The MTT assay for chemosensitivity testing of human tumors of the central nervous system. Part II: Evaluation of patient- and drug-specific variables

A Potential New Treatment for High-Grade Glioma: A Study Assessing Repurposed Drug Combinations against Patient-Derived High-Grade Glioma Cells

Repurposed drugs have demonstrated in vitro success against high-grade gliomas; however, their clinical success has been limited due to the in vitro model not truly representing the clinical scenario. In this study, we used two distinct patient-derived tumour fragments (tumour core (TC) and tumour margin (TM)) to generate a heterogeneous, clinically relevant in vitro model to assess if a combination of repurposed drugs (irinotecan, pitavastatin, disulfiram, copper gluconate, captopril, celecoxib, itraconazole and ticlopidine), each targeting a different growth promoting pathway, could successfully treat high-grade gliomas. To ensure the clinical relevance of our data, TC and TM samples from 11 different patients were utilized. Our data demonstrate that, at a concentration of 100µm or lower, all drug combinations achieved lower LogIC₅₀ values than temozolomide, with one of the combinations almost eradicating the cancer by achieving cell viabilities below 4% in five of the TM samples 6 days after treatment. Temozolomide was unable to stop tumour growth over the 14-day assay, while combination 1 stopped tumour growth, with combinations 2, 3 and 4 slowing down tumour growth at higher doses. To validate the cytotoxicity data, we used two distinct assays, end point MTT and real-time IncuCyte life analysis, to evaluate the cytotoxicity of the combinations on the TC fragment from patient 3, with the cell viabilities comparable across both assays. The local administration of combinations of repurposed drugs that target different growth promoting pathways of high-grade gliomas have the potential to be translated into the clinic as a novel treatment strategy for high-grade gliomas.

Tumor Chemosensitivity Assays Are Helpful for Personalized Cytotoxic Treatments in Cancer Patients

Tumor chemosensitivity assays (TCAs), also known as drug response assays or individualized tumor response tests, have been gaining attention over the past few decades. Although there have been strong positive correlations between the results of these assays and clinical outcomes, they are still not considered routine tests in the care of cancer patients. The correlations between the assays' results (drug sensitivity or resistance) and the clinical evaluations (e.g., response to treatment, progression-free survival) are highly promising. However, there is still a need to design randomized controlled prospective studies to secure the place of these assays in routine use. One of the best ideas to increase the value of these assays could be the combination of the assay results with the omics technologies (e.g., pharmacogenetics that gives an idea of the possible side effects of the drugs). In the near future, the importance of personalized chemotherapy is expected to dictate the use of these omics technologies. The omics relies on the macromolecules (Deoxyribonucleic acid -DNA-, ribonucleic acid -RNA-) and proteins (meaning the structure) while TCAs operate on living cell populations (meaning the function). Therefore, wise combinations of TCAs and omics could be a highly promising novel landscape in the modern care of cancer patients.

DRAQ7 as an Alternative to MTT Assay for Measuring Viability of Glioma Cells Treated With Polyphenols

BACKGROUND/AIM

The tetrazolium-based MTT cytotoxicity assay is well established for screening putative anti-cancer agents. However, it has limitations including lack of reproducibility with glioma cells treated with polyphenols. The aim of this study was to evaluate whether a flow cytometric assay with the anthraquinone, DRAQ7, was a better alternative than the colorimetric MTT assay for measuring cell viability.

MATERIALS AND METHODS

Two glioma cell lines (IPSB-18, U373) and 1 pancreatic cancer cell line (AsPC-1) were treated with 4 polyphenols, namely red grape seed extract, red clover extract, anthocyanin-rich extract and curcumin. Cell viability was assessed using MTT assay and DRAQ7 staining.

RESULTS

Limitations of MTT assay included lack of sensitivity and interference with the structure and absorbance spectra of polyphenols. Also, DMSO was toxic to glioma cells. Microscopic observations of cells treated with polyphenols confirmed the range of IC₅₀ values evaluated by DRAQ7, but not by the MTT assay.

CONCLUSION

DRAQ7 is a better alternative than MTT for measuring viability of glioma cells treated with brightly coloured polyphenols.

