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Biomedical subjects

A M Sizeland

Publications and source records attributed to A M Sizeland.

12 recordsLinked to original sources
PubMed2001

Palliative surgery for neoplastic unilateral vocal cord paralysis.

BACKGROUND: Locally advanced, recurrent or metastatic neoplasms are the commonest causes of unilateral vocal cord paralysis (UVCP). The aim of the present study was to evaluate both survival and results of treatment of vocal cord medialization procedures in this group of patients. METHODS: Fifty-seven patients (36 male, 21 female) with UVCP considered to be due to advanced malignancy who underwent medialization (Teflon injection or type I thyroplasty) between January 1994 and July 2000 were retrospectively reviewed. RESULTS: The malignancy responsible for UVCP was non-small-cell lung carcinoma (NSCLC) in 43 patients, small-cell lung carcinoma (SCLC) in four patients, thyroid carcinoma in three patients and metastatic lower cervical lymph nodes in seven patients. All patients complained of dysphonia and 29 patients had symptoms of aspiration. Teflon injection was performed in 44 patients and thyroplasty in 13. Improvement in voice occurred in 51 patients (89%) and resolution of aspiration in 28 patients (97%) after 2 months. The median time from onset of symptoms of UVCP to death in NSCLC was 170 days; SCLC, 69 days; thyroid carcinoma, 783 days; and metastatic lower cervical lymph nodes, 304 days. CONCLUSION: Surgical treatment of neoplastic UVCP provides satisfactory palliation of symptoms, and management decisions should be based on patient survival expectations.

Aged↗
PubMed1999

Smad7 differentially regulates transforming growth factor beta-mediated signaling pathways.

Smad7 has been identified as a negative regulator of transforming growth factor beta (TGF-beta) signaling by interfering with the phosphorylation of other Smad proteins by TGF-beta receptor type I (TbetaRI). We established a mink lung epithelial (Mv1Lu) cell line where ectopic expression of Smad7 is tightly controlled by doxycycline using an improved Tet-on system. Once induced by doxycycline, the recombinant Smad7 was localized predominantly in the perinuclear region and in the cytoplasm. However, the type of culture surface alters the subcellular localization of Smad7: on plastic or on fibronectin-coated glass, Smad7 was localized in the cytoplasm; but when the cells were cultured on glass, nuclear localization was observed. TGF-beta stimulation did not alter substantially the cellular distribution of Smad7. Importantly, the expression of recombinant Smad7 differentially inhibited TGF-beta signaling pathways. Consistent with previous studies, Smad7 inhibited TGF-beta-stimulated induction of type 1 plasminogen activator inhibitor as measured by p3TP-Lux reporter. However, expression of Smad7 had little effect on TGF-beta-induced growth inhibition.

Activin Receptors, Type I↗
PubMed1999

Extracellular domain of the transforming growth factor-beta receptor negatively regulates ligand-independent receptor activation.

We have previously proposed that transforming growth factor (TGF)-beta receptor activation occurs via a relative rotation between the receptors. This model suggests that in the absence of the ligand the receptor extracellular domain negatively regulates the activation of the receptor complex. To investigate this proposition, four TGF-beta type I and II receptor extracellular/transmembrane-cytoplasmic and extracellular-transmembrane/cytoplasmic chimeras, TbetaRII-I-I and TbetaRI-II-II as well as TbetaRII-II-I and TbetaRI-I-II, and two extracellular domain truncated receptors TbetaRI-STC and TbetaRII-STC were generated. In either mutant mink lung R1B (lacking functional type I receptor) or DR26 (where the type II receptor is nonfunctional) cells, coexpression of two chimeric receptors, which are complementary in extracellular and cytoplasmic domains, transduced TGF-beta induced signaling, as measured by the transcriptional activation of a p3TP-Lux reporter gene. Coexpression of this type of chimeric receptor with a wild-type receptor containing the opposite cytoplasmic domain exhibited a varied level of constitutive activity depending on the particular combination of the extracellular domains. In general, the type I-type I extracellular domain combination gave higher constitutive activity than the type I-type II or type II-type II combinations. Furthermore, coexpression of the extracellular domain truncated receptor with any receptor containing the opposite cytoplasmic domain always resulted in ligand independent receptor signaling. Immunoprecipitation studies showed that the formation of the receptor complexes paralleled the ligand independent activation of p3TP-Lux. Our results support the conclusion that the TGF-beta receptor extracellular domain plays a negative regulatory role in receptor activation in the absence of ligand.

