Comparison of cisplatin and carboplatin cytotoxicity in human ovarian cancer cell lines using the MTT assay

Single-Cell ICP-MS in Combination with Fluorescence-Activated Cell Sorting for Investigating the Effects of Nanotransported Cisplatin(IV) Prodrugs

The combined use of fluorescence-activated cell sorting (FACS) and single-cell inductively coupled plasma mass spectrometry (SC-ICP-MS) is reported, for the first time, in this work. It is applied to evaluate the differences between the cellular uptake of ultrasmall iron oxide nanoparticles (FeNPs) loaded with cisplatin(IV) prodrug (FeNPs-Pt(IV)) and cisplatin regarding cell viability. For this aim, FACS is applied to separate viable, apoptotic, and necrotic A2780 ovarian cancer cells after exposing them to the nanotransported prodrug and cisplatin, respectively. The different sorted cell populations are individually analyzed using quantitative SC-ICP-MS to address the intracellular amount of Pt. The highest Pt intracellular content occurs in the apoptotic cell population (about 2.1 fg Pt/cell) with a narrow intercellular distribution when using FeNPs-Pt(IV) nanoprodrug and containing the largest number of cells (75% of the total). In the case of the cisplatin-treated cells, the highest Pt content (about 1.6 fg Pt/cell) could be determined in the viable sorted cell population. The combined methodology, never explored before, permits a more accurate picture of the effect of the intracellular drug content together with the cell death mechanisms associated with the free drug and the nanotransported prodrug, respectively, and opens the door to many possible single-cell experiments in sorted cell populations.

Binding of Intracellular Myeloperoxidase to αV/β1 Integrin Serves as a Mechanism of Survival in Epithelial Ovarian Cancer

We were the first to report that epithelial ovarian cancer (EOC) cells and tissues express myeloperoxidase (MPO) that is known to play a role in immune surveillance and inflammation by myeloid cells. Additionally, we reported that MPO is colocalized with inducible nitric oxide synthase (iNOS), a key pro-oxidant enzyme, and plays a key role in regulating apoptosis in EOC cells. Whereas myeloid cells express MPO in a dimeric form, intriguingly, here we report the unique expression of only the monomeric form of MPO in EOC cells, tissues, and blood of an ovarian cancer patient. Additionally, we have identified a cell membrane receptor, αV/β1 integrin, that is uniquely expressed by both chemosensitive and chemoresistant EOC cells with significantly higher expression in chemoresistant EOC cells. More importantly, we have demonstrated that monoclonal antibodies against αV/β1 integrin induced cytotoxicity in EOC cells, but not in normal cells, that is also synergistic with conventional chemotherapies. Cytotoxicity of αV/β1 antibodies is due to conformational changes in αV/β1 integrin which prevents monomeric MPO binding to αV/β1 integrin inhibiting the activation of MPO, leading to increased apoptosis. Since normal epithelial cells and macrophages lack monomeric MPO and αV/β1 integrin system, targeting this unique MPO-dependent survival mechanism will selectively eliminate EOC cells and will be the target for developing specific ovarian cancer therapies.

Measurement of Cell Death in Mammalian Cells

Methods for assessing mammalian cell death are presented in this article, which is divided into six sections: (1) a brief overview of cytotoxicity and pathways of cell death; (2) a method to measure cell death using lactate dehydrogenase (LDH) release as a marker of membrane integrity; (3) a flow cytometry method that simultaneously measures two types of cell death, necrosis and apoptosis; (4) use of fluorescence microscopy and nuclear morphology to assess apoptosis and necrosis; (5) the use of multi-well plates and high-content analysis imaging systems to assess nuclear morphology; and (6) a discussion of the use of cytotoxicity assays to determine the mechanisms of cell death. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Measurement of plasma membrane integrity and viability using LDH release Basic Protocol 2: Measurement of necrosis and apoptosis using flow cytometry Basic Protocol 3: Determination of nuclear morphology and membrane integrity Alternate Protocol 1: Assessment of nuclear morphology and membrane integrity using DAPI and PI Alternate Protocol 2: Assessment of nuclear morphology using multi-well plates Basic Protocol 4: Measurement of time-dependent toxicity using cell death markers.

