Intracellular adenosine triphosphate as a measure of human tumor cell viability and drug modulated growth

WEE1 and PARP-1 play critical roles in myelodysplastic syndrome and acute myeloid leukemia treatment

BACKGROUND

Myelodysplastic syndrome (MDS) is a clonal bone marrow disorder defined by cytopenia and is associated with an increased risk of transformation to acute myeloid leukemia (AML). The outcome of MDS is poor, so alternative therapeutic approaches are needed to improve survival. The inhibition of the DNA damage response pathway, including poly (ADP-ribose) polymerase-1 (PARP-1), has been approved to treat several cancers. In addition, WEE1, a nuclear kinase, is overexpressed in many cancers. Therefore, a WEE1 inhibitor combined with a PARP-1 inhibitor could inhibit the proliferation of MDS and AML.

METHODS

We analyzed whether WEE1 was regulated in the progression of MDS and AML. We also evaluated the efficacy of MK-1775 (WEE1 inhibitor) and talazoparib (PARP-1 inhibitor).

RESULTS

PARP-1 expression was higher in the AML cells than in the MDS cells. However, WEE1 expression remained unchanged. MK-1775 or talazoparib alone inhibited MDS and AML cells after 72 h, and cellular cytotoxicity and caspase 3/7 activity were increased. The combined use of MK-1775 and talazoparib produced superior efficacy than either drug alone and SKM-1 colony formation was reduced. Significant cell populations in the sub-G1 phase were found in the cell-cycle analyses. Additionally, γ-H2AX expression and caspase 3 activity were increased. The combined treatment also changed the mitochondrial membrane potential.

CONCLUSIONS

The combination of a WEE1 inhibitor and PARP-1 inhibitor had enhanced efficacy and is proposed as a new therapeutic option for patients with MDS or AML. Our findings have clinical implications for a potential novel therapeutic strategy for MDS and AML patients.

Cancer Cell Culture: The Basics and Two-Dimensional Cultures

Despite significant advances in investigative and therapeutic methodologies for cancer, 2D cell culture remains an essential and evolving competency in this fast-paced industry. From basic monolayer cultures and functional assays to more recent and ever-advancing cell-based cancer interventions, 2D cell culture plays a crucial role in cancer diagnosis, prognosis, and treatment. Research and development in this field call for a great deal of optimization, while the heterogenous nature of cancer itself demands personalized precision for its intervention. In this way, 2D cell culture is ideal, providing a highly adaptive and responsive platform, where skills can be honed and techniques modified. Furthermore, it is arguably the most efficient, economical, and sustainable methodology available to researchers and clinicians alike.In this chapter, we discuss the history of cell culture and the varying types of cell and cell lines used today, the techniques used to characterize and authenticate them, the applications of 2D cell culture in cancer diagnosis and prognosis, and more recent developments in the area of cell-based cancer interventions and vaccines.

Standardized Protocol for the Preparation of Precision-Cut Kidney Slices: A Translational Model of Renal Fibrosis

Renal fibrosis is a hallmark of progressive renal diseases. To date, there is a lack of effective therapeutics for the treatment of renal fibrosis, in part due to the scarcity of clinically relevant translational disease models. Since the early 1920s, hand-cut tissue slices have been used as a means to better understand organ (patho)physiology in a variety of scientific fields. From that time, the equipment and methodology for the preparation of tissue slices has continuously improved, thereby expanding the applicability of the model. Nowadays, precision-cut kidney slices (PCKS) have been demonstrated to be an extremely valuable translation model for renal (patho)physiology, bridging the gap between preclinical and clinical research. A key feature of PCKS is that the slices contain all cell types and acellular components of the whole organ in the original configuration while preserving cell-cell and cell-matrix interactions. In this chapter, we describe how to prepare PCKS and how the model can be implemented in fibrosis research.

