The effect of retinoic acid on chemosensitivity of PA-1 human teratocarcinoma cells and its modulation by an activated N-ras oncogene.

Combination of chemotherapeutic drugs with agents that induce cell differentiation is a possible means of improving cancer chemotherapy. To explore this approach we used 4 cell lines established from the human teratocarcinoma-derived cell line PA-1; 2 retinoic acid (RA)-sensitive lines compared to 2 RA-resistant lines transformed by an activated N-ras oncogene. Equal numbers of colony-forming cells were exposed for 72 hr to 10(-6)M RA and subsequently to a range of concentrations of cisplatinum, etoposide or bleomycin. Enhanced cytotoxicity of cisplatin and etoposide (3- to 5-fold) was observed in the N-ras-transformed cell lines compared to the non-transformed lines. Treatment with RA caused an increase in the cytotoxicity of all 3 drugs to the 2 RA-sensitive cell lines. In contrast, a reduction of cytotoxicity was observed in the 2 N-ras-transformed lines. Our results indicate that sensitivity to cytotoxic agents can be increased by RA in RA-sensitive cells, but the opposite effect is seen in N-ras transformed, RA-resistant cells. Therefore, a general rationale for combination therapy with RA and cytotoxic drugs cannot be inferred.     

Influence of the phosphodiesterase-5 inhibitor,sildenafil, on sensitivity to chemotherapy in breast tumor cells

Studies were performed to determine the influence of the phosphodiesterase-5 inhibitor, sildenafil, on sensitivity to Adriamycin (doxorubicin) in four human breast tumor cell lines and one murine breast tumor line. Sildenafil did not interfere with the effectiveness of Adriamycin in any of the cell lines tested. Sildenafil also failed to protect MDA-MB231 cells against the cytotoxicity of cisplatin, taxol or camptothecin. Sildenafil enhanced sensitivity to Adriamycin markedly in the p53 mutant MDA-MB231 and p53 null MCF-7/E6 cells and moderately in the MCF-7/caspase 3 and 4T1 cell lines. In the MDA-MB231 cells, sildenafil increased the extent of DNA damage induced by Adriamycin as well as the extent of apoptotic cell death. Sildenafil did not influence sensitivity to Adriamycin in bone marrow cells or macrophages. In an immunocompetent model of breast cancer (4T1 mammary carcinoma in Balb/c mice), sildenafil did not attenuate the antitumor effects of Adriamycin; furthermore, the combination of sildenafil with Adriamycin was no more toxic to the animals than Adriamycin alone. Given that sildenafil has been shown to have the potential to protect the heart against the toxicity of Adriamycin, these studies suggest that the inclusion of sildenafil with conventional chemotherapeutic protocols involving Adriamycin (and possibly cisplatin, camptothecin and/or paclitaxel) should not compromise the antitumor effectiveness of these drugs nor enhance their toxicity to the patient.     

Induction of apoptosis by taxol and cisplatin and effect on cell cycle-related proteins in cisplatin-sensitive and -resistant human ovarian cells.

The effect of taxol (TX) and cisplatin (CDDP), singly or in association, was assessed on two human ovarian cancer cell lines, one sensitive (A2780) and one resistant (A2780 cp8) to CDDP. Cell lines showed a similar sensitivity to TX, whereas different cytotoxicity results were obtained in the two cell lines as a function of TX and CDDP sequence. Specifically, TX followed by CDDP induced simply additive effects in both cell lines, whereas the opposite sequence produced antagonistic effects in A2780 cells and synergistic effects in A2780 cp8 cells. TX, with or without CDDP, induced oligonucleosomal DNA fragmentation typical of the apoptotic process, but the biochemical mechanisms undergoing apoptosis were different in the two cell lines. In fact, in A2780 cells, TX (with or without CDDP) treatment markedly increased p53 as well as p21waf1 protein expression. In A2780 cp8 cells, drug treatment enhanced p53 levels, whereas the expression of p21waf1 was always undetectable at mRNA and protein levels. In the latter cell line, a premature activation of p34cdc2 kinase was observed in correspondence with the drug-induced increase in the S-phase cell fraction. Such an activation was not ascribable to an increase in the overall expression of p34cdc2 or cyclin B1 proteins, but to a dephosphorylation of p34cdc2 kinase. Overall, our results indicate that TX-induced apoptosis in human ovarian cancer cells may be sustained by different events at the cell cycle-control level.     

