Combination cytotoxic effects of cis-diamminedichloroplatinum(II) and 5-fluorouracil with and without leucovorin against human non-small cell lung cancer cell lines

Both cisplatin (CDDP) and leucovorin (LV) have been shown to enhance cytotoxicity of 5-fluorouracil (FUra) against murine and human neoplasms by increasing intracellular reduced folate concentrations. We were interested in their use in a combination to inhibit non-small cell lung cancer (NSCLC) cell growth and therefore conducted an in vitro study to investigate the cytotoxic activities of combinations of CDDP plus FUra, with and without LV (20 microM), against seven NSCLC cell lines. A tetrazolium assay with application of the classical isobole method was used to test drug combinations. We found that LV enhanced FUra but not CDDP cytotoxicity and that the degree of enhancement was negatively correlated with the effect of FUra. There was an overall additive combination effect of CDDP plus FUra, although there may be synergy at higher effect levels. There was synergy to a combination of CDDP, FUra, and LV, presumably primarily related to the synergistic effects of adding LV to FUra. In summary, LV and CDDP enhanced FUra cytotoxicity in a complementary fashion and there was clear synergy of a combination of CDDP, FUra, and LV against a panel of NSCLC cell lines. Our in vitro results provide a rationale for controlled clinical studies of this three-drug regimen in patients with NSCLC.     

Importance of the irradiation timing within a chemoradiotherapy sequence including cisplatin and 5-FU-folinic acid. Experimental results

The objective of the present in vitro study was to determine an optimal timing of the irradiation in the combination cisplatin (CDDP) and 5-fluorouracil-folinic-acid (5-FU-FA) allowing a maximal cytotoxic effect on a human cell line derived from a head and neck carcinoma (CAL 27 cells). The various tested chemoradiotherapy sequences were applied in parallel to human keratinocytes in culture (SVK 14 cells). This was done in order to define the best sequence allowing the achievement of an optimal selectivity of the cytotoxic effects. The drug sequence was: CDDP over 2 h then fresh medium was added including the tandem 5-FU-d,I FA applied 6 h after CDDP, for 5 days. Irradiation was applied only once and at various times within the drug sequence. The cytotoxicity effects of the different chemoradiotherapy combinations were assessed by the MTT semi-automated test. The part taken by the 5-FU-FA combinations in the overall cytotoxicity was examined; an effect was apparent on CAL 27 cells only. The evolution of the radiation effect (RE = cell survival after drugs/cell survival after drugs plus irradiation) was analysed as a function of the different times of irradiation within the given drug sequence. Clearly, the RE values were dependent upon time at which the radiation dose in the chemoradiotherapy regimen was administered. For CAL 27 cells, irradiation effects were maximal at the first irradiation time tested after the end of the CDDP exposure (i.e. t = 3.5 h). In contrast, this optimal chemoradiotherapy timing for better cytotoxicity on CAL 27 cells did not correspond to that of SVK 14 cells. Consequently, it was possible to establish that the best time for the selectivity index was located shortly after the CDDP exposure.     

Agreement between face-to-face and telephone-administered mood ratings in patients with rapid cycling bipolar disorder

BACKGROUND AND PURPOSE: Clinical trials have demonstrated that high dose radiation therapy and daily cisplatin (CDDP) could increase local control and survival in carcinoma from various sites. The present phase I-II study has combined high dose radiation therapy and daily CDDP at escalating dosages. METHODS: From August 1994 to December 1995, 23 patients with non-resectable carcinoma of the pancreas were enrolled in a phase I-II multicentric, pilot study to test the toxicity and the effectiveness of high dose radiotherapy and daily cisplatin (CDDP) at escalating dosages. A dose of 6 mg/sqm/day of CDDP was selected for the phase II step since no grade IV toxicity occurred in any patient in the phase I step. RESULTS: Toxicity was considered fairly acceptable. At the time of analysis, the 23 patients who entered the study had clear evidence of evolutive disease either locally or distantly in the liver. It is suggested that high dose radiotherapy (60 Gy continuously) and daily CDDP have little effect on local control of the tumor and survival, and only a moderate effect on pain. CONCLUSIONS: In unresectable, apparently non-metastatic cancers of the pancreas, there is an urgent need for new agents or new combinations of agents to be tested.     