A novel NCI-H69V small cell lung cancer functional mini-tumor model for future treatment screening applications

Small cell lung cancer (SCLC) is aggressive and despite multiple clinical trials, its standard of care is unchanged for the past three decades. In vitro cancer models are crucial in chemotherapy development, and three-dimensional (3D) models aim to bridge the gap between two-dimensional (2D) flat cultures and in vivo testing. Functional 3D spheroids can better represent the in vivo situation and tumor characteristics than 2D models. An NCI-H69V SCLC mini-tumor model was developed in a clinostat-based rotating bioreactor system. Spheroid growth and viability were characterized for 30 days, and the ideal experimental window with mature and metabolically stable spheroids was determined. Application of the model for anticancer treatment screening was validated with the standard chemotherapeutic drug irinotecan, for an exposure period of 72 h. The following parameters were measured: soluble protein content, planar surface area measurements, intracellular adenosine triphosphate and extracellular adenylate kinase levels, and glucose consumption. Histological morphology of the spheroids was observed. The established model proved viable and stable, while treatment with irinotecan caused a decrease in cell growth, viability, and glucose consumption demonstrating reactivity of the model to chemotherapy. Therefore, this NCI-H69V SCLC functional spheroid model could be used for future anticancer compound screening.

Bisphenol S Impairs Invasion and Proliferation of Extravillous Trophoblasts Cells by Interfering with Epidermal Growth Factor Receptor Signaling

The placenta supports fetal growth and is vulnerable to exogenous chemical exposures. We have previously demonstrated that exposure to the emerging chemical bisphenol S (BPS) can alter placental endocrine function. Mechanistically, we have demonstrated that BPS interferes with epidermal growth factor receptor (EGFR) signaling, reducing placenta cell fusion. Extravillous trophoblasts (EVTs), a placenta cell type that aids with vascular remodeling, require EGF to invade into the maternal endometrium. We hypothesized that BPS would impair EGF-mediated invasion and proliferation in EVTs. Using human EVTs (HTR-8/SVneo cells), we tested whether BPS could inhibit the EGF response by blocking EGFR activation. We also evaluated functional endpoints of EGFR signaling, including EGF endocytosis, cell invasion and proliferation, and endovascular differentiation. We demonstrated that BPS blocked EGF-induced phosphorylation of EGFR by acting as a competitive antagonist to EGFR. Transwell assay and a three-dimensional microfluidic chip invasion assay revealed that BPS exposure can block EGF-mediated cell invasion. BPS also blocked EGF-mediated proliferation and endovascular differentiation. In conclusion, BPS can prevent EGF-mediated EVT proliferation and invasion through EGFR antagonism. Given the role of EGFR in trophoblast proliferation and differentiation during placental development, our findings suggest that maternal exposure to BPS may contribute to placental dysfunction via EGFR-mediated mechanisms.

Anticancer Potential of Sutherlandia frutescens and Xysmalobium undulatum in LS180 Colorectal Cancer Mini-Tumors

Colorectal cancer remains to be one of the leading causes of death worldwide, with millions of patients diagnosed each year. Although chemotherapeutic drugs are routinely used to treat cancer, these treatments have severe side effects. As a result, the use of herbal medicines has gained increasing popularity as a treatment for cancer. In this study, two South African medicinal plants widely used to treat various diseases, Sutherlandia frutescens and Xysmalobium undulatum, were evaluated for potential activity against colorectal cancer. This potential activity for the treatment of colorectal cancer was assessed relative to the known chemotherapeutic drug, paclitaxel. The cytotoxic activity was considered in an advanced three-dimensional (3D) sodium alginate encapsulated LS180 colorectal cancer functional spheroid model, cultured in clinostat-based rotating bioreactors. The LS180 cell mini-tumors were treated for 96 h with two concentrations of each of the crude aqueous extracts or paclitaxel. S. frutescens extract markedly decreased the soluble protein content, while decreasing ATP and AK per protein content to below detectable limits after only 24 h exposure. X. undulatum extract also decreased the soluble protein content, cell viability, and glucose consumption. The results suggested that the two phytomedicines have potential to become a source of new treatments against colorectal cancer.

