Biomedical subjects

Jonathan Grim

Publications and source records attributed to Jonathan Grim.

3 recordsLinked to original sources

PubMed2005

Estrogen effects on tubulin expression and taxane mediated cytotoxicity in prostate cancer cells.

BACKGROUND: The present study was designed to determine if estrogens change microtubule polymerization and modulate cell cycle progression in vitro, related to modulation of tubulin expression and to determine if estrogens had antagonistic or synergistic effects with microtubule active agents. METHODS: cDNA array analysis of LNCaP cells treated with the estrogens, estradiol, estrone, diethylstilbestrol (DES), and 2-methoxyestradiol (2-ME) was carried out and the results confirmed by PCR and Western blotting. Microtubule arrays in cells treated with estrogens were assessed using indirect immunofluorescence. The effects of combining estrogens with taxane was assessed by MTT assay and flow cytometry for cell cycle kinetics. Human prostate cancer xenografts were treated with DES and docetaxel to assess the effects of combining estrogens and taxane in vivo. RESULTS: Treatment of LNCaP cells with DES and 2-ME suppressed transcripts and protein for beta-tubulin isotype IVa. This effect on tubulin synthesis was not blocked by estrogen or androgen receptor modulators. Other estrogens had no effect on beta-tubulin expression. 2-ME and DES decreased the density of microtubules. The administration of DES or 2-ME with paclitaxel enhanced cytotoxicity and G(2)-M arrest in vitro. DES enhanced tumor suppression in a human prostate cancer xenograft model when combined with the taxane docetaxel. CONCLUSION: The use of DES and 2-ME enhances the effects of taxanes and may be a novel and important means of increasing therapeutic efficacy of cytotoxic chemotherapy against prostate carcinoma.

Blotting, Western↗

PubMed2003

Werner syndrome protein limits MYC-induced cellular senescence.

The MYC oncoprotein is a transcription factor that coordinates cell growth and division. MYC overexpression exacerbates genomic instability and sensitizes cells to apoptotic stimuli. Here we demonstrate that MYC directly stimulates transcription of the human Werner syndrome gene, WRN, which encodes a conserved RecQ helicase. Loss-of-function mutations in WRN lead to genomic instability, an elevated cancer risk, and premature cellular senescence. The overexpression of MYC in WRN syndrome fibroblasts or after WRN depletion from control fibroblasts led to rapid cellular senescence that could not be suppressed by hTERT expression. We propose that WRN up-regulation by MYC may promote MYC-driven tumorigenesis by preventing cellular senescence.

Cell Division↗

PubMed2003

Multisite phosphorylation by Cdk2 and GSK3 controls cyclin E degradation.

Autophosphorylation-triggered ubiquitination has been proposed to be the major pathway regulating cyclin E protein abundance: phosphorylation of cyclin E on T380 by its associated CDK allows binding to the receptor subunit, Fbw7, of the SCFFbw7 ubiquitin ligase. We have tested this model in vivo and found it to be an inadequate representation of the pathways that regulate cyclin E degradation. We show that assembly of cyclin E into cyclin E-Cdk2 complexes is required in vivo for turnover by the Fbw7 pathway; that Cdk2 activity is required for cyclin E turnover in vivo because it phosphorylates S384; that phosphorylation of T380 in vivo does not require Cdk2 and is mediated primarily by GSK3; and that two additional phosphorylation sites, T62 and S372, are also required for turnover. Thus, cyclin E turnover is controlled by multiple biological inputs and cannot be understood in terms of autophosphorylation alone.

Animals↗