Paclitaxel enhances in vitro radiosensitivity of squamous carcinoma cell lines of the head and neck

Squamous cell carcinoma of the head and neck is the fourth most common cancer in the United States, and therapy for very advanced cases is relatively ineffective. Paclitaxel has activity against cancers of the breast, lung, prostate, cervix, and ovary. The activity of paclitaxel for squamous cell carcinoma of the head and neck is less certain, and results of its radiosensitization properties have been variable. The radiation responses of two squamous carcinomas, SCC-9 (oropharynx) and HEP-2 (larynx), were examined to determine the radiosensitizing potential of paclitaxel. In vitro exposures for 24 and 48 h with paclitaxel concentrations of 10(-4) to 6 x 10(-2) microg/ml were followed by irradiation of 0.1-10 Gy. Percent survival was calculated by colony count, and the paclitaxel-radiation interaction was quantitated by the median effect principle and the combination index method of Chou and Talalay. The paclitaxel-radiation combination resulted in multiphasic interactions in both 24 and 48 h paclitaxel pretreatment in SCC-9 and HEP-2 cell lines. In general there was slight synergism [combination index (CI) <1] at low dose-low effect levels (e.g., at a paclitaxel concentration of 0.002 microg/ml or lower and radiation of 0.1-0.3 Gy), moderate antagonism (CI >1) at median dose ranges and strong synergism (CI <1) at high dose ranges (e.g., at a paclitaxel concentration of 0.012-0.06 microg/ml and radiation doses of 3-10 Gy), especially at a surviving fraction of <0.1, which is therapeutically relevant. The median effect principle and combination index method provided a simple way to quantitate the synergism or antagonism of a paclitaxel-radiation interaction under various conditions. This analysis demonstrated that paclitaxel-radiation synergy exists at doses that are readily achievable in the clinical scenario for both agents and that greater synergy occurred at high dose-high effect levels. These results suggest that the combination of both therapies should be explored further in clinical trials assessing the treatment of squamous cell carcinomas of the head and neck.     

Radiosensitivity of new and established human melanoma cell lines: comparison of [3H]thymidine incorporation and soft agar clonogenic assays

Seven new low-passage melanoma lines were developed in this laboratory from clinical melanoma specimens and characterised for chromosome complement, DNA ploidy and S-phase content. The radiosensitivity of these lines was compared with that of eight established melanoma cell lines, FME, MM-96, SK-MEL-5, SK-MEL-28, SK-MEL-2, MALME-3M, M19-MEL and LOX-IMVI, using a 96-well microculture assay technique. Dose-response curves were determined using a 5-day incubation period and 6-h terminal [3H]thymidine-labelling period. Radiation (60Co source) was carried out under a lead wedge to provide a radiation dose range of 0-10 Gy, or by irradiating part of the plate (radiation dose 0 or 2 Gy). Data for a range of cell densities in a single 96-well plate were combined into a single regression equation incorporating linear quadratic terms for radiation dose and cell density. SF2 values were defined as the amount of thymidine incorporated following a radiation dose of 2 Gy, expressed as a fraction of that of unirradiated cells, and varied from 0.36 to 0.93. The reproducibility in repeat assays, as defined by the standard error of determinations at different passage numbers, was +/- 0.04. The newly developed lines exhibited a similar range of radiosensitivity to that of the established lines, and melanin content did not correlate with resistance. For nine of the lines, radiation parameters were also determined using a modified Courtenay clonogenic soft agar assay technique, and the results compared with the thymidine incorporation results, and a significant linear correlation was found between SF2 and SF2' (r = 0.89). The linear (alpha) and quadratic (beta) terms of the best-fit linear quadratic dose-response curves, were significantly correlated between the two assays. It is concluded for this series of human melanoma lines that proliferation assays in 96-well plates provide radiosensitivity parameters comparable to those using clonogenic assays.     

