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At least 991 records · Page 55Linked to original sources

PubMed1989

Rapid fluorescence-based assay for radiosensitivity and chemosensitivity testing in mammalian cells in vitro.

An efficient and rapid cytotoxicity assay has been developed, particularly for radiobiological studies, utilizing 96-well microtiter plates. Several days after treatment, cell numbers per well were measured by fluorescent intensity using an automatic reader after staining with the DNA specific dye Hoechst 33258. For radiobiological applications, a microtiter plate irradiation box was designed and built which allowed a variable number of wells (minimum 4, maximum 16) to be irradiated at one time. In this manner, complete dose-response curves could be obtained from one plate. The assay depends on the growth of surviving and untreated cells, and by appropriate choice of conditions (cell numbers plated, time of assay), cell survival curves for this quick fluorescence assay were in reasonable agreement with those from a clonogenic assay for cisplatin and X-ray-induced cell killing. The assay can span 1.5-2 decades of cell survival and is suitable for any cell line which grows as a monolayer. Radiobiological applications were tested using agents or conditions which modified radiation damage. Firstly, sublethal damage repair could be demonstrated in RIF1 mouse tumor cells by comparing the survival curve for a single X-ray dose with that for two fractions separated by 4 h. Secondly, incorporation of 5-iodo-2'-deoxyuridine into cellular DNA was shown to radiosensitize Chinese Hamster cells, with similar enhancement ratios obtained from the fluorescence and clonogenic assays. Thirdly, radiosensitization by cisplatin and radioprotection by cysteamine could be readily measured using the quick fluorescence assay. The ability to have multiple dose groups per plate makes it an efficient assay for both radiosensitivity and chemosensitivity testing.

Animals↗

PubMed1989

Chemosensitivity and radiosensitivity of small cell lung cancer cell lines studied by a newly developed 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) hybrid assay.

The 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) hybrid assay was developed by technically combining the human tumor clonogenic assay and the MTT assay to make the most of both assays. This assay was able to estimate the in vitro growth of cultured cell lines and of tumor cells in pleural effusion, suggesting the possibility of its use for assessment of chemosensitivity and radiosensitivity of fresh tumor samples. Multiple cell lines [including morphological and/or phenotypical in vitro converters and cisplatin (CDDP)-resistant lines] were established from three patients with small cell lung cancer at different stages of the disease. Chemosensitivity of these cell lines to four commonly used chemotherapeutic drugs was tested by the MTT hybrid assay. SK1 and SK3 lines were established from Patient S. K. before and after chemotherapy and radiotherapy, respectively. SK3/CDDP, a CDDP-resistant line derived from the SK3 line, was 30-fold more resistant to CDDP [50% inhibiting dose (IC50), 21.5 micrograms/ml] than the SK1 line. In Patient M. O., MOA2/CDDP, a CDDP-resistant line derived from MOA2 (an in vitro converter from the MO line), was 41-fold more resistant to CDDP (IC50, 37 micrograms/ml) than the parent MO line. From Patient T. M., TM1 and TM2 lines were established before and after chemotherapy, respectively. The latter showed 6-fold more resistance to CDDP than the former. Chemosensitivity of these lines to three other drugs, 4-hydroperoxycyclophosphamide, Adriamycin, and etoposide, suggested cross-resistance between CDDP and 4-hydroperoxycyclophosphamide. Radiosensitivity study was also carried out with the MTT hybrid assay. The MOA2 line was more resistant [Do, 3.0 Gy; extrapolation number (n), 4.0] than the parental MO line (Do, 1.6 Gy; n, 2.1). There was no clear difference in radiosensitivity between the cell lines established before and after radiation therapy in Patient S. K.

Antineoplastic Agents↗

PubMed1989

[Prediction of radiosensitivity by DNA analysis].

The aim of the study is to investigate the relationship between DNA histogram and radiosensitivity on tumor specimens taken directly from patients. Flow cytometric DNA content analysis with PI (Propidium iodide) was performed on specimens of cervical carcinoma. Radiosensitivities of respective tumors were determined on biopsy specimens that were taken 3 weeks after the start of radiotherapy. Five parameters (over 4C, %G2M, %S, PI, DI) were calculated from DNA Histogram. Among these parameters over 4C, %G2M and PI correlated well to radiosensitivity.

Adult↗

PubMed1978

In vivo evaluation of the radiosensitizing and cytotoxic properties of newly synthesized electron-affinic drugs.