The Effect of Anticancer Drug Sequence in Experimental Combination Chemotherapy

A series of drug combination sequence studies was conducted in vitro using HEC-IA human endometrial carcinoma cells or 8226 myeloma cells. Four drugs were evaluated for schedule-dependent and sequence-dependent inhibition of human tumor colony formation in soft agar. Six different two-drug combinations were analyzed using the median dose effect method, and three different three-drug combinations were examined using the cumulative surviving fraction method. The results show that the specific sequence and method of drug exposure significantly influenced the production of antagonistic, additive, or synergistic cytotoxicity patterns. Drug combinations that were consistently synergistic included bleomycin or mitomycin C and cisplatin in 8226 cells, and etoposide plus bleomycin in human endometrial cancer (HEC-IA) cells. Most other two-drug combinations of bleomycin, etoposide, cisplatin, and mitomycin C were antagonistic in vitro, irrespective of the sequence of exposure. Among the three-drug combinations tested, consisrent synergism was noted with cisplatin, etoposide, and bleomycin when either of the latter two agents was tested as a continuous exposure in vitro. Within individual two- and three-drug combinations, it was possible to observe synergism, additivity, or antagonism based on the particular exposure sequence tested. These results suggest that an-titumor agent cytotoxicity in vitro can be radically influenced by the sequence of drug administration, a feature commonly overlooked in many clinical combination drug regimens.     

Effects of iron, copper, cobalt, and their chelators on the cytotoxicity of bleomycin

Bleomycin is widely used for treating several types of human tumors as well as a variety of experimental tumors. The ability of this antibiotic to bind and to damage DNA has been proposed to be responsible for its antitumor effect. Bleomycin is also a good chelator for several metals, e.g., iron, copper, and others. Bleomycin:metal complexes have been investigated in detail particularly for their action on isolated DNA. The conclusions from these studies indicate that metal-chelated bleomycin either is ineffective or more effective in damaging DNA. In this paper, we tested the effect of iron, copper, cobalt, and their chelators on bleomycin cytotoxicity. Our results suggest that chelating bleomycin with copper or adding an iron chelator (deferoxamine), diethylenetriamine pentaacetic acid, and a copper chelator (penicillamine) shows no effect on bleomycin cytotoxicity. On the other hand, iron dextran and a metal chelator, diethyldithiocarbamate (DDC), with bleomycin show enhanced cytotoxicity. Cobalt-chelated bleomycin is not cytotoxic but is cytotoxic when combined with DDC. We suggest that different mechanisms are contributing to the enhanced toxicity of bleomycin with iron dextran and DDC. Bleomycin acts as a ferrous oxidase which promotes the iron toxicity. In the case of DDC, it can act as a reducing agent or it can help to maintain the bleomycin:metal complex in the reduced form which can generate radicals.     

Feasibility and safety of electrochemotherapy (ECT) in the pancreas: a pre-clinical investigation

Background.

Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease generally refractory to standard chemotherapeutic agents; therefore improvements in anticancer therapies are mandatory. A major determinant of therapeutic resistance in PDAC is the poor drug delivery to neoplastic cells, mainly due to an extensive fibrotic reaction. Electroporation can be used in vivo to increase cancer cells’ local uptake of chemotherapeutics (electrochemotherapy, ECT), thus leading to an enhanced tumour response rate. In the present study, we evaluated the in vivo effects of reversible electroporation in normal pancreas in a rabbit experimental model. We also tested the effect of electroporation on pancreatic cancer cell lines in order to evaluate their increased sensitivity to chemotherapeutic agents.

Materials and methods.

The application in vivo of the European Standard Operating Procedure of Electrochemotherapy (ESOPE) pulse protocol (1000 V/cm, 8 pulses, 100 μs, 5 KHz) was tested on the pancreas of normal New Zealand White Rabbits and short and long-term toxicity were assessed. PANC1 and MiaPaCa2 cell lines were tested for in vitro electrochemotherapy experiments with and without electroporation. Levels of cell permeabilization were determined by flow cytometry, whereas cell viability and drug (cisplatin and bleomycin) sensitivity of pulsed cells were measured by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay.

Results.

In healthy rabbits, neither systemic nor local toxic effects due to the electroporation procedure were observed, demonstrating the safety of the optimized electric parameters in the treatment of the pancreas in vivo. In parallel, we established an optimized protocol for ECT in vitro that determined an enhanced anti-cancer effect of bleomycin and cisplatin with respect to treatment without electroporation.

