TCA-100 tumour chemosensitivity assay: differences in sensitivity between cultured tumour cell lines and clinical studies

Cancer Chemoresistance; Recent Challenges and Future Considerations

Cancer remains one of the serious health hazards and major causes of human mortality across the world. Despite the development of many typical antineoplastic drugs and introduction of novel targeted agents, chemoresistance constitutes a major challenge in the effective therapeutic management of cancer. Drug inactivation, efflux of anticancer agents, modification of target sites, enhanced repair of DNA damage, apoptosis failure and induction of epithelial-mesenchymal transition are the principal mechanisms of cancer chemoresistance. Moreover, epigenetics, cell signaling, tumor heterogeneity, stem cells, microRNAs, endoplasmic reticulum, tumor microenvironment and exosomes have also been implicated in the multifaceted phenomenon of anticancer drug resistance. The tendency of resistance is either intrinsically possessed or subsequently acquired by cancerous cells. From clinical oncology standpoint, therapeutic failure and tumor progression are the most probable consequences of cancer chemoresistance. Combination therapy can help to overcome the issue of drug resistance, and therefore, the development of such treatment regimens is recommended for counteracting the emergence and dissemination of cancer chemoresistance. This chapter outlines the current knowledge on underlying mechanisms, contributory biological factors and likely consequences of cancer chemoresistance. Besides, prognostic biomarkers, diagnostic methods and potential approaches to overcome the emergence of antineoplastic drug resistance have also been described.

TWIST1 Gene Expression as a Biomarker for Predicting Primary Doxorubicin Resistance in Breast Cancer

Doxorubicin is one of the most commonly used chemotherapeutic agents for adjuvant chemotherapy of breast cancer. In the studies focused on finding biomarkers to predict the response of the patients and tumors to the drugs used, the Twist transcription factor has been suggested as a candidate biomarker for predicting chemo-resistance of breast tumors. In this study, we aimed to investigate the relationship between TWIST transcription factor expression and the effectiveness of doxorubicin treatment on directly taken primary tumor samples from chemotherapy-naive breast cancer patients. Twenty-six primary breast tumor samples taken from 26 different breast cancer patients were included in this study. Adenosine triphosphate tumor chemo-sensitivity assay (ATP-TCA) has been used to determine tumor response to doxorubicin and real-time reverse-transcription polymerase chain reaction (RT-PCR) was used for analyzing the TWIST1 gene expression of tumors. There was a significant difference in TWIST gene expression between responder and non responder tumors (p <0.05). The TWIST gene expression of the drug-resistant group was higher than the responsive group. This difference was not dependent on the histopathological features of tumors. In conclusion, compatible with earlier studies that have been performed with cell lines, the current study supports the role of higher TWIST gene expression as a biomarker for predicting the response of breast tumors to chemo-therapeutic agent doxorubicin.

Molecular chess? Hallmarks of anti-cancer drug resistance

Background

The development of resistance is a problem shared by both classical chemotherapy and targeted therapy. Patients may respond well at first, but relapse is inevitable for many cancer patients, despite many improvements in drugs and their use over the last 40 years.

Review

Resistance to anti-cancer drugs can be acquired by several mechanisms within neoplastic cells, defined as (1) alteration of drug targets, (2) expression of drug pumps, (3) expression of detoxification mechanisms, (4) reduced susceptibility to apoptosis, (5) increased ability to repair DNA damage, and (6) altered proliferation. It is clear, however, that changes in stroma and tumour microenvironment, and local immunity can also contribute to the development of resistance. Cancer cells can and do use several of these mechanisms at one time, and there is considerable heterogeneity between tumours, necessitating an individualised approach to cancer treatment. As tumours are heterogeneous, positive selection of a drug-resistant population could help drive resistance, although acquired resistance cannot simply be viewed as overgrowth of a resistant cancer cell population. The development of such resistance mechanisms can be predicted from pre-existing genomic and proteomic profiles, and there are increasingly sophisticated methods to measure and then tackle these mechanisms in patients.

Conclusion

The oncologist is now required to be at least one step ahead of the cancer, a process that can be likened to ‘molecular chess’. Thus, as well as an increasing role for predictive biomarkers to clinically stratify patients, it is becoming clear that personalised strategies are required to obtain best results.

Improved in vitro human tumor models for cancer gene therapy

Developing effective anticancer treatments is a particular challenge, as agents must contend with not only the target cellular biology, but also with the complex tumor microenvironment. Here we discuss various in vitro strategies that have sought to address this issue, with a particular focus on new methodologies that utilize clinical samples in basic research and their application in gene therapy and virotherapy.