Hemicyanine based naked-eye ratiometric fluorescent probe for monitoring lysosomal pH and its application

Lysosome as the typical acidic organelle involved in many biological processes, the dysfunction of its pH would alter many diseases. Small-molecule fluorescent probe has been considered as vital tool for monitoring pH fluctuation in living cells. Herein, a hemicyanine based ratiometric fluorescent probe was synthesized, namely, 2,3-trimethy-3-[2-(dimethyl-amino-4-yl) vinyl]-3H-benzo[e]indole (BiDL), for rapidly detection pH under acidic conditions. BiDL exhibited ratio fluorescence emission (F_534nm/F_622nm) characteristic with pK_a 4.25. BiDL showed good linearly response in pH 3.4-4.82, indicating that the probe can be used for quantitative detection pH. The probe also displayed large Stokes shift (112 nm/201 nm) under neutral and acidic conditions, respectively, which could effectively reduce the excitation interference. BiDL had excellent cell membrane permeability, good photo-stability and low toxicity in living cells. The dual-channel confocal fluorescent microscopic ratiometric imaging application of pH in HeLa cells and lysosome were achieved successfully, indicating that BiDL has good potential for investigating lysosome-relevant pathological and physiological processes.

Imidazole and beta-carotene photoprotection against photodynamic therapy evaluated by synchrotron infrared microscopy

In order to better understand the role of β-carotene and imidazole on the Photodynamic Therapy (PDT) mechanism, synchrotron infrared microscopy was used to detect the associated intracellular biochemical modifications following the visible light irradiation of HeLa cells incubated with these compounds as typical hydrophobic and hydrophilic singlet oxygen quenchers, respectively. For this purpose, PDT was performed employing the hydrophilic sensitizer 5,10,15,20-Tetrakis (1-methyl-4-pyridinio) porphyrin tetra (p-toluenesulfonate), TMPyP, and the hydrophobic sensitizer 5-(4-Methoxycarboxyphenyl)-10,15,20-triphenyl-21H,23H-porphyrin. The single cell IR spectra of PDT-treated, PDT plus quencher-treated and control HeLa cells were recorded at the SOLEIL Synchrotron Infrared SMIS beamline targeting specifically the cell nucleus. Principal Component Analysis (PCA) was used to assess the IR spectral changes. PCA revealed that there is a frequency shift of the protein Amide I vibrational band for the assays with the TMPyP sensitizer, indicating changes in the protein secondary structures of the PDT-treated cancer cells compared to the controls. In addition, the scores in those cells treated with both quenchers appear to be similar to the controls indicating a photoprotective effect. Comparative experiments carried out with SKMEL-28 and HaCat cells showed non- significant photoprotective effects of β-carotene and imidazole.

Drug screening of cancer cell lines and human primary tumors using droplet microfluidics

Precision Medicine in Oncology requires tailoring of therapeutic strategies to individual cancer patients. Due to the limited quantity of tumor samples, this proves to be difficult, especially for early stage cancer patients whose tumors are small. In this study, we exploited a 2.4 × 2.4 centimeters polydimethylsiloxane (PDMS) based microfluidic chip which employed droplet microfluidics to conduct drug screens against suspended and adherent cancer cell lines, as well as cells dissociated from primary tumor of human patients. Single cells were dispersed in aqueous droplets and imaged within 24 hours of drug treatment to assess cell viability by ethidium homodimer 1 staining. Our results showed that 5 conditions could be screened for every 80,000 cells in one channel on our chip under current circumstances. Additionally, screening conditions have been adapted to both suspended and adherent cancer cells, giving versatility to potentially all types of cancers. Hence, this study provides a powerful tool for rapid, low-input drug screening of primary cancers within 24 hours after tumor resection from cancer patients. This paves the way for further technological advancement to cutting down sample size and increasing drug screening throughput in advent to personalized cancer therapy.

Cytotoxicity of gemcitabine enhanced by polyphenolics from Aronia melanocarpa in pancreatic cancer cell line AsPC-1

AIMS

Extending work with brain tumours, the hypothesis that micronutrients may usefully augment anticancer regimens, chokeberry (Aronia melanocarpa) extract was tested to establish whether it has pro-apoptotic effects in AsPC-1, an established human pancreatic cell line, and whether it potentiates cytotoxicity in combination with gemcitabine. Pancreatic cancer was chosen as a target, as its prognosis remains dismal despite advances in therapy.

METHODS

An MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay was used to assess the growth of the single pancreatic cancer cell line AsPC-1, alone and in comparison or combination with gemcitabine. This was backed up by flow cytometric DRAQ7 cell viability analysis. TUNEL assays were also carried out to investigate pro-apoptotic properties as responsible for the effects of chokeberry extract.

RESULTS

Chokeberry extract alone and its IC75 value (1 µg/mL) in combination with gemcitabine were used to assess the growth of the AsPC-1 cell line. Gemcitabine in combination with chokeberry extract was more effective than gemcitabine alone. TUNEL assays showed apoptosis to be a mechanism occurring at 1 µg/mL concentration of chokeberry, with apoptotic bodies detected by both colourimetric and fluorometric methods.

