Sarcoma-180 cells and human colorectal tumor cells under in vitro hypoxic conditions are more sensitive to mitomycin C and carboquone

The effects of oxygen concentration on the chemosensitivity of mouse sarcoma-180 (S-180) cells and human colorectal cancer tissues to mitomycin C (MMC) or carboquone (CQ) were determined in vitro, since evidence had been obtained that these drugs are more effective in HeLa cells. The results were as follows: (a) S-180 cells exposed to various concentrations of MMC or CQ for 2 h under conditions of normal aeration (about 20%) or hypoxia (5.0% and 0%) were then maintained under normal conditions of aeration for 3 days. Change of viability was assessed by succinate dehydrogenase (SD) activity. With exposure of the cells to MMC or CQ, under anoxic conditions (O2:0%), SD activity decreased to a greater extent than seen in the control cells. The value for CQ was from 61.5% to about 36.2%. (b) The decrease in the SD activity of 20 colorectal cancer tissues kept under conditions of anoxia was compared with findings under normally aerated conditions, following exposure to 30 microM of MMC or 1.6 microM of CQ. On exposure to MMC or CQ under anoxic conditions, SD activity decreased significantly, compared with normally aerated conditions (P less than 0.001 for MMC; P less than 0.05 for CQ). As colorectal cancer is less sensitive than other tissues to various chemotherapeutic agents, we recommend that MMC and CQ be prescribed to treat patients with these malignant lesions.     

Hypoxia and acidity increase the cytotoxicity of mitomycin C and carboquone to human tumor cells in vitro.

To clarify the influence of hypoxic and acidic environments on the cytotoxicity of mitomycin C (MMC) and carboquone (CQ), the cytotoxicity was assessed based on decreases in intracellular ATP levels of HeLa cells exposed to the drugs at various acidic pH (pH 5.8-6.8) and low oxygen tension (5% and 0% O2) in vitro. Hypoxia and acidity individually increased the cytotoxicity of MMC, although hypoxia no longer increased it under acidic conditions. On the other hand, the cytotoxicity of CQ was enhanced in the presence of hypoxic and acidic conditions, and even more so with their combination. We conclude that acidity is a determining factor and excels hypoxia in influencing the cytotoxicity of MMC and that these two factors act synergistically on CQ.     

Effects of anthracyclines on oxygenated and hypoxic tumor cells

The cytotoxic effects of anthracyclines and other chemotherapeutic agents were examined in normally aerated and hypoxic Sarcoma 180 and EMT6 tumor cells in vitro. Adriamycin, daunomycin, and mitomycin C were selectively toxic to hypoxic Sarcoma 180 cells. The augmented sensitivity was not the result of an increase in susceptibility of oxygen-deprived cells toward antitumor agents in general. 1,3-Bis(2-chloroethyl)-1-nitrosourea, for example, exhibited equal cytotoxicity toward normally aerated and hypoxic cells, while streptonigrin was selectively toxic toward normally aerated cells. The cellular levels of [3H]daunomycin in both Sarcoma 180 and EMT6 cells were not different under the two conditions of oxygenation, and no greater production of either the alcohol or aglycone metabolites of daunomycin occurred in hypoxic cells, compared with their normally aerated counterparts. In addition, analysis of cellular pellets for residual drug remaining after exhaustive extraction showed no significant difference between normally aerated and hypoxic cells. The effects of reoxygenation of hypoxic cells on their sensitivity to mitomycin C and to Adriamycin were studied in both Sarcoma 180 and EMT6 cells. The enhanced efficacy of mitomycin C as a cytotoxic agent observed under hypoxia was reversed after a 2-hr reoxygenation. In contrast, the augmented toxicity of Adriamycin toward hypoxic cells was not reversible in either cell line after 2 or 4 hr of reoxygenation. The results suggest that neither the formation of a reactive oxygen species nor direct involvement of an alkylating agent generated by drug metabolism is an obligatory step in the cytotoxic action of these anthracyclines.     