Measurement of cytotoxicity by ATP-based luminescence assay in primary cell cultures and cell lines

Drug discovery and toxicological safety testing share a need for dependable in vitro cellular toxicity tests. Ideally such tests should be objective, quantitative, reproducible and able to lend themselves to automation. A number of assays fulfil these criteria well, but recently it has become clear that the molecular phenotype of the cell tested and the complex interplay between different cell types can radically alter the response to individual agents. The differences observed between primary cell cultures and cell lines make it preferable to use primary cultures for assessment of toxicity, yet the problems of using primary cell cultures are considerable as the number of cells available for testing is often small. Recently, we have developed a short-term cell culture assay based on the detection of ATP by the luciferin-luciferase reaction. Four drugs/agents can be tested in triplicate at seven dilutions in one 96-well microplate with 1000 cells/well in the case of cell lines, or 10,000 cells/well for primary tumour tissue. The small number of cells required is a major advantage of this method. Initially developed as a tumour chemosensitivity assay, the assay has shown considerable promise as a general in vitro toxicity assay allowing both cell lines and primary tissue cultures to be tested. Heterogeneity of sensitivity is present in benign tissue biopsies as well as tumours. Molecular alterations within the cell and the interplay of different cell types have been addressed in a number of different model systems using the assay, suggesting that this technology may have more general application.

Isolation and culture of ovarian cancer cells and cell lines

Ovarian carcinomas show considerable heterogeneity of origin, both in terms of site and tissue. The most important and also most frequent of these tumors arise from the coelomic epithelium and are therefore characterized as epithelial ovarian carcinomas (EOC). EOC is often large and advanced at the time of presentation, so that cells are readily obtainable from surgical specimens or effusions. While the primary tumor may be chemosensitive, they often develop resistance and may do so rapidly. Due to the easy access to tumor cells and its biological behavior, EOC is considered to be an ideal model to investigate principal mechanisms of both antineoplastic drug sensitivity and resistance. Although studies on primary EOC cells are now preferred for many of these investigations, EOC cell line studies remain important too. This chapter gives an overview over major techniques required to establish and maintain primary EOC cell cultures and to initiate and cultivate permanently growing EOC cell lines.

The effect of pentamidine on melanoma ex vivo

Pentamidine is a small molecule inhibitor of the Ca(+)-binding protein S100B and disrupts the S100B-p53 protein-protein interaction; this is thought to restore wild-type p53 tumour suppressor function in melanoma. Additional anticancer effects may be the result of inhibition of regenerating liver family phosphatases. In this study, we have used a standardized ATP-tumour chemosensitivity assay to investigate the effect of pentamidine on cells derived from 18 skin melanoma samples and one uveal melanoma sample. The cells were tested at six concentrations from which the IC(50) and IC(90) were calculated. To allow comparison between samples, an index(sum) was calculated based on the percentage of tumour growth inhibition at each concentration. Of the skin melanoma samples tested, 78% exhibited an index(sum) less than 300 indicating strong inhibition. The median index(sum) of 237 also indicates considerable activity against these samples. The median IC(90) (30.2 micromol/l) may be clinically achievable in a proportion of patients. The uveal melanoma sample exhibited an index(sum) of 333 indicating moderate inhibition, and 86% inhibition at test drug concentration (37.96 micromol/l). These results show that pentamidine has activity against melanoma, and support the prospect of its development for therapeutic use.

Evaluation of novel histone deacetylase inhibitors as therapeutic agents for colorectal adenocarcinomas compared to established regimens with the histoculture drug response assay

BACKGROUND AND AIMS

This study was to evaluate the efficacy of histone deacetylase (HDAC) inhibitors in colorectal cancer together with other established regimens.

MATERIALS AND METHODS

Chemosensitivities of 114 colorectal cancer patients to established regimens (fluorouracil (5-FU with leucovorin (FL), capecitabine, FL with irinotecan (FLIRI), and FL with oxaliplatin (FLOX)) as well as five hydroxamic acid derivatives (suberoylanilide hydroxamic acid, PXD101, and three novel candidates of CG-1, CG-2, and CG-3) were comparatively evaluated using the histoculture drug response assay.