Association Between Dose and Duration of Cisplatin Exposure with Cytotoxicity Effect on Nasopharyngeal Carcinoma Stem Cell

Nasopharyngeal carcinoma (NPC) is ranked 6th of malignant tumors in Indonesia. To analyze the correlation of dose and duration of cisplatin exposure with cytotoxic effects on nasopharyngeal carcinoma stem cells. The biopsy NPC tissue was cultured and processed to obtain NPC stem cells to be treated with cisplatin different doses and durations (24 and 48 h). The number of dead cells after exposure will be calculated using a hemocytometer. Death stem cell density of NPC at exposure of 2 μg/ml cisplatin dose was 81.37%, while the smallest death cell density a dose of 0.05 μg/ml after a 72-h observation was 21.3%. The coefficient correlation 0.827 and value p = 0.000 (p < 0.05). The analysis of the correlation between cisplatin exposure duration and death cell was also significant with the correlation coefficient - 0.357 and the value p = 0.001 (p < 0.05). There was a correlation between the increased dose of cisplatin with the cytotoxicity effects on NPC stem cell.

Specific point mutations in key redox enzymes are associated with chemoresistance in epithelial ovarian cancer

Oxidative stress plays an important role in the pathophysiology of ovarian cancer. Resistance to chemotherapy presents a significant challenge for ovarian cancer treatment. Specific single nucleotide polymorphisms (SNPs) in key redox enzymes have been associated with ovarian cancer survival and progression. The objective of this study was to determine whether chemotherapy induces point mutations in key redox enzymes that lead to the acquisition of chemoresistance in epithelial ovarian cancer (EOC). Human EOC cell lines and their chemoresistant counterpart were utilized for this study. Specific SNPs in key redox enzymes were analyzed by TaqMan SNP Genotyping. Activities and levels of key redox enzymes were determined by real-time RT-PCR, ELISA and a greiss assay. Point mutations in key redox enzymes were introduced into sensitive EOC cells via the CRISPR/Cas9 system. Cell viability and IC₅₀ for cisplatin were determined by the MTT Cell Proliferation Assay. Data was analyzed with SPSS using Student's two-tailed t-tests and One-way ANOVA followed by Dunnett's or Tukey's post hoc tests, p<0.05. Here, we demonstrate that chemoresistant EOC cells are characterized by a further enhancement in oxidative stress as compared to sensitive counterparts. Additionally, chemoresistant EOC cells manifested specific point mutations, which are associated with altered enzymatic activity, in key redox enzymes that are not detected in sensitive counterparts. Supplementation of an antioxidant was able to successfully sensitize EOC cells to chemotherapeutics. Causality was established by the induction of these point mutations in sensitive EOC cells, which resulted in a significant increase in the level of chemoresistance. These findings indicate that chemotherapy induces specific point mutations in key redox enzymes that contribute to the acquisition of chemoresistance in EOC cells, highlighting a potential novel mechanism. Identification of targets for chemoresistance with either biomarker and/or screening potential will have a significant impact for the treatment of this disease.

Microenvironment mesenchymal cells protect ovarian cancer cell lines from apoptosis by inhibiting XIAP inactivation

Epithelial ovarian carcinoma is characterized by high frequency of recurrence (70% of patients) and carboplatin resistance acquisition. Carcinoma-associated mesenchymal stem cells (CA-MSC) have been shown to induce ovarian cancer chemoresistance through trogocytosis. Here we examined CA-MSC properties to protect ovarian cancer cells from carboplatin-induced apoptosis. Apoptosis was determined by Propidium Iodide and Annexin-V-FITC labelling and poly-ADP-ribose polymerase cleavage analysis. We showed a significant increase of inhibitory concentration 50 and a 30% decrease of carboplatin-induced apoptosis in ovarian cancer cells incubated in the presence of CA-MSC-conditioned medium (CM). A molecular analysis of apoptosis signalling pathway in response to carboplatin revealed that the presence of CA-MSC CM induced a 30% decrease of effector caspases-3 and -7 activation and proteolysis activity. CA-MSC secretions promoted Akt and X-linked inhibitor of apoptosis protein (XIAP; caspase inhibitor from inhibitor of apoptosis protein (IAP) family) phosphorylation. XIAP depletion by siRNA strategy permitted to restore apoptosis in ovarian cancer cells stimulated by CA-MSC CM. The factors secreted by CA-MSC are able to confer chemoresistance to carboplatin in ovarian cancer cells through the inhibition of effector caspases activation and apoptosis blockade. Activation of the phosphatidylinositol 3-kinase (PI3K)/Akt signalling pathway and the phosphorylation of its downstream target XIAP underlined the implication of this signalling pathway in ovarian cancer chemoresistance. This study reveals the potentialities of targeting XIAP in ovarian cancer therapy.