Synergistic interaction between cisplatin and gemcitabine in vitro

2',2'-Difluorodeoxycytidine (dFdC; gemcitabine) is a new antineoplastic agent that is active against ovarian carcinoma, non-small-cell lung carcinoma, and head and neck squamous cell carcinoma. cis-diamminedichloroplatinum (CDDP; cisplatin) is used commonly for the treatment of these tumors. Because the two drugs have mechanisms of action that might be complementary, we investigated a possible synergism between dFdC and CDDP on growth inhibition. The combination was tested in the human ovarian carcinoma cell line A2780, its CDDP-resistant variant ADDP and its dFdC-resistant variant AG6000, the human head and neck squamous cell carcinoma cell line UMSCC-22B, and the murine colon carcinoma cell line C26-10. The cells were exposed to dFdC and CDDP as single agents and to combinations in a molar ratio of 1:500 for 1, 4, 24, and 72 h with a total culture time of 72 h. Synergy was evaluated using the multiple drug effect analysis. In A2780 and ADDP cells, simultaneous exposure to the drugs for 24 and 72 h resulted in synergism, but shorter exposure times were antagonistic. No synergism was found in the UMSCC-22B and C26-10 cell lines at prolonged simultaneous exposure. However, a preincubation with CDDP for 4 h followed by a dFdC incubation for 1, 4, 24, and 72 h was synergistic in all cell lines except C26-10 cells. A 4-h preincubation with dFdC followed by an incubation with the combination for 20 and 68 h was synergistic in all cell lines. Initial studies of the mechanism of interaction concentrated on the effect of CDDP on dFdCTP accumulation and DNA strand break formation. In all cell lines, CDDP failed to increase dFdCTP accumulation at 4- or 24-h exposure to dFdC; in two cell lines, CDDP even tended to decrease dFdCTP accumulation. Neither dFdC nor CDDP caused more than 25% double strand break formation, whereas in the combination, CDDP even tended to decrease this type of DNA damage. The synergistic interaction between the two drugs is possibly the result of dFdC incorporation into DNA and/or CDDP-DNA adduct formation, which may be affected by each other.     

In vitro and in vivo effects of cisplatin and etoposide in combination on small cell lung cancer cell lines

The effects of cisplatin (CDDP) and etoposide (ETP) in combination were evaluated in vitro and in vivo using small cell lung cancer cell lines. The combination effects in vitro were investigated using isobologram analysis. Used together, CDDP and ETP showed a synergistic effect against cell growth on only 1 cell line (SBC-3), additive effects on 6 (SBC-2, SBC-5, Lu130, Lu134AH, Lu135T and H69) and an antagonistic effect on 1 (SBC-1). In the in vivo experiment, nude mice were inoculated with SBC-1, SBC-3 and SBC-5 cells. Two or 5 mg/kg CDDP and 10 or 30 mg/kg ETP were administered intraperitoneally alone and simultaneously in combination to nude mice. The in vivo effects of the combination were determined by comparing the observed growth ratio in mice treated with the combination with the expected value of this ratio calculated based on the assumption that the effects of the drugs were simply additive. According to this definition, synergistic effects were observed against all 3 tumors. Thus, the in vivo and in vitro effects differed. The toxicity of the combination therapy, which was analyzed by estimating the body weight change of mice, was no higher than that of CDDP or ETP alone. These results suggest that the excellent clinical effects of CDDP and ETP combination therapy may be attributable not to drug interaction at the cellular level but to the feasibility of combined use of them at full doses without overlapping side effects.     