Biosynthesis and characterization of gold nanoparticles using Brazilian red propolis and evaluation of its antimicrobial and anticancer activities

Gold nanoparticles (AuNPs) are highlighted due to their low toxicity, compatibility with the human body, high surface area to volume ratio, and surfaces that can be easily modified with ligands. Biosynthesis of AuNPs using plant extract is considered a simple, low-cost, and eco-friendly approach. Brazilian Red Propolis (BRP), a product of bees, exhibits anti-inflammatory, anti-tumor, antioxidant, and antimicrobial activities. Here, we described the biosynthesis of AuNPs using BRP extract (AuNPextract) and its fractions (AuNPhexane, AuNPdichloromethane, AuNPethyl acetate) and evaluated their structural properties and their potential against microorganisms and cancer cells. AuNPs showed a surface plasmon resonance (SPR) band at 535 nm. The sizes and morphologies were influenced by the BRP sample used in the reaction. FTIR and TGA revealed the involvement of bioactive compounds from BRP extract or its fractions in the synthesis and stabilization of AuNPs. AuNPdichloromethane and AuNPhexane exhibited antimicrobial activities against all strains tested, showing their efficacy as antimicrobial agents to treat infectious diseases. AuNPs showed dose-dependent cytotoxic activity both in T24 and PC-3 cells. AuNPdichloromethane and AuNPextract exhibited the highest in vitro cytotoxic effect. Also, the cytotoxicity of biogenic nanoparticles was induced by mechanisms associated with apoptosis. The results highlight a potential low-cost green method using Brazilian red propolis to synthesize AuNPs, which demonstrated significant biological properties.

Characterization of an Alginate Encapsulated LS180 Spheroid Model for Anti-colorectal Cancer Compound Screening

Colorectal cancer is one of the leading causes of cancer-related deaths. A main problem for its treatment is resistance to chemotherapy, requiring the development of new drugs. The success rate of new candidate cancer drugs in clinical trials remains dismal. Three-dimensional (3D) cell culture models have been proposed to bridge the current gap between in vitro chemotherapeutic studies and the human in vivo, due to shortcomings in the physiological relevance of the commonly used two-dimensional cell culture models. In this study, LS180 colorectal cancer cells were cultured as 3D sodium alginate encapsulated spheroids in clinostat bioreactors. Growth and viability were evaluated for 20 days to determine the ideal experimental window. The 3- (4,5- dimethylthiazol- 2- yl)-2,5-diphenyltetrazolium bromide assay was then used to establish half maximal inhibitory concentrations for the standard chemotherapeutic drug, paclitaxel. This concentration was used to further evaluate the established 3D model. During model characterization and evaluation soluble protein content, intracellular adenosine triphosphate levels, extracellular adenylate kinase, glucose consumption, and P-glycoprotein (P-gp) gene expression were measured. Use of the model for chemotherapeutic treatment screening was evaluated using two concentrations of paclitaxel, and treatment continued for 96 h. Paclitaxel caused a decrease in cell growth, viability, and glucose consumption in the model. Furthermore, relative expression of P-gp increased compared to the untreated control group. This is a typical resistance-producing change, seen in vivo and known to be a result of paclitaxel treatment. It was concluded that the LS180 sodium alginate encapsulated spheroid model could be used for testing new chemotherapeutic compounds for colorectal cancer.

Gold quantum dots impair the tumorigenic potential of glioma stem-like cells via β-catenin downregulation in vitro

BACKGROUND

Over the past several decades, the incidence of solid cancers has rapidly increased worldwide. Successful removal of tumor-initiating cells within tumors is essential in the field of cancer therapeutics to improve patient disease-free survival rates. The biocompatible multivarient-sized gold nanoparticles (MVS-GNPs) from quantum dots (QDs, <10 nm) to nanosized (up to 50 nm) particles have vast applications in various biomedical areas including cancer treatment. The role of MVS-GNPs for inhibition of tumorigenic potential and stemness of glioma was investigated in this study.

METHODS

Herein, MVS-GNPs synthesized and characterized by means of X-ray diffraction pattern (XRD) and transmission electron microscopy (TEM) techniques. Afterwards, interaction of these GNPs with glioma stem-cell like cells along with cancer cells were evaluated by MTT, cell motility, self-renewal assays and biostatistics was also applied.

RESULTS

Among these GNPs, G-QDs contributed to reduce metastatic events and spheroid cell growth, potentially blocking the self-renewal ability of these cells. This study also uncovers the previously unknown role of the inhibition of CTNNB1 signaling as a novel candidate to decrease the tumorigenesis of glioma spheroids and subsequent spheroid growth. The accurate and precise biostatistics results were obtained at quantify level.

CONCLUSION

In summary, G-QDs may exhibit possible contribution on suppressing the growth of tumor-initiating cells. These data reveal a unique therapeutic approach for the elimination of residual resistant stem-like cells during cancer treatment.