We are synthesizing and testing various 2-nitroimidazole analogs with different octanol/water partition coefficients for their radiosensitizing and cytototoxic properties. Our hypothesis is that, unlike the situation in vitro, lipophilicity will play a major role in determining the extent of radiosensitization of hypoxic tumour cells in vivo and also the degree of animal toxicity. The radiosensitivity testing involves determination of the surviving fraction of EMT6 tumour cells irradiated in vivo under different conditions following drug injection, and subsequent assay in vitro. Data obtained to date on eight 2-nitroimidazoles do not indicate any compound clearly superior to misonidazole (Ro-07-0582), although one or two are close and may prove better at the completion of testing. Cytotoxicity of the compounds is assayed by cell survival and histologically. Data obtained on the toxicity of misonidazole to the cells of EMT6 tumours suggest that a large proportion of the anoxic cells in these tumours are not near necrotic areas, but rather result from the temporary closure of blood vessels.

Animals↗

PubMed1978

Platinum complexes as radiosensitizers of hypoxic mammalian cells.

Cis-dichlorodiammineplatinum (II), or cis-PDD, has recently been shown to be a potent radiosensitizer of bacteria, particularly under conditions of acute hypoxia. This study extends this observation to include the radiosensitization of mammalian cell (V-79) by low concentrations of cis-PDD, cis-dichlorobis(aziridine) platinum (II), and the trans-isomer of PDD as measured from survival curve analysis. This radiosensitization was obtained at concentrations of 10 micrometer, 60 micrometer, and 100 micrometer for the cis-PDD, aziridine-platinum, and trans-isomer respectively. The corresponding drug toxicity survival levels were 8, 40 and 50%. Dose modification factors of around 1.3 to 1.4 were observed.

Aziridines↗

PubMed1989

The influence of interleukin-2, feeder cells, and timing of irradiation on the radiosensitivity of human T lymphocytes assessed by the colony-forming assay.

The radiosensitivity of human lymphocytes was investigated by the method of colony formation in the absence of interleukin-2 (IL2) and feeder cells, both of which enhance growth of T-cell colonies. The shape of the survival curve and the radiosensitivity was shown to depend upon the ability of lymphocytes to produce IL2: the survival curve for lymphocytes that were the most competent producers of IL2 is the closest to linearity; the lymphocytes that were poor producers show biphasic survival curves. The radiosensitivity of the lymphocytes from the first group is less than that of the latter, when the comparison is based on the first part of the biphasic survival curve. This is more easily seen when cultures are irradiated 24 h after stimulation by phytohemagglutinin (the time of the peak IL2 production) than when cultures are irradiated 2 h before stimulation. This study demonstrates that growth conditions influence the response of lymphocytes to irradiation and that optimal growth conditions result in a linear survival curve.

Adult↗

PubMed1989

Radiosensitization of human colorectal tumor cells by 4-nitro-5-sulfonatoimidazoles.

Misonidazole, a clinically-effective 2-nitroimidazole hypoxic cell radiation sensitizer, and 12 4-nitro-5-sulfonatoimidazoles were tested in cultured human SW1116 colorectal adenocarcinoma cells for radiosensitizing efficiency. Octanol-water partition coefficients and HPLC capacity factors were determined for all agents as measurements of lipophilicity, and an excellent correlation was found between the two measurements. Cytotoxicity, in vitro glutathione reactivity, and one-electron reduction potential were also determined for each compound to evaluate potential utility as macromolecularly transported radiosensitizers. Ten members of the set were found to be 40 to 300 times more radiotoxic than misonidazole, but no correlation was found between their radiosensitizing efficiencies and the chemical and physical parameters.

Adenocarcinoma↗

PubMed1988

Differential radiosensitivity among B cell subpopulations.