Measurement of cell death in mammalian cells

This unit presents methods used to assess cell death in mammalian cells. The unit is divided into five sections: (1) a brief overview of cytotoxicity and pathways of cell death, (2) an improved method to measure cell death using lactate dehydrogenase (LDH) release as a marker of membrane integrity, (3) a flow cytometry method that simultaneously measures two types of cell death, oncosis and apoptosis, (4) use of nuclear morphology to assess apoptosis and oncosis, and (5) a brief discussion of the use of cytotoxicity assays to determine the mechanisms of cell death.

URI is an oncogene amplified in ovarian cancer cells and is required for their survival

Abrogation of negative feedback control represents a fundamental requirement for aberrantly activated signaling pathways to promote malignant transformation and resistance to therapy. Here we identify URI, which encodes a mitochondrial inhibitor of PP1γ and PP1γ-mediated feedback inhibition of S6K1-BAD survival signaling, as an oncogene amplified and overexpressed in ovarian cancer cell lines and human ovarian carcinomas. URI is an "addicting" oncogene selectively required for the survival of ovarian cancer cells with increased URI copy number. By constitutively detaining PP1γ in inactive complexes, URI sustains S6K1 survival signaling under growth factor-limiting conditions and mediates resistance of cells to cisplatin. Thus, oncogenic activation of URI defines an important mechanism for activating mitochondrial S6K1-BAD signaling and promoting cell survival through disabling PP1γ-dependent negative feedback inhibition.

DNA damage induced by cis- and carboplatin as indicator for in vitro sensitivity of ovarian carcinoma cells

Background

The DNA damage by platinum cytostatics is thought to be the main cause of their cytotoxicity. Therefore the measurement of the DNA damage induced by cis- and carboplatin should reflect the sensitivity of cancer cells toward the platinum chemotherapeutics.

Methods

DNA damage induced by cis- and carboplatin in primary cells of ovarian carcinomas was determined by the alkaline comet assay. In parallel, the reduction of cell viability was measured by the fluorescein diacetate (FDA) hydrolysis assay.

Results

While in the comet assay the isolated cells showed a high degree of DNA damage after a 24 h treatment, cell viability revealed no cytotoxicity after that incubation time. The individual sensitivities to DNA damage of 12 tumour biopsies differed up to a factor of about 3. DNA damage after a one day treatment with cis- or carboplatin correlated well with the cytotoxic effects after a 7 day treatment (r = 0,942 for cisplatin r = 0.971 for carboplatin). In contrast to the platinum compounds the correlation of DNA damage and cytotoxicity induced by adriamycin was low (r = 0,692), or did not exist for gemcitabine.

Conclusion

The measurement of DNA damage induced by cis- and carboplatin is an accurate method to determine the in vitro chemosensitivity of ovarian cancer cells towards these cytostatics, because of its quickness, sensitivity, and low cell number needed.

Erythropoietin treatment of human ovarian cancer cells results in enhanced signaling and a paclitaxel-resistant phenotype

Erythropoietin (Epo), a glycoprotein hormone that is the principal regulator of erythropoiesis, is known to act also on nonhematopoietic cell types. Epo receptors have been reported on several normal and neoplastic human cells and tissues, including ovarian cancer cells. We found that long-term Epo treatment of A2780 cells resulted in the development of a phenotype exhibiting both enhanced Epo signaling, evidenced by increased peak levels of phospho-Erk1/2 and increased paclitaxel resistance. This phenotypic effect was specific for paclitaxel, since no change in cisplatin or carboplatin sensitivity was observed. In addition, the change in phenotype was stable, even after the removal of Epo. Measurement of mono- and oligonucleosome formation revealed that long-term Epo treated A2780 cells exhibited markedly less apoptosis than nonerythropoietin treated cells at essentially all concentrations of paclitaxel tested. Western blot analyses revealed that the long-term Epo treated cells had significantly reduced expression of apoptosis-related proteins Bcl-2 and Bcl-10. These findings may have implications for the clinical use of recombinant human Epo and other erythropoiesis stimulating agents to correct anemia in paclitaxel-treated cancer patients.