Prediction of individual response to anticancer therapy: historical and future perspectives

Since the introduction of chemotherapy for cancer treatment in the early 20th century considerable efforts have been made to maximize drug efficiency and at the same time minimize side effects. As there is a great interpatient variability in response to chemotherapy, the development of predictive biomarkers is an ambitious aim for the rapidly growing research area of personalized molecular medicine. The individual prediction of response will improve treatment and thus increase survival and life quality of patients. In the past, cell cultures were used as in vitro models to predict in vivo response to chemotherapy. Several in vitro chemosensitivity assays served as tools to measure miscellaneous endpoints such as DNA damage, apoptosis and cytotoxicity or growth inhibition. Twenty years ago, the development of high-throughput technologies, e.g. cDNA microarrays enabled a more detailed analysis of drug responses. Thousands of genes were screened and expression levels were correlated to drug responses. In addition, mutation analysis became more and more important for the prediction of therapeutic success. Today, as research enters the area of -omics technologies, identification of signaling pathways is a tool to understand molecular mechanism underlying drug resistance. Combining new tissue models, e.g. 3D organoid cultures with modern technologies for biomarker discovery will offer new opportunities to identify new drug targets and in parallel predict individual responses to anticancer therapy. In this review, we present different currently used chemosensitivity assays including 2D and 3D cell culture models and several -omics approaches for the discovery of predictive biomarkers. Furthermore, we discuss the potential of these assays and biomarkers to predict the clinical outcome of individual patients and future perspectives.

Purinergic signalling and cancer

Receptors for extracellular nucleotides are widely expressed by mammalian cells. They mediate a large array of responses ranging from growth stimulation to apoptosis, from chemotaxis to cell differentiation and from nociception to cytokine release, as well as neurotransmission. Pharma industry is involved in the development and clinical testing of drugs selectively targeting the different P1 nucleoside and P2 nucleotide receptor subtypes. As described in detail in the present review, P2 receptors are expressed by all tumours, in some cases to a very high level. Activation or inhibition of selected P2 receptor subtypes brings about cancer cell death or growth inhibition. The field has been largely neglected by current research in oncology, yet the evidence presented in this review, most of which is based on in vitro studies, although with a limited amount from in vivo experiments and human studies, warrants further efforts to explore the therapeutic potential of purinoceptor targeting in cancer.

PARP-1 inhibition induces a late increase in the level of reactive oxygen species in cells after ionizing radiation

Poly(ADP-ribose) polymerase 1 (PARP1), an enzyme activated by DNA strand breaks, synthesizes polymers of poly(ADP-ribose) (PAR) that modify chromatin and other proteins and play a role in DNA repair. Inhibition of PARP1 activity is considered a potentially important strategy in clinical practice, especially to sensitize tumor cells to chemo- and radio-therapy. Here we examined the influence of inhibition of PARP1 on formation of reactive oxygen species (ROS) and on DNA repair in cells exposed to ionizing radiation (IR). K562 (human myelogenous leukaemia) cells were grown and exposed to 4 or 12 Gy of ionizing radiation in presence or absence of the PARP inhibitor NU1025 (100 μM). Intracellular ROS were assayed using the probe 2,7-dichlorofluorescein with detection by flow cytometry and the rejoining of DNA strand breaks were followed by alkaline single cell gel electrophoresis (comet) assays. In untreated cells a significant increase in PAR formation occurred during the first 5 min after IR, followed by a gradual decrease up to 30 min. Addition of a PARP inhibitor arrested the production of PAR almost completely and decreased the rate of rejoining of DNA strand breaks significantly; however, 3h after irradiation we observed no difference in the amount of DNA strand breaks between PARP inhibitor-treated and untreated cells. Twelve to 48 h after irradiation, an increase of ROS concentration was observed in irradiated cells and ROS levels in PARP inhibitor-treated cells were significantly higher than in cells without inhibitor. Irradiated cells grown in the presence or absence of PARP inhibitor did not differ in the frequencies of apoptotic and necrotic cells or in the activity of caspases at 24, 48 and 72 h after irradiation. Poly(ADP-ribosylation) and inhibition of PARP1 appeared to modulate DNA strand break rejoining and influence the concentration of ROS in irradiated cells.