Conclusions.

Our data suggest that electroporation is a safe procedure in the treatment of PDAC because it does not affect normal pancreatic parenchyma, but has a potentiating effect on cytotoxicity of bleomycin in pancreatic tumour cell lines. Therefore, ECT could be considered as a valid alternative for the local control of non-resectable pancreatic cancer.     

Collateral susceptibility of adriamycin-, melphalan- and cisplatin-resistant human ovarian tumor cells to bleomycin

Three cell lines resistant to adriamycin, melphalan and cisplatin were established in vitro from human ovarian cancer cell line A2780. Each subline showed a resistance to its inducing drug of 75-fold in the case of adriamycin, 6-fold in the case of melphalan and 11-fold in the case of cisplatin. However, all of these sublines showed collateral sensitivity to bleomycin. Approximately a 2-fold higher susceptibility to bleomycin was observed generally. The biochemical mechanisms of this collateral sensitivity are not clear at present, but the higher concentration of glutathione in these resistant tumor cell lines might be related to the high susceptibility of these resistant cells to bleomycin.     

In vitro colony inhibition of carboplatin against stomach and lung cancer cell lines in comparison with cisplatin

Summary The effects of carboplatin and cisplatin on colony formation in stomach and lung cancer cell lines were examined and compared. The colony-inhibitory activity of carboplatin against stomach and lung cancer cell lines was similar to that of cisplatin when one-tenth of the peak plasma concentration of each drug was used (r=0.80). One of the four stomach cancer cell lines was sensitive to carboplatin although all the stomach cancer cell lines were resistant to cisplatin. Of the three small cell lung cancer cell lines tested, two were sensitive to both carboplatin and cisplatin; and only one cell line (N857) was resistant to cisplatin; all the non-small cell cancer cell lines tested were resistant to both drugs. On the basis of these preliminary results, we suggest that carboplatin has potential therapeutic activity against stomach cancer and should be evaluated carefully from this aspect.This work was supported in part by a grant-in-aid for cancer research from the Comprehensive Ten-Year Strategy for Cancer Control, from the Ministry of Health and Welfare, and from the Adult Disease Clinic Memorial Foundation. JRJ's and WSH's visits were supported, as part of the visiting scientist program, by the Foundation for Program of Cancer Research based on the Comprehensive Ten-Year Strategy for Cancer Control     

Cytotoxicity of lonidamine alone and in combination with other drugs against murine RIF-1 and human HT1080 cells in vitro

Lonidamine is an agent that is reported to inhibit recovery from potentially lethal damage. By itself, it has only mild anticancer activity. We have examined the ability of lonidamine to enhance the cytotoxicity of several drugs against a mouse and a human fibrosarcoma cell line in vitro. By itself, lonidamine showed only a limited cytotoxic effect with drug exposure up to 100 micrograms/ml and 24-h duration. Lower concentrations and shorter term exposures were not toxic to either of these tumor cell lines. When tested against the mouse line, the cytotoxicity of 5-fluorouracil, methotrexate, and etoposide was enhanced by lonidamine if the latter drug was given either before or after the exposure of the cells to the cytotoxic agents. For cisplatinum, bleomycin, mitomycin C, doxorubicin, and Actinomycin D, cytotoxicity was also enhanced, but only if lonidamine followed the other agents. In contrast, potentiation of 1,3-bis(2-chloroethyl)-1-nitrosourea toxicity was maximum when lonidamine preceded the nitrosourea. The human cells were more resistant to lonidamine and to the combination treatments than were the mouse cells. Nevertheless, substantial enhancement was seen particularly for cisplatin and mitomycin C. We examined in more detail the enhancement of cisplatin. Maximum interaction was obtained when lonidamine was given immediately following (or in conjunction with) the platinum agent. Our results suggest that lonidamine enhances the effects of several other agents in a time- and concentration-dependent manner and indicate a potential usefulness for lonidamine in multidrug therapy.     

Elimination of mycoplasma from leukemia-lymphoma cell lines using antibiotics.