受缺氧反应元件调控的荧光素酶报告基因在缺氧肿瘤细胞内的表达活性研究

 目的 研究缺氧反应元件调控的荧光素酶报告基因在肿瘤细胞内的缺氧反应性。方法 将pGL3-6HRE-TATA-luciferase-SV40pa报告载体以Lipofectamine 2000介导瞬时转染Hela S3和HepG2细胞，分别于缺氧（1 % O2）和常氧（21 % O2）培养后检测相对荧光素酶活性。结果 pGL3-6HRE- TATA- luciferase-SV40pa报告载体转染细胞后，缺氧培养条件下相对荧光素酶的活性较常氧培养条件下显著上调，差异具有统计学意义（P＜0.01），并且该缺氧诱导性具有一定的时间依赖性，即Hela S3细胞中，缺氧培养12～24 h，相对荧光素酶的活性上升到了最高值；而HepG2细胞中，缺氧培养36 h，相对荧光素酶的活性上升到了最高值。结论 6HRE人工启动子在肿瘤细胞内具有显著的缺氧诱导性；6HRE人工启动子缺氧诱导性具有一定的时间效应，并且在不同肿瘤细胞中其诱导效应和时间效应可存在着差异。研究结果为实体肿瘤基因治疗奠定了理论和实验基础。     

Effects of antineoplastic agents and hyperthermia on cytotoxicity toward chronically hypoxic glioma cells.

The effects of hyperthermia and antineoplastic agents on the cytotoxicity to normally oxygenated and chronically hypoxic glioma cells were investigated in vitro. Exposure to temperatures above 43.0 degrees C was less cytotoxic to hypoxic cells which predominantly accumulated in the G0/G1 phase fraction. On the other hand, mitomycin C (MMC) and adriamycin (ADM) were preferentially cytotoxic to hypoxic cells not only at 37 degrees C but also at elevated temperatures (42 degrees C and 43 degrees C). These two agents showed marked synergistic effects with hyperthermia under both oxygenated and hypoxic conditions. In contrast, bleomycin (BLM), cis-diamminedichloroplatinum(II) (CDDP), and vincristine (VCR) were preferentially cytotoxic to oxygenated cells at both 37 degrees C and elevated temperatures. CDDP showed cytotoxic synergism with hyperthermia that appeared to be oxygen-dependent. A nitrosourea derivative, 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU), showed no major preferential toxicity under either oxygenated or hypoxic conditions. This study suggests that hyperthermia in combination with MMC or ADM would have a greater cytotoxic effect on hypoxic cell subpopulations of malignant gliomas.     

Oxygen and exposure kinetics as factors influencing the cytotoxicity of porfiromycin, a mitomycin C analogue, in Chinese hamster ovary cells

Some factors affecting the cytotoxicity of porfiromycin (PM), an analogue of mitomycin C (MMC), were investigated in suspension cultures of wild-type (AA8-4) and repair-deficient (UV-20) Chinese hamster ovary cells. Oxygen was an important modulator of PM toxicity in AA8-4 cells. The aerobic toxicity was significantly less, and toxicity under extremely hypoxic conditions was significantly greater for PM than MMC. Porfiromycin cytotoxicity at intermediate O2 levels was similar to that observed previously for MMC. While the aerobic/hypoxic ratio was greater for PM than MMC, survival at intermediate oxygen concentrations could limit the therapeutic utility of these drugs as adjuncts to radiotherapy. Ascorbic acid was found to increase the aerobic, but not hypoxic, cytotoxicity of PM in AA8-4 cells, as was observed previously for MMC. Investigation of various exposure times and drug concentrations revealed that drug toxicity for both aerobic and hypoxic cells was dependent on the product of drug concentration and time, and that the aerobic/hypoxic differential observed in AA8-4 cells was constant over a broad range of exposure conditions. The sensitivity of UV-20 cells was also a linear function of concentration and time, but no aerobic/hypoxic differential was observed in these cells. It is suggested that the sensitivity of UV-20 to PM and MMC, and its lack of an hypoxic/aerobic differential could result from lethality being due to a different lesion than in wild-type cells.     