CONCLUSIONS

The implication of this study, using single cancer cell line, is that chemotherapy (at least with gemcitabine) might be usefully augmented with the use of micronutrients such as chokeberry extract.

Induction of apoptosis and reduction of MMP gene expression in the U373 cell line by polyphenolics in Aronia melanocarpa and by curcumin

Malignant brain tumours are rare but are the most challenging types of cancers to treat. Despite conventional multimodality approaches available for their management, the outlook for most patients remains dismal due to the ability of the tumour cells to invade the normal brain. Attention has now focused on novel therapeutic interventions such as as the use of micronutrients. Both chokeberry extract (Aronia melanocarpa), which is rich in natural pigments such as anthocyanins and curcumin (diferuloylmethane) found in turmeric (Curcuma longa) have been reported to possess anticancer properties in other cancers. The aim of this study was to extend our previous research to evaluate the therapeutic potential of these two agents by testing their ability to induce apoptosis in an established glioblastoma cell line (U373). This was accomplished by treating the cells for 48 h with either chokeberry extract or curcumin, and using the Annexin-V assay. Gene profiles of 8 MMPs (2, 9, 14, 15, 16, 17, 24 and 25) and 4 TIMPs (1, 2, 3 and 4) were analysed for effects of mediators of invasion by quantitative real-time polymerase chain reaction (RT-PCR). The IC50 values determined for curcumin and chokeberry extract were 15 and 200 µg/ml, respectively. Our results also suggest that curcumin induces apoptosis but chokeberry extract is necrotic to this cell line. It is possible that chokeberry extract kills the cells by other non-apoptotic pathways. In addition, the RT-PCR results show downregulation of the gene expression of MMP-2, -14, -16 and -17 for both micronutrients. Taken together, the comparative data suggest that both curcumin and chokeberry extract may exhibit their anticancer potential by inducing apoptosis and inhibiting invasion by reducing MMP gene expression.

A rapid survival assay to measure drug-induced cytotoxicity and cell cycle effects

We describe a rapid method to accurately measure the cytotoxicity of mammalian cells upon exposure to various drugs. Using this assay, we obtain survival data in a fraction of the time required to perform the traditional clonogenic survival assay, considered the gold standard. The dynamic range of the assay allows sensitivity measurements on a multi-log scale allowing better resolution of comparative sensitivities. Moreover, the results obtained contain additional information on cell cycle effects of the drug treatment. Cell survival is obtained from a quantitative comparison of proliferation between drug-treated and untreated cells. During the assay, cells are treated with a drug and, following a recovery period, allowed to proliferate in the presence of bromodeoxyuridine (BrdU). Cells that synthesize DNA in the presence of BrdU exhibit quenched Hoechst fluorescence, easily detected by flow cytometry; quenching is used to determine relative proliferation in treated vs. untreated cells. Finally, this assay can be used in high-throughput format to simultaneously screen multiple cell lines and drugs for accurate measurements of cell survival and cell cycle effects after drug treatment.

Flow cytometry analysis of neural differentiation markers expression in human glioblastomas may predict their response to chemotherapy

Glioblastoma multiforme (GBM) represents an extremely chemoresistant tumour type. Here, authors analysed the immunophenotype of GBM tumours by flow cytometry and correlated the immunophenotypic characteristics with sensitivity to chemotherapy. The expression of selected neural and non-neural differentiation markers including A2B5, CD34, CD45, CD56, CD117, CD133, EGFR, GFAP, Her-2/neu, LIFR, nestin, NGFR, Pgp and vimentin was analysed by flow cytometry in eleven GBM (WHO gr.IV) patients. The sensitivity of tumour cells to a panel of chemotherapeutic agents was tested by the MTT assay. All tumours were positive for A2B5, CD56, nestin and vimentin. CD133, EGFR, LIFR, NGFR and Pgp were expressed only by minor tumour cell subpopulations. CD34, CD45, CD117, GFAP and Her-2/neu were constantly negative. Direct correlations were found between the immunophenotypic markers and chemosensitivity: A2B5 vs lomustine (r(2) = 0.642, P = 0.033), CD56 vs cisplatin (r(2) = 0.745, P = 0.013), %Pgp(+) vs vincristine (r(2) = 0.846, P = 0.008), and %NGFR(+) vs daunorubicine (r(2) = 0.672, P = 0.047) and topotecan (r(2) = 0.792, P = 0.011). In contrast, inverse correlations were observed between: EGFR vs paclitaxel (r(2) = -0.676, P = 0.046), CD133 vs dacarbazine (r(2) = -0.636, P = 0.048) and LIFR vs daunorubicine (r(2) = -0.878, P = 0.004). Finally, significant associations were also found among sensitivities to different chemotherapeutic agents and among different immunophenotypic markers. In conclusion, histopathologically identical GBM tumours displayed a marked immunophenotypic heterogeneity. The expression of A2B5, CD56, NGFR and Pgp appeared to be associated with chemoresistance whereas CD133, EGFR and LIFR expression was characteristic of chemosensitive tumours. We suggest that flow cytometric imunophenotypic analysis of GBM may predict chemoresponsiveness and help to identify patients who could potentially benefit from chemotherapy.