Mycoplasmal contamination of cell culture systems continues to present major problems for basic research and for manufacturing of bioproducts. Previous work suggested that certain antibiotics have strong anti-mycoplasma properties and raised the prospect that the technically rather simple antibiotic treatment may be an appropriate means for mycoplasma eradication. We have developed and validated an effective strategy to eliminate mycoplasma from chronically infected cell cultures using antibiotics which have shown strong activity against these contaminants. Here, we describe our experience with the treatment of 123 consecutive mycoplasma-positive leukemia-lymphoma cell lines, comparing five different antibiotic regimens (in total 433 treatments). We optimized the antibiotic dose schedules and the duration of treatments. The various antibiotic treatments which were employed in parallel had a high efficacy, as 71% to 86% of the infected cultures were cleansed. Treatment failure may result from the resistance of the mycoplasmas to antibiotic therapy and the inability of the eukaryotic cells to survive the cytotoxic effects of the antibiotics. Resistance to mycoplasma eradication was observed in 3% to 20% of the cultures. Loss of the cell culture caused by cytotoxicity was seen in 3% to 11% of the treatments. With regard to the overall outcome, 96% of the cell lines were rendered mycoplasma-free with at least one of the antibiotic treatments and were permanently cured. In conclusion, antibiotic treatment represents the most practical and efficient option to cleanse mycoplasma-positive cell lines.     

Concurrent blockade of the NF-κB and Akt pathways potently sensitizes cancer cells to chemotherapeutic-induced cytotoxicity

Nuclear factor-κB (NF-κB) and Akt are two major cell survival pathways that are often constitutively activated and can be further stimulated by chemotherpeutics in cancer cells. Although individually targeting the NF-κB or Akt has been reported to sensitize caner therapy, the effectiveness of concurrent blocking these two pathways for chemosensitizing of cancer cells to genotoxic therapeutics has not been investigated. In the present study, we investigate the activation of the NF-κB and Akt pathways by two frontline anticancer drugs cisplatin and etopside in a variety of cancer cell lines. The effects of blocking these two survival pathways individually or concurrently on cisplatin- or etopside-induced cytotoxicity were detected. The results show that cisplatin and etopside activate both NF-κB and Akt in cancer cells. Blockade of either of these pathways with chemical inhibitors or siRNA moderately sensitized cancer cells to cisplatin- or etopside-induced cytotoxicity. Strikingly, much more effective potentiation of cytotoxicity to these anticancer drugs was achieved when NF-κB and Akt were concurrently blocked. These data suggest that NF-κB and Akt cooperatively attenuate therapeutic-induced cytotoxicity and concurrently blocking these pathways is an effective strategy for improving the anticancer efficacy of therapeutics.     

Synergistic cytotoxicity of different alkylating agents for epithelial ovarian cancer

Alkylating agents have been used individually and in combination to treat epithelial ovarian carcinoma. In this study, the cytotoxicity of 7 alkylating agents has been measured using a serial dilution clonogenic assay. When individual agents were evaluated, markedly different activity was observed against several ovarian cancer cell lines. Among 4 cell lines tested, OVCA 432 was the most sensitive to cisplatin, thiotepa and melphalan. When alkylating agents were used in combination against OVCA 432, synergistic activity was observed with cisplatin and each of several other alkylating agents including thiotepa, melphalan, 4-hydroperoxycyclophosphamide (4HC) and carboplatin. The combination of cisplatin and thiotepa also exerted synergistic activity against the OVCA 420, 429 and 433 cell lines, but had only additive or subadditive activity against the NIH:OVCAR-3 cell line. Sequential treatment of tumor cell lines with the different alkylating agents was as effective as simultaneous treatment. Synergistic anti-tumor activity in cell culture is consistent with clinical observations that alkylating agents in combination appear more effective than single agents for treatment of advanced epithelial ovarian cancer. In addition, our study suggests that cisplatin in combination with thiotepa, 4HC or melphalan might prove useful for high-dose therapy with autologous bone-marrow support.     

HS3ST1对肺癌细胞增殖、迁移、侵袭及顺铂耐药的作用机制研究

目的:研究HS3ST1对肺癌细胞A549增殖、迁移、侵袭及顺铂耐药的影响.方法:利用慢病毒感染并构建HS3ST1过表达细胞株;利用Western blot、RT-PCT检测HS3ST1的表达;利用CCK8实验、Transwell迁移实验和细胞毒性实验检测HS3ST1对A549细胞增殖、迁移、侵袭和顺铂耐药的影响;利用W...     