Modulating effect of alpha-[N,N-[bis(2-hydroxyethyl)]-amino-N- (o-methoxyphenyl)-pyrrolidin-2,5-dione on the chemotherapy of murine tumours

alpha-[N,N-[bis(2-hydroxyethyl)]-amino]-N- (o-methoxyphenyl)pyrrolidin-2,5-dione (I), an intermediate in the synthesis of pyrrolidinedione-N-mustards, did not exhibit antitumour activity against P388 lymphocytic leukemia, Sarcoma 180 (ascites) and Ehrlich (ascites) carcinoma tumours. The effect of co-administration of (I) with established anticancer drugs was studied against these murine tumours. The activity of 5-fluorouracil against Sarcoma 180 (ascites) and Ehrlich (ascites) carcinoma was significantly enhanced by co-administration with (I). Other anticancer drugs, when co-administered with (I), did not show any enhancing effect.     

Laserthermia enhances the clastogenic effects of antineoplastic agents in aerobic and chronically hypoxic HeLa cells in vitro

The interactive clastogenic effects of Nd-YAG laser induced hyperthermia (laserthermia) in combination with antineoplastic agents on normally oxygenated and chronically hypoxic HeLa cells were investigated. Exponentially growing HeLa cells were treated with bleomycin sulfate (BLM) (2-4 microg/ml), adriamycin (ADM) (2-4 microg/ml) and actinomycin D (ACT) (0.2-0.4 microg/ml) alone or in combination with laser at various powers (7-13 W) or different laser induced elevated temperatures (39.5-43.5 degrees C). HeLa cells were incubated with 3 microg/ml cytochlasin B for 36 h after treatments and the frequency of micronuclei (MN) were determined in binucleated cells. Results showed a relatively high frequency of MN formation after drug treatments in normally oxic and chronically hypoxic cells, although there was a decrease in the frequency of MN in hypoxic cells compared to oxygenated cells. Laserthermia at various powers and different induced temperatures produced a slight increase in MN formation both in oxic and hypoxic cells. When drug treatment and laserthermia was combined, a profound synergistic effect in MN formation was observed for all three drugs used in these experiments. ACT at a concentration of ten times lower than ADM and BLM produced similar effect. Also, ADM showed a marked synergistic effect with laserthermia compared to BLM at similar concentrations. This study suggests that laserthermia in combination with ADM, BLM or ACT would have a greater genotoxic effect on hypoxic cell populations. Therefore, Nd-YAG laser induced hyperthermia may be a useful modality for elimination of the radioresistant hypoxic cells.     

Tumor tissue is more sensitive to mitomycin C, carboquone, and aclacinomycin A than is adjacent normal tissue in vitro

In tissues obtained from patients undergoing gastrectomy or colectomy, sensitivity to mitomycin C (MMC), carboquone (CQ), and aclacinomycin A (ACR) was examined in 20 tumors (15 gastric, 5 colorectal) and in the adjacent normal mucosal tissues, using the in vitro succinate dehydrogenase inhibition test. The succinate dehydrogenase (SD) activity decreased to a greater extent in the tumor tissues than in adjacent normal tissues, at rates of 80% for MMC, 80% for CQ, and 90% for ACR. There were no correlations between SD activities of tumor and adjacent normal tissue, r = 0.157 for MMC, r = 0.435 for CQ, and r = 0.375 for ACR. Normal tissues were sensitive to MMC in 25% of cases sensitive to MMC in the tumor tissues, 46% for CQ, and 38% for ACR. These results show that the antitumor effects of MMC, CQ, and ACR are relatively specific for tumor tissues and that the assay of chemosensitivity of normal tissues is meaningful for predicting the toxic effects of antitumor drugs on these tissues.     

Efficacy of chemotherapeutic agents under hypoxic conditions in pulmonary adenocarcinoma multidrug resistant cell line

Hypoxia is often observed in solid tumors. The aim of this study was to investigate the efficacy of seven cytotoxic drugs against the pulmonary adenocarcinoma multidrug-resistant cell line A549/MDR under hypoxia (3% O(2)), and to explore the possible mechanisms for the change of efficacy. The efficacy of cytotoxic drugs under hypoxic conditions was different from that under normoxia. Proliferation of A549/MDR cells was enhanced under hypoxia and no close correlation was found between proliferation and cytotoxic effects. Under hypoxia, the efficacy of rhodamine123 efflux was unchanged; the culture medium became more acidic and the generation of reactive oxygen species (ROS) was decreased. The intracellular fluorescence intensity of daunorubicin was much lower in this acidic microenvironment. These results indicate that susceptibility to drugs was greatly influenced by hypoxia and different intracellular drug concentrations induced by microenvironment acidification which may be the main cause of the change in drug efficacy. In addition, proliferation may change resistance to study drugs under hypoxia for A549/MDR cells. The decreased generation of ROS may be another reason for the resistance of A549/MDR cell line to daunorubicin under hypoxic conditions. Drug exclusion mediated by P-gp may not be the key reason.     