Characterization of erythropoietin receptor and erythropoietin expression and function in human ovarian cancer cells

The identification of erythropoietin receptors (EpoR) on cancer cells has caused concern, since it implies the possibility that treatment of cancer patients with erythropoietin (Epo) and related agents with demonstrable antiapoptotic activity could enhance cancer growth and progression. However, the function and even the validity of the identification of these receptors have been called into question. We now report the characterization of EpoR and Epo expression by 4 human ovarian cancer cell lines: A2780, CaOV, SKOV and OVCAR-3. Using semiquantitative RT-PCR, restriction digestion of the PCR products and DNA sequence analysis, we determined that each of the lines expresses the EpoR and Epo at the mRNA level. A2780 cells were the highest expressers of both genes. We demonstrated EpoR protein both by western blotting and by immunofluorescence and biologically active Epo protein by quantitative in vitro bioassay. The EpoR on A2780 cells was shown to be functional, since Epo stimulation resulted in phosphorylation of Erk1/2, an important EpoR mitogenic signaling intermediate. None of the cell lines exhibited a growth response in culture to exogenous Epo. However, addition of a neutralizing anti-Epo antibody to A2780 cells resulted in partial growth inhibition that was reversed by the addition of excess Epo, providing evidence for an autocrine/paracrine mechanism of growth enhancement in these cells.

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.

Apoptosis-based evaluation of chemosensitivity in ovarian cancer patients

OBJECTIVE

Induction of apoptosis in target cells is a key mechanism by which chemotherapy induces cell killing. We have established an in vitro system for determining the chemosensitivity of epithelial ovarian cancer cells to carboplatin and paclitaxel (Taxol). Practical assays to predict the likelihood of individual tumor sensitivity are needed to facilitate the choice of adequate treatment. We sought to determine whether epithelial ovarian cancer cells (EOC) collected from the ascites fluid of patients known to be clinically chemosensitive or chemoresistant to carboplatin and paclitaxel would show a similar response to chemotherapeutic drugs after in vitro treatment.

METHODS

Thirteen patients with stage III and IV ovarian cancer treated with carboplatin and paclitaxel were studied. Caspase-3 activation was used as a surrogate marker for activation of chemotherapy-induced programmed cell death. We compared the in vitro apoptotic response to the clinical response of the patients from whom the tumor cells were isolated. Clinical sensitivity was defined as no evidence of disease recurrence for 6 months after optimal debulking surgery and completion of chemotherapy.

RESULTS

Of seven chemosensitive patients, five cell samples treated in vitro had increased caspase-3 activity in response to both carboplatin and paclitaxel. Five of six chemoresistant cases did not show caspase-3 activity in response to only one or to neither agent.

CONCLUSION

Quantifiable markers of apoptosis such as caspase-3 activation have the potential to predict the clinical response to chemotherapy. Application of this assay in clinical laboratories could optimize the potential for efficient treatment and avoid the toxicities of ineffective drugs.

Pre-treatment mitotic index versus computer-quantitated Ki-67 nuclear antigen labeling index as predictors of response to neoadjuvant chemotherapy in uterine cervical carcinoma