Treatment of recurrent glioblastoma: can local delivery of mitoxantrone improve survival?

In this study, the records of 276 adult patients with recurrent glioblastoma (GBM) treated at recurrence at our institution between 2004 and 2006 were reviewed for progression-free survival (PFS), overall survival (OS), and toxicity. At recurrence, all patients underwent systemic treatment with temozolomide (200 mg/sqm on days 1-5 every 28 days) until tumor progression. Patients, whose tumor was judged resectable without risk of adjunctive neurological deficit, underwent a second surgery with or without positioning of a Rickam/Ommaya reservoir. The reservoir was used for locoregional chemotherapy with mitoxantrone. Two hundred seventy-six rGBL patients (pts) were divided into three subgroups: A 161 pts treated only with temozolomide, B 50 pts re-operated-on +temozolomide, and C 65 pts re-operated on + temozolomide + locoregional CHT. For group A, the 6 month PFS and 6 month survival (ST) were 39.3 and 43%, respectively, with a median survival time (mST) of 5 months (range 4-6) and 25% of pts alive at 9 months. For group B, the 6 month PFS and 6 month survivors were 64 and 74.1%, respectively, with a mST of 8 months (range 6-10) and 25% of pts alive at 12 months. For group C, the 6 month PFS and 6 month survivors were 70.7 and 87.7%, respectively, with a mST of 11 months (range 9-13) and 25% of pts alive at 18 months (A vs. B vs. C, log-rank P < 0.001) (B vs. C, P = 0.041) (A vs. B P = 0.009). Cox proportional hazard model was used to obtain Hazard Ratio (HR) for type of treatment corrected by age and time (in months) between diagnosis and first recurrence: second tumor debulking was statistically effective for survival, reducing by 36% the risk of death (HR = 0.64; 0.46-0.89), but the most significant favorable prognostic factor for survival was the local delivery of mitoxantrone which reduced the risk of death to 50% (HR = 0.50; 0.38-0.68).

Interindividual differences in anticancer drug cytotoxicity in primary human glioblastoma cells

Glioblastoma multiforme is a malignant astrocytic tumor characterized by rapid growth, extensive invasiveness and high vascularity. Despite advances in surgical techniques and in the development of new protocols in radio- and chemotherapy, the prognosis for patients suffering from this malignancy remains poor. Since the clinical response to chemotherapy varies greatly owing to different interindividual gene expression profiles, it would be of considerable interest to develop an in vitro model able to evaluate anticancer drug toxicity and the effectiveness of therapeutic strategies on cells obtained from individual patients. In the protocol for obtaining primary cultures of glioblastoma cells described in this report, a confluent monolayer of cells can be obtained within 1 or 2 weeks. A complementary immunocytochemical assay using glial fibrillary acidic protein (GFAP) to reliably mark glial cells confirms the glial origin of the cultured cells. A cytotoxicity test based on mitochondrial activity is then used to evaluate in vitro drug efficacy. Cell dedifferentiation as evidenced by loss of GFAP expression after a few passages requires determination of drug toxicity before the fourth passage. Data show a wide range of response to temozolomide (1000 microM) after 72 h with 24-81% cell death depending on patients. Results presented confirm the heterogeneity of response to anticancer drugs between the patients and methods described allow to carry out cytotoxicity studies in order to determine the individualized most effective treatment.