Role of dt-diaphorase as a determinant of sensitivity to mitomycin analogs in nonsmall cell lung-cancer cell-lines

DT-diaphorase (DT-D) is regarded as a two-electron reductase that plays an important role in the biotransformation of mitomycin C (MMC) to antitumor metabolites, which is enhanced under hypoxic conditions. To evaluate the role of DT-D as a bioactivator of MMC and its analogue, KW-2149, in non-small cell lung cancer (NSCLC) cell lines under an aerobic or hypoxic condition, we examined the inhibitory effect of dicumarol which was regarded as an inhibitor of DT-D on the sensitivity to these anticancer agents in vitro. In this study, we used an MMC-resistant NSCLC cell line (PC-9/MC4) which was established in our laboratory from a PC-9 cell line as a parent cell line by continuous exposure to MMC. The subline PC-9/MC4 was 6.7-fold more resistant to MMC than PC-9, the parent cell line, under aerobic conditions, and 5.2-fold more resistant even under hypoxic conditions. PC-9/MC4 cell lines did not show collateral resistance to KW-2149, a newly developed MMC analogue. The IC50 value of PC-9 against MMC significantly decreased by co-incubation with dicumarol under aerobic, but not under hypoxic conditions. KW-2149 was cytotoxic to PC-9/MC4 as well as PC-9 cells, and the sensitivity to KW-2149 was not altered by coincubation with dicumarol or exposure to hypoxia. There were no significant differences in intracellular uptake of MMC and the activities of cytosolic detoxification enzymes, GST and GSH, between PC-9 and PC-9/MC4 cell lines under aerobic conditions. These findings suggest a partial role of DT-D in bioactivation of MMC, but not of KW-2149, under aerobic conditions. However, the detailed mechanisms of drug resistance to MMC under hypoxic conditions are still not clear.     

Flavone acetic acid increases the cytotoxicity of mitomycin C when combined with hyperthermia

 Flavone acetic acid (FAA, NSC 347512) is known to selectively reduce tumor blood flow. Taking advantage of this pharmacodynamic effect, we have previously shown that FAA in combination with hyperthermia (HT) can produce a marked improvement in antitumor response in mice. In the present study, we investigated whether FAA could increase the cytotoxicity of mitomycin C (MMC), a bioreductive drug with selective cytotoxicity against hypoxic cells, under either normothermic or hyperthermic conditions. In vitro, the cytotoxicity of MMC against B16 melanoma cells was not enhanced with exposure to FAA at concentrations less than 100 μg/ml, even when combined with HT (43°C, 60 min). The cytotoxicity of MMC (1 μg/ml) at pH 6.5, however, was enhanced by exposure of cells to hypoxia in combination with HT. In vivo, the tumor growth time, calculated as the time required to double the initial tumor volume, was 5.2, 6.8, 8.5, and 15.0 days with FAA (150 mg/kg) alone, MMC (4 mg/kg) alone, FAA+MMC, or FAA+MMC+HT (43°C, 15 min) treatment groups, respectively. Antitumor response obtained in animals treated with FAA plus MMC with HT was clearly better than that obtained in any of the other groups. Scheduling of FAA, MMC, and HT was found to be important in producing optimal antitumor response. Administration of MMC (4 mg/kg) prior to FAA (150 mg/kg) and subsequent HT treatment was superior to administration of FAA before MMC. In an attempt to explain these findings, the influence of FAA on blood flow in skeletal muscle and in tumor was examined using a laser blood flowmeter. FAA administration to mice produced a 75% reduction in blood flow to the tumor for up to 2 h but had no detectable effect on normal skeletal blood flow. Our current explanation of the increased antitumor response achieved with the combination of MMC, FAA, and HT is as follows. The FAA-mediated decrease in blood flow to the tumor, when combined with HT, may produce sufficiently hypoxic conditions to significantly increase the antitumor efficacy of the bioreductive drug, MMC. We believe that clinical testing of this combined drug treatment with hyperthermia is warranted. Received: 1 February 1995/Accepted: 6 July 1995     

