Change in blood test after irradiation with high doses for inactivation of Lassa virus.

In 2006 we had a patient with Lassa fever in the University Hospital of Frankfurt. To insure a short turn-around time from the laboratory, it was necessary to have blood which was not contaminated with viruses. One method of achieving this is by irradiating the blood with high doses of ionising radiation. Inactivation of arena viruses requires doses between 12 kGy and 20 kGy, depending on temperature. In this study we investigated if plasma and serum parameters are changed by irradiation with 5 kGy, 10 kGy, 15 kGy, 20 kGy or 40 kGy of 10 MeV electrons. For the 22 serum parameters measured there was no influence of radiation up to 20 kGy. Only at 40 kGy was a significant decrease noted. For the six plasma parameters the values were significantly dose dependent. To correct this a mathematical function was defined. It is possible to inactivate Lassa virus with high doses of radiation. Most of the measured blood values don't change. For those which were influenced it was possible to define a mathematical function.

Radiation enhancement of gemcitabine in two human squamous cell carcinoma cell lines.

BACKGROUND: Gemcitabine (dFdC) is a new nucleoside analogue with promising activity in different solid tumors. We investigated whether dFdC enhances the effect of irradiation in human squamous carcinoma cells of the oropharynx (#4197) and of the uterine cervix (HeLa) with special regard to the time-dose-relationship concerning dFdC and the dependence upon the timing of irradiation. MATERIALS AND METHODS: Under standardized conditions monolayers of cells were exposed to various dFdC concentrations (0.003-10 mumol/l) for different times (4-24 h). Irradiation (0-6 Gy) followed immediately or 12 h after dFdC exposure (0.003-0.03 mumol/l; 4-24 h). RESULTS: The cytotoxic effect of dFdC depends on its concentration and the exposure duration. Exposed to non and/or slightly cytotoxic concentrations (> or = 0.003-0.03 mumol/l) for 4, 8, 16 and 24 h and followed by immediate irradiation the radiation enhancement ratio (RER) is 1.03-1.67 in #4197 cells and 1.04-2.47 in HeLa cells, respectively. Irradiated 12 h after 24 h exposure (dFdC 0.01-0.03 mumol/l) the RER is reduced to 1.10-1.17 (#4197) and 1.18-1.72 (HeLa). CONCLUSIONS: Depending on the drug concentration, exposure duration, and timing of irradiation, dFdC enhances the irradiation effect on human squamous cell carcinoma cell lines (#4197, HeLa).

[The intensification of the radiotherapeutic effect on HeLa cells by gemcitabine]. / Verstärkung der radiotherapeutischen Wirkung auf HeLa-Zellen durch Gemcitabine.

BACKGROUND: Gemcitabine (2'.2'-difluorodeoxycytidine; dFdC) is a new nucleoside analog with promising activity in different solid tumors in vivo and in vitro. As published up to now, combined with irradiation dFdC demonstrates a radiosensitizing effect on pancreas and colon carcinoma cell lines. We investigated the influence of dFdC on the radiosensitization of human squamous carcinoma cells of the cervix (HeLa-cells, ATCC CCL-2). MATERIAL AND METHODS: Under standardized conditions monolayer cultures of HeLa-cells were incubated in medium with dFdC for different times (4 to 24 hours) and exposed to different concentrations (0.003, 0.01 and 0.03 mumol/l). Irradiation (2 to 6 Gy, electron beam) followed immediately or 12 hours after dFdC-exposure. Cell survival was determined by colony forming assay. Using the linear-quadratic model cell survival curves were fit after correction for drug-induced cytotoxicity and the mean inactivation dose (MID) was calculated. Radiation enhancement was defined as the ratio MIDRT(= Control)/MIDRT + dFdC > 1. RESULTS: Exposed to gemcitabine for 4 and 8 hours and followed by immediate irradiation the radiation enhancement ratio (Table 1) is 1.07 to 1.14 and 1.04 to 1.22, respectively, if dFdC concentration is > or = 0.01 to 0.03 mumol/l. Further increase of the irradiation effect is demonstrated in cells exposed to > or = 0.003 to 0.03 mumol/l dFdC for 16 and 24 hours (radiation enhancement ratio 1.08 to 2.0 and 1.08 to 2.48, respectively) (Figure 3). If irradiation is applied 12 hours after 24-hour-exposure (0.01 and 0.03 mumol/l) the enhancement ratio was 1.18 and 1.7, respectively (Figure 4). CONCLUSIONS: In cell cultures the assays combining irradiation with dFdC demonstrate that dFdC is a potent radiation sensitizer of HeLa-cells. The effect of irradiation on cells pre-treated with non- and hardly cytotoxic concentrations of dFdC is increased in dependence of dose and time of exposure.