Naturally occurring resistance of bone marrow mononuclear and metastatic cancer cells to anticancer agents

Numerous cancer patients fail standard chemotherapy or develop resistance to chemotherapy during the course of treatment. The purpose of this study is to elucidate the overall response of cells obtained from cancer patients and from normal individuals to chemotherapeutic agents. We analysed the chemosensitivity of cancer cells derived from bone marrow and from pleural effusions or ascites fluids from patients with different cancers. Chemosensitivity to doxorubicin, cisplatin and paclitaxel was determined using the MTT assay. We also determined the response of bone marrow mononuclear (BMMN) cells. There was a wide range of responses to chemotherapy drugs in samples from different individuals. This was observed in cells derived from bone marrow and from ascites or pleural fluids. Large variations were also observed among morphologically normal BMMN cells and metastatic cancer cells from chemo-naïve patients. Cancer cells can easily be collected from ascites or pleural fluids and reliably assayed for chemosensitivity. We describe here that inherent chemoresistance may be a reason for the lack of response to chemotherapy in some patients. We discuss the potential of using the determination of natural resistance to dictate the drugs to be employed for treatment.

Systemic temozolomide combined with loco-regional mitoxantrone in treating recurrent glioblastoma

Twenty-two recurrent GBM patients were enrolled for second tumor debulking with local positioning of a Rickam reservoir, in order to locally deliver chemotherapy with the aim of controlling local tumor recurrence. We designed a protocol using systemic temozolomide (150 mg/sqm days 1-5 every 28) in association with mitoxantrone, delivered through the reservoir (4 mg/day 1-5 every 28) positioned into the area of tumor exeresis. After re-operation a residual tumor mass no larger than 2 cm was identified in 18/22 patients. The patients were treated with monthly cycles of chemotherapy until evolution of the tumor, but in no case for more than 10 cycles. Responses were evaluated by MRI scans performed every 2 months and images assessed according to MacDonald's criteria. Response rate: no complete responses (CR), 5 partial responses (PR), 13 stable disease (SD) and 4 progressive disease (PD) occurred. The median progression-free survival (PFS) and survival time (ST) of the whole group of treated patients was 7 and 11 months, respectively and more than a quarter of the patients survived over 18 months. During the study, the patients' compliance was complete and no dropouts occurred. Hematological toxicity was mild and after repeated local injections only minor neurological side-effects occurred. Despite some bias in patients' selection not excluded in this pilot study, results are interesting: the PFS was as long as the survival of recurrent GBM reported in the literature.

Chlorimipramine: A novel anticancer agent with a mitochondrial target

Mitochondria have been suggested to be a potential intracellular target for cancer chemotherapy. In this report, we demonstrate the ability of the tricyclic antidepressant chlorimipramine to kill human glioma cells in vitro by a molecular mechanism resulting in an increase in caspase 3 activity following inhibition of glioma oxygen consumption. Studies with isolated rat mitochondria showed that chlorimipramine specifically inhibited mitochondrial complex III activity, which causes decreased mitochondrial membrane potential as well as mitochondrial swelling and vacuolation. The use of chlorimipramine in human as an effective, non-toxic cancer therapeutic having a strong selectivity between cancer cells and normal cells on the basis of their mitochondrial function is discussed.

Features of proliferation and in vitro drug resistance in central primitive neuro-ectodermal tumours

The features of proliferation in brain tumours are related with clinical prognosis for several types of brain tumours, especially gliomas. For childhood central primitive neuro-ectodermal tumours (cPNET), including medulloblastoma, this relation has previously been unclear. The aim of this study is to investigate the relationship between proliferative features of cPNET and in vitro resistance for cytostatic drugs measured with the 3-4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium-bromide (MTT) assay. Tumour material was obtained from 23 surgical specimens of cPNET. The expression of the proliferation markers Ki-67, proliferating cell nuclear antigen (PCNA) and cyclin D1 was determined with immunohistochemistry, while S-phase and DNA ploidy were analysed by flowcytometric analysis cell scan (FACS). The in vitro resistance for 10 cytostatic drugs was determined with the MTT assay. Drug resistance levels were available in 19 (83%) of the 23 samples with a complete profile of 10 cytostatic drugs tested in 14 samples. An excellent correlation in drug resistance scores was found between pharmacologically related drugs. The Ki-67 staining in 20 samples varied from 10 to 60% and from 30 to 100% for PCNA. Cyclin D1 staining was negative in 11 out of 18 samples. The S-phase in 16 samples ranged from 2 to 16%. Increased staining of Ki-67 was related with actinomycin D sensitivity (r -.603; P=0.022), while cells with a higher S-phase percentage were more resistant to ifosfamide (r.952; P<0.0001). In vitro drug resistance testing of central primitive neuro-ectodermal tumours (PNET) is feasible with the MTT assay. Ifosfamide resistance was related with increased Ki-67 and S-phase percentage of the tumour cells, while increased Ki-67 was also related with actinomycin D sensitivity. These findings suggest a cell cycle dependent activity of cytostatic drugs in vitro.