Hyperbaric oxygen and radiobiology of a C3H mouse mammary carcinoma

A series of radiation dose-tumor control response assays was performed on the first-to-fourth generation isotransplants of a C3H/J mouse mammary carcinoma for radiation administered under four different conditions: hypoxia, a clamp across the root of the tumor-bearing part for 1 minute before treatment; air, animal respiring air at one atmosphere of pressure; O2 30 or 44 psi, animal respiring pure oxygen at 30 or 44 psi for 15 minutes before and during local tumor irradiation. When radiation was administered as a single dose (v = 1) to 250 mm3 tumors, high pressure oxygen was only modestly effective in reducing the tumor control dose (TCD50); TCD50 hypoxia/O2 30 psi and TCD50 hypoxia/O2 44 psi were only 1.2 and 1.3, respectively. However, for similar treatment of 0.6 mm3 tumors and of even smaller "microcolonies," the ratios TCD50 hypoxia/O2 44 psi were 2.5 and 3.2, respectively. These results are discussed with respect to simple tumor models so as to estimate the proportion of hypoxic cells present in tumors under normal conditions and the influence of oxygen breathed at increased pressure on that proportion. High pressure oxygen was found much more effective when combined with fractionated irradiation (v = 10) than with single-dose therapy. Thus TCD50 hypoxia/O2 30 psi was 2.2 (v = 10) instead of 1.2 (v = 1). Finally, the ratio TCD50 hypoxia = 10/v = 1 was 2.15. These results are reviewed and inferences drawn as to the extent of tumor cell proliferation between treatments, repair of sublethal radiation injury by hypoxic cells, and the movement of cells from the hypoxic compartment to the aerobic compartment during fractionated irradiation (v = 10) under normal conditions.     

Some new aryl-sydnones: effects on murine tumours.

The effects of new aryl-sydnones: 3-[4-X-3-nitrophenyl]-1,2,3-oxadiazolium-5-olates, where X = Cl (SYD-1); pyrrolidino (SYD-2); piperidino (SYD-3) and morpholino (SYD-4) on the survival of mice bearing Sarcoma 180, Ehrlich carcinoma, B10MCII (Fibrous histiocytoma) and L1210 leukemia ascitic tumours, on the proliferation of cultured tumour cells and on the synthesis of DNA in L1210 leukemia were determined. SYD-1 and SYD-2 in vivo significantly enhanced the survival of S180, Ehrilich and B10MCII tumour-bearing mice. Furthermore, SYD-2 showed significant activity against L1210. SYD-3 and SYD-4 did not show antitumour activity. SYD-1, in vitro was the most cytotoxic against all the above tumour cells. All of the drugs tested inhibited thymidine uptake by L1210 cells, SYD-4 being the least active.     

Lethal effect of bleomycin and peplomycin on HeLa cells in multicell tumor spheroids

The lethal effects of bleomycin and its derivative, peplomycin, were determined for HeLa S3 cells grown in multicell spheroids cocultured with human diploid fibroblasts. Both drugs were less effective for cells in spheroids than for cells grown exponentially in monolayers. However, HeLa cells from spheroids exposed to the drugs in single-cell suspension were more sensitive to the drugs than were cells in monolayers. Sequential trypsinization of spheroids after exposure to both drugs showed that the surviving fraction increased sharply with increasing depth of cell layers in the spheroids. The presence of 0.5 mM misonidazole, a hypoxic radiosensitizer, enhanced the lethal effect of peplomycin only for the cells in the deeper layer. These findings suggest that the drug resistance of cells in spheroids was due, at least in part, to the microenvironment of the deeper layers. When spheroids were incubated in fresh medium following exposure to both drugs, the cells recovered from the potentially lethal damage within 1 hr. The extent of the recovery from a fixed drug concentration was higher in cells of the superficial layers than in cells of the deeper layers. It is suggested that the limitation of the lethal effects of bleomycin and peplomycin in solid tumors may be overcome by improving the state of oxygenation of hypoxic cells and by combining either drug with one which inhibits recovery from potentially lethal damage.     

