Biomedical subjects

J E Kalns

Publications and source records attributed to J E Kalns.

5 recordsLinked to original sources

PubMed2001

Expression of DT-diaphorase and cytochrome P450 reductase correlates with mitomycin C activity in human bladder tumors.

Mitomycin C (MMC) is activated by DT-diaphorase (DTD) and cytochrome P450 reductase (P450R). In cancer cell lines, MMC cytotoxicity is correlated with DTD and P450R expression levels. The present study investigated the relationship between enzyme expression/activity and MMC cytotoxicity in patient bladder tumors. DTD and P450R expression was detected by competitive reverse transcription-PCR and their activity was measured by bioreductive assays. The expression of DTD and P450R in patient tumors (n = 29), as ratios to beta-actin levels, varied from 0 to 90% and 0 to 29%, respectively. The DTD expression was significantly correlated with P450R expression (r(2), 0.32; P < 0.01), whereas the average DTD level was 2-fold higher than that of P450R (P < 0.01). Among the 29 tumors, 21 provided sufficient materials to evaluate tumor sensitivity to MMC. The concentration of MMC required to produce 50% inhibition (IC(50)) of DNA precursor incorporation for a 2-h treatment ranged from 0.17 to 18.1 microg/ml, indicating a 110-fold intertumor variation, with the high-grade and more invasive tumors being less chemosensitive compared with the low-grade and less invasive tumors. Tumor sensitivity to MMC, as indicated by the inverse of IC(50) values, was positively correlated with the expression of DTD (r(2), 0.28; P < 0.05) and P450R (r(2), 0.26; P < 0.05). Multivariate analysis indicates DTD expression and P450R expression as better determinants of MMC activity compared with other pathobiological factors (e.g., tumor grade, stage, and labeling index) that have been shown to significantly correlate with MMC activity. Eleven tumors were studied for the relationship between gene expression level and enzyme activity of DTD and P450R. The DTD activity was significantly correlated with the gene expression level (r(2), 0.84; P < 0.001). For P450R, there is a trend of a correlation between enzyme activity and its mRNA level, but the correlation was not statistically significant (r(2), 0.28; P = 0.09). These data indicate that the sensitivity of patient bladder tumors to MMC is correlated with the expression of DTD and P450R in tumors and suggest that the lower expression of these enzymes in the high-grade and more invasive tumors is a cause of the lower efficacy of intravesical MMC in these tumors.

Adult↗

PubMed1999

Exposure to hyperbaric oxygen induces cell cycle perturbation in prostate cancer cells.

Cell cycle synchronization of tumor cells by exposure to hyperbaric oxygenation (HBO) may increase the efficacy of chemotherapy or radiation by placing cells into a chemosensitive portion of the cycle. The purpose of the current study was to examine oxygen pressure-dependent relationships with respect to the cell cycle in prostate tumor cells in vitro. LNCaP cells were grown in an incubator at 21% O2 and then exposed to 100% oxygen at pressures up to 6 atmospheres (atm) for 1.5 h. Cells were then returned to the incubator and evaluated for DNA content by propidium iodide and new DNA synthesis with a pulse-chase experiment. Cell cycle effects were evaluated by flow cytometry. Exposure to HBO increased the percentage of cells synthesizing new DNA in a dose-dependent fashion: 0 atm, 44%; 6 atm, 65%. Cells that synthesize new DNA accumulate in G2/M as a function of partial pressure of oxygen. These results suggest that HBO induces cells to enter the cell cycle and accumulate in G2/M. Cell cycle synchronization and entry of senescent cells into the cell cycle suggest that HBO may be a useful adjuvant to chemotherapy or radiation in the treatment of prostate cancer. There are two potential mechanisms of action that may make HBO efficacious in the treatment of prostate cancer. HBO may potentiate cancer chemotherapeutic agents that cause damage to DNA during DNA synthesis or HBO may inhibit cell division causing accumulation in G2/M.

Atmospheric Pressure↗

PubMed1999

Fibroblast response to rapid decompression and hyperbaric oxygenation.

