The independent action of radiation and cisplatin on the survival or recovery of human normal or tumour cells in vitro or in vivo

Impact of fractionated cisplatin and radiation treatment on cell growth and accumulation of DNA damage in two normal cell types differing in origin

Evidence on the impact of chemotherapy on radiotherapy-induced second malignant neoplasms is controversial. We estimated how cisplatin modulates the in vitro response of two normal cell types to fractionated radiation. AHH-1 lymphoblasts and VH10 fibroblasts were irradiated at 1 Gy/fraction 5 and 3 times per week during 12 and 19 days, respectively, and simultaneously treated with 0.1, 0.2, 0.4, 0.8, 1.7 and 3.3 µM of cisplatin twice a week. Cell growth during treatment was monitored. Cell growth/cell death and endpoints related to accumulation of DNA damage and, thus, carcinogenesis, were studied up to 21 days post treatment in cells exposed to radiation and the lowest cisplatin doses. Radiation alone significantly reduced cell growth. The impact of cisplatin alone below 3.3 µM was minimal. Except the lowest dose of cisplatin in VH10 cells, cisplatin reduced the inhibitory effect of radiation on cell growth. Delayed cell death was highest in the combination groups while the accumulation of DNA damage did not reveal a clear pattern. In conclusion, fractionated, concomitant exposure to radiation and cisplatin reduces the inhibitory effect of radiation on cell proliferation of normal cells and does not potentiate delayed effects resulting from accumulation of DNA damage.

Modulation of radiosensitivity in Chinese hamster lung fibroblasts by cisplatin

The effects of cisplatin exposure time, concentration, and irradiation sequence on the sensitivity of Chinese hamster lung fibroblasts (V79) to gamma-ray exposure were examined. Based on clonogenic cell survival, the cisplatin concentrations corresponding to 50% cell survival (EC(50)) for exposure times of 1 h to 7 days followed a 2-phase exponential decay and ranged from 28.26 +/- 3.32 to 1.53 +/- 0.24 micromol/L, respectively. When cells were treated at EC(50) for exposures of less than 4 h and irradiated immediately, cisplatin inhibited the effect of radiation. Exposures of 4-6 h did not affect radiosensitivity. For exposures of 8-12 h, radiosensitization was observed, which disappeared at 14 h and reappeared for much longer cisplatin treatments. At the lowest achievable EC(50) (1.53 micromol/L), radiosensitization was observed if irradiation was delayed for 1-8 h. This enhancement in radiosensitivity disappeared for irradiation delays of 10-12 h, but reappeared when irradiation was delayed for 14-18 h. These data demonstrate that the mode of interaction between cisplatin and gamma-irradiation depends on the concentration and exposure time of cisplatin, as well as on the timing of irradiation after cisplatin administration. Consideration of changes in cell cycle kinetics may contribute to the improvement of treatment outcomes in adjuvant chemoradiotherapy involving cisplatin.

Radiosensitization by oxaliplatin in a mouse adenocarcinoma: influence of treatment schedule

PURPOSE

The aim of our study was to investigate if oxaliplatin (1-OHP) could be used as a radiosensitizer in vivo.

MATERIALS AND METHODS

Experiments were performed in mice (C3D2F1) bearing a transplanted mammary carcinoma in a foot. Drugs, 1-OHP and cis-diammine-dichloro-platinum (CDDP), were administered i.p. Results were analyzed in terms of tumor growth delay (TGD).

RESULTS

1-OHP and CDDP were tested in single doses of 6 and 10 mg/kg body weight. Administration of either 1-OHP or CDDP produced a significant TGD but only with the dose of 10 mg/kg. Single dose combined X-ray (10 Gy) and 1-OHP (6 and 10 mg/kg) treatments were performed with different sequences and time intervals (1 h, 4 h, and 24 h). All TGDs of these combined treatments were uniform among themselves (indicating that sequence and time interval did not influence the results), and did not depend on the drug dose. In X-ray (10 and 20 Gy) and 1-OHP (6 and 10 mg/kg) combined treatment, the TGDs increased only with X-ray dose. Different 1-OHP administration schedules were performed for fractionated experiments: two treatments every 4 days. The least toxic protocol (1-OHP total dose from 6 to 14 mg/kg) was selected for combined treatments with 10 daily X-ray treatments of 2 Gy. A clear drug dose-effect relationship was observed in those treatments with 1-OHP doses from 10 to 14 mg/kg.