Cross-disciplinary approaches for measuring parasitic helminth viability and phenotype

Parasitic worms (helminths) within the Phyla Nematoda and Platyhelminthes are responsible for some of the most debilitating and chronic infectious diseases of human and animal populations across the globe. As no subunit vaccine for any parasitic helminth is close to being developed, the frontline strategy for intervention is administration of therapeutic, anthelmintic drugs. Worryingly, and unsurprising due to co-evolutionary mechanisms, many of these worms are developing resistance to the limited compound classes currently being used. This unfortunate reality has led to a renaissance in next generation anthelmintic discovery within both academic and industrial sectors. However, a major bottleneck in this process is the lack of quantitative methods for screening large numbers of small molecules for their effects on the whole organism. Development of methodologies that can objectively and rapidly distinguish helminth viability or phenotype would be an invaluable tool in the anthelmintic discovery pipeline. Towards this end, we describe how several basic techniques currently used to assess single cell eukaryote viability have been successfully applied to parasitic helminths. We additionally demonstrate how some of these methodologies have been adopted for high-throughput use and further modified for assessing worm phenotype. Continued development in this area is aimed at increasing the rate by which novel anthelmintics are identified and subsequently translated into everyday, practical applications.

Human glioma demonstrates cell line specific results with ATP-based chemiluminescent cellular proliferation assays

Alteration of tumor cell growth kinetics is the goal of nearly all current or proposed therapies for human neoplasms. The adenosine triphosphate (ATP) chemiluminescent assay has been used for some time as a surrogate marker of in vitro cell growth. Here we present data showing that three human glioblastoma cell lines (U87, U251, G55) demonstrate significantly different cell number to luminescence relationships when subjected to this assay. We plated progressively increasing numbers of cells per well; from 1000 to 50,000 were grown in Dulbecco's modified Eagle's medium without serum and cultured for 6 hours. Cells were then lysed and subjected to the chemiluminescent assay to measure ATP levels and a linear relationship between cell number and measured luminescence was found. Despite this, we found that the slope of the regression line (β) varied markedly between different cell lines (U251 [β = 0.968 ± 0.3] vs. U87 [β = 0.772 ± 0.2] vs. G55 [β = 0.757 ± 0.2]; p < 0.0001), suggesting a difference in ATP luminescence per cell between these cell lines. Thus, we have demonstrated that luminescence values are internally linear within a given cell population, but luminescence level per cell varies significantly between different glioma cell lines. Our findings suggest that different glioma cell lines have unique levels of ATP per cell.

In vitro chemosensitivity testing of hematological cancer patients: detection of ornithine decarboxylase

The development of reliable methods for the in vitro testing of sensitivity of cancer cells to various drugs has been a longstanding objective in cancer research and treatment Early attempts to develop individualized chemotherapy were based on clonogenic assays. These attempts failed because of low plating efficiencies. Nonclonogenic assays, such as the MMT test or ATP determinations, are based on metabolic activities and do not reflect the ability of cells to proliferate. To detect proliferation, we selected a universal marker--ornithine decarboxylase (ODC), which is expressed early in the cell cycle and has a short half-life. This marker was detected in hematological cancer cells by quantitative immunohistochemical analyses using an ODC antibody and a FITC-linked second antibody. Drug resistance was detected in five patients, who subsequently died. Lymphocytes from normal individuals were sensitive to all drugs tested, whereas 33 leukemia and lymphoma patients showed different sensitivities to certain drugs. The method also permitted testing of the effect of new drugs on the proliferation of lymphocytes from hematological cancer patients. This test is sensitive, and 100-1,000 cells are required per assay, which can be completed within 2 days. It is very likely that the assay could also be used to test solid tumor patients.

Predictive value of the ATP chemosensitivity assay in epithelial ovarian cancer

OBJECTIVE

The aims of this study were to define the specific parameters of the ATP chemosensitivity assay which most accurately predict a patient's clinical response to chemotherapeutic agents in epithelial ovarian cancer and to assess the clinical utility of the ATP assay.