UCN-01 in ovary cancer cells: effective as a single agent and in combination with cis-diamminedichloroplatinum(II)independent of p53 status

Our goal was to determine the cytotoxicity of 7-OH-hydroxystaurosporine (UCN-01) as a single agent and in combination with cis-diamminedichloroplatinum(II) (CDDP) in a panel of ovarian carcinoma cells. We sought to examine the role of p53 gene function and alterations in cell cycle progression or other mechanisms of action of UCN-01 including perturbation of the apoptosis pathway mediated by NF-kappaB and Bcl-2/Bax. Cytotoxicity was determined from dose-response curves established by the Alamar blue vital dye indicator assay. Restoration of wild-type p53 in a p53 null cell line, SKOV 3, was achieved by transfection of a p53 expression vector. Cell cycle distribution was measured by fluorescence-activated cell sorting analysis of ethidium bromide-stained nuclei. Apoptosis was measured by quantitative fluorescence microscopy. NF-kappaB DNA binding activity was measured by electrophoretic mobility shift assay. Bcl-2 and Bax levels were determined by Western immunoblotting. UCN-01 was effective as a cytotoxic agent alone and in combination with CDDP in all cell lines studied, regardless of p53 status. The degree of sensitization to CDDP conferred by UCN-01, however, was found to correlate with p53 gene status. p53 wild-type cells seem to be more sensitive to the cytotoxic effects of the combination of UCN-01 + CDDP than the p53 mutant cells. This was confirmed in cells in which p53 wild-type function was restored by transfection of p53 cDNA, but these cells are also significantly more sensitive to CDDP alone. The effects of UCN-01 on cell cycle progression also appear to be p53 dependent but may not be the primary mechanism of action. The rate of apoptosis is increased 4-fold in UCN-01 + CDDP-treated cells compared to either agent alone. UCN-01 does not effect NF-kappaB DNA binding activity or Bcl-2 and Bax levels. UCN-01 enhances CDDP cytotoxicity and apoptosis in ovary cancer cells. This occurs regardless of p53 status, but wild-type p53 seems to increase the degree of sensitization.     

Concomitant treatment with mild hyperthermia, cisplatin and low dose-rate irradiation in human ovarian cancer cells sensitive and resistant to cisplatin

Hyperthermia has been shown to be an effective radiation sensitizer. Cisplatin has also been shown to cause radiosensitization. In part, the sensitization is through the inhibition of repair of radiation damage. In this study we have set out to combine low dose-rate irradiation (during which extensive repair occurs) with both cisplatin and hyperthermia to maximize the radiation sensitizing effect. Two human ovarian carcinoma cell lines, one parental (A2780S) and the other a cisplatin resistant derivative (A2780CP) cell line were used in these experiments. Long duration hyperthermia at 40 degrees C was combined with low concentrations of cisplatin (0.5-3 microg/ml) and low dose-rate irradiation (LDRI). The responses to the individual treatments showed that there was cross resistance in the two cell lines for cisplatin and radiation, but for hyperthermia the opposite effect was found. When all treatments were given concurrently the response was greater than the calculated response of all three individual treatments, indicating a synergistic interaction. The effect was greater in the cisplatin resistant cell line. The combination of mild hyperthermia, low dose cisplatin and LDRI are a good combination for potential clinical application. In addition, this could be a good approach to deal with cisplatin resistance.     

Camptothecin analogues/cisplatin: an effective treatment of advanced bladder cancer in a preclinical in vivo model system

OBJECTIVE: To evaluate the impact of the camptothecin analogs on human TCC xenograft, both as monotherapy and in combination with cisplatin (CDDP). MATERIALS AND METHODS: Human transitional cell carcinoma (TCC) xenograft tumor line (DU4184) tested by subrenal capsule assay in 112 nude mice(NM-SRCA). CDDP and the camptothecin analogs irinotecan (CPT-11) and 9-aminocamptothecin(9-AC) were evaluated. RESULTS: Both of the camptothecin analogs showed significant short term tumor inhibition which translated into enhanced survival. Maximal tumor inhibition (>95%) was achieved when either of the camptothecin analogs was combined with CDDP with minimal host toxicity. This translated into 400% increase in median survival. While all controls were dead 39 days following tumor implantation, none of the combination treated animals had died. CONCLUSION: The combination of CDDP with these camptothecin analogs is an effective therapy against this model of advanced TCC. These observations suggest potential clinical value.     

