Interaction between low dose-rate irradiation, mild hyperthermia and low-dose caffeine in a human lung cancer cell line.

PURPOSE: To investigate cell killing by means of low dose-rate irradiation (LDRI) combined with concurrent mild hyperthermia and to determine the effect of low-dose caffeine on this combination treatment. MATERIALS AND METHODS: Human lung adenocarcinoma cells, LK87, were treated with LDRI (50 cGy/h) in combination with mild hyperthermia at 41 degrees C and low-dose caffeine (1 mM). Cell survival was estimated by clonogenic assay. Flow-cytometry was performed with PI staining using FACScan. Heat-shock protein (HSP72/73) was measured by the Western blotting method. All treatments were simultaneously performed for up to 48 h (24 Gy). RESULTS: LDRI cytotoxicities were enhanced by hyperthermia at 41 degrees C. D0 calculated from the dose-response curve for LDRI combined with 41 degrees C was 3.46 Gy whereas it was 6.55 Gy for LDRI alone. The survival curve for LDRI +41 degrees C demonstrated no chronic thermotolerance up to 48 h. For LDRI + simultaneous low-dose caffeine, cell killing was also enhanced, where D0 was 3.38 Gy at 37 degrees C. Radiosensitization caused by caffeine was enhanced by combination with simultaneous mild hyperthermia at 41 degrees C, where D0=1.78 Gy. Cell cycle analysis demonstrated remarkable G2 and mild G1 arrest for LDRI alone, but only G1 arrest was observed for LDRI combined with 41 degrees C and for LDRI combined with caffeine. Strong and early G1 arrest was observed in the treatment with LDRI + caffeine at 41 degrees C. The amount of HSP72/73 in the combination of LDRI with caffeine at 41 degrees C was less than that at 41 degrees C alone. CONCLUSION: LDRI cytotoxicity was enhanced by non-lethal hyperthermia. Low dose caffeine produced further cell killing in the combination of LDRI with mild hyperthermia.

Early radiation effects in highly apoptotic murine lymphoma xenografts monitored by 31P magnetic resonance spectroscopy.

PURPOSE: Phosphorus-31 magnetic resonance spectra (31P-MRS) were obtained from highly apoptotic murine lymphoma xenografts before and up to 24 hr following graded doses of radiation ranging from 2 to 30 Gy. Radiation-induced apoptosis was also estimated up to 24 hr by scoring apoptotic cells in tumor tissue. METHODS AND MATERIALS: Highly apoptotic murine lymphoma cells, EL4, were subcutaneously transplanted into C57/BL mice. At 7 days after transplantation, radiation was given to the tumor with a single dose at 3, 10, and 30 Gy. The beta-ATP/Pi, PME/Pi, and beta-ATP/PME values were calculated from the peak area of each spectrum. Radiation-induced apoptosis was scored with counting apoptotic cells on hematoxylin and eosin stained specimens (% apoptosis). RESULTS: The values of % apoptosis 4, 8, and 24 hr after radiation were 21.8, 19.6, and 4.6% at 3 Gy, 35.1, 25.6, and 14.8% at 10 Gy, 38.4, 38.0, and 30.6% at 30 Gy, respectively (cf. 4.4% in control). There was no correlation between early change in beta-ATP/Pi and % apoptosis at 4 hr after radiation when most of the apoptosis occurred. An early decrease in PME/Pi was observed at 4 hr after radiation dose at 30 Gy. For each dose, the values of beta-ATP/Pi 24 hr after radiation were inversely related to radiation dose. CONCLUSION: The increase in beta-ATP/Pi observed by 31P-MRS was linked to the degree of histological recovery from radiation-induced apoptosis.

Cytotoxic enhancement of low dose-rate irradiation in human lung cancer cells by mild hyperthermia.