Efficacy of intratumoral delivery of mitoxantrone in recurrent malignant glial tumours

Ninety-nine patients bearing recurrent malignant glioma sequentially selected according to strict eligibility criteria (72 GBL and 27 AA) entered the study. All patients were previously managed with radiotherapy 60 Gy total dose and chemotherapy with nitrosoureas and platinum compounds. At recurrence they were subdivided in homogeneous groups, all treated with the same systemic chemotherapy protocol: 27 GBL (group A) only systemically treated, 20 GBL (group B) treated also locally by delivering 4mg of mitoxantrone every 20 days through the Ommaya reservoire, and 25 GBL (group C) treated with a second surgery and locally as group B. Of the AA group, 13/27 were treated locally trough the Ommaya reservoir after repeat surgery. A trend to different demographic features among subgroups (with locoregionally treated patients and patients undergoing repeat surgery being younger than the others) was seen in this non-randomized study, but this was not statistically significant. Median overall survival was 27, 26 and 15.5 months respectively for groups c, b and a (log-rank = 0.1). After tumor recurrence median survival was 16.8, 12 and 6.6 months respectively for groups c, b and a (log-rank = 0.001) For the 29 AA, overall survival was 48.5 and 100 months (log-rank = 0.03) if treated locally with second tumor debulking. Our results stress the opinion that a second operation could be indicated only if it is a part of a therapeutic protocol to allow a locoregional treatment. Moreover we can finally assume that local delivery of chemotherapy after tumor recurrence, possibly extends patients survival but certainly improves the number of long-survivors.

Interstitial chemotherapy plus systemic chemotherapy for glioblastoma patients: improved survival in sequential studies

We investigated the efficacy of 3 different systemic chemotherapy regimes in 122 patients with histologically confirmed glioblastoma, KPS > 60, age < 65. Locoregional chemotherapy was delivered to 22 patients from all three systemic chemotherapy groups. Chemotherapy was given before and during radiotherapy, which was the same for all patients consisting of unconventional fractionation with a break between courses. Survival (Kaplan-Meier) was significantly longer in the subgroup receiving cisplatinum plus BCNU compared to those receiving cisplatinum plus etoposide or carboplatinum plus BCNU with median survival time 21.5 months, 15 months and 15 months respectively (log rank test p = 0.01). Survival was also significantly longer in patients who received locoregional therapy compared to those who received only systemic chemotherapy (21 vs 15 months, p = 0.01). Univariate analysis showed that age, postoperative Karnofsky status and extent of resection were not predictive of survival in the series, although there were trends to better outcome in younger patients and those undergoing total/subtotal resection. Age, systemic chemotherapy type and interstitial treatment were included in a multivariate analysis, and both locoregional treatment and chemotherapy with cisplatinum plus BCNU were significantly predictive of survival [P = 0.01]. These encouraging preliminary results suggest that further trials with locoregional and systemic therapy prior to radiotherapy are worth pursuing.

Chemotherapy in experimental brain tumor, part 2: pretreatment with leukotriene C4 prolongs survival

Previous work in our laboratory has shown a correspondence between the chemosensitivity of C6 rat glioma and that of human glioblastoma (GBM) to a panel of chemotherapeutic agents in vitro, as determined by the MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide] colorimetric assay. In the present study, an in vivo model of intracerebral C6 glioma in Sprague-Dawley rats was used to determine if a correlation exists between in vitro chemosensitivity and in vivo survival of the animals, and post-mortem histopathological changes in the tumor. Cisplatin (CDDP) and methotrexate (MTX), agents previously shown to demonstrate high and low in vitro cytotoxicity, respectively, against C6, were administered by intra-carotid infusion over the course of two days. In a separate series of animals, LTC4 was administered prior to infusion of CDDP or MTX; LTC4 was used in view of its known, selective, vasogenic effect on the permeability of brain tumor capillaries. It was found that survival of animals treated with CDDP alone was increased, although this did not reach statistical significance; histopathologically, CDDP-treated animals showed significant tumor necrosis. However, in CDDP-treated animals, pre-treatment with LTC4 increased survival to a statistically significant degree. When administered alone, LTC4 (not followed by CDDP) had no effect on either survival or histology. The survival-enhancing effect of CDDP, when combined with LTC4, was probably not due to any cytotoxic effect of LTC4; this is based on our finding that, on the in vitro MTT colorimetric assay, LTC4 showed low cytotoxicity for C6 glioma cells. By contrast with CDDP, MTX -- with or without pretreatment with LTC4 -- affected neither survival nor tumor histology. With respect to the question of correspondence between the MTT colorimetric in vitro assay and in vivo effect, MTX showed a clear correlation: low cytotoxicity in vitro and poor in vivo response. In the case of CDDP, the correspondence was not clear-cut: there was a high level of in vitro chemosensitivity of the C6 cell line to CDDP as well as post-mortem tumor necrosis, but in vivo testing showed no significant prolongation of survival. However, pre-treatment with LTC4 did significantly extend survival in animals treated with CDDP.