Usefulness of micronucleus assay in radiosensitivity tests using human cancer cell lines

BACKGROUND: Recently, micronucleus assay is expected to be one of the radiosensitivity tests. The usefulness of micronucleus assay was compared with MTT assay and clonogenic assay using 5 human derived urological cancer cell lines, NBT-2, T24, PC3, OS-RC-2, and RERF-LC-AI in vitro. The correlation between the results in vitro assay and the radiation effects of nude mouse in vivo was investigated. METHODS: In vitro, the micronucleus frequency of 2 Gy radiation was scored in micronucleus assay. The survival fraction of 2 Gy radiation was obtained in MTT assay and clonogenic assay. The correlation between 3 assays was investigated. In vivo, cancer cells was inoculated to nude mouse and the tumor volume was measured at 3-7 days interval in control group and 10 Gy irradiated group. The tumor volume ratio in irradiated group to control group was calculated as a radiation effect in each cell lines, the correlation between this ratio in vivo and each value of 2 Gy radiation in vitro was studied. RESULTS: The correlation between micronucleus frequency and survival fraction in clonogenic assay was statistically significant (r = 0.941, p = 0.0169). But the correlation of the survival fraction between MTT assay and clonogenic assay is not statistically significant. The correlation between micronucleus frequency and the tumor volume ratio in vivo was statistically significant (r = 0.990, p = 0.0011). The correlation between survival fraction in clonogenic assay and the tumor volume ratio in vivo was also statistically significant (r = 0.914, p = 0.0298). However, the correlation between survival fraction in MTT assay and the tumor volume ratio in vivo was not statistically significant (r = 0.782, p = 0.118). CONCLUSION: In this 5 cell lines, micronucleus assay was most correlated to nude mouse radiation effect. This result suggested the possibility of micronucleus assay to be a better predictive method than clonogenic assay for radiosensitivity test.     

Responses of human glioblastoma cells to human natural tumor necrosis factor-alpha: susceptibility, mechanism of resistance and cytokine production studies

Responses and susceptibility of 14 human glioblastoma cell lines to human natural tumor necrosis factor-alpha (TNF) were studied in vitro. Susceptibility of glioblastoma cells to TNF varied in experimental conditions applied. Most of glioblastoma cell lines were resistant to cytotoxic activity of TNF in a MTT assay at concentrations below 16 U/ml for 72 h exposure. However, TNF at higher dose, in prolonged exposure and against low density of target cells was antiproliferative for certain glioblastoma cultures. TNF exposure at 10 U/ml for 48 h suppressed DNA synthesis in 9 of 14 glioblastoma cultures, but increased in 3 cultures. In addition, colony forming assay showed anti-clonogenic activity of TNF in 5 of 6 glioblastoma cell lines tested. In spite of their low susceptibility to TNF, glioblastoma cells well responded to TNF stimulation at low dose (10 U/ml) for a short period in the absence of cell damage. Productions of Interleukin-6 (IL-6), IL-8-like activity, granulocyte-macrophage colony stimulating factor (GM-CSF), prostaglandin E2 (PGE2) and manganous superoxide dismutase (Mn-SOD) were enhanced or induced by the low-dose TNF stimulation. Mn-SOD, a protein protective against oxidative cell damage, was well induced in time- and dose-dependent manner, however did not correlate with TNF resistance. Whereas the levels of PGE2 in TNF-susceptible cell lines, H-4 and SF-188, were higher than those of other lines. In conclusion, most of glioblastoma cells are resistant to TNF cytotoxic effects, but highly responsive to TNF stimulation. Its effect on glioblastoma cells appears to modulate cell differentiation rather than to kill the cells.     

Isolation of a cytotoxin from L-form Salmonella typhimurium

A cytotoxic protein was isolated from the sodium dodecyl sulphate (SDS)-solubilized extract of the stable L forms of Salmonella typhimurium by ion-retardation chromatography, ion-exchange chromatography, isoelectric focusing and gel filtration. The purified toxin, with a molecular mass of 32 kDa and with isoelectric point of 6.4, was thermolabile and trypsin-sensitive. Against mouse macrophages, its cytolytic effect was detectable in vitro at concentrations higher than 0.7 micrograms/ml, with a complete lysis obtained at 5 micrograms/ml. In contrast, it stimulated C3H/HeJ macrophages in the dose range of 0.1-0.5 micrograms/ml to allow the cell to respond to endotoxin, resulting in the significant production of tumor necrosis factor alpha. By Northern blot analysis, this effect was detectable at a dose as low as 0.01 micrograms/ml. These findings suggest that the transformation of bacillary S. typhimurium into L forms in vivo may induce alterations in host resistance against murine typhoid.     