METHODS

In our laboratory from 1992 to 1994, fresh tumor specimens from patients with epithelial ovarian carcinomas were assayed with the ATP chemosensitivity assay (ATP-CSA) for their in vitro responses to several chemotherapeutic agents including cisplatin, paclitaxel, and cyclophosphamide. Clinical data on 161 of those patients including all follow-up assessments were then collected, and an investigator blinded to the in vitro assay results determined the patients' responses to chemotherapy. In order to determine which parameter of the assay was the best predictor of clinical response for each drug, receiver-operator characteristic (ROC) curves were constructed for several parameters, including the amount of cell kill at particular dosage levels of drug, the slope of the dose-response curve, and the IC50, or the average concentration of drug at which 50% of the cells were nonviable.

RESULTS

The specific parameter of the ATP-CSA which was most predictive of clinical response differed for each drug tested. The resulting positive predictive values for cisplatin, cyclophosphamide, and paclitaxel ranged from 70.0 to 78.3% and negative predictive values from 46.2 to 60.9%, with overall ATP-CSA positive and negative predictive values of 83.0 and 56.5%. Overall, patients whose tumors tested sensitive to an agent in vitro were almost twice as likely (83% versus 43%) to show a clinical response (RR 1.91, 95% CI 1.34-2.71).

CONCLUSION

Analysis of the ROC curves in this study shows that different parameters of the ATP-CSA need to be utilized for each drug tested in order to give the best prediction of clinical chemosensitivity. Although the ATP-CSA shows predictive ability, routine use of the ATP-CSA for clinical selection of drug therapy in patients with epithelial ovarian cancer would not be warranted without a prospective study comparing chemotherapy treatment based on assay results versus clinician selection of drug.

Anti-neoplastic activity of topotecan versus cisplatin, etoposide and paclitaxel in four squamous cell cancer cell lines of the female genital tract using an ATP-Tumor Chemosensitivity Assay

We evaluated the in vitro cytotoxicity of topotecan (TPT), versus cisplatin, etoposide (VP-16) and paclitaxel (PTX) in four squamous cell cancer cell lines of the cervix uteri and vulva. Four established human squamous cancer cell lines from the cervix uteri (A-431, Ca Ski and C-33) and vulva (CAL-39) were used. The cytotoxic effects of the agents were examined using the ATP-Tumor Chemosensitivity Assay (ATP-TCA). In addition to the single agents, the following combinations were tested: TPT+cisplatin, TPT+VP-16 and TPT+PTX. Three cell lines (C-33, Ca Ski and CAL-39) were highly sensitive to TPT, but one cell line (A-431) was less sensitive. Furthermore, the cytotoxic activity of TPT was superior to that of cisplatin in Ca Ski and C-33 cells, but inferior in CAL-39 and A-431. TPT was also more active than VP-16 in CAL-39 and Ca Ski. On the other hand, the cytotoxic activity of TPT was weaker than PTX in C-33, CAL-39 and A-431. TPT increased the cytotoxic activity of cisplatin and VP-16 in C-33, Ca Ski and A-431. However, synergistic features were observed only in A-431 cells. TPT also enhanced the cytotoxic activity of PTX in A-431 and Ca Ski. In CAL-39 and C-33, however, increased cytotoxic activity occurred only at higher drug concentrations, whereas antagonism was observed at lower drug concentrations. In conclusion, our results suggest that TPT has a significant cytotoxic effect on most squamous cell cancer cell lines which may be superior to cisplatin, VP-16 and PTX in some instances. Furthermore, TPT is likely to potentiate the cytotoxic activity of these agents in individual cell lines tested.

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.

Assessment of effect of photosensitizers on cytotoxicity of photodynamic therapy in human breast cancer cell cultures

BACKGROUND

Photodynamic therapy (PDT) might be of clinical value for patients with breast cancer with local recurrences or metastasis. However, there is a need for improved photosensitizers that are effective in combination with laser light and have few, if any, side-effects. We evaluated in vitro the effectiveness of a second generation photosensitizer by testing the influence of laser light on cell cultures of a human breast carcinoma cell line, incubated with meta-tetrahydroxyphenylchlorin (m-THPC) (= Temoporfin).

EXPERIMENTAL DESIGN

Five thousand MCF-7 cells were plated in 96-well plates. Forty-eight hours before laser treatment, the cells were plated to achieve a monolayer configuration. Twenty-four hours after plating, they were incubated with m-THPC. On day 6 after treatment with m-THPC we lysed the cells to extract the intracellular ATP that correlates with the number of living cells. The ATP-CVA was used to assess the cytotoxicity of the tested photosensitizer m-THPC at various concentrations and the relevant laser light alone prior to their combination after six days of culture.