Dichloroacetate metabolically targeted therapy defeats cytotoxicity of standard anticancer drugs

Purpose

The observation that the orphan drug dichloroacetate (DCA) selectively promotes mitochondria-regulated apoptosis and inhibits tumour growth in preclinical models by shifting the glucose metabolism in cancer cells from anaerobic to aerobic glycolysis attracted not only scientists??, clinicians?? but also patients?? interests and prompted us to further evaluate DCA effects against paediatric malignancies.

Methods

The effects of DCA on mitochondrial membrane potential (????m), cell viability and induction of apoptosis were evaluated in paediatric tumour cell lines and the non-malignant cell line HEK293. In addition, combinations of DCA with the standard anticancer drugs cisplatin, doxorubicin, and temozolomide were tested and intra- and extra-cellular platinum species analysed.

Results

DCA selectively induced phosphatidylserine externalisation and reduced ????m in paediatric tumour cells compared to HEK293 cells, but DCA concentrations ??10?mmol/L only moderately inhibited the growth of 18 paediatric tumour cell lines. DCA neither influenced the in vitro stability of cisplatin nor the cellular cisplatin uptake, but it abrogated the cytotoxicity of cisplatin in 7 out of 10 cell lines. DCA also affected the cytotoxicity of doxorubicin but did not influence the cytotoxicity of temozolomide. Despite phosphatidylserine externalisation, DCA failed to activate caspase 3/7 and, moreover, suppressed caspase 3/7 activation by cisplatin and doxorubicin.

Conclusions

Our results indicate that apart from the intriguing effects of DCA on the glucose metabolism of cancer cells, the use of DCA for cancer treatment has to be evaluated carefully. Moreover, compassionate use of the orally available drug by patients with cancer themselves without medical supervision is strongly discouraged at present.     

Cisplatin loaded albumin mesospheres for lung cancer treatment

The low solubility of cisplatin in aqueous solution limits the treatment effectiveness and the application of cisplatin in various kinds of drug-eluting devices. Although cisplatin has a high solubility in Dimethyl sulfoxide (DMSO), the toxicity of cisplatin can be greatly reduced while dissolved in DMSO. In this study, the solid powder of cisplatin-loaded albumin mesospheres (CDDP/DMSO-AMS), in a size range of 1 to 10 µm, were post-loaded with cisplatin and showed high cisplatin content (16% w/w) and effective cytotoxicity to lung cancer cells. Cisplatin were efficiently absorbed into the albumin mesospheres (AMS) in DMSO and, most importantly, the toxicity of cisplatin was remained at 100% after the loading process. This CDDP/DMSO-AMS was designed for the intratumoral injection through the bronchoscopic catheter or dry powder inhalation (DPI) due to its high stability in air or in solution. This CDDP/DMSO-AMS showed a fast cisplatin release within 24 hours. In the in vitro study, CDDP/DMSO-AMS showed high effectiveness on killing the lung cancer cells including the non-small cell lung cancer (NCL-H23 and A549), malignant mesothelioma (CRL-2081) and the mouse lung carcinoma (Lewis lung carcinoma) cell lines. The albumin based mesospheres provide an ideal loading matrix for cisplatin and other metal-based drugs due to the high swelling degree and fast uptake rate in the organic solvents with high polarity. In addition, to investigate the effects of polysaccharides, such as chitosan and chondroitin, on enhancing loading efficiency and lasting cytotoxicity of cisplatin, the polysaccharide-modified albumin mesospheres were synthesized and loaded with cisplatin in this study.     

Cisplatin in combination with Phenethyl Isothiocyanate (PEITC), a potential new therapeutic strategy for malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is a very aggressive form of cancer with a poor diagnosis and prognosis. The first line treatment for MPM is a combination of cisplatin and Pemetrexed, which displayed limited efficacy and severe side effects. The naturally occurring compound phenethyl isothiocyanate (PEITC) previously showed interesting anti-tumor properties on several cancer cell lines. We thus aim at evaluating PEITC used alone or in combination with cisplatin in order to improve MPM treatment.Nine MPM cell lines and primary mesothelial cells (PMC), co-cultured or not with M2 macrophages present in MPM microenvironment, were used to assess PEITC and cisplatin anti-tumor properties. Compounds were used alone or in combination.Both PEITC and cisplatin were cytotoxic on MPM cells in a dose dependent manner. We herein showed that PEITC-induced cytotoxicity was due to the generation of reactive oxygen species. Moreover, we showed that cisplatin-PEITC combination allowed the potentialization of both compounds'' cytotoxic effects and prevented the emergence of resistant MPM cells. Interestingly, PMC were not sensitive to the combination. Finally, we showed that M2 macrophages did not alter the anti-tumor properties of the combination. Cisplatin-PEITC combination thus represents a promising strategy to induce a selective toxicity towards malignant cells.     