Sensitization of human bladder cancer cells to Fas-mediated cytotoxicity by cis-diamminedichloroplatinum (II)

PURPOSE: The resistance of bladder cancer to anticancer chemotherapeutic drugs is a major problem. Several immunotherapeutic approaches have been developed to treat drug-resistant tumor cells. The Fas antigen (Fas)-Fas ligand pathway is involved in cytotoxic T lymphocyte and natural killer cell-mediated cytotoxicity. Like the Fas ligand, anti-Fas monoclonal antibody (mAb) induces apoptosis in tumor cells expressing Fas. Several anticancer drugs also mediate apoptosis and may share with Fas common intracellular pathways leading to cell killing. We reasoned that treatment of drug-resistant cancer cells with a combination of anti-Fas mAb and drugs might overcome their resistance. This study has investigated whether anticancer drugs synergize with anti-Fas mAb in cytotoxicity against bladder cancer cells. MATERIALS AND METHODS: Cytotoxicity was determined by a 1-day microculture tetrazolium dye assay. Synergy was assessed by isobolographic analysis. RESULTS: Treatment of the T24 human bladder cancer cell line with anti-Fas mAb in combination with 5-fluorouracil, mitomycin C or methotrexate did not overcome resistance to these agents. However, treatment of T24 tumor cells with a combination of anti-Fas mAb and cisdiamminedichloroplatinum (II) (CDDP) resulted in a synergistic cytotoxic effect. In addition, the CDDP-resistant T24 line (T24/CDDP) was sensitive to treatment with a combination of anti-Fas mAb and CDDP. Synergy by combination of anti-Fas mAb and CDDP was also achieved in three other bladder cancer lines and four freshly derived human bladder cancer cells. The combination of anti-Fas mAb and carboplatin also resulted in a synergistic cytotoxic effect on T24 cells; however, the combination of anti-Fas mAb and trans-diamminedichloroplatinum (II) resulted in an additive cytotoxic effect. Treatment with CDDP enhanced the expression of Fas on T24 cells. The synergy achieved in cytotoxicity with anti-Fas mAb and CDDP was also achieved in apoptosis. Incubation of T24 cells with anti-Fas mAb increased the intracellular accumulation of CDDP. Treatment of freshly isolated bladder cancer cells with CDDP enhanced their susceptibility to lysis by autologous lymphocytes. CONCLUSIONS: This study demonstrates that combination treatment of bladder cancer cells with anti-Fas mAb and CDDP overcomes their resistance. Synergy was achieved with established CDDP-resistant bladder cancer cells and freshly isolated bladder cancer cells. In addition, the sensitization required low concentrations of CDDP, thus supporting the potential in vivo application of combination of CDDP and immunotherapy in the treatment of CDDP- and/or immunotherapy-resistant bladder cancer.     

Sensitivity of human prostatic carcinoma cell lines to low dose rate radiation exposure