Chemotherapy in experimental brain tumor, part 1: in vitro colorimetric MTT assay

This study concerns the use of the MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide] colorimetric assay to evaluate the chemosensitivity of the C6 rat glioma cell line to a panel of twelve chemotherapeutic agents. In a previous study of in vitro chemosensitivity of human glioma cell lines, the present authors found a range of sensitivities of the respective cell lines to a panel of chemotherapeutic agents [1]. We then devised an experimental strategy to begin an in vivo evaluation of the correlation between in vitro chemosensitivity and clinical response in an in vivo animal model, such as the model employing the C6 rat glioma cell line. As a step towards utilizing the C6 rat glioma in vivo model, we carried out the present study (Part 1) to determine the correspondence between chemosensitivity to human glioma cell lines and the rat C6 glioma cell line. If a correspondence were to be found, this would enable experimental use of the C6 tumor model for in vivo testing of chemotherapeutic agents. As reported in this paper (Part 1), a correspondence was found, suggesting that the C6 rat glioma represents a suitable model of human glioma for chemotherapeutic studies. This finding served as a basis for proceeding with an in vivo study of chemotherapeutic efficacy which is the subject of a companion report [2].

Mitoxantrone-induced DNA strand breaks in cell-cultures of malignant human astrocytoma and glioblastoma tumors

In this study mitoxantrone (Mtx) induced DNA strand breaks were measured with the alkaline elution technique in short term cell cultures derived from human gliomas. Glioblastomas or astrocytomas from 5 patients who underwent intracranial surgery were cultured and incubated i h with different concentrations of Mtx (0, 0.01, 0.1 and 1.0 microgram/ml). The alkaline elution method was modified to measure DNA lesions in human gliomas. Mtx induced DNA strand breaks in a dose dependent manner in all cell cultures tested. There was a linear increase of DNA strand break frequency induced by Mtx between 0.01-1.0 microgram/ml. concerning these in vitro data, Mtx might be potentially useful for the treatment of patients with malignant brain tumors.

Interstitial chemotherapy with mitoxantrone in recurrent malignant glioma: preliminary data

We undertook a phase I-II trail of loco-regional mitoxantrone in 12 patients affected by malignant gliomas. Mitoxantrone was delivered at tumor recurrence by Ommaya reservoir, with 2 cycles and a 1 month interval between each cycle, in conjunction with systemic chemotherapy (8 pts) or not (4 pts). Treatment tolerability was good, and 9 of the patients showed either response or stable disease at the end of the treatment schedule. Regardless of associated chemotherapy, time to further tumor progression was at 6 months. A combination of early systemic and loco-regional chemotherapy with surgery and radiotherapy seems worth while pursuing in the therapeutic approach to malignant gliomas.

Relationship between expression of a major apurinic/apyrimidinic endonuclease (APEX nuclease) and susceptibility to genotoxic agents in human glioma cell lines

The multifunctional DNA repair enzyme (APEX nuclease) having apurinic/apyrimidinic (AP) endonuclease, 3'-5' exonuclease, DNA 3' repair diesterase and DNA 3'-phosphatase activities is thought to be involved in repair of AP sites and single-strand breaks with 3'-blocked termini. To investigate the biological role of the enzyme, we studied the correlation between APEX AP endonuclease activity in several human glioma cell lines having various degree of its expression and cellular susceptibility to cytotoxic agents such as methyl methanesulfonate (MMS), 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3- (2-chloroethyl)-3-nitrosourea hydrochloride (ACNU), cis-diamminedichloroplatinum(II) (CDDP), etoposide (VP-16), hydrogen peroxide (H2O2), hyperthermia and X-ray. The cell lines having lower APEX expression showed higher sensitivity to MMS and H2O2 which are known to induce AP sites and single strand breaks on DNA, respectively. The cellular susceptibility to the other agents tested was not significantly correlated to the APEX expression. The present results are thought to support the notion that APEX nuclease plays an important role on repair of AP sites and single-strand DNA breaks with 3'-blocked termini in mammalian cells.

