cavities in 60 endodontically treated teeth were restored using six different methods. Copper rings were filled with commercial hard-setting cement and the teeth were placed up to the level of the cemento-enamel junction. The teeth were grouped according to restorative method, mounted in an Instron TT machine, and the buccal walls subjected to a slowly increasing compressive force until fracture occurred. The force of fracture of the walls of each tooth was recorded and the results in the various groups compared. All teeth fractured in a similar manner irrespective of the restorative method used. All groups restored with the newer bonding system had higher resistance to fracture than those restored with an acid etch chemically cured composite resin technique. The groups restored with Den-Mat Tenure Core Paste or a Variglass VLC base and Prisma APH were significantly stronger than the acid etch Concise restored teeth (P < 0.05). No statistically significant differences were found between the other groups (P > 0.05).

Acrylic Resins↗
PubMed1994

Molecular analysis of the von Hippel-Lindau disease tumor suppressor gene in human lung cancer cell lines.

The deletion of the short arm of chromosome 3 is frequently observed in lung cancer. To determine whether the von Hippel-Lindau (VHL) disease tumor suppressor gene located at 3p25 is responsible for oncogenesis in lung cancer, we searched the known open reading frame using the single-strand conformation polymorphism (SSCP) technique for mutations in the VHL gene in 72 cancer cell lines including small cell (SCLC) and non-small cell (NSCLC) lung cancers, carcinoids, and mesotheliomas. SSCP analysis showed that four cell lines have altered SSCP patterns within the coding region and one in an intron of the VHL gene. SCLC line NCI-H1672 had a somatic mutation, G to A at nucleotide (nt) 530, leading to amino acid substitution (glycine to aspartic acid) compared to normal DNA from the same patient. Mesothelioma line NCI-H28 had T to A mutation at nt 479 leading to leucine to histidine amino acid change. We found one frequent polymorphism A (0.72) or G (0.28) at nt 19 resulting in either serine or glycine at this position, changes also found in normal peripheral blood cell DNA, often in a heterozygous state. In addition, we found single rare polymorphisms which did not alter the coding region including: C to G at nt 396, G to T at nt 843, and C to T change in an intron. These results suggest that the VHL gene is only rarely mutated in thoracic malignancies.

Base Sequence↗