We have previously shown that low doses of ionizing radiation selectively impair a functionally defined B cell subpopulation. Normal mice, after exposure to 200 rad of ionizing radiation, have normal or near normal splenic plaque-forming cell responses to thymus-independent type 1 Ag, but reduced responses to thymus-independent type 2 Ag. Here, we confirm and extend the original findings by using hapten-specific serum RIA to demonstrate this differential radiosensitivity is systemic. We also examined splenocytes stained with a panel of lymphocyte surface Ag by FACS analysis to determine if these functional changes are accompanied by a physical alteration of the B cell pool of irradiated mice. Single-parameter FACS analyses demonstrate a diminution in both B cell number and the heterogeneity of membrane Ag expression within the surviving B cell pool after irradiation. In contrast, T cells are relatively radioresistant as the relative percentage of T cells in the irradiated splenocyte pool increases, whereas the heterogeneity of membrane Ag expression remains constant. Multiparameter FACS analyses indicate that B cells with the sIgM much greater than sIgD phenotype are more radiosensitive than B cells of the sIgM much less than sIgD phenotype. In addition, immunohistochemical analysis of splenic sections stained with anti-IgM or anti-IgD reveal the enhanced radiosensitivity of marginal zone B cells.

Animals↗

PubMedDate not supplied

[Comparative radiosensitivity of clonogenic tumor cells of the transplantable Ehrlich carcinoma in the ascitic and solid forms of growth].

Survival of clonogenic cells of solid Ehrlich ascites tumor (EAT) exposed to 60Co-gamma-radiation in vitro under the oxygenation conditions was investigated and the clonogenic capacity and radiosensitivity of these cells and cells of the previously studied EAT ascitic form and Lewis solid tumor comparatively studied to elucidate how the efficiency of colony formation (ECF) would affect their radiosensitivity. ECF for solid EAT cells was 2.6 +/- 0.3%, which was lower, by about an order of magnitude, than that for ascitic form of this tumor and was nearly the same as that for Lewis tumor cells. A median cell lethal dose (D0) was practically the same for all tumors under study. It is suggested that the differences in ECF do not substantially influence the radiosensitivity of clonogenic cells of the studied tumors.

Animals↗

PubMed1987

In vivo radiosensitivity and recovery pattern of the hematopoietic precursor cells and stem cells in mouse bone marrow.

Survival curves were determined for colony-forming hematopoietic stem cells (CFU-Mix and CFU-S10) as well as precursor cells (CFU-E, CFU-C, CFU-F, and BFU-E) in bone marrow of the mouse at various times up to 4 weeks after whole-body irradiation (1.5 or 3.0 Gy) in order to elucidate in vivo radiosensitivity and recovery patterns. These measurements represented the first attempts to examine CFU-Mix simultaneously with the other cell populations. CFU-E (D0 = 53 rad) and BFU-E (D0 = 68 rad) were the most radiosensitive. CFU-S10 (D0 = 81 rad) had intermediate radiosensitivity. CFU-Mix (D0 = 144 rad) and CFU-C (D0 = 157 rad) were relatively radioresistant. CFU-F (D0 = 257 rad) was the most radioresistant. The precursor and stem cells could be classified into three groups based on the recovery pattern. The first group, consisting of CFU-Mix, BFU-E, and CFU-S10, showed very slow recovery and did not reach normal levels even after day 28. CFU-E, the second group, showed the most severe depletion immediately after irradiation, and recovered most quickly with an overshoot at day 5. CFU-C and CFU-F cells, forming the third group, decreased more gradually and slightly, and recovered to the normal level after a transient rise by day 10-14.

Animals↗

PubMed1988

Radiosensitivity of late recurrences following radiotherapy of murine fibrosarcomas.

Radiosensitivity of late recurrent tumors which emerged after radiotherapy was investigated. Tumors observed were fibrosarcomas. Recurrences emerged in the irradiated area approximately 200 days after a 50% tumor control dose of radiation of 60Co gamma rays or mixed irradiation with fast neutrons and gamma rays. The recurrent and radiation-induced tumors were differentiated by karyotype analysis. Once transplanted into fresh mice, the recurrent tumors grew more slowly than the original tumor. Tumorigenicity of the late recurrences was lower than that of the original tumor. Radiosensitivity of the late recurrences, which was examined using methods to assess control, tumor growth delay, and colony forming assays, was significantly higher than that of the original tumor. D0 values of hypoxic tumor cells were significantly smaller in two of the three recurrences compared to the original tumor. Oxic cells, when irradiated in vitro, also showed smaller D0 values for the recurrent tumors than the original tumor. Hypoxic cell fractions were between 0 and 14% in the late recurrences and 10% in the original tumor. These results are consistent with the hypothesis that radiotherapy causes mutation of tumor cells which results in increased radiosensitivity of surviving tumor cells.

Animals↗

PubMed1988

[Chromosome radiosensitivity in 2 successive mitotic cycles of human lymphocytes].