CONCLUSION

Although low-dose 1-OHP did not induce a TGD when administered alone, in combined protocols it increased X-ray efficacy.

Combined chemoradiotherapy with daily low-dose cisplatin in locally advanced inoperable non-small cell lung cancer

Sixty-one consecutive patients with locally advanced inoperable non-small-cell lung cancer were treated with chemoradiation with 60 Gy and concomitant daily low-dose cisplatin (6 mg/m(2)) in a single uninterrupted course. Toxicity was mild, 80% of patients were treated as outpatients. The median survival of 70 weeks compares favorably to the literature.

Improvement of combined modality therapy with cisplatin and radiation using electroporation of tumors

PURPOSE

To evaluate whether a local drug delivery method, i.e., electroporation of tumors, increases the radiosensitizing effect of cisplatin.

METHODS AND MATERIALS

Subcutaneous Ehrlich-Lettre ascites (EAT) tumors in CBA mice were treated either by cisplatin, electric pulses, or ionizing radiation. In electrochemotherapy protocol, electric pulses were given to the tumor 3 min after intravenous injection of cisplatin. The interval between electrochemotherapy and irradiation was 20 min. Treatment effectiveness was evaluated by tumor growth delay and local tumor curability.

RESULTS

Electrochemotherapy of EAT tumors proved to be effective treatment, resulting in 12% tumor cures, whereas treatment with cisplatin or electric pulses alone did not yield any tumor cures. As expected, injection of cisplatin 20 min prior to irradiation, increased radioresponse of tumors from 27% to 73% tumor cures. Electroporation of tumors also increased radiation response of tumors to 54% tumor cures. Electrochemotherapy given prior to irradiation increased radioresponsiveness of tumors, resulting in 92% tumor cures.

CONCLUSIONS

This study shows that delivery of cisplatin into the cells by electroporation of tumors increases the radiosensitizing effect of cisplatin. However, some effect may also be ascribed to application of electric pulses to the tumors that in our study also predisposed tumor cells to radiation damage.

[Radiochemotherapy and radiosensitization for locally advanced non-small-cell bronchial cancer]

Combined chemotherapy and radiotherapy can improve the survival of patients with locally advanced non-small cell lung cancer, when compared to irradiation alone. This survival benefit is essentially due to an increased control of distant micrometastases, whereas local control remains poor. In order to improve local control, new radiotherapy modalities such as 3D conformal treatment, hyperfractionation or accelerated hyperfractionation, are under development. Cytotoxic drugs given at low doses concomitantly to radiotherapy may act as radiosensitizers on the primary tumor. Concomitant chemotherapy at cytotoxic doses and radiotherapy would also allow better control on micrometastases and better local control due to radiosensitization by chemotherapy. However, the concomitant use of chemotherapy and radiotherapy is limited by increased toxicity on normal tissues, more particularly on the esophagus. Randomized comparisons of these modalities versus induction chemotherapy followed by radiotherapy are needed to determine the optimal treatment sequence.