RESULTS

The chemosensitivity with established regimens was between 34.2% and 52.6%, when the cutoff value of the inhibition ratio was set at 30%, and between 54.5% and 84.1% with HDAC inhibitors. All HDAC inhibitors displayed synergistic effects in combination with established regimens of FLOX and FLIRI (P < or = 0.0001-0.002). Advanced T- and N-category tumors and patients with synchronous adenoma displayed higher chemosensitivity to CG-3, CG-2, and CG-1, respectively, on a multivariate analysis (P = 0.023, 0.044, and 0.045, respectively). Tumors with mismatch repair defects were closely correlated with chemosensitivities to combined regimens of PDX101 with FLOX and FLIRI (P = 0.044 and 0.048, respectively).

CONCLUSIONS

Our findings firstly demonstrated the chemo-responsiveness of colorectal cancers to HDAC inhibitors with therapeutic efficacy comparable to the established regimens. Additionally, tumor growth and heredity were significantly associated with specific regimens, supporting their possible role as chemosensitive predictors.

Comparison of pretherapeutic and posttherapeutic expression levels of chemotherapy-associated genes in adenocarcinomas of the esophagus treated by 5-fluorouracil- and cisplatin-based neoadjuvant chemotherapy

We analyzed expression of genes associated with metabolism of chemotherapeutic drugs in locally advanced esophageal adenocarcinomas before and after neoadjuvant chemotherapy to study whether there is a change in gene expression induced by chemotherapy and whether such changes are associated with tumor response or nonresponse. We included 21 patients with locally advanced esophageal adenocarcinomas treated by cisplatin- and 5-fluorouracil (5-FU)-based neoadjuvant chemotherapy before surgery. Messenger RNA was extracted from formalin-fixed, paraffin-embedded preoperative endoscopic esophageal tumor biopsy specimens and tumor tissue specimens after surgical resection. Expression levels of chemotherapy metabolism-associated genes thymidylate synthase (TYMS), thymidine phosphorylase (TP), dihydropyrimidine dehydrogenase (DPD), methylenetetrahydrofolate reductase (MTHFR), multidrug resistance-associated protein 1 (MRP1), and multidrug-resistance gene 1 (MDR1) were determined by quantitative real-time reverse transcriptase-polymerase chain reaction. There was a significant posttherapeutic reduction in the expression levels of TP (P = .028) and MRP1 (P = .006). Furthermore, down-regulation of MRP1 (P = .041) and TYMS (P = .028) after chemotherapy was associated with tumor response to chemotherapy, assessed clinically and by histopathologic tumor regression. Down-regulation of chemotherapy metabolism-associated genes occurs after neoadjuvant chemotherapy and may modulate tumor response to chemotherapy.

Cytotoxicity of Orthodontic Wire Corroded in Fluoride Solution In Vitro

OBJECTIVE

To investigate the toxicity of fluoride corrosion extracts of stainless steel (SS) and nickel-titanium (NiTi) wires on a human osteosarcoma cell line (U2OS).

MATERIALS AND METHODS

The SS and NiTi wires were corroded by an electrochemical method with the application of three kinds of electrolytes: 0.2% pH 3.5 acidulated phosphate fluoride (NaF) in artificial saliva, and pH 4 and pH 6.75 artificial saliva solutions. The extracts were analyzed for nickel, chromium, and titanium ions by the atomic absorption method. The extracts were diluted with medium to different concentrations (1, 0.1, and 0.01 microL/mL). The cell survival rate was determined by the ability of test cells to cleave the tetrazolium salt to form a formazan dye.

RESULTS

The results were compared using one-way analysis of variance. Differences between the treatment means were analyzed using a Student-Newman-Keuls (SNK) test and were considered significant at P < .05. The release of ionic nickel was different in different extract groups (P < .05). The SS and NiTi wires in the 0.2% pH 3.5 NaF artificial saliva group caused a dose-dependent decrease in the survival rate (P < .05). Survival rates of cells in the groups exposed to extracts of SS and NiTi wires in pH 4 and pH 6.75 artificial saliva solutions showed no statistical differences (P >.05).

CONCLUSIONS

Orthodontic wires in acidulated fluoride saliva solution can cause U2OS cell toxicity.

