Effects of hypoxic cell radiosensitizer doranidazole (PR-350) on the radioresponse of murine and human tumor cells in vitro and in vivo.

We have investigated the radiosensitizing effect of doranidazole, a hypoxic cells radiosensitizer, using SCCVII tumor cells of C3H mice and CFPAC-1 and MIA PaCa-2 human pancreatic tumor cells. The radiosensitivity of hypoxic SCCVII cells in vitro increased with 1 mM doranidazole by a factor of 1.34 and 1.68, when determined by clonogenic survival and micronucleus (MN) formation, respectively. The radiation-induced growth delay of SCCVII tumors was significantly enhanced and the TCD(50/120) was reduced by a factor of 1.33 when 200 mg/kg doranidazole was injected, i.v., 20 min prior to tumor irradiation. The in vivo-in vitro excision assay showed that radiosensitivity of SCCVII cells in vivo increased by a factor of 1.47 with 200 mg/kg doranidazole. The radiation-induced growth delay of CFPAC-1 xenografts in nude mice was significantly enhanced and the TCD(50/90) was reduced by a factor of 1.30 by 200 mg/kg doranidazole. On the other hand, 200 mg/kg of doranidazole exerted no influence on the radiation-induced growth delay in MIA PaCa-2 xenografts. The tumor oxygenation status, as determined with an oxygen sensitive needle probe and the immunohistological study using pimonidazole, indicated that MIA PaCa-2 tumors are better oxygenated than CFPAC-1 tumors. The relatively well-oxygenated status in MIA PaCa-2 tumor may account for the lack of radiosensitization by doranidazole. It is concluded that the magnitude of radiosensitization of tumors by doranidazole is dependent on the oxygenation status of the tumors and that doranidazole may be useful in increasing the response of hypoxic human pancreatic tumor to IORT.

A novel mycological analysis valuable for evaluating therapeutic efficacy of antimycotics against experimental dermatophytosis in guinea pigs.

Although antimycotic effects are mainly evaluated with regard to whether or not the fungi grow from a specimen obtained from the drug-treated skin, the potential for discrepancies in skin specimens in which the fungi are grown has not been evaluated, in the experimental tinea model. In this study, to evaluate the therapeutic effectiveness of antimycotic agents against fungal skin infection, a novel form of mycological assessment, which focuses on the size of colonies grown from skin specimens was examined and developed. When microconidia of Trichophyton mentagrophytes were inoculated onto a Sabouraud dextrose agar (SDA) plate and incubated at 27 degrees C for 5 days, a linear relationship was observed between the growth area of mycelia and the logarithm of the quantity of microconidia. This relationship between the growth area and the logarithm of the number of T. mentagrophytes microconidia did not change with the addition of skin homogenate and/or keratin powder. Next, the number of fungi in skin blocks attendant upon experimental, cutaneous infection in guinea pigs was evaluated and analyzed via a calibration curve, determined based on a microconidium suspension of T. mentagrophytes. Estimates of severity of dermatophytic infection in experimental animals were parallel to, but more reliable than, results obtained via the conventional mycological method (fungus-positive skin ratio of treated skin) in culture studies of infected dermal tissues. This new analytical method may also be applicable to the in vivo assessment of the therapeutic effect against dermatophytosis experimentally produced in guinea pigs.

Caspase-independent necrotic cell death induced by a radiosensitizer, 8-nitrocaffeine.

Molecular mechanisms of apoptosis have been extensively studied, but little is known about non-apoptotic cell death. To study the mechanism of non-apoptotic cell death, we searched for non-apoptotic cell death inducers for U937 cells, which are highly sensitive to apoptosis induction by various stimuli. We found that 8-nitrocaffeine and its analog, which are candidate radiosensitizers for cancer therapy, induced exclusively caspase-independent necrotic cell death in cell lines such as U937, HL-60, K562 and Jurkat. The 8-nitrocaffeine-induced necrotic cell death was mediated by reactive oxygen species (ROS) because (i) ROS were produced in the 8-nitrocaffeine-treated cells, (ii) ROS scavengers inhibited the caspase-independent necrotic cell death induced by 8-nitrocaffeine, and (iii) the necrotic cell death was completely suppressed in hypoxic cells. Cells selected for resistance to nitrocaffeine showed cross resistance to CH-11, an anti-Fas antibody, suggesting that the necrotic process plays an important role in Fas-mediated cell death in this cell line. Since cancer cells are often derived from a selected population of cells resistant to apoptosis, inducers of necrotic cell death could be beneficial to kill cancer cells that have acquired resistance to apoptosis-induction therapy.