A culture of human lymphocytes was irradiated with gamma-quanta (0.5 Gy) after incubation during different time intervals, i.e. at different relative frequencies of cells in the first and second mitotic cycle. The frequency of aberrations produced in the G2 stage was analysed. The total yield of aberrations gradually increased with the increase of time lapse between the onset of cultivation and irradiation. If, however, the relative frequencies of the first and second mitoses are taken into account, it could be concluded that radiosensitivity of chromosomes remains constant in each cycle and independent from its duration. Besides, radiosensitivity of chromosomes during the second cycle is one and half times stronger, as compared to the first cycle. In accordance with the data of other authors, 5-bromodeoxyuridine has been found to significantly increase radiosensitivity.

Bromodeoxyuridine↗

PubMed1987

The modification of hemoglobin affinity for oxygen and tumor radiosensitivity by antilipidemic drugs.

It has been recognized for some time that alterations in the affinity of Hb for oxygen could offer a means of improving oxygen delivery to tumors and achieving radiosensitization. Three antilipidemic drugs, clofibrate, bezafibrate, and gemfibrozil, two of which had previously been shown to reduce Hb/O2 affinity in vitro, were tested in mice for their ability to affect Hb/O2 affinity and to alter the radiosensitivity of the RIF-1 sarcoma. Each of the drugs produced a significant increase in the P50 of the blood, from a mean control value of 45 mm Hg to 55, 74, and 51 mm Hg after a dose of 1 g/kg of clofibrate, bezafibrate, and gemfibrozil, respectively. However, they had very different effects on the radiosensitivity of the RIF-1 tumor. When the mice breathed air at the time of irradiation, clofibrate produced a marked sensitization equivalent at the optimum time to a 20-fold reduction in hypoxic fraction; bezafibrate gave a lower sensitization equivalent to a 4-fold reduction, while gemfibrozil caused dramatic radioresistance equivalent to a 10-fold increase in hypoxic fraction. When the mice were given 95% O2/5% CO2 to breathe at the time of irradiation to ensure complete Hb saturation in the lungs, a large increase in the sensitization by bezafibrate was seen, but there was only a small change with clofibrate. We conclude that drugs which reduce Hb/O2 affinity could have a role in sensitizing tumors to radiation.

Animals↗

PubMed1987

Radiosensitizing and cytocidal effects of misonidazole: evidence for separate modes of action.

Hypoxic BP-8 murine sarcoma cells were exposed to misonidazole and/or radiation and the kinetics and extent of cell death were evaluated with the [125I]iododeoxyuridine-prelabeling assay. Cell death after treatment with lethal doses of misonidazole was rapid and essentially complete within 2 or 3 days after drug exposure. In contrast, radiation death became apparent only after a delay period of 4 days and was complete by Day 10 after irradiation. Radiosensitization by short exposures to sublethal doses of misonidazole affected only the delayed component of cell death, that is, the radiation component of death. In experiments involving sequential radiation and drug treatment, prior irradiation of cells did not enhance the direct cytocidal effects of misonidazole, as evidenced by the fact that the early component of cell death was equal in control and preirradiated cells. However, postirradiation treatment with misonidazole did enhance the delayed radiation component of cell death. These results suggest that radiosensitization and direct killing by misonidazole are two distinct phenomena mediated by different cellular mechanisms, and radiosensitization by misonidazole represents a two-component effect composed of true dose modification and dose additive damage interactions, but these additive effects must occur at a site different from the cellular structure responsible for direct drug-induced cell death.

Animals↗

PubMed1987

Chloronitroimidazoles as radiosensitizers of hypoxic cells in vitro.

Some results of the first more complex studies in vitro on radio-sensitizing efficiency, cytotoxicity and reactivity with blood-thiols of a series of 4- or 5-nitroimidazoles substituted in the 5, 4 or 2 position with chlorine are presented. The derivatives of 4-nitroimidazole substituted in 5 position ("ortho" position) with Cl show higher radiosensitizing efficiency than one may expect from their reduction potential, E1/2. At the same time they are extremely toxic, especially for aerobic cells. It is considered that high biological activity of ortho-substituted 4-nitroimidazoles is connected with their considerable chemical reactivity towards thiols and suppression of those natural protective compounds in the cells. The corresponding 5-nitro isomers are about tenfold weaker sensitizers, and simultaneously much less cytotoxic, either in aerobic or in hypoxic conditions. The chloro-4(5)-nitroimidazoles nonsubstituted at N-1 and ionizable in aqueous solution are relatively weaker at the same time less toxic radiosensitizers. It is evaluated that potential application in radiotherapy may have those chloronitroimidazoles which show low aerobic cytotoxicity, moderate radiosensitizing ability and no reactivity towards thiols. On the basis of the study in vitro, we have selected such a compound: 1-methyl-2-chloro-4-nitroimidazole (P13) for screening in vivo.