INTRODUCTION: The cellular basis for symptoms associated with rapid decompression and the use of hyperbaric oxygenation treatment (HBO) is not established. METHODS: Image analysis, sulforhodamine B assay and bromodeoxyuridine (BrDU) incorporation were used to identify cellular changes associated with rapid decompression (RD) or hyperbaric oxygenation (HBO). Human fibroblasts were exposed to RD or HBO and compared with untreated cells. Immediately following treatment, the fraction of cells synthesizing DNA was measured by detection of cells incorporating the BrDU. At 1 d and 3 d following the treatments, total cell protein adherent to the bottom of wells was measured using a sulforhodamine B assay. Cell density was observed with light microscopy and quantified with image analysis. RESULTS: RD increased total protein significantly, (p < 0.05) relative to control, while HBO had less effect. The fraction of cells synthesizing DNA was increased by HBO and reduced by RD relative to control (p < 0.05). Image analysis showed that cell density at day 1 was: control>HBO>RD; and at day 3: RD>HBO>control, indicating an increase in proliferation induced by the treatments. CONCLUSION: This data shows that HBO and RD increase the proliferation of fibroblasts for 24 h following treatment. HBO increased DNA replication. While there was a decrease in DNA replication following RD, protein synthesis was enhanced.

Bromodeoxyuridine↗

PubMed1997

Prolonged weightlessness affects promyelocytic multidrug resistance.

An immortalized promyelocytic cell line was studied to detect how doxorubicin uptake is affected by microgravity. The purpose of this experiment was to identify the effect that microgravity may have on multidrug resistance in leukocytes. HL60 cells and HL60 cells resistant to anthracycline (HL60/AR) were grown in RPMI and 10% FBS. Upon reaching orbit in the Space Shuttle Endeavour, the cells were robotically mixed with doxorubicin. Three days after mixing, cells were fixed with paraformaldehyde/glutaraldehyde. Ground control experiments were conducted concurrently using a robot identical to the one used on the Shuttle. Fixed cells were analyzed within 2 weeks of launch. Confocal micrographs identified changes in cell structure (transmittance), drug distribution (fluorescence), and microtubule polymerization (fluorescence). Flight cells showed a lack of cytoskeletal polymerization resulting in an overall amorphic globular shape. Doxorubicin distribution in ground cells included a large numbers of vesicles relative to flight cells. There was a greater amount of doxorubicin present in flight cells (85% +/- 9.7) than in ground control cells (43% +/- 26) as determined by image analysis. Differences in microtubule formation between flight cells and ground cells could be partially responsible for the differences in drug distribution. Cytoskeletal interactions are critical to the function of P-glycoprotein as a drug efflux pump responsible for multidrug resistance.

Biological Transport↗

PubMed1995

Design and analysis of in vitro antitumor pharmacodynamic studies.

The relationship between drug concentration (C), exposure time (t), and the resulting effect (h) for a chemotherapeutic agent is expressed as Cn x t = h. The value of n, derived from curve fitting of the C versus t plot, indicates the relative importance of concentration and exposure time. The selection of concentrations and exposure times in a pharmacodynamic experiment may affect the precision and accuracy of parameter estimation. The use of optimal designs is even more critical when the numbers of experimental conditions are limited by tumor availability (e.g., small size of surgical specimens from patients). The present study used computer-simulated data to define the most efficient in vitro pharmacodynamic experimental designs and the optimal method of pharmacodynamic data analysis. All studies used Monte Carlo simulations to compare designs with varying numbers of drug concentrations, exposure times, and replications. For each selected design, 50-100 error-containing data sets were created by addition of experience-based random errors to expected concentration-response profiles. To compare methods of data analysis, the same 1250 simulated data sets were analyzed by two methods (i.e., surface response method and traditional method). The results showed that simultaneous fitting of drug effect at all concentrations and all exposure times by the surface response method yielded n estimates that had greater precision and accuracy than a traditional method that required sequential determination of the effective inhibitory concentration (e.g., IC50) and then the n value using the IC50 at different exposure times. Subsequent studies were analyzed using the surface response method. To evaluate the effect of selection of concentrations and exposure times on the precision of n estimation, between 1100 and 2200 simulated data sets, with 400 observations per data set, were generated using different exposure times and drug concentrations. Because the number of observations was limited to 400, the number of replications at each condition varied depending on the total number of selected conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

Antineoplastic Agents↗