Biomedical subjects

George Vande Woude

Publications and source records attributed to George Vande Woude.

7 recordsLinked to original sources

PubMed2006

BRAF and MEK mutations make a late entrance.

The small guanosine triphosphatase KRAS and the protein kinases BRAF, which is a mitogen-activated protein kinase kinase kinase (MAPKKK), and mitogen-activated protein kinase kinase 1 and 2 (MAPKK1/2, also known as MKK1/2 or MEK1/2) are signaling partners in the MAPK signal transduction pathway. They are involved in many biological processes and play crucial roles during embryonic development. When inappropriately expressed, KRAS, BRAF, and MEK1/2 are also frequently implicated in tumor progression. Hence, it might reasonably have been predicted that either loss- or gain-of-function germline mutations in the genes that encode them would cause embryonic death. However, in a surprising development, two articles report that germline mutations in the KRAS, BRAF, and MEK1/2 genes are associated with cardio-facio-cutaneous (CFC) syndrome. This unexpected discovery demonstrates that mutations in KRAS, BRAF, and MEK can pass through the germline to cause specific developmental syndromes. This finding will undoubtedly stimulate further research into the function of these proteins in development and in both inherited and sporadic cancers.

Abnormalities, Multiple↗

PubMed2005

Hepatocyte growth factor promotes cancer cell migration and angiogenic factors expression: a prognostic marker of human esophageal squamous cell carcinomas.

PURPOSE: Hepatocyte growth factor/scatter factor (HGF/SF) and its receptor, c-Met, play important roles in tumor development and progression. In this study, we measured the serum HGF levels in patients with esophageal squamous cell carcinoma (ESCC) to evaluate its relationships with clinicopathologic features and the role of HGF in ESCC. EXPERIMENTAL DESIGN: One hundred and forty-nine patients with ESCC were studied. Pretherapy serum was collected and ELISA was used to detect the concentrations of HGF, vascular endothelial growth factor (VEGF), and interleukin 8 (IL-8). The function of HGF was shown by invasion chamber assay. RESULTS: Pretherapy serum HGF was found to be significantly higher in patients with ESCC than in control subjects. The levels of HGF correlated significantly with advanced tumor metastasis stage and survival. Multivariate analyses showed that serum HGF level in cell migration was an independent prognostic factor. Increased HGF serum levels correlated positively with serum levels of VEGF and IL-8. Our results also showed that HGF was overexpressed in ESCC tissues and cell lines. In vitro study showed that HGF could stimulate ESCC cell to express VEGF and IL-8 and markedly enhance invasion and migration of ESCC cells. Furthermore, HGF-induced IL-8 and VEGF expression was dependent on extracellular signal-regulated kinase signaling pathways. The inhibition of extracellular signal-regulated kinase activation reduced HGF-mediated IL-8 and VEGF expression. CONCLUSIONS: Our results suggest that serum HGF may be a useful biomarker of tumor progression and a valuable independent prognostic factor in patients with ESCC. HGF may be involved in the progression of ESCC as an autocrine/paracrine factor via enhancing angiogenesis and tumor cell invasion and migration.

Aged↗

PubMed2005

Geldanamycin derivative inhibition of HGF/SF-mediated Met tyrosine kinase receptor-dependent urokinase-plasminogen activation.

Ansamycins, including geldanamycin and the derivative 17-allylamino-17-demethoxygeldanamycin, and radicicol are known for their ability to tightly bind to the ATP-binding site of the amino-terminal domain region of heat shock protein 90. We have found that geldanamycin and some of its derivatives can inhibit hepatocyte growth factor/scatter factor-mediated Met tyrosine kinase receptor-dependent urokinase-plasminogen activation at femtomolar levels. Assessment is made of structural requirements for such an activity and evidence is given that distinguishes the target of such an activity from that of heat shock protein 90.

Benzoquinones↗

PubMed2004

Activating Met mutations produce unique tumor profiles in mice with selective duplication of the mutant allele.