Animals↗
PubMed1999

A pivotal role for the transmembrane domain in transforming growth factor-beta receptor activation.

Transforming growth factor-beta (TGF-beta) delivers diverse growth and differentiation signals by binding two distantly related transmembrane serine/threonine kinase receptors: the type I receptor (TbetaRI) and the type II receptor (TbetaRII). In an attempt to establish the role of the transmembrane domain in receptor signaling, two chimeric TGF-beta receptors, TbetaRI-II-I and TbetaRII-I-II, containing the opposite transmembrane domain were generated. When transfected into a mutant mink lung epithelial cell line R1B, which lacks functional TbetaRI, TbetaRI-II-I restored TGF-beta1-induced transcriptional activation of a TGF-beta reporter p3TP-Lux to approximately 25% of the levels restored by wild-type TbetaRI. In the mutant mink lung epithelial cell line DR26, which contains a truncated, nonfunctional TbetaRII, wild-type receptor TbetaRII restored the TGF-beta responsiveness, while the TbetaRII-I-II cDNA was inactive. When both TbetaRI and TbetaRII were transfected into R1B, DR26, or Mv1Lu cells, a low level of constitutive p3TP-Lux activity was observed. However, cotransfection of both transmembrane chimeric receptors, TbetaRI-II-I and TbetaRII-I-II, or the wild-type TbetaRI with the transmembrane chimeric TbetaRII-I-II resulted in high levels of ligand-independent receptor activation. These results suggest that the transmembrane domains of both TGF-beta receptors are essential and play a pivotal role in receptor activation. To investigate the role of the transmembrane domain further, four type II transmembrane mutants were generated: TbetaRIIDelta-1, TbetaRIIDelta-2, TbetaRIIDelta-3, and TbetaRIIDelta-4, which have one, two, three, or four amino acids deleted at the N terminus of the transmembrane domain, respectively. Interestingly, co-expression of TbetaRIIDelta-1 with the wild-type TbetaRI in DR26 cells resulted in high levels of constitutive activation, while only low levels of the activation were observed when TbetaRIIDelta-2, TbetaRIIDelta-3, or TbetaRIIDelta-4 were co-expressed with the wild-type TbetaRI. However, TbetaRIIDelta-1 restored very little the TGF-beta responsiveness in DR26cells. Expression of TbetaRIIDelta-2, TbetaRIIDelta-3, and TbetaRIIDelta-4 resulted in a progressive increase in TGF-beta responsiveness, with TbetaRIIDelta-4 reaching the level of activity of the wild-type TbetaRII. Furthermore, like TbetaRII-I-II, co-expression of TbetaRIIDelta-1 with TbetaRI-II-I also resulted in high levels of constitutive activation. These results are consistent with an important role for the transmembrane region of the receptors. We further propose a model of receptor activation in which receptor activation occurs via relative orientational rotation.

Amino Acid Sequence↗
PubMed1993

Association of Sos Ras exchange protein with Grb2 is implicated in tyrosine kinase signal transduction and transformation.

The proteins Grb2-Sem-5, Shc and Sos have been implicated in the signalling pathway from tyrosine kinase receptors to Ras. Grb2-Sem-5 binds directly to murine Sos1, a Ras exchange factor, through two SH3 domains. Sos is also associated with ligand-activated tyrosine kinase receptors which bind Grb2-Sem-5, and with the Grb2-Sem-5 binding protein, Shc. Ectopic expression of Drosophila Sos stimulates morphological transformation of rodent fibroblasts. These data define a pathway by which tyrosine kinases act through Ras to control cell growth and differentiation.

Adaptor Proteins, Signal Transducing↗
PubMed1992

Anti-sense transforming growth factor alpha oligonucleotides inhibit autocrine stimulated proliferation of a colon carcinoma cell line.