Effect of culture conditions on the chemosensitivity of ovarian cancer cell lines

The aim of this study was to define the chemosensitivity profile of a series of human ovarian cancer cell lines representing the human primary ovarian tumours under altered culture conditions and to compare the results with those from tumour-derived cells. In this study, we used a standardized ATP-based tumour chemosensitivity assay to measure the activity of cytotoxics in the seven ovarian carcinoma cell lines and ovarian tumour-derived cells. The use of adherence-free polypropylene plates and a serum-free medium slowed down cell proliferation in all cell lines tested, mimicking the slow growth rate of solid tumours in this type of plastic. The seeding density was optimized for each cell line and was in the range of 2000-4000 cells/well. Heterogenous sensitivity to different cytotoxics was observed in the seven ovarian cancer cell lines tested in the ATP-based tumour chemosensitivity assay. The human ovarian carcinoma cell line, OVCA433, was found to be the most resistant cell line and 75% of the drugs showed an Index(SUM) above 300. Our results suggest that the use of appropriate culture conditions i.e. a serum-free culture environment, adherence-free growth and optimum seeding density can induce cell lines to behave more like tumour-derived cells in response to cytotoxic agents. On the basis of the comparison of chemosensitivity profiles of tumour-derived cells and cell lines derived from the corresponding tumour, a panel of cell lines can be selected. Such a panel could be used to screen and develop anticancer drugs.

Evaluation of the sensitivity of three sublethal cytotoxicity assays in human HepG2 cell line using water contaminants

The in vitro toxicological index IC50 (the millimolar concentration of compound which inhibits response assay by 50% compared to the solvent control) of 11 water contaminants (acrylamide, atrazine, B[a]P, BPA, 2,4-DAT, 17-alphaEE, H(2)O(2), 4-OP, sodium bromate, sodium chlorate, sodium nitrate) was evaluated on the human hepatoma (HepG2) cells using three short-term bioassays related to their morbidity status [radiometric RNA synthesis assay (RNA), luminometric ATP assay (ATP), fluorometric Alamar blue assay (AB)]. Among all substances, we were not able to determine atrazine IC50 value whatever the test used. Furthermore, B[a]P was not cytotoxic in the ATP and AB assays. Statistical analysis revealed a correlation between the IC50 values obtained in the three assays. Except with 4-OP, RNA assay was always inhibited at lower concentrations than those required in the other assays, suggesting that this assay is a very sensitive indicator of the presence of toxic compounds. ATP and AB assays responded to a similar pattern. Due to its higher sensitivity and its reliability, RNA synthesis assay using HepG2 cell line provides the most suitable tool for the screening of water contaminants.

Pilot studies of the effect of zoledronic acid (Zometa) on tumor-derived cells ex vivo in the ATP-based tumor chemosensitivity assay

There is debate regarding the direct effect of bisphosphonates against visceral metastases from solid tumors, despite their proven efficacy against the skeletal complications of metastasis. The aim of this study was to determine whether zoledronic acid showed direct activity against five ovarian cell lines and tumor-derived cells, and whether addition of zoledronic acid to cytotoxic agents increased their cytotoxicity. In this study we used a standardized ATP-based tumor chemosensitivity assay (ATP-TCA) to measure the activity of alendronate, clodronate and zoledronic acid in five ovarian carcinoma cell lines and human solid tumors (breast, lung, ovarian, unknown primary carcinoma, and cutaneous and uveal melanoma) (n=34). We also tested the combination of zoledronic acid with paclitaxel and cisplatin in tumor-derived cells. All five cell lines exhibited greater sensitivity to bisphosphonates than the tumor-derived cells and in all five the IC50 for zoledronic acid was less than 4 muM. In the tumor-derived cells, zoledronic acid showed concentration-dependent inhibition with a median IC50 for all tumors tested of 17 muM and evidence of apoptosis (caspase activation). Simultaneous addition of zoledronic acid to cisplatin or paclitaxel showed no major increase in cytotoxicity. We conclude that the activity of bisphosphonates was greater in cell lines than in tumor-derived cells. However, the pattern of activity of bisphosphonates was the same in cell lines and tumor derived cells. This study suggests a direct, or possibly an indirect, effect of zoledronic acid and other nitrogen-containing bisphosphonates against neoplastic cells, but simultaneous addition with cisplatin or paclitaxel does not substantially increase the activity of the cytotoxic agent.

Cancer cell adaptation to chemotherapy

Background

Tumor resistance to chemotherapy may be present at the beginning of treatment, develop during treatment, or become apparent on re-treatment of the patient. The mechanisms involved are usually inferred from experiments with cell lines, as studies in tumor-derived cells are difficult. Studies of human tumors show that cells adapt to chemotherapy, but it has been largely assumed that clonal selection leads to the resistance of recurrent tumors.