Combination of cisplatin and radiation in cell culture: effect of duration of exposure to drug and timing of irradiation

Responses to the combination of cisplatin (CDDP) and radiation in experimental and clinical studies have been reported to vary from high radiosensitization to clear sub-additivity. We examined the combined effect of CDDP with ionizing radiation in both murine mammary adenocarcinoma (EMT-6) and human ovarian carcinoma (OV-1063) cells with special reference to the duration of CDDP exposure and timing of irradiation. Cell survival was measured with a colorimetric assay of cell density. The nature of interaction of cisplatin and radiation was evaluated using isobolograms and a combination index (CI). Exposure of both cell lines to CDDP for 24 hr before irradiation yielded an additive or slightly sub-additive response only if the exposure was extended for a few more hours after irradiation. In EMT-6 cells, the combination of radiation with subsequent continuous as well as short-term (4 to 6 hr) CDDP treatment was found to have a clear sub-additive effect; dose escalation of each modality reduced the additional effect of the other. The sub-additive effect may be explained by a radiation-induced arrest of cells in late S phase, which was dose- and time-dependent. Post-radiation exposure to CDDP further increased the S-phase arrest. In contrast, a 2 hr post-radiation drug exposure resulted in a supra-additive combined effect. Our results stress the crucial role of the timing and the doses of both modalities as well as the duration of post-radiation drug exposure on their combined effect.

Sensitivity to cis-diamminedichloroplatinum in human cancer cells is related to expression of cyclin D1 but not c-raf-1 protein

Although several oncogenes, including c-myc, ras and c-raf-1, have been implicated in cellular resistance to ionising radiation, there is less information relating oncogene expression to cis-diamminedichloroplatinum (CDDP) resistance. However, transfection of c-myc or v-H-ras and activation of protein kinase C (PKC), which contributes to the RAF-1, MAP kinase signal transduction pathway, can influence therapeutic response to CDDP. Activation of PKC increases CDDP sensitivity, whilst transfected c-myc or v-H-ras induce CDDP resistance. We have previously reported that human in vitro cell lines show different patterns of sensitivity to CDDP and 4 MeV X-irradiation. In these cells radiation sensitivity is related to high levels of expression of the C-raf-1 proto-oncogene. We thus predicted that cells sensitive to CDDP might show a different relationship to c-raf-1 expression. In addition, because cyclin D1 expression can be upregulated by the myc or ras oncogenes, we also chose to study putative relationships between cyclin D1 protein levels and intrinsic cellular sensitivity to CDDP and gamma-irradiation. We report that in the 16 human cell lines which we have studied, high cyclin D1 expression is related to CDDP resistance but has no relationship with radiation responsiveness, whereas high c-raf-1 expression, although related to radiosensitivity has no relationship with CDDP responsiveness.

Simultaneous cisplatin and radiation in endometrial adenocarcinoma cell lines

The effects of concomitantly administered cisplatin and radiation were evaluated in four recently established endometrial adenocarcinoma cell lines. We used the 96-well clonogenic assay to obtain survival data which were fitted to the linear quadratic model. The area under the survival curve (AUC) was obtained by numerical integration. It turned out that there was only a systematic additive cytotoxic effect and no supra-additive, true radiosensitising effect could be found. The results were not affected by the cisplatin dose used, the intrinsic radiosensitivity of the cell lines or the sensitivity of the cells to cisplatin.

Concurrent irradiation and intratumoral chemotherapy with cisplatin: a pilot study in dogs with spontaneous tumors

PURPOSE

A preliminary study was undertaken to determine whether the addition of a collagen gel in the formulation of cisplatin for intratumoral administration of cisplatin affected platinum plasma concentrations. A second study was undertaken to determine the local effects of intratumoral administration of cisplatin mixed with collagen given concurrently with irradiation.

METHODS AND MATERIALS

Twelve dogs with advanced stage tumors were administered a dose of 0.25 mg of cisplatin per kg of body weight intratumorally with or without collagen using a two-period crossover design. Twelve additional dogs received concurrent irradiation (48 Gy) delivered in 12 fractions over 4 weeks and intratumoral cisplatin chemotherapy given the first day of each week at a dose of 0.5 mg of cisplatin per cm3 of tissue.