PURPOSE: Low dose rate radioemitters, such as 125I, 103Pd, and 89Sr, have been used both for local and systemic treatment of prostate cancer. Most normal cells exposed to ionizing radiation characteristically activate cell cycle checkpoints, resulting in cell cycle arrest at the G1/S and G2/M transition points. Cancer cells are typically quite sensitive to radiation killing late in the G2 phase of the replicative cell cycle. Furthermore, most cancer cells accumulating at the G2/M transition point as a result of low dose rate radiation exposure appear to become sensitive to further low dose rate irradiation. For this reason, protracted exposure of cancer cells to low dose rate radiation has been proposed to result in increased cancer cell killing as compared with brief exposures of cancer cells to high dose rate radiation. Since many human prostatic carcinomas contain somatic genome alterations targeting genes which affect the cell cycle and radiation-associated cell cycle checkpoints, we evaluated the effects of low dose rate radiation exposure on the cell cycle and on clonogenic survival for various human prostatic carcinoma cell lines. MATERIALS AND METHODS: Human prostatic carcinoma cells from the LNCaP, DU 145, PC-3, PPC-1, and TSU-Pr1 cell lines were exposed to low dose rate (0.25 Gy/hour) or high dose rate (60 Gy/hour) radiation in vitro and then assessed for radiation cytotoxicity by clonogenic survival assay. Cell cycle perturbations following protracted exposure to low dose rate radiation were evaluated using flow cytometry. RESULTS: For LNCaP cells, low dose rate radiation exposure resulted in an accumulation of cells at both the G1/S and the G2/M cell cycle transition points. For DU 145, PC-3, PPC-1, and TSU-Pr1 cells, treatment with low dose rate radiation triggered G2/M cell cycle arrest, but not G1/S arrest. Unexpectedly, the cell cycle redistribution pattern phenotypes observed, G1/S and G2/M cell cycle arrest versus G2/M arrest alone, appeared to have little effect on low dose rate radiation survival. Furthermore, while PC-3, PPC-1, and TSU-Pr1 cells exhibited increased cytotoxic sensitivity to low dose rate versus fractionated high dose rate radiation treatment, DU 145 and LNCaP cells did not. CONCLUSIONS: Radiation-associated pertubations in replicative cell cycle progression were not dominant determinants of low dose rate radiation killing efficacy in human prostate cancer cell lines in vitro.     

Pharmacokinetic analysis of low-dose intra-peritoneal cis-platinum administration

Pharmacokinetic parameters after intra-peritoneal administration of low-dose cis-platinum (CDDP) were analysed in order to evaluate the possibility of applying low-dose 5-FU/CDDP therapy (1-FP) for outpatients. Four patients with advanced gastric cancer were the subjects of this study. CDDP at a dose of 20 mg/body was administered intra-peritoneally, and peripheral venous blood was collected at 30 min, 4, 8, 24, 48, 72, 96 and 120 hr after drug administration. The plasma platinum (Pt) concentration was determined by atomic absorption spectrometry. Pharmacokinetic parameters were calculated using a two-compartment open model. C max, AUC, t1/2 alpha and t1/2 beta of total-Pt were 1. 27 +/- 0.21 micrograms/ml, 95.28 +/- 16.93 micrograms.hr/ml, 1.91 +/- 0.76 hr and 190.2 +/- 125.6 hr, respectively. Total-Pt concentration at 120 hr, after administration was 0.54 +/- 0.14 microgram/ml. This result suggests that intraperitoneal low-dose CDDP administration is a promising method for 1-FP therapy for outpatients, because the plasma total-Pt level is maintained at a sufficiently high level for a long period.     

Tranilast and cisplatin as an experimental combination therapy for scirrhous gastric cancer

We examined the effect of Tranilast on the reduction of the administered dose of cisplatin using a scirrhous gastric cancer model. Scirrhous gastric cancer cell line, OCUM-2M, and gastric fibroblasts, NF-10, were used. The IC50 values of CDDP to OCUM-2M cells were decreased by Tranilast in vitro. The combination treatment with Tranilast and CDDP decreased the xenografted tumor size. The combination therapy decreased fibrosis and mitosis, and increased apoptosis. These findings suggest that Tranilast increased the CDDP response on scirrhous gastric cancer. The combination treatment with Tranilast and CDDP may be useful as a new therapy for scirrhous gastric carcinoma.     