Methods

Cells derived from 47 tumors of breast, ovarian, esophageal, and colorectal origin and 16 paired esophageal biopsies were exposed to anticancer agents (cisplatin; 5-fluorouracil; epirubicin; doxorubicin; paclitaxel; irinotecan and topotecan) in short-term cell culture (6 days). Real-time quantitative PCR was used to measure up- or down-regulation of 16 different resistance/target genes, and when tissue was available, immunohistochemistry was used to assess the protein levels.

Results

In 8/16 paired esophageal biopsies, there was an increase in the expression of multi-drug resistance gene 1 (MDR1) following epirubicin + cisplatin + 5-fluorouracil (ECF) chemotherapy and this was accompanied by increased expression of the MDR-1 encoded protein, P-gp. Following exposure to doxorubicin in vitro, 13/14 breast carcinomas and 9/12 ovarian carcinomas showed >2-fold down-regulation of topoisomerase IIα (TOPOIIα). Exposure to topotecan in vitro, resulted in >4-fold down-regulation of TOPOIIα in 6/7 colorectal tumors and 8/10 ovarian tumors.

Conclusion

This study suggests that up-regulation of resistance genes or down-regulation in target genes may occur rapidly in human solid tumors, within days of the start of treatment, and that similar changes are present in pre- and post-chemotherapy biopsy material. The molecular processes used by each tumor appear to be linked to the drug used, but there is also heterogeneity between individual tumors, even those with the same histological type, in the pattern and magnitude of response to the same drugs. Adaptation to chemotherapy may explain why prediction of resistance mechanisms is difficult on the basis of tumor type alone or individual markers, and suggests that more complex predictive methods are required to improve the response rates to chemotherapy.

Ex vivo characterization of XR11576 (MLN576) against ovarian cancer and other solid tumors

XR11576 (MLN576) is a novel monophenazine with a mechanism of action that includes interaction with both topoisomerase (Topo) I and II. The aim of this study was to evaluate its cytotoxicity against fresh tumor cells taken from patients with a variety of solid tumors. Cells were obtained from 89 patients and exposed for 6 days to XR11576 alone, or in combination with doxorubicin, cisplatin, treosulfan, paclitaxel or vinorelbine. Cell survival was measured using the ATP-Tumor Chemosensitivity Assay (ATP-TCA). Immunohistochemical staining of Topo I, Topo IIalpha and MDR1 was performed on paraffin-embedded blocks in those tumors for which tissue was available (n = 49). Overall, the median IC90 and IC50 values of XR11576 in tumor-derived cells were 242 and 110 nM, respectively. In all samples XR11576 was more potent than the other cytotoxics tested. Breast and gynecological malignancies were most sensitive to XR11576, while the potency of this compound was slightly attenuated in gastrointestinal tumors, in which the median IC90 and IC50 values were 308 and 212 nM, respectively. Cases of synergism were identified when combining XR11576 with vinorelbine (nine of 30 samples) and doxorubicin (12 of 38 samples), while the addition of paclitaxel resulted in an antagonistic effect (CI50>1.2) in 38 of 42 tumors. A very modest correlation by linear regression analysis was found between the intensity of MDR1 staining and the IC50 of XR11576 (r = 0.311, p = 0.0312), but not with the IC90 (r = 0.247, NS). These data support the rapid introduction of XR11576 to clinical trials and suggest that it may be effective against a broad spectrum of tumor types.

Comparison of the usefulness of the MTT, ATP, and calcein assays to predict the potency of cytotoxic agents in various human cancer cell lines

Cell viability assays are important tools in oncological research and clinical practice to assess the tumor cell sensitivity of individual patients. The purpose of this study was to demonstrate the comparability of 3 widely used assays (MTT, ATP, calcein assays) by principal component analysis. The study included 4 different cytostatics (cisplatin, docetaxel, doxorubicin, vinblastine) and 3 different human cancer cell lines (MCF-7, A2780, doxorubicin resistant A2780adr). Ninety-three percent of the total variance of all variables included in the principal component analysis (resulting from 3 cell lines and 3 assays) could be explained by 1 principal component. Factor loadings were > 0.937 except for the variable MTT-A2780adr, which was 0.872. These results indicate the similarity of the 3 assays. A 2nd principal component analysis included literature data and showed accordance of data from this study and the literature. The MTT assay was further improved as a high-throughput screening-capable assay. The ATP assay is able to detect effects of cytostatics already after 1 h incubation. The determination of resistance factors allowed to differentiate cytostatics into P-gp or non-P-gp substrates. In conclusion, this study provides improved microplate reader-based cell viability assays and sets a statistically solid basis for a future comparison of data obtained in different laboratories by any of the 3 assays.