Bioreductive drugs: from concept to clinic

One of the key issues for radiobiologists is the importance of hypoxia to the radiotherapy response. This review addresses the reasons for this and primarily focuses on one aspect, the development of bioreductive drugs that are specifically designed to target hypoxic tumour cells. Four classes of compound have been developed since this concept was first proposed: quinones, nitroaromatics, aliphatic and heteroaromatic N-oxides. All share two characteristics: (1) they require hypoxia for activation and (2) this activation is dependent on the presence of specific reductases. The most effective compounds have shown the ability to enhance the anti-tumour efficacy of agents that kill better-oxygenated cells, i.e. radiation and standard cytotoxic chemotherapy agents such as cisplatin and cyclophosphamide. Tirapazamine (TPZ) is the most widely studied of the lead compounds. After successful pre-clinical in vivo combination studies it entered clinical trial; over 20 trials have now been reported. Although TPZ has enhanced some standard regimens, the results are variable and in some combinations toxicity was enhanced. Banoxantrone (AQ4N) is another agent that is showing promise in early phase I/II clinical trials; the drug is well tolerated, is known to locate in the tumour and can be given in high doses without major toxicities. Mitomycin C (MMC), which shows some bioreductive activation in vitro, has been tested in combination trials. However, it is difficult to assign the enhancement of its effects to targeting of the hypoxic cells because of the significant level of its hypoxia-independent toxicity. More specific analogues of MMC, e.g. porfiromycin and apaziquone (EO9), have had variable success in the clinic. Other new drugs that have good pre-clinical profiles are PR 104 and NLCQ-1; data on their clinical safety/efficacy are not yet available. This paper reviews the pre-clinical data and discusses the clinical studies that have been reported.     

Trimodality therapy (drug/hyperthermia/radiation) with BCNU or mitomycin C

To develop multimodality treatment combinations with high curative potential in advanced local disease, BCNU (N,N'-bis(2-chloroethyl)-N-nitro-sourea) and mitomycin C were tested with hyperthermia and radiation in the FSaIIC fibrosarcoma system. Growth delay experiments demonstrated that, while neither BCNU nor mitomycin C produced dose modification of the radiation response, and hyperthermia (43 degrees C, 30 min) produced only a moderate dose modification (1.4 +/- 0.2), the combination of BCNU plus hyperthermia resulted in a radiation dose modifying factor (DMF) of 1.9 +/- 0.3, and mitomycin C plus hyperthermia a dose modifying factor of 2.1 +/- 0.4. Tumor cell survival over a range of BCNU doses administered i.p. immediately before hyperthermia resulted in a dose modifying factor of 1.8 +/- 0.2 versus drug alone. With mitomycin C however, giving the drug immediately prior to heating produced a dose modifying factor due to hyperthermia of only 1.2 +/- 0.10. Hoechst 33342 diffusion was used to separate tumor cells into predominately oxic and hypoxic subpopulations. Administration of the single, double and trimodality therapies showed that BCNU was 3.1-fold more toxic to the oxic versus the hypoxic cells whereas mitomycin C was 3.5-fold more toxic to the hypoxic compared to the oxic cells. Hyperthermia was 1.4-fold more toxic to the hypoxic versus the oxic cells whereas 10 Gy of radiation was 2.0-fold more toxic to the oxic compared to the hypoxic cells. The combination of hyperthermia plus radiation increased killing in both Hoechst dye defined subpopulations but relatively more in the hypoxic cells in which killing was 1.8-fold greater than in the oxic cells. When heat was delivered immediately after i.p. administration of the anticancer drugs, hyperthermia increased BCNU killing in the oxic cells by 17.2-fold versus 4.4-fold in the hypoxic cells and increased mitomycin-killing by 2.6-fold in the oxic cells versus 17-fold in the hypoxic cells. Use of the full trimodality treatment, given in the sequence drug (BCNU, 50 mg/kg or mitomycin-C 5 mg/kg)----heat (43 degrees C, 30 min)----radiation (10 Gy) produced a 3 log kill in the oxic cells versus a 2 log kill in the hypoxic cells with BCNU and a 2 log kill in the oxic cells versus a 3 log kill in the hypoxic cells with mitomycin C. These results indicate that the use of selected anticancer drugs with hyperthermia and radiation can produce highly cytotoxic interactions which markedly modify the effect of radiation.(ABSTRACT TRUNCATED AT 400 WORDS)     