Augmented antitumor efficacy of combination chemotherapy of nedaplatin with 5-fluorouracil in in vivo murine and human tumor model

Augmented antitumor activity was demonstrated in combination chemotherapy of Nedaplatin (NDP) or Cisplatin (CDDP) with 5-fluorouracil (5-FU) against murine lung carcinoma and human squamous carcinoma from head and neck. Either NDP or CDDP (1/4 to 1 maximum tolerated dose; MTD) was injected once and 5-FU (1/16 MTD) was injected daily for five days via tail vein to tumor-implanted mice. The sequential administration of either NDP or CDDP prior to 5-FU (NF or CF therapy) showed severe body weight loss followed by the toxic death of tumor-bearing mice at the MTD of NDP or CDDP. In contrast, the reverse sequence of the treatment, that is, 5-FU prior to NDP or CDDP (FN or FC therapy), resulted in the synergistically enhanced inhibition of tumor growth and the prolonged survival in comparison with NDP, CDDP or 5-FU monotherapy. The antitumor activities of the combinations of CDDP with 5-FU was less than those of the combination of NDP with 5-FU. Especially, at the MTD of NDP in FN therapy, long-term tumor-free survival was frequently observed. Thus, FN therapy was thought to be the most efficient regimen in combination of NDP with 5-FU as a clinical therapy.     

Therapeutic potential of analogues of amiloride: inhibition of the regulation of intracellular pH as a possible mechanism of tumour selective therapy

The extracellular pH (pHe) in solid tumours is frequently lower than the pHe in normal tissues. Cells within an acidic environment depend on mechanisms which regulate intracellular pH (pHi) for their survival, including the Na+/H+ antiport which exports protons in exchange for Na+ ions. Amiloride and its analogues DMA (5-(N,N-dimethyl)amiloride), MIBA (5-(N-methyl-N-isobutyl)amiloride) and EIPA (5-(N-ethyl-N-isopropyl)amiloride) are known to inhibit the Na+/H+ antiport and therefore decrease the cells ability to regulate pHi. All three analogues were found to be potent inhibitors of the antiport in human MGH-U1 and murine EMT-6 cells, with DMA being approximately 20, MIBA 100 and EIPA 200-fold as potent as amiloride; EIPA also gave more complete suppression of the Na+/H+ antiport. These agents were not toxic to cells when used alone; however, in combination with nigericin, an agent which acidifies cells, all three analogues were toxic to cells at pHe < 7.0, and markedly enhanced the toxicity of nigericin alone. Cell killing was greatest for nigericin used with EIPA or MIBA. None of the agents were toxic to cells at pHe 7.0 or above. When used against variant cells lacking the Na+/H+ antiport (PS-120 cells) EIPA did not enhance the cytotoxicity of nigericin alone, suggesting that the observed effect was due to inhibition of Na+/H+ exchange, rather than due to non-specific effects. The combination of EIPA and nigericin gave similar cell killing in previously dissociated and intact MGH-U1 spheroids, suggesting that the agents have good penetration of solid tissue. Preliminary experiments using EMT-6 tumours in mice suggested that EIPA and nigericin were able to enhance the toxicity of radiation in vivo, presumably through selective effects against the hypoxic (and probably acidic) subpopulation of cells that is resistant to radiation.     

Personalities and alimentary behaviors in obese patients

The ability of lonidamine (LND), an energolytic derivative of indazole-carboxylic acid, to modulate the cytotoxic activity of cisplatin (CDDP) and epidoxorubicin (EPI), singly or in combination, was investigated in two human breast cancer cell lines (MCF7 and T47D). A 72-hr post-incubation with a non-cytotoxic concentration of LND (75 microM) increased the activity of a 1-hr CDDP treatment as well as that of a 1 to 16-hr EPI treatment. A different pattern of interaction among the drugs and modulator was observed as a function of the sequence of drug treatment. Specifically, supra-additive or additive effects of the combination were obtained in the two cell lines according to the different treatment schemes. In particular, the maximum potentiation was observed in MCF7 cells simultaneously exposed to CDDP, EPI and LND for 1 hr and then post-incubated with LND for 72 hr, and in T47 first exposed to EPI and LND, then to CDDP and LND, and finally post-incubated with LND. Flow cytometric analysis of MCF7 cell distribution in the different cycle phases showed that combined treatment with EPI/CDDP/LND was able to stabilize cell cycle perturbations (mainly G2M accumulation) induced by individual agents. The ability of LND to potentiate CDDP and EPI cytotoxicity, and the consideration that LND causes side effects different from those caused by alkylating agents and anthracyclines, make this compound an attractive candidate for multidrug combination therapy in breast cancer.