The RBE of negative pions in the treatment of tumors with different volumes.

For negative pions, large differences exist between experimental RBE values obtained by in vivo investigations with animals and corresponding data being used in clinical tumor therapy. Therefore, the influence of the treatment volume on the radiation quality and respectively on the RBE is examined. The RBE for euoxic mammalian cells is measured with high precision in different volumes irradiated in the spot-scan mode with the PIOTRON at the Paul Scherrer Institute. It is shown experimentally that the RBE is reduced if the radius of the irradiation volume is increased. Using a simple mathematical approximation for the spot-scan technique this relation can be understood quantitatively. The same approximation is also used to calculate dose mean values for the lineal energy yD present in different irradiated volumes. The good agreement with existing experimental data for yD indicates that the approximation used is adequate and the main physical parameters have been taken into consideration. The above mentioned differences between animal experiments and treatment of patients can be explained by changes in the effective radiation quality due to the scanning procedure used in the clinical treatments.

Tumor response to ionizing radiation and combined 2-deoxy-D-glucose application in EATC tumor bearing mice: monitoring of tumor size and microscopic observations.

The present study deals with the changes induced by two fractionation schedules (5 x 9 Gy and 10 x 4.5 Gy; 30 MeV-electrons) of ionizing radiations and 2-deoxy-D-glucose (2-DG) application on EATC tumor bearing swiss albino mice. The monitoring of tumor response was carried out by means of caliper measurement on the macroscopic level and by histopathological examination of tumor preparations stained with hematoxiline and eosine on the microscopic level. The tumor material was assessed at suitable intervals after treatment by killing the animals. The tumor response was analysed in the histological preparations and the thickness of the tumor band was determined quantitatively by an ocular micrometric technique. Tumor damage was most extensive in the combined treated animals (5 x 9 Gy + 2-DG). Only in this group local tumor control was achievable. The histological analysis of tumor preparations revealed additional data about treatment-induced changes in the tumor compared to the measurement of the tumor volume with mechanical calipers. We also found that the treatment outcome could be predicted from the histopathological analysis. It is concluded that studies involving histopathological examinations may give some insight into the way cancer is controlled by radiotherapy and may be of value in prognosis and selection of treatment in patients.

The RBE of euoxic and hypoxic Ehrlich ascites tumour cells irradiated with negative pions in vitro and in vivo.

Ehrlich ascites tumour cells (EAT-F5) were irradiated in vitro with the sparsely ionizing "plateau pions" and with the more densely ionizing "peak pions". From cell survival curves obtained under euoxic and hypoxic conditions, the RBE for the production of irreparable lethal and potentially lethal damage was derived. Cells of the same strain were used to produce solid tumours in the leg muscle of mice. Survival of these cells irradiated in vivo was compared with the corresponding in vitro data. It can be concluded that a large fraction of hypoxic cells is present in these tumours and that repair takes place in vivo at least as much as under the in vitro conditions. These solid tumours were irradiated with 5 dose fractions of fast protons as reference radiation, and the probability pT of tumour destruction was determined as a function of dose. Irradiation with a spot of "plateau pions" indicated the same pT as a function of dose, but side effects in the intestinal tract increased also with dose, leading to the death of the animals. The probability for avoiding these side effects in the animals, pS, was also determined. Using both values, pT and pS, the probability for local tumour control was estimated. Irradiation with "peak pions" resulted in an RBE of about 2.5 for tumour destruction corresponding to the RBE found in vitro for the production of irreparable lethal lesions in hypoxic cells. Side effects in the mouse gut showed a RBE of 2.0, corresponding to irreparable lethal lesions in euoxic in vitro cells.

Repair inhibition in tumours irradiated with fast protons and negative pions.

Solid Ehrlich mouse tumours were irradiated in the 80 MeV proton beam of the Paul-Scherrer-Institute. The tumour volume was measured as a function of time after irradiation and two experimental endpoints were determined: local tumour control and minimal tumour volume after irradiation. The application of 2-deoxy-D-glucose (2-DG; 2 mg/kg) increased the radiation effect of protons by a factor of 1.4. The same tumour system was used with negative pions. Human tumours are usually irradiated with a mixed radiation produced by the "spot-scan-technique". This radiation quality was simulated in the mouse experiment by two successive irradiations with a spot of densely ionizing peak pions and a spot of sparsely ionizing plateau pions. Application of 2-DG raised the radiation effect due to the sparsely ionizing component again by a factor of 1.4. This indicates that clinical results in radiotherapy might be improved by application of 2-DG during the treatment.