Tyrosine kinase-activating mutations in Met have been observed in hereditary papillary renal carcinomas as well as in other cancers. These mutations have been examined in several in vitro systems, where they cause constitutive Met activation, focus formation, and cell motility, and are tumorigenic in xenografts. To study the influence of these mutations on tumorigenesis in vivo, we generated mice with targeted mutations in the murine met locus. The following five mouse lines with mutant Met were created: WT, D1226N, Y1228C, M1248T, and M1248T/L1193V. We observed that mice harboring D1226N, Y1228C(,) and M1248T/L1193V mutations developed a high frequency of sarcomas and some lymphomas, whereas the M1248T mice developed carcinomas and lymphomas. Of considerable interest, we observed trisomy of chromosome 6 and duplication of the mutant met allele in a majority of the tumors, similar to what has been reported in patients with hereditary renal papillary carcinomas. These results demonstrate that activating Met mutations and met amplification play key roles in promoting tumorigenesis in vivo. Moreover, our findings show that different mutations in the Met kinase domain can influence the types of cancers that develop.

Alleles↗

PubMed2004

Normalization and analysis of cDNA microarrays using within-array replications applied to neuroblastoma cell response to a cytokine.

The quantitative comparison of two or more microarrays can reveal, for example, the distinct patterns of gene expression that define different cellular phenotypes or the genes that are induced in the cellular response to certain stimulations. Normalization of the measured intensities is a prerequisite of such comparisons. However, a fundamental problem in cDNA microarray analysis is the lack of a common standard to compare the expression levels of different samples. Several normalization protocols have been proposed to overcome the variabilities inherent in this technology. We have developed a normalization procedure based on within-array replications via a semilinear in-slide model, which adjusts objectively experimental variations without making critical biological assumptions. The significant analysis of gene expressions is based on a weighted t statistic, which accounts for the heteroscedasticity of the observed log ratios of expressions, and a balanced sign permutation test. We illustrated the use of the techniques in a comparison of the expression profiles of neuroblastoma cells that were stimulated with a growth factor, macrophage migration inhibitory factor (MIF). The analysis of expression changes at mRNA levels showed that approximately 99 genes were up-regulated and 24 were reduced significantly (P <0.001) in MIF-stimulated neuroblastoma cells. The regulated genes included several oncogenes, growth-related genes, tumor metastatic genes, and immuno-related genes. The findings provide clues as to the molecular mechanisms of MIF-mediated tumor progression and supply therapeutic targets for neuroblastoma treatment.

Gene Expression Profiling↗

PubMed2003

Endosomal dynamics of Met determine signaling output.

Proteasomal activity is required for Met receptor degradation after acute stimulation with hepatocyte growth factor (HGF). Inhibition of proteasomal activity with lactacystin leads to a block in the endocytic trafficking of Met such that the receptor fails to reach late endosomes/lysosomes, where degradation by acid-dependent proteases takes place (). In this article, we have biochemically determined Met internalization rates from the cell surface and shown that lactacystin does not inhibit the initial HGF-dependent internalization step of Met. Instead, it promotes the recycling pathway from early endosomes at the expense of sorting to late endosomes, thereby ensuring rapid return of internalized Met to the cell surface. We have used this perturbation of Met endosomal sorting by lactacystin to examine the consequences for HGF-dependent signaling outputs. In control cells HGF-dependent receptor autophosphorylation reaches a maximal level over 5-10 min but then attenuates over the ensuing 50 min. Furthermore, Met dephosphorylation can be kinetically dissociated from Met degradation. In lactacystin-treated cells, we observe a failure of Met dephosphorylation as well as Met degradation. Elements of the mitogen-activated protein kinase cascade, downstream of receptor activation, show a normal kinetic profile of phosphorylation, indicating that the mitogen-activated protein kinase pathway can attenuate in the face of sustained receptor activation. The HGF-dependent phosphorylation of a receptor substrate that is localized to clathrin-coated regions of sorting endosomes, Hrs, is dramatically reduced by lactacystin treatment. Reduction of cellular Hrs levels by short interfering RNA modestly retards Met degradation and markedly prevents the attenuation of Met phosphorylation. HGF-dependent Hrs phosphorylation and Met dephosphorylation may provide signatures for retention of the receptor in coated regions of the endosome implicated in sorting to lysosomes.

Acetylcysteine↗

PubMed2002

Grappling with metastatic risk: bringing molecular imaging of Met expression toward clinical use.

The availability of a test to assess the likelihood that a given tumor will invade or metastasize would be a useful development in clinical oncology. We propose that multimodality imaging of tumor expression of Met could serve as a prototype for metastatic risk stratification (MRS). Met, a receptor protein tyrosine kinase, is expressed by most solid tumors, and aberrant expression of Met is associated with poor clinical prognosis. We summarize the current status and predict the future direction of research in four areas of molecular imaging and cancer therapy that exploit Met.

Animals↗