In order to evaluate the usefulness of the mitotic index (MI) and the Ki-67 nuclear antigen labeling index (Ki67LI) in pre-treatment biopsy specimens as predictors of response to chemotherapy for uterine cervical carcinomas, twelve patients with squamous cell carcinoma who received neoadjuvant chemotherapy before radical surgery were investigated. The MI and computer-quantitated Ki67LI were determined using H&E and immunostained slides of biopsy specimens collected before chemotherapy. Tumor size was measured three-dimensionally by MR imaging, and assessed before and after chemotherapy. We compared the values of MI and Ki67LI with changes in tumor size and the following results were obtained. 1) The percentage reduction in tumor size ranged from 0 to 98%. The MI ranged from 0.5 to 15, and Ki67LI ranged from 0.01 to 50.1%. 2) A significant positive correlation was observed between response to chemotherapy assessed on MR image and MI [Spearman's correlation coefficient (r) =0.66, n=12, p=0.027], and between response to chemotherapy and Ki67LI (r=0.72, n=12, p=0.017). 3) A significant correlation was observed between MI and computer-assessed Ki67 LI [Pearson's correlation coefficient (r) =0.80, n=12, p=0.002]. Therefore, pre-chemotherapy MI and Ki67LI were both good predictors of response to platinum-based chemotherapy. Because MI is technically more convenient and economically less expensive than computer-quantitated Ki67LI, MI remains a simple and reliable predictor from the clinical point of view.

Establishment of new ovarian and colon carcinoma cell lines: differentiation is only possible by cytokeratin analysis

Two human ovarian (OV-MZ-10, OV-MZ-15) and two colon cancer cell lines (CO-MZ-5, CO-MZ-6) were newly established in permanent cell culture. These cell lines have been maintained in vitro for 5-6 years, the passage number varying from 25 to 228. They were established from ascites or solid tumours at the time of primary surgery. By clinical and histopathological judgement alone all four cell lines would have been interpreted as ovarian cancer cell lines. Morphological criteria or the expression of the tumour-associated antigens CA-125 and CEA allowed no differential diagnosis. Only the analysis of the expression of different cytokeratins and vimentin enabled us to verify the different origin of the cell lines. Ovarian cancer cell lines, in contrast to the colon cancer cell lines, are positive for the expression of cytokeratin (CK) 7 and for vimentin. CK 20 proved to be the marker with the best discrimination. CK 20 was found exclusively in the colon carcinoma cell lines, but not in the ovarian carcinoma cell lines. The evaluation of cytokeratin expression is a helpful diagnostic modality in differentiating between adenocarcinoma cell lines derived from ovarian and colon tumours.

Comparative evaluation of cisplatin and carboplatin sensitivity in endometrial adenocarcinoma cell lines

Platinum analogues are frequently used in the treatment of advanced or recurrent endometrial cancer. To study the sensitivity of endometrial cancer to cisplatin and carboplatin, we tested two long-established (RL95-2, KLE) and six new cell lines (UM-EC-1, UM-EC-2, UM-EC-3, UT-EC-2A, UT-EC-2B, UT-EC-3) using the 96-well-plate clonogenic assay. This assay has proven to be suitable for testing chemosensitivity of both adenocarcinoma and squamous cell carcinoma. The chemosensitivity was expressed as an IC50 value, the drug concentration causing 50% inhibition of clonogenic survival. IC50 values were obtained from dose-response curves after fitting the data by the linear quadratic equation, F = exp[-(alpha D + beta D2)]. The IC50 values of the two platinum derivatives varied considerably. The values for cisplatin varied between 0.022 microgram ml-1 and 0.56 microgram ml-1 and the corresponding values for carboplatin were 0.096-1.20 microgram ml-1. The range of the ratios between carboplatin IC50 and cisplatin IC50, from 1.5:1 to 4.4:1, was rather narrow. However, no constant ratio between carboplatin IC50 and cisplatin IC50 could be detected. The equivalent doses with regard to efficacy of these two platinum analogues remain to be determined.

Bullatacin--in vivo and in vitro experience in an ovarian cancer model

The cytotoxicity and antitumor effects of the acetogenin Bullatacin were evaluated in vitro in multiple ovarian cancer cell lines and in vivo in a murine ovarian teratocarcinoma (MOT) model in C3HeB/FeJ mice. The in vitro cytotoxicity of Bullatacin against four human ovarian epithelial tumor cell lines (OC-194, OC-222, OVCAR-3, and A-2780) was assessed in 48- and 72-h tetrazolium-dye (MTT) cytotoxicity assays. The percentage of cytotoxicity was determined on the basis of the mean optical density of the respective untreated cells and the