PURPOSE: The aim of this study was to investigate the cell killing induced by low dose-rate irradiation (LDRI) simultaneously combined with long duration mild hyperthermia in LK87 human lung cancer cells. Cell cycle alteration due to this combined treatment was also observed. MATERIALS AND METHODS: Human lung adenocarcinoma cells, LK87, were treated with concurrent LDRI (50 cGy/hr) and mild hyperthermia (38 to 42 degrees C). Cell survival was estimated by clonogenic assay. Flow cytometry was performed with FACScan. The treatments were simultaneously performed for up to 48 hr (24 Gy). RESULTS: Survival curves of mild hyperthermia alone revealed development of chronic thermotolerance up to 48 hr, whereas LDRI plus hyperthermia caused an exponential decrease in survival. The LDRI cytotoxicities were enhanced by mild hyperthermia over a non-lethal temperature range. The Do values calculated from dose response curves at 37, 38, 39, 40, 41 41.5 and 42 degrees C were 6.55, 5.25, 4.24, 3.99, 3.46, 1.83 and 0.70 Gy, respectively. Cell cycle analysis demonstrated a remarkable G2 and a mild G1 block for LDRI alone, but only a G1 block was observed for LDRI combined with 41 degrees C hyperthermia. CONCLUSION: The LDRI cytotoxicity was enhanced by long duration mild temperature hyperthermia. The suppression of chronic thermotolerance was considered to be a mechanism involved in this sensitization.

Thermal enhancement of pirarubicin (THP-adriamycin) by mild hyperthermia in vitro.

It has been demonstrated that hyperthermia can enhance the cytotoxicity of several anticancer drugs. Pirarubicin (THP-adriamycin) is a less cardiotoxic derivative of adriamycin. The thermal enhancement of cytotoxicity of pirarubicin was studied at various elevated temperatures in vitro by using a Chinese hamster cell line, V79. Cell survival curves were obtained at elevated temperatures for V79 cells treated with heat given alone or in combination with pirarubicin, and D0, the treatment time to reduce cell survival from S to S/e, was obtained for each cell survival curve. The relationship between the logarithm of the D0 and the treatment temperature for cells treated with heat alone was biphasic with a breaking point at 43 degrees C, although that for cells treated with a combination of heat and pirarubicin was exponential with no breaking point. The slope of this relationship for heat alone > 43 degrees C was -0.72 +/- 0.094 h/degree C which was not significantly different from the slope for combined heat and pirarubicin, -0.64 +/- 0.032 h/degree C. The results indicated that the cytotoxicity of pirarubicin was thermally enhanced specifically by mild hyperthermia. Pirarubicin uptake into the V79 cells during hyperthermia was independent of the treatment temperature (37, 42, and 44 degrees C), suggesting that the thermal enhancement of pirarubicin was not due to the increased drug-uptake at elevated temperatures. Based on these results, it is predictable that hyperthermia combined with pirarubicin is more effective below 43 degrees C which is easily achievable clinically.

Dermal patch anesthesia: pain-free puncture of blood access in hemodialysis patients.

Clinical application of dermal patch anesthesia to relieve pain at venous cannulation of blood-access was studied in hemodialysis patients. Aqueous gel of 10% lidocaine base with 3% glycyrrhetinic acid monohemiphthalate disodium (GA MHPh 2Na) was applied for 60 minutes to the skin of the patients. Degree of pain was expressed as a pain score. Analgesic effect of the lidocaine gel was evaluated in 16 patients in a placebo-controlled, double-blind, cross-over design by comparing the gel with lidocaine with a placebo gel without lidocaine. The mean pin-prick pain score (1.0 +/- 0.5) in the lidocaine gel patch (n = 16) was significantly lower than that (2.3 +/- 0.3) in the placebo gel patch (P < 0.01). In 8.8% of the patients, blood pressure was elevated after venous cannulation, but this tendency was modified by dermal patch anesthesia with the lidocaine gel. Plasma concentration of lidocaine was under the detection limit of assay (< 0.05 micrograms/mL) after dermal patch anesthesia in six subsequent dialysis treatments.