The ex vivo characterization of XR5944 (MLN944) against a panel of human clinical tumor samples

XR5944 (MLN944) is a novel DNA targeting agent with potent antitumor activity, both in vitro and in vivo, against several murine and human tumor models. We have used an ATP-tumor chemosensitivity assay to assess the ex vivo sensitivity of a variety of solid tumors (n = 90) and a CCRF-CEM leukemia cell line selected with XR5944. Differences in gene expression between the parental CCRF-CEM and the resistant subline were investigated by quantitative reverse transcription-PCR. Immunohistochemistry for topoisomerases I and IIα and multidrug resistance (MDR1) protein was done on those tumors for which tissue was available (n = 32). The CCRF-CEM XR5944 line showed increased mRNA levels of MDR1, major vault protein, and MDR-associated protein 1 compared with the parental line, whereas the expression of topoisomerases I, IIα, and IIβ was essentially unchanged, suggesting that XR5944 is susceptible to MDR mechanisms. The median IC90 and IC50 values for XR5944 in tumor-derived cells were 68 and 26 nmol/L, respectively, 6-fold greater than in resistant cell lines. XR5944 was 40- to 300-fold more potent than the other cytotoxics tested, such as doxorubicin, topotecan, and paclitaxel. Breast and gynecologic malignancies were most sensitive to XR5944, whereas gastrointestinal tumors showed greater resistance. A positive correlation (r = 0.68; P &lt; 0.0001) was found between the IC50 values of XR5944 and P-glycoprotein/MDR1 staining but not with either topoisomerase I or IIα immunohistochemistry index. These data support the rapid introduction of XR5944 to clinical trials and suggest that it may be effective against a broad spectrum of tumor types, especially ovarian and breast cancer.

Chemosensitivity testing as an aid to anti-cancer drug and regimen development

The ATP-based chemosensitivity assay has proved particularly useful for the evaluation of new anti-cancer agents and combinations. The majority of our publications in this area have concentrated on topoisomerase inhibitors. Comparison of mitoxantrone with doxorubicin convinced us that these two agents were not completely cross-resistant and led to the design of the mitoxantrone + paclitaxel regimen which is now in clinical practice. Re-assessment of treosulfan in uveal melanoma led to the design of a new regimen combining this alkylating agent with gemcitabine, again with rapid introduction of this combination to clinical practice. The assay has recently been used to examine the concentration-activity curve to determine which tumours might benefit from liposomal preparations capable of delivering 4-16 times the standard dose without cardiotoxicity. Assay-directed use of Caelyx is producing encouraging results, and we are now examining this drug in combination with others. We recently showed that XR5000, a combined inhibitor of topoisomerase I and II, was effective against melanoma as well as ovarian cancer, but at concentrations which were unlikely to be achieved in patients. These data confirm our suggestion that use of the assay could reduce the time to introduction of new anti-cancer drugs and the cost of this process.

An evaluation of the cytotoxic effects of orthodontic bonding adhesives upon a primary human oral gingival fibroblast culture and a permanent, human oral cancer-cell line

The purpose of this investigation was to determine the cytotoxic effects of three different kinds of orthodontic adhesive on a human primary gingival fibroblast culture (GF) and a human oral cancer-cell line (OC2). The adhesives comprised a self-cure bonding resin, a light-cure bonding resin, and a hybrid glass ionomer. Any differences between the cytotoxic potencies of eluates of the orthodontic materials on GF and OC2 cells were quantified colorimetrically (MTT test). The results are as follows: For the hybrid glass ionomer, the survival rate of GF cells exposed to the liquid component revealed a significant dose-dependent decrease (p < 0.05). The liquid component and the mixed hybrid glass-ionomer material reflected a significant dose-dependent decrease (p < 0.05) in exposed OC2 cell survival. Associated with an increase in the cell exposure concentration of Resin A, Resin B, Paste A, Paste B, Resin A + B, Paste A + B and the set material of the self-cure resin adhesive, was a significant decrease in survival rate for cultured GF and OC2 cells (p < 0.05). Associated with an increase in the concentration of the primer, paste, and mixed material of the light-cure resin adhesive to which test cells were exposed, the survival rate reflected a decrease for GF cells (p < 0.05). The survival rate of cells exposed to light-cure resin paste reflected no difference for OC2 cells. It is concluded that the liquid of the hybrid glass-ionomer cement, Resin A and Resin B and Resin A + B of the self-cure resin and the primer of the light-cure resin are toxic agents to the GF and OC2 cell lines. Primary human gingival fibroblasts were found to be more sensitive than the tested human oral carcinoma cell line from most of the substances.