RESULTS

The cumulative cisplatin plasma concentrations varied over time from dog to dog, but the use of collagen in the formulation significantly reduced the systemic exposure of cisplatin. For the dogs given intratumoral cisplatin and irradiation, complete responses were observed in 10 dogs. Seven dogs had local recurrence. One dog had tumor recurrence in the radiochemotherapy field and six dogs had recurrence at the margin of the radiochemotherapy field, but within the irradiation field. Normal tissue reactions were similar in the radiochemotherapy field and in the margin treated with radiation only. Cumulative effect of repeated intratumoral administration on plasma concentration of cisplatin was not observed.

CONCLUSIONS

These findings provide support for an extended investigation of this combined regimen. The lack of systemic toxicity associated with intratumoral administration of cisplatin mixed with collagen may allow a safe clinical evaluation of the interaction between cisplatin and radiation.

Potentiation of CB 1954 cytotoxicity by reduced pyridine nucleotides in human tumour cells by stimulation of DT diaphorase activity

The toxicity of CB 1954 [5-(aziridin-1-yl)-2,4-dinitrobenzamide] towards human cells was greatly enhanced by NADH (when foetal calf serum was present in the culture medium) and by nicotinamide riboside (reduced) (NRH), but not by nicotinate riboside (reduced). Co-treatment of human cells with CB 1954 and NADH resulted in the formation of crosslinks in their DNA. The toxicity produced by other DNA crosslinking agents was unaffected by reduced nicotinamide compounds. When caffeine was included in the medium, a reduction in the cytotoxicity of CB 1954 occurred. The toxicity experienced by human cell lines after exposure to CB 1954 and NADH was proportional to their levels of the enzyme DT diaphorase NAD(P)H dehydrogenase (quinone), EC 1.6.99.2. It is concluded that NRH, which we have shown to be a co-factor for rat DT diaphorase (Friedlos et al., Biochem Pharmacol 44: 25-31, 1992), is generated from NADH by enzymes in foetal calf serum, and stimulates the activity of human DT diaphorase towards CB 1954.

Additive effects of cisplatin and radiation in human tumor cells under oxic conditions

The interaction of cisplatin and irradiation was studied in vitro in four human cell lines. Additive effects were observed for the combination given either simultaneously or sequentially. No influence on recovery was seen in split-dose experiments. It is concluded that radiosensitization cannot be presumed in every clinical setting of combined treatment with radiation and cisplatin.

Significance and measurement of DNA double strand breaks in mammalian cells

Techniques for measuring DNA double strand breaks in mammalian cells are being used increasingly by researchers studying both physiological processes, such as recombination, replication, and apoptosis, as well as pathological processes, such as clastogenesis induced by ionizing radiation, chemotherapeutic drugs, and chemical toxicants. In this review we evaluate commonly used assays for measuring DNA double strand breaks, focusing on neutral filter elution and pulsed field gel electrophoresis, and explore the advantages and limitations of applying these techniques to problems of current interest in carcinogenesis and genetic toxicology.

Cisplatin and radiation: interaction probabilities and therapeutic possibilities

This paper examines the probability of interactions occurring between drug lesions and radiation lesions in DNA for the cytotoxic and radiosensitizing agent cisplatin. The number of cisplatin-induced DNA adducts and radiation-induced strand breaks after a given dose of each agent are known for given cell systems, from which the probability that these lesions will interact can be estimated. Results of these calculations indicate that the probability of interaction could be high, depending on the distance over which two lesions can interact and the probability of repair of the interaction lesion. Calculated lesion numbers have been compared with known data on radiation modification, including illustrations of inconsistencies. In the second part of the paper, ways in which combined therapy with cisplatin and radiation can be improved are described. Development of methods to predict which types of tumor and which individual tumors within a given type are sensitive to the cytotoxic and radiosensitizing effects of the drug would aid rational selection of patients for combination treatments. Immunocytochemical methods sensitive enough to monitor cisplatin-DNA interactions in patients are available and may be useful in this context. The delivery and maintenance of higher tumour concentrations of radiosensitizer offers a further possibility for improvement. Studies of intratumoral injection of cisplatin have shown promise for achieving this goal while limiting normal tissue toxicity.