Enhancement of the efficacy of anticancer drugs with electroporation: Successful electrochemotherapy against gastric cancer cell lines in vivo and in vitro

Background The purpose of this study was to determine whether micropore formation caused by application of an electric current can increase the influx of anticancer drugs across cancer cell membranes with a concomitant increase in dose intensity and, therefore, toxicity to cancer cells. Methods Two cell lines, GCIY and KATO III, both established from human gastric cancers, were used as target cells to assess the effects of combining electroporation and anticancer drug therapy. Results were measured as the proliferation of cells to 50% of the value in control mice (IC₅₀). Results When GCIY cells were used as targets in vitro, the IC₅₀ value for bleomycin was decreased significantly by the electroporation, to 10⁻⁴ of the dose for the chemotherapeutic agent alone, and the IC₅₀ values of cisplatin and 5-fluorouracil were decreased to one tenth of their baseline values. In the case of KATO III cells, the IC₅₀ value for bleomycin was reduced by 10⁻², but that of cisplatin did not change. The IC₅₀ value for doxorubicin did not change when GCIY cells, showing multidrug resistance, or when KATO III cells, lacking multidrug resistance, were subjected to electroporation. When GCIY cells were transplanted subcutaneously into nude mice, the resultant tumors decreased to a minimum size at 2 weeks after combined treatment with bleomycin and electroporation. Conclusion Electroporation seems to be a promising adjunct to cancer chemotherapy.     

Vinblastine, bleomycin, and cisplatin in malignant germ cell tumors of the ovary

Fourteen patients with malignant ovarian germ cell tumors were treated with vinblastine, bleomycin, and cisplatin. A complete clinical response was achieved in all 14 patients; however, 1 patient had small macroscopic disease present at second-look laparotomy. One patient died of bleomycin pulmonary toxicity. The remaining 13 patients are alive and free of disease from 20 months to 8 years and 8 months after initial diagnosis. Serum alpha-fetoprotein and beta-human chorionic gonadotropin levels were monitored in all patients and were found to be reliable indicators of response to treatment and disease status. The uninvolved ovary was preserved in seven patients without compromising the response to treatment, and one patient subsequently became pregnant. Vinblastine, bleomycin, and cisplatin chemotherapy appears to be a safe, effective combination and is recommended as the primary treatment of choice in the management of patients with malignant ovarian germ cell tumors.     

Test for chemotherapeutic sensitivity of cerebral gliomas: use of colorimetric MTT assay

Summary This study was undertaken to evaluate the colorimetric MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide] assay as a means of testing the sensitivity of gliomas to chemotherapeutic agents in vitro. Eight human glioma established cell lines were plated in 96-well tissue culture plates and incubated for 4 days with 10 different anti-cancer agents; 5 different concentrations of each drug were tested. The MTT dye was then added to the wells, and the resulting formazan precipitate was solubilized with dimethylsulfoxide (DMSO). The spectrophotometric absorbance (measured at 570 nm) of control and experimental wells was used to calculate the cytotoxicity index (CI). Values with a CI greater than 50% growth inhibition indicated cytotoxic efficacy (sensitivity to the chemotherapeutic drug).Six of the seven (85.7%) glioma cell lines were highly sensitive at varying concentrations to mitomycin C, cisplatin, and doxorubicin. Four of the seven (57.1%) cell lines demonstrated intermediate sensitivity to mitoxantrone and vinblastine. Five of the seven (71.4%) cell lines exhibited resistance to etoposide, bleomycin, cosmegen, and BCNU. One of the cell lines tested, U-138MG, failed to produce the MTT formazan precipitate, so that the sensitivity of this cell line to the panel chemotherapeutic drugs could not be determined. The variability of the results indicates the need for an in vitro screening method to evaluate the effectiveness of clinical and experimental chemotherapeutic agents. The MTT assay provides a rapid method of screening antineoplastic agents against gliomas for cytotoxicity.