Heterogeneity of chemosensitivity of colorectal adenocarcinoma determined by a modified ex vivo ATP-tumor chemosensitivity assay (ATP-TCA)

Advanced colorectal cancer (CRC) has a poor prognosis with a 5-year survival of only 5% despite treatment with chemotherapeutic agents. Response rate and overall survival varies little between the commonly used single agents, although combinations achieve better outcomes. It is well established that considerable heterogeneity exists between cancers of the same tissue type, but it has been difficult to establish this for CRC. We therefore investigated the heterogeneity of chemosensitivity in CRC using a modified version of the ex vivo ATP-tumor chemosensitivity assay (ATP-TCA) capable of handling infected tumor tissue. Fifty-three specimens of primary solid or malignant effusions of CRC were tested, of which 46 (87%) were evaluable. There were considerable differences in sensitivities between individuals. The most active single cytotoxic agents in the assay were identified as 5-fluorouracil, irinotecan and mitomycin C (MMC). Cells were exposed to combinations of drugs added simultaneously at the same concentrations tested as single agents. All drug combinations achieved greater growth inhibition than drugs used alone. MMC+gemcitabine was found to be the most effective combination in 83% of specimens. The ATP-TCA has previously been shown to be a good predictor of response to chemotherapy in other tissue types. The degree of heterogeneity demonstrated from these results suggests that the ATP-TCA could be used to identify patients who might benefit from specific chemotherapeutic agents alone or in combination.

Multidrug resistance in ovarian cancer: comparing an immunocytochemical study and ATP-tumor chemosensitivity assay

The aim of our study was to evaluate the possible prognostic and predictive significance of the expression of P-glycoprotein, a transmembrane transport protein related to multidrug resistance, in previously untreated patients with FIGO stage III ovarian cancer; to compare the results of immunocytochemical analysis of tissue sections of tumors to the in vitro chemosensitivity to cytotoxic drug of fresh samples of the same tumors; and to evaluate survival in women who underwent the same surgical treatment and the same adjuvant chemotherapy.

Uveal melanomas express vascular endothelial growth factor and basic fibroblast growth factor and support endothelial cell growth

BACKGROUND

Tumour microvascularity is a significant determinant of prognosis for a large number of different tumours, including uveal melanoma. The development of blood vessels within these and other tumours is partly controlled by soluble pro-angiogenic cytokines, of which basic fibroblast growth factor (bFGF) and vascular endothelial growth factor-A (VEGF) are the best described.

METHODS

Because VEGF has been inconsistently found within uveal melanomas and bFGF is described as an autocrine growth factor in cutaneous melanoma, the authors looked at the expression of these cytokines in uveal melanomas using immunohistochemistry and reverse transcriptase polymerase chain reaction (RT-PCR). The cross talk between uveal melanoma cells and endothelial cells was then assessed in an in vitro co-culture model.

RESULTS

While most tumour cells expressed bFGF at the protein level by immunohistochemistry (89%), relatively few (22%) expressed VEGF, and this was of limited extent. All 20 tumours tested by RT-PCR contained mRNA for both bFGF and VEGF. Co-culture experiments using an ATP based bioassay showed that uveal melanomas could support the growth of a rat brain endothelial cell line (GPNT) and human umbilical vein endothelial cells (HUVEC), and that this could be modulated by cytokines and anti-cytokine antibodies.

CONCLUSION

These results suggest that angiogenesis within uveal melanoma may be the result of a complex interplay between endothelial and tumour cells, and that bFGF and VEGF could play a part.