Many carcinoma cells secrete transforming growth factor alpha (TGF alpha). A 23 base anti-sense oligonucleotide that recognizes the TGF alpha mRNA inhibits both DNA synthesis and the proliferation of the colon carcinoma cell line LIM 1215. The effects of the anti-sense TGF alpha oligonucleotide are reversed by epidermal growth factor (EGF) at 20 ng/ml. When the LIM 1215 cells are grown under serum free conditions, the anti-sense TGF alpha oligonucleotides have their greatest effects at high cell density (2 x 10(5) cells/cm2), indicating that the secreted TGF alpha is acting as an exogenous growth stimulus. In addition, at higher cell densities, the kinase activity of the EGF receptor is activated and the receptor is down-modulated. The cell density dependent activation of the EGF receptor is inhibited by the application of the antisense TGF alpha oligonucleotides.

Amino Acid Sequence↗
PubMed1991

The proliferative and morphologic responses of a colon carcinoma cell line (LIM 1215) require the production of two autocrine factors.

The role of autocrine growth factors in tumor cell growth has been difficult to prove. Our results indicate that more than one autocrine factor is required for the autonomous growth of the LIM 1215 colonic carcinoma cell line. Furthermore, the morphologic changes induced by epidermal growth factor (EGF) are also density dependent and appear to require a synergistic autocrine factor. The serum-free proliferation of the colonic carcinoma cell line LIM 1215 depends on cell density and the presence of EGF (A. Sizeland, S. Bol, and A.W. Burgess, Growth Factors 4:129-143, 1991). At cell densities below 10(4)/cm2, conditioned medium (from cells at a density of 10(5)/cm2) was required for the cells to elicit a mitogenic response to exogenous EGF. At higher cell densities (10(5)/cm2), the cells were independent of both exogenous EGF and conditioned medium. In addition, the EGF receptor was found to be phosphorylated on tyrosine in LIM 1215 cells proliferating at high density, suggesting that the autocrine production of transforming growth factor alpha (TGF alpha) and subsequent ligation to the EGF receptor was occurring. The proliferation of cells at high density was partly inhibited by TGF alpha antibodies but was almost completely inhibited by an antisense oligonucleotide to TGF alpha. The antisense inhibition could be overcome by the addition of EGF, indicating that the effect of the antisense TGF alpha oligonucleotide was on the production of autocrine TGF alpha. LIM 1215 cells were also observed to undergo morphologic changes (spreading and actin cable organization) in response to EGF. These changes were density dependent, but they occurred with a cell density dependence different from that of the proliferative response. These results suggest two possibilities: that the morphologic changes and proliferative responses have different sensitivities to the autocrine factors or that the actions of the autocrine factors are mediated through different signal transduction pathways.

Actins↗
PubMed1990

PCR cloning and sequence of gastrin mRNA from carcinoma cell lines.

The hypothesis that a gastrin-like peptide is acting as an autocrine growth factor in gastric and colonic carcinoma cell lines requires that the cells should synthesize a gastrin-like mRNA. Although no gastrin mRNA was observed in the gastric line Okajima or the colonic lines HCT 116 or LIM 1215 by Northern blotting, gastrin mRNA was detected by application of the polymerase chain reaction. Two products were observed corresponding to mRNA with and without a 130 bp intron. The sequences of both products were identical to the sequences predicted from the normal human gastrin gene.

Base Sequence↗
PubMed1987

Lymph node dissection for head and neck cancer.

A retrospective analysis of 141 neck dissections performed at the Royal Melbourne Hospital from 1975 to 1981 has been carried out with a view to identifying the prognostic factors. When a neck dissection is performed, the site of the primary disease did not affect the 5 year survival rate. A conservation neck dissection, especially when performed electively, had the best prognosis. Radiotherapy did not affect the overall survival rate in patients having a neck dissection, while chemotherapy appeared to exert a beneficial effect on patients with advanced disease. While clinical nodal staging was an important prognostic indicator, the number of nodes pathologically involved was not. Histologic differentiation of the tumour was not prognostically significant, whereas extracapsular nodal disease was. Most (70%) treatment failures occurred in the neck, while systemic metastases occurred in 12% of patients.

Adult↗