Biomedical subjects

R R de Jonge

Publications and source records attributed to R R de Jonge.

4 recordsLinked to original sources

PubMed1998

Functional characterization of transforming growth factor beta type II receptor mutants in human cancer.

We recently identified missense mutations at amino acid residues 526 and 537 located within the highly conserved subdomain XI of the transforming growth factor beta type II receptor (TbetaR-II) serine-threonine kinase in two human squamous carcinoma cell lines. These cell lines are resistant to transforming growth factor beta-mediated inhibition of growth. Moreover, treatment with transforming growth factor beta fails to increase the levels of type 1 plasminogen activator inhibitor and fibronectin synthesis. To test the effects of the mutations on receptor function, mutant TbetaR-II cDNAs were expressed in TbetaR-II-deficient T47D cells. Cyclin A promoter activity was reduced by 50% in cells expressing wild-type TbetaR-II but increased 2-fold in cells transfected with either of the two mutant receptors. Conversely, plasminogen activator inhibitor type 1 promoter activity was increased 6-fold in cells transfected with wild-type receptor but not with either of the two mutant receptors. Moreover, the activity of both mutant serine-threonine kinases was strongly reduced compared to that of the wild-type receptor. Thus, the amino acid residues at positions 526 and 537 seem to be essential for kinase function and signaling activity of the TbetaR-II.

Carcinoma, Squamous Cell↗

PubMed1997

Transfer of chromosome 18 into human head and neck squamous carcinoma cells: evidence for tumor suppression by Smad4/DPC4.

Cytogenetic, allelotype, and somatic cell hybrid studies of human head and neck cancers had suggested that the long arm of chromosome 18 might carry a tumor suppressor gene locus. To directly test this hypothesis, we introduced a wild-type copy of chromosome 18 into FaDu-Hyg-R head and neck squamous carcinoma cells. Five of 10 chromosome 18 hybrid clones formed invasive carcinomas in nude mice at a significantly lower rate and after a longer latency than the parental tumor cells, whereas the five remaining clones were tumorigenic. These results indicate that tumor formation was suppressed by chromosome 18. A homozygously deleted region of 18q in FaDu-Hyg-R cells included the candidate tumor suppressor gene, Smad4/DPC4, and extended into the DCC tumor suppressor gene locus, but not Smad2/MADR2. Each of the hybrid cell lines carried a full-length donor copy of the DCC gene, independently of their capability to form tumors in vivo. In contrast, each of the hybrid clones that were either completely or partly suppressed carried an intact copy of Smad4/DPC4, whereas this gene was deleted in the two most highly tumorigenic clones. Furthermore, the presence of Smad4/DPC4 correlated with partial restoration of cellular responsiveness to transforming growth factor beta. These results provide strong evidence for tumor suppression by Smad4/DPC4.

Animals↗

PubMed1997

Frequent inactivation of the transforming growth factor beta type II receptor in small-cell lung carcinoma cells.

Small-cell lung cancer (SCLC) has a significantly worse prognosis than other forms of bronchogenic carcinoma. Because transforming growth factor beta (TGF-beta) appears to play an important role in the pathogenesis of SCLC, we examined the status of the TGF-beta receptor system in a series of 11 human small-cell carcinoma cell lines. None of these cell lines expressed more than one-tenth the level of TGF-beta type II receptor (T beta R-II) gene mRNA produced by TGF-beta-sensitive normal epithelial cells. In addition, one of the cell lines expressed a second truncated T beta R-II transcript, which is predicted to encode a protein that lacks the terminal two-thirds of the serine-threonine kinase domain. No other structural alterations in the promoter or coding sequences of the T beta R-II gene were found in any of the cell lines, nor could the loss of T beta R-II mRNA expression be ascribed to de novo hypermethylation of promoter/enhancer sequences. These findings indicate that inactivation of the TGF-beta signaling pathway caused by the loss of T beta R-II gene expression is a common and, therefore, probably pathogenetically important feature of small-cell lung carcinoma.

Carcinoma, Small Cell↗

PubMed1979

Interpreting ear differences in static compliance measurements.

The value of static compliance measurements is limited by marked variability and considerable overlap of results among normal and abnormal middle ears. However, a procedure that compares static compliance measurements between the right and left ear of each individual overcomes this problem in large part. The methods and data to support the applicability of this approach for evaluating unilateral middle ear disorders are discussed further.

Acoustic Impedance Tests↗