Use of firefly luciferase in ATP-related assays of biomass, enzymes, and metabolites

The kinetics of ATP reagents not affected by product inhibition or other forms of inactivation of luciferase during the measurement time has been clarified. Under these conditions the decay rate of the light emission expressed as percentage per minute is a measure of luciferase activity and can be given as the rate constant k (min-1), directly reflecting the degradation of ATP in the luciferase reaction. Three types of reagents with different analytical characteristics and different application possibilities have been identified. Stable light-emitting reagents are suitable for measurements of ATP down to 1000 amol. This is the only type of reagent suitable for monitoring ATP-converting reactions, i.e., assays of enzymes or metabolites, assays of oxidative phosphorylation, photophosphorylation, and so on. A higher luciferase activity resulting in a slow decay of the light emission by approximately 10% per minute (k = 0.1 min-1) gives a reagent suitable for measurements down to 10-100 amol. The slow decay of light emission allows use of manual luminometers without reagent dispensers. A further increase of the luciferase activity resulting in a decay rate of approximately 235% per min (k = 2.35 min-1) and only 10% of the light emission remaining after 1 min is suitable for measurements down to 1 amol corresponding to half a bacterial cell. With this type of flash reagent the total light emission can be calculated from two measurements of the light intensity on the decay part of the light emission curve. This new measure is not affected by moderate variations in luciferase activity, but only by changes in quantum yield and self-absorption of the light in the sample. Flash-type reagents require the use of reagent dispensers. The stringent requirements for ATP-free cuvettes, pipette tips, and contamination-free laboratory techniques make it unlikely that flash reagents would be useful in nonlaboratory surroundings. A potential application for this type of reagent is sterility testing. In general, it is concluded that one should select the ideal ATP reagent carefully for each application. Obviously the reagents used in a particular application do not have to match the decay rates given earlier exactly. However, various applications of the ATP technology and the properties of manual and automatic luminometers fall quite nicely into categories corresponding to the properties of the three reagents described. The rapidly growing interest in ATP technology has already resulted in the development of a greater variety of luminometers, from hand-held instruments to high-throughput systems. The continuation of efforts in both reagent and instrument development will undoubtedly result in many new applications.

Application of a new high sensitivity luminometer for industrial microbiology and molecular biology

A compact new luminometer (FB12) has been developed based on a 370-630 nm photon counter and measuring chamber that can accommodate a range of sample formats. The FB12 permits measurements as low as 1000 molecules of luciferase in reporter gene assays. Its sensitivity for ATP is limited by reagent background. If ATP assay reagents had no chemical background, 2 fg of ATP could be detected using 3 SD of instrument background as the detection limit. The FB12 has a dynamic range of six decades and operates under its own microprocessor programme or protocol-based PC software that is integrated with Microsoft(R) Excel(R). An injector port above the sample measuring position allows connection of external reagent injectors. Applications are performed using protocols provided with the FB12 or user defined protocols. Examples are presented that illustrate use of the instrument for research and industrial applications.

Heterogeneity of in vitro chemosensitivity in perioperative breast cancer cells to mitoxantrone versus doxorubicin evaluated by a microplate ATP bioluminescence assay

Apart from clinical trials, mitoxantrone (MX) is rarely used in breast cancer (BC) due to the anticipated anthracycline cross-resistance. We have examined this drug versus doxorubicin (DOX) using data obtained from in vitro microplate ATP tumor chemosensitivity assays (ATP-TCA) of BC cells which were derived from 55 chemotherapy-naive patients at time of primary surgery. Both drugs were tested at 6 different concentrations ranging from 6.25% to 200% peak plasma concentration in vivo (PPC). Differences between DOX and MX observed for mean IC50, IC90, and a sensitivity index (SI) were not statistically significant. In vitro response rates were 44% for DOX and 52% for MX. 34 of 52 eligible assays (65%) showed comparable activity of both drugs whereas a lack of cross-resistance was observed in the remaining 18 (35%) tumors as indicated by differences for SI. Cumulative concentration-response plots of tumors responding in vitro with a > or = 50 percent or > or = 90 percent tumor cell inhibition showed a strong dose-dependence for both DOX and MX at concentrations which normally can be achieved within clinical tumors (i.e. 6.25%-50% PPC). At higher concentrations, however, cytotoxicity of DOX and MX could not be improved by further in vitro dose escalation. Moreover, a substantial proportion of BC specimens (DOX: 48.1%; MX: 40.4%) did not experience a > or = 90 tumor cell inhibition at 200% PPC. In conclusion, in vitro results obtained by ATP-TCA indicate that there is no cross-resistance between MX and DOX in a substantial proportion of BC patients. This may be clinically useful and suggests that combinations including MX should be tested in patients clinically resistant to DOX containing regimens. Since both drugs produced sigmoidal concentration-response curves, dose escalation beyond a certain point may not produce increased sensitivity.