RESULTS

We found a dose-response for m-THPC alone ranging from 2 to 16 micrograms/ml. The calculated inhibition concentration to produce 50% cell kill (IC50) was 4.55 micrograms/ml. We also observed a very low cytotoxicity for laser irradiation alone but a very strong cell kill for the combination of m-THPC together with laser light.

CONCLUSIONS

PDT gave almost total cell kill at m-THPC concentrations that are not toxic in vitro.

Use of an ATP bioluminescent assay to evaluate viability of Pneumocystis carinii from rats

A bioluminescent assay which employs the luciferin-luciferase ATP-dependent reaction was used to evaluate the viability of populations of Pneumocystis carinii derived from infected rat lungs. Contamination with host cells was reduced by a purification method which involved a combination of low- and high-speed centrifugations resulting in a 1,000-fold reduction of the rat cells while enriching for the trophic form of P. carinii. A linear correlation for the number of P. carinii nuclei versus the amount of ATP was observed. The ATP content of the organism populations could be maintained at inoculum levels for one week, although the number of organisms did not increase. Addition of respiratory chain inhibitors dramatically decreased the ATP content of the P. carinii after 24 h of incubation, with the exception of the antibiotic oligomycin B. Low concentrations of trimethoprim-sulfamethoxazole and pentamidine isethionate reduced the organism ATP content by over 50% after 24 h of exposure, while no effect was observed with 100-fold greater concentrations of ampicillin. The bioluminescent assay was found to be a more sensitive indicator of viability than a dual fluorescent staining technique. This assay does not require replication of P. carinii and should be a useful method for in vitro drug screening and viability assessment of P. carinii populations.

Characteristics of the combination paclitaxel plus doxorubicin in breast cancer cell lines analyzed with the ATP-cell viability assay

Preliminary clinical data show promising activity regarding the combination of paclitaxel (Taxol) (TAX) and doxorubicin (Adriamycin) (ADR) in the treatment of breast cancer. This combination needs both further preclinical and clinical investigations to better understand the drug interaction, and to optimize the dose and schedule of these drugs. This study was done to evaluate the combination effect of TAX and ADR in three human breast cancer cell lines. The ATP-Cell-Viability Assay was used to evaluate the chemosensitivity profiles and to obtain dose response curves. For quantitation of synergism and antagonism the median-effect principle was applied and the corresponding combination index values were calculated. Drug synergism/antagonism was shown to be dose-related; synergism was enhanced at higher fractions affected. From this preclinical data, we have concluded that TAX-ADR is highly effective and partly synergistic in vitro. In spite of severe initial toxicities in early clinical trials in metastatic breast cancer patients, further clinical studies appear to be justified in order to define a tolerable dosage.

Prediction of response to drug therapy of cancer. A review of in vitro assays

Cancer chemotherapy has witnessed a great deal of progress since the introduction of the nitrogen mustards in the 1940s. Unfortunately, individual patients with apparently identical tumour histologies do not always respond identically to the same drug regimen. Determining the sensitivity and resistance of an organism before treatment has been the standard of care in infectious diseases for many years, while in oncology treatment has been initiated according to tumour histology rather than the tumour's sensitivity to a given agent. Attempts to individualise therapy have been the goal of oncologists since the 1950s. Since that time a number of in vitro assays have been developed to predict therapeutic outcome prior to the start of therapy. In the 1970s, with the introduction of the human tumour stem cell assay, it was generally believed that oncology was on the threshold of entering an era of predictive in vitro chemosensitivity testing. Unfortunately, this assay was shown to have a number of technical drawbacks including the low plating efficiencies of many primary tumour samples which thus limits the percentage which can be evaluated, leaving us still at this threshold today. Several recent developments, such as the Kern assay, which measures inhibition of radioactive precursors into tumour cells in the presence of antineoplastic agents, ATP bioluminescence assays, and the fluorescent cytoprint assay offer the promise of rapid and sensitive results. Other assays, such as the tetrazolium-based MTT and the sulphorhodamine blue assay appear to hold more promise in the screening and evaluation of potential new agents in established tumour cell lines than for evaluating chemosensitivity of clinical specimens. However, before a particular assay can be considered as an in vitro test of chemosensitivity or resistance, controlled prospective studies must be carried out to validate the assay in a number of different tumour types.