In vitro and in vivo cytotoxicity of gossypol against central nervous system tumor cell lines

Gossypol is a lipid soluble polyphenolic compound isolated from cotton seed oil which has been previously shown to have antiproliferative activity in vitro against a variety of human solid tumor cell lines. It has been extensively tested in clinical trials as a male contraceptive agent and found to be well tolerated. Its mechanism of action is thought to be inhibition of cellular energy metabolism. It inhibits glycolysis through inhibition of LDH isoenzyme type 5, and it inhibits mitochondrial oxidative phosphorylation and electron transport. We tested the in vitro antiproliferative effect of gossypol against four well characterized human glioma cell lines, HS 683, U373, U87 and U138, and one rat glioma cell line, C6, using the colorimetric Microculture Tetrazolium Assay (MTT). Cytotoxicity was found to be concentration and time dependent and increased with incubation times up to 8 days. The relative sensitivity of the glioma cell lines to gossypol at 48 hour incubation correlated with their respective LDH isoenzyme profiles, with the more sensitive cell lines expressing increased cathodal LDH isoenzymes (LDH5). The in vitro cytotoxicity of gossypol to these CNS tumor lines was compared to the other non central nervous system solid tumor cell lines which had been previously reported as being sensitive to gossypol, including SW-13 (adrenal), MCF-7 (breast), T47-D (breast), and HeLa (cervical). Additional lines tested included SK-MEL-3 (melanoma), Colo 201 (colon) and BRW, a line established in our laboratory from a patient with a Primitive Neuroectodermal tumor. C6, HS 683, and BRW had similar IC50s as the sensitive solid tumor cell lines. U373, U87 and U138 had significantly less sensitivity at 48 hours. There was greater cytotoxicity and no significant differences in the IC50s between any of cell lines at 8 day incubations. Additionally, we tested the cytotoxicity of gossypol against BRW in vivo, using the nude mouse xenograft model. Gossypol, given at a dose of 30 mg/kg per day five days a week for four weeks orally via gavage, was found to decrease the mean tumor weight of treated xenografts by more than 50% as compared to untreated xenografts. These findings suggest that gossypol has potential for further study as an agent for the treatment of primary CNS malignancies.

Enhancement of ACNU cytotoxicity by pretreatment with O6-methylguanine in ACNU-resistant brain tumors

O6-Methylguanine is a substrate of the DNA repair enzyme O6-methylguanine-DNA methyltransferase, which is involved in the repair mechanism of DNA damage induced by chloroethylnitrosoureas such as 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU). We tested the enhancement effect of O6-methylguanine pretreatment on ACNU cytotoxicity in ACNU-resistant brain tumors. Exposure to O6-methylguanine at various times ranging from 2 to 48 hours increased the cytotoxic effects of ACNU on C6-1 cells, and this effect was highest at higher concentrations 500 and 1,000 microM. Colorimetric cytotoxicity assay revealed at least a two-fold increase in ACNU cytotoxicity relative to controls without O6-methylguanine. Intraarterial ACNU after treatment with O6-methylguanine (two intravenous bolus injections of 80 and 40 mg/kg) significantly (P < 0.05 or P < 0.01) reduced the proliferation activity of transplanted C6-1 tumors for 96 hours after injection, whereas intravenous ACNU together with O6-methylguanine significantly (P < 0.05) reduced C6-1 activity for only 48 hours. Thus, pretreatment with O6-methylguanine prolonged the suppression effect of ACNU. The C6-1 tumors treated only with intravenous or intraarterial ACNU showed transient inhibition and rapid regrowth for 24 hours after treatment. These results indicate that O6-methylguanine increases ACNU cytotoxicity in an in vitro and in vivo brain tumor model.

The MTT assay for chemosensitivity testing of human tumors of the central nervous system. Part I: Evaluation of test-specific variables

The aim of this study was to optimize the experimental conditions of the MTT assay for primary cultures of human brain tumors. This assay is based on the mitochondrial reduction of MTT-(3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) salt to formazan crystals by living cells. Formazan can be quantified spectrophotometrically. This assay measures the antimetabolic and, by using an adequate recovery period for the cells, also the antiproliferative effects of cytotoxic drugs. Our results suggest the following experimental design for its application as an chemosensitivity assay for human brain tumors: 1-h drug exposure followed by a seven days recovery period without drugs. Then tumor cells are incubated 4 hours with 1 mg MTT/ml and final absorbance readings are performed at 550 nm and 630 nm as test and reference wavelengths respectively. In this way, the assay seems to be a reliable and simple method for rapid chemosensitivity testing in human brain tumors.