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Biomedical subjects

D Mays

Publications and source records attributed to D Mays.

10 recordsLinked to original sources
PubMed2001

Kinetics of p53 binding to promoter sites in vivo.

Downstream target genes of p53 are thought to mediate its tumor-suppressive activity, but it is unknown whether differential transactivation of these genes is regulated at the level of p53 binding to their promoters. To address this issue, p53 binding in vivo to consensus sites in the p21(Waf1), MDM2, and PIG3 promoters was investigated in cells exposed to adriamycin (ADR) or ionizing radiation as well as in an inducible p53 cell line. p53-DNA complexes were cross-linked in vivo by treating the cells with formaldehyde and processed by chromatin immunoprecipitation-PCR. This methodology allowed for the analysis of relevant p53-DNA complexes by preventing redistribution of cellular components upon collection of cell extracts. Increased p53 binding to the p21(Waf1), MDM2, and PIG3 promoters occurred within 2 h after p53 activation; however, significant increases in PIG3 transcription did not occur until 15 h after p53 binding. Gel shift analyses indicated that p53 had lower affinity for the consensus binding site in the PIG3 promoters compared to its consensus sites in the p21 and MDM2 genes, which suggests that additional factors may be required to stabilize the interaction of p53 with the PIG3 promoter. Further, acetylated p53 (Lys382) was found in chemically cross-linked complexes at all promoter sites examined after treatment of cells with ADR. In summary, the kinetics of p53 binding in vivo to target gene regulatory regions does not uniformly correlate with target gene mRNA expression for the p53 target genes examined. Our results suggest that target genes with low-affinity p53 binding sites may require additional events and will have delayed kinetics of induction compared to those with high-affinity binding sites.

Gene Expression Regulation, Neoplastic↗
PubMed1999

Defective G1-S cell cycle checkpoint function sensitizes cells to microtubule inhibitor-induced apoptosis.

Defective cell cycle checkpoint function has been linked to enhanced sensitivity of tumor cells to certain genotoxic agents. To determine whether loss of the G1-S checkpoint function would sensitize tumor cells to microtubule inhibitor (MTI)-induced apoptosis, we examined the effect of the MTIs, Taxol and vincristine, on the cell cycle kinetics and survival of two isogenic cell lines, HCT116 p21+/+ and HCT116 p21-/-, which differ only at the p21 locus. p21-deficient cells displayed a dose-dependent, enhanced chemosensitivity to MTIs in both monolayer and soft agar assays as well as in mice xenograft tumors. The increased sensitivity of the p21-deficient cells to MTIs correlated with prolonged cyclin B1/Cdc2 activity and the occurrence of endoreduplication. Furthermore, sensitivity of p53-deficient cells to MTI-induced apoptosis was significantly reduced by induction of ectopic p21 protein. The results suggest that the status of G1-S checkpoint function in tumor cells may be an important determinant in the efficacy of MTIs used clinically.

Animals↗
PubMed1999

Treatment with farnesyl-protein transferase inhibitor induces regression of mammary tumors in transforming growth factor (TGF) alpha and TGF alpha/neu transgenic mice by inhibition of mitogenic activity and induction of apoptosis.

Mouse mammary tumor virus-transforming growth factor alpha (MMTV-TGF alpha) and MMTV-TGF alpha/neu transgenic mice develop mammary tumors after a long latency and therefore provide useful model systems for breast cancer with its recognized activation of receptor tyrosine kinase signaling. We used these mice to study the antitumor effect of L-744,832 (FTI), a potent and selective inhibitor of farnesyl-protein transferase, and hence of Ras function. A total of 55 mice were assigned randomly to treatment with FTI or vehicle, and one-half of the mice were crossed over after initial treatment to the opposite group. L-744,832 induced reversible regression of mammary tumors that was paralleled by a decrease in serum levels of TGF alpha secreted by the tumor cells. There was no difference in response to treatment with FTI between MMTV-TGF alpha mice, in which tumorigenesis was accelerated by multiparity or the chemical carcinogen 7,12-dimethylbenzanthracene, and MMTV-TGF alpha/neu mice. The tumor histological type had no impact on FTI sensitivity. For mechanistic analyses, tumor excision biopsies were obtained from 12 mice before and after treatment with L-744,832. In these samples, tumor regression was paralleled biochemically by inhibition of mitogen-activated protein kinase activity and biologically by an increase in G1-phase and decrease in S-phase fractions, as well as induction of apoptosis. These results suggest that the potential clinical use of FTI could be expanded to include cancers harboring activated receptor tyrosine kinases as well as those containing activated Ras.