Chemical enhancement of cisplatin cytotoxicity in a human ovarian and cervical cancer cell line

While many advances have been made in the chemotherapy of gynecologic cancers, treatment failures remain a major clinical problem. A growing understanding of the mechanisms of tumor cell resistance to antineoplastic drugs provides a framework for the development of chemotherapy regimens containing agents capable of modulating tumor response. Using a short-term ATP bioluminescence assay we studied the ability of two methylxanthines (caffeine, pentoxifylline) and an inhibitor of ADP-ribosyl transferase (3-aminobenzamide) to enhance cisplatin cytotoxicity in gynecologic cancer cell lines. Our findings of significantly enhanced cisplatin-induced cytotoxicity with two different analysis techniques confirms the effectiveness of these agents. These results may have future clinical significance.

Scoring of Cytotoxicity by Image Analysis using Animal Cell Cultures

The estimation and assessment of toxic effects can be made clearer by direct observation of the target object — the living cell. Following this approach we continuously assess the reactions of cell cultures (at a range of densities) by using image analysis equipment. The parameters evaluated are: growth rate, alteration of cell cycle time, cell progeny, and mortality rate. The use of multi-well culture plates during the observation period enables the effects of different agents at different concentrations to be examined simultaneously under the same experimental conditions. The automatic observation of the fate of many individual cells permits the accurate quantification and characterisation of cytotoxic effects for the exposed cells and their progeny. Using this method, we have examined ethyl methanesulfonate (EMS), cetyltrimethyl-ammonium chloride (CTAC), and Na-aciclovir (NaA), and we demonstrate the distinction between reversible and irreversible cell damage.

The flavonoid tangeretin inhibits invasion of MO4 mouse cells into embryonic chick heart in vitro

Tangeretin, a flavonoid from citrus plants, was found to inhibit the invasion of MO4 cells (Kirsten murine sarcoma virus transformed fetal mouse cells) into embryonic chick heart fragments in vitro. The flavonoid appeared to be chemically stable in tissue culture medium, and the anti-invasive effect was reversible on omission of the molecule from the medium. Unlike (+)-catechin, another anti-invasive flavonoid, tangeretin bound poorly to extracellular matrix. It did not alter fucosylated surface glycopeptides of MO4 cells. Tangeretin seemed not to act as a microtubule inhibitor, as immunocytochemistry revealed no disturbance of the cytoplasmic microtubule complex. However, at anti-invasive concentrations of tangeretin, cell proliferation and thymidine incorporation appeared to be inhibited. When cultured on an artificial substrate, treated MO4 cells were less elongated, covered a larger surface area and exhibited a slower directional migration than untreated cells. From the decrease in ATP content in MO4 cells after tangeretin treatment, we deduce that this flavonoid inhibits a number of intracellular processes, which leads to an inhibition of cell motility and hence of invasion.

Application of an ATP-bioluminescence assay in human tumor chemosensitivity testing

Intracellular adenosine triphosphate (ATP) is the primary energy unit of living cells, and can be quantitated by measuring the light generated with luciferase-luciferin reagent in a luminometer. The use of an ATP-bioluminescence assay, to determine tumor cell viability after exposure to chemotherapeutic agents, has been adapted to test tumor chemosensitivity in vitro. This presentation will illustrate the method of the ATP-chemosensitivity assay (ATP-CSA) using an ovarian cancer cell line NIHL:OVCAR-3 as an example and present preliminary data on 54/56 successful in vitro ATP-CSA's from 46 patients with pelvic malignancies. Fresh human tumor specimens were generally tested for single and combined drug effects at two drug concentrations (0.2 X and 1 X peak plasma concentrations). Correlation of in vitro drug sensitivity and in vivo patient response was obtained for 23 treatment regimens in 22 patients with ovarian carcinoma. The true positive rate was 100% and the true negative rate 66.7%. Our data demonstrate (a) that the ATP-CSA, measuring total cell viability, is a feasible in vitro assay for human tumor drug testing and (b) that specific criteria of in vitro chemosensitivity for this assay need to be defined by further studies, for single and combined drug exposure at different concentrations, to permit a meaningful correlation with in vivo clinical response.