The difference in chemosensitivity to antineoplastic agents of human hepatocellular carcinoma cells under normo-oxygenated or hypoxic conditions.

In order to select more effective drugs under hypoxia for the treatment of hepatocellular carcinoma, the cytotoxicity of antineoplastic agents for two hepatoma cell lines, PLC/PRF/5 and HuH-7, was examined under both oxygenated and hypoxic conditions. Mitomycin C was observed potentially to have enhanced cytotoxicity under hypoxic conditions for both hepatoma cell lines. Carboquone showed enhanced cytotoxicity under hypoxia for PLC/PRF/5 alone. On the other hand, there was no cytotoxic enhancement of adriamycin or cisplatin in either cell line. Thus, the sensitivity of tumour cells to the cytotoxic agents altered according to the conditions to which the tumour was exposed. The selection of the antineoplastic drugs for chemotherapy therefore should depend not only on the sensitivity of individual tumours to various drugs, but the alteration of the cytotoxicity of the drugs under certain conditions should also be carefully taken into account.     

Enhancement of interstitial photodynamic therapy by mitomycin C and EO9 in a mouse tumour model

The tumoricidal effect of interstitial photodynamic therapy (IPDT) using Photofrin was found to increase when combined with the bioreductive alkylating agent mitomycin C (MMC) and, to a lesser extent, with the indoloquinone EO9. When MMC was given prior to IPDT of RIFI tumours, the light dose required for a given regrowth time or for 50% cure was reduced by a factor of 2 compared with IPDT alone. MMC given immediately after illumination did not increase the effects of IPDT, although MMC plus illumination without photosensitizer produced a significant increase in regrowth time compared with MMC or light alone. Combination of IPDT with EO9, given directly before illumination, only marginally increased the tumour regrowth times at non-toxic doses. These results demonstrate that combining IPDT with MMC greatly improves the tumour response. Factors such as PDT-induced hypoxia, pH changes, temperature in-creases and production of toxic reactive oxygen species by both drugs may play a role in the enhanced MMC cvtotoxicity.     

Addition of misonidazole, etanidazole, or hyperthermia to treatment with fluosol-DA/carbogen/radiation

The antitumor efficacy of adding the nitroimidazole radiosensitizing drugs misonidazole and etanidazole or hyperthermia (43 degrees C for 30 min) to Fluosol-DA/carbogen (95% O2/5% CO2) and irradiation was tested in the FSaIIC tumor system. Both the nitroimidazole drugs and hyperthermia produced additional tumor growth delays and tumor cell cytotoxicity when given with Fluosol-DA/carbogen, either before or after irradiation. For each of the modalities tested, the dose-modifying effect was greater when that therapy preceded rather than followed irradiation (misonidazole 2.7 vs. 1.9, etanidazole 2.4 vs. 1.7, hyperthermia 4.0 vs. 1.7 relative to the effect of radiotherapy alone). Because the nitroimidazole drugs must be present before radiation is administered to exert their radiosensitizing effect, the increase in tumor growth delay observed when these drugs cytotoxic to hypoxic cells were administered following Fluosol-DA/carbogen and irradiation suggests that Fluosol-DA/carbogen could not fully oxygenate the tumors and that the nitroimidazole drugs were effectively toxic to residual hypoxic cells. The treatment Fluosol-DA/carbogen----hyperthermia----irradiation produced a marked increase in tumor growth delay not seen with the sequence Fluosol-DA/carbogen----irradiation----hyperthermia. The results indicate that a treatment combination of radiation sensitizers may be more effective than irradiation plus Fluosol-DA with oxygen breathing alone.