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Biomedical subjects

M Mendenhall

Publications and source records attributed to M Mendenhall.

7 recordsLinked to original sources
PubMed2001

Butyrate alters the expression and activity of cell cycle components in anaplastic thyroid carcinoma cells.

Anaplastic thyroid carcinoma (ATC) is the most malignant and aggressive form of thyroid cancer. Most patients die within months of diagnosis, primarily due to the absence of effective chemotherapeutic strategies. Identifying alternative therapies is necessary to increase long-term survival. Butyrate elicits a number of responses from cancer cells both in vitro and in vivo including growth repression, cell cycle arrest, differentiation, and apoptosis. Even though many types of cancer cells have been studied, little is known of the response of ATC cells to this drug. In this study, we report that butyrate induces differential cell cycle arrest (arrest in G1 and G2/M phases) in an ATC cell line that correlates with changes in the expression, phosphorylation, and activity of key components of the cell cycle machinery. Exposure to butyrate increases the expression of the cyclin-dependent kinase inhibitors, p21/Cip1 and p27/Kip1, decreases the expression of cyclin A and cyclin B, inhibits the phosphorylation of the retinoblastoma protein (pRb), and decreases the activity of cdk1 and cdk2-associated kinases. These results suggest that butyrate may be useful in the clinical treatment of ATC.

Butyrates↗
PubMed2001

Histone deacetylase inhibitors promote apoptosis and differential cell cycle arrest in anaplastic thyroid cancer cells.

Little information exists concerning the response of anaplastic thyroid carcinoma (ATC) cells to histone deacetylase inhibitors (HDAIs). In this study, the cellular response to the histone deacetylase inhibitors, sodium butyrate and trichostatin A, was analyzed in cell lines derived from primary anaplastic thyroid carcinomas. HDAIs repress the growth (proliferation) of ATC cell lines, independent of p53 status, through the induction of apoptosis and differential cell cycle arrest (arrested in G1 and G2/M). Apoptosis increases in response to drug treatment and is associated with the appearance of the cleaved form of the caspase substrate, poly-(ADP-ribose) polymerase (PARP). Cell cycle arrest is associated with the reduced expression of cyclins A and B, the increased expression of the cyclin-dependent kinase inhibitors, p21(Cip1/WAF1) and p27Kip1, the reduced phosphorylation of the retinoblastoma protein (pRb), and a reduction in cdk2 and cdk1-associated kinase activities. In ATC cells overexpressing cyclin E, drug treatment failed to replicate these events. These results suggest that growth inhibition of ATC cells by HDAIs is due to the promotion of apoptosis through the activation of the caspase cascade and the induction of cell cycle arrest via a reduction in cdk2- and cdk1-associated kinase activities.

Apoptosis↗
PubMed2000

Granulocyte macrophage colony-stimulating factor and interleukin 4 enhance the number and antigen-presenting activity of circulating CD14+ and CD83+ cells in cancer patients.

Antigen-presenting cells (APCs) are essential for stimulating antigen-specific immunity, including immunity against tumor cells. We hypothesized that systemic administration of granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4, which promote monocytes to differentiate into dendritic cells in vitro, might enhance the number and antigen-presenting activity of CD14+ cells in vivo. Patients with metastatic solid malignancies were treated with daily s.c. injections of either GM-CSF alone (2.5 microg/kg/day) or GM-CSF in combination with IL-4 (0.5-6.0 microg/kg/day) in a multicohort study. When given alone, GM-CSF increased the number of CD14+ cells but did not enhance the cells' expression of APC markers or antigen-presenting activity. In contrast, combination therapy with GM-CSF and IL-4 stimulated CD14+ cells to acquire several APC characteristics including increased expression of HLA-DR and CD11c, decreased CD14, increased endocytotic activity, and the ability to stimulate T cells in a mixed leukocyte reaction. Combination therapy also induced a dose-dependent increase in the number of CD14-/CD83+ cells with APC activity. Clinically significant and sustained tumor regression was observed in one patient. Systemic therapy with GM-CSF and IL-4 may provide a mechanism for increasing the number and function of APCs in patients with cancer.

Antigen-Presenting Cells↗
PubMed1999

The cyclin-dependent kinase inhibitory domain of the yeast Sic1 protein is contained within the C-terminal 70 amino acids.

By inhibiting the activity of Cdc28/Clb cyclin-dependent protein kinase (CDK) complexes, Sic1 prevents the premature initiation of S phase in the yeast Saccharomyces cerevisiae. By testing a series of Sic1 truncation mutants, we have mapped the minimal domain necessary for Cdc28/Clb inhibition in vivo to the C-terminal 70 amino acids of Sic1. Site-directed mutagenesis was used to show that a sequence that matches the zRxL motif found in mammalian CDK inhibitors is essential for Sicl function. This motif is not found in the Schizosaccharomyces CDK inhibitor p25rum1, which appears to be a structural and functional homolog of Sicl. Based on the mutational data and sequence comparisons, we argue that Sic1 and p25rum1 are structurally distinct from the known mammalian CDK inhibitors, but may bind CDK complexes in a manner more closely resembling CDK substrates like the retinoblastoma and E2F proteins.

Amino Acid Sequence↗
PubMed1994

Tissue ablation by a free-electron laser tuned to the amide II band.

Efforts to ablate soft tissue with conventional lasers have been limited by collateral damage and by concern over potential photochemical effects. Motivated by the thermal-confinement model, past infrared investigations targeted the OH-stretch mode of water with fast pulses from lasers emitting near 3,000 nm (refs 1, 7-9). What does a free-electron laser offer for the investigation of tissue ablation? Operating at non-photochemical single-photon energies, these infrared sources can produce trains of picosecond pulses tunable to the vibrational modes of proteins, lipids and/or water. We report here that targeting free-electron laser radiation to the amide II band of proteins leads to tissue ablation characterized by minimal collateral damage while maintaining a substantial ablation rate. To account for these observations we propose a novel ablation mechanism based on compromising tissue through resonant denaturation of structural proteins.

Amides↗
PubMed1994

Computer-assisted surgical techniques using the Vanderbilt Free Electron Laser.

The Vanderbilt Free Electron Laser (FEL) is capable of lasing between 2.0 and 8.0 microns with a high peak intensity pulsed structure. The FEL is used to investigate potential applications in otolaryngology. Charring of temporal bones and thermal stress patterns in Plexiglas indicate thermal buildup at 20 and 10 Hz repetition rates of the laser. Also, transient temperature changes measured with thermocouples in a gelatin model reveal that significant heat production occurs at these laser repetition rates. To utilize the fastest laser repetition rates and maintain minimal lateral thermal damage, a computer-controlled scanning system was devised. The authors have also used the computer control with the carbon dioxide laser and experienced improved ablation.

Animals↗