Aerobiosis↗

PubMed1987

The repair of double-strand DNA breaks correlates with radiosensitivity of L5178Y-S and L5178Y-R cells.

To better understand the basis for the difference in radiosensitivity between the variant murine leukemic lymphoblast cell lines L5178Y-R (resistant) and L5178Y-S (sensitive), the production and repair of DNA damage after X irradiation were measured by the DNA alkaline and neutral elution techniques. The initial yield of single-strand DNA breaks and the rates of their repair were found to be the same in both cell lines by the DNA alkaline elution technique. Using the technique of neutral DNA elution, L5178Y-S cells exhibited slightly increased double-strand breakage immediately after irradiation, most significantly at lower doses (i.e., less than 10 Gy). Nevertheless, even at doses that yielded equal initial double-strand breakage of both cell lines, the survival of L5178Y-S cells was significantly less than that of L5178Y-R cells. When the technique of neutral DNA elution was employed to measure the kinetics of DNA double-strand break repair, both cell lines exhibited biphasic fast and slow components of repair. However, the double-strand repair rate was much lower in the radiosensitive L5178Y-S cells than in the L5178Y-R cells (T1/2 of 60 vs 16 min). This difference was more pronounced in the fast-repair component. These results suggest that the repair of double-strand DNA breaks is an important factor determining the radiosensitivity of L5178Y cells.

Animals↗

PubMed1985

Radiosensitizers of hypoxic mammalian cells. 1-(Hydroxyaminoalkyl)-substituted nitroimidazoles.

A series of novel 1-(hydroxyaminoalkyl)-substituted nitroimidazoles has been synthesized as potential radiosensitizers for hypoxic mammalian cells. These compounds were synthesized via N-(hydroxyalkyl)phthalimide nitroimidazole intermediates which, on reaction with hydrazine hydrate, yielded the corresponding amines. The intermediates were prepared by reacting the epoxide derived from nitroimidazole with phthalimide and/or the epoxide derived from phthalimide with the nitroimidazole. The method was used successfully for the preparation of 2-, 4- and 5-nitroimidazole derivatives. In a modification of this procedure, 1-(2-aminoethyl)-2-nitroimidazole has been prepared by a new route which avoids the use of aziridine. These agents were tested for cytotoxicity and radiosensitizing ability in vitro using Chinese hamster V79 cells. All of the 2-nitroimidazoles tested showed toxicity similar to that previously reported for misonidazole and Ro 03-8799 (1-(2-hydroxy-3-piperidinopropyl)-2-nitroimidazole), two compounds currently undergoing clinical evaluation. In addition, all the novel primary amines were shown to function as hypoxic cell radiosensitizers. The 2-nitroimidazole derivatives were the most efficient compounds to be examined and showed at least as much activity as misonidazole.

Animals↗

PubMed1979

Differential radiosensitivity of two mammalian cell lines after hyperthermic pretreatment.

Hyperthermia in combination with 60Co-gamma-therapy not only increases the radiosensitivity of mammalian cells, it also can create a greater selectivity between individual cell populations. Tw established Chinese hamster cell lines (V79 and B14F28) showed a similar radiosensitivity at 37 degrees C, but exhibited a marked difference in their response to 60Co-gamma-rays when they were pretreated with mild hyperthermia (1 hour at 42 degrees C): About 50% of each cell type survived a dose of 400 rad 60Co-gamma-rays alone, while the same dose delivered in combination with hyperthermia was survived by 40% of the B14F28 cells and by only 2.4% of the V79 cells. Heat alone also caused cell death and cell cycle changes (as measured by flow-microfluorometry) to a different extent: 4 hours at 42 degrees C decreased survival of V79 cells to 1.3% while 70% of the B14F28 cells formed colonies. This differential response to hyperthermic killing and thermal radiosensitization is similar to the different RBE-values for survival of both cell lines after high LET pion irradiation.

Animals↗