Alkyl and Aryl Transferases↗
PubMed1998

Mitotic phosphorylation of Bcl-2 during normal cell cycle progression and Taxol-induced growth arrest.

There is increasing evidence that prolonged mitotic arrest initiates apoptosis; however, little is known about the signaling pathways involved. Several studies have associated deregulated Cdc2 activity with apoptosis. Herein, we report that the anti-apoptotic protein, Bcl-2, undergoes cell cycle-dependent phosphorylation during mitosis when there is elevated Cdc2 activity. We found that paclitaxel (Taxol(R)) treatment of epithelial tumor cells induced a prolonged mitotic arrest, elevated levels of mitotic kinase activity, hyperphosphorylation of Bcl-2, and subsequent cell death. The Taxol-induced Bcl-2 phosphorylation was dose-dependent. Furthermore, phosphorylated Bcl-2 remained complexed with Bax in Taxol-treated cells undergoing apoptosis. Immunoprecipitation experiments revealed a Bcl-2-associated kinase capable of phosphorylating histone H1 in vitro. However, the kinase was likely not cyclin B1/Cdc2, since cyclin B1/Cdc2 was not detectable in Bcl-2 immunoprecipitates, nor was recombinant Bcl-2 phosphorylated in vitro by cyclin B1/Cdc2. The results of this study further define a link between mitotic kinase activation and the apoptotic machinery in the cell. However, the role, if any, of prolonged Bcl-2 phosphorylation in Taxol-mediated apoptosis awaits further definition of Bcl-2 mechanism of action. Taxol may increase cellular susceptibility to apoptosis by amplifying the normal downstream events associated with mitotic kinase activation.

Antineoplastic Agents, Phytogenic↗
PubMed1994

Hypothyroidism associated with aminoglutethimide in patients with prostate cancer.

OBJECTIVE: The administration of aminoglutethimide and hydrocortisone is a second-line hormonal maneuver commonly prescribed for the treatment of metastatic prostate cancer. We determine the incidence of aminoglutethimide-induced primary hypothyroidism in an elderly population who have prostate cancer. DESIGN: Prospective evaluation. PATIENTS: Twenty-nine men with stage D2 prostate cancer who were treated at the National Cancer Institute, Bethesda, Md, in 1992. RESULTS: Clinical and biochemical evidence of hypothyroidism (thyrotropin levels greater than 10 mU/L) was noted in nine of 29 patients treated following the initiation of aminoglutethimide (250 mg four times daily). The elevation in thyrotropin and the clinical symptoms of hypothyroidism were reversed by the administration of levothyroxine (n = 4). CONCLUSION: Hypothyroidism should be included in the differential diagnosis of lethargy in elderly patients who are receiving aminoglutethimide for prostate cancer. Furthermore, patients who are receiving this agent at a dosage of 1000 mg/d or greater should have their serum thyrotropin levels monitored, and replacement therapy with levothyroxine should be initiated when abnormally elevated levels are noted.

Aged↗
PubMed1992

Comprehensive evaluation of a Thorotrast patient: an overview.

For several decades, thousands of people received Thorotrast during the course of angiography and other radiologic procedures. Eventually, as the hazards of this radioactive, radiographic contrast agent became apparent, research was initiated to further evaluate its associated adverse effects. In 1988 and 1989, Charles W. Mays, together with colleagues at a variety of sites, developed a detailed protocol for the comprehensive postmortem evaluation of one subject who had been administered Thorotrast 36 y previously. This case represents the first holistic approach to the analysis of Thorotrast in a whole body, simultaneously assembling clinical and autopsy findings with dosimetric, radiochemical, autoradiographic, and molecular evaluations.

Aged↗
PubMed1992

Nursing research in the VA system. A consortium approach.

Five Veterans' Administration Medical Centers formed a consortium to promote nursing research. Consortium arrangements focusing on research are reviewed based on the literature, the consortium's experience, and a survey of 171 VA facilities. Consortiums are suggested for multisite facilities, such as city, state, proprietary, and religious hospital systems, to increase the quality and quantity of nursing research where institutional mechanisms for overcoming the difficulties of meeting and sharing information are already in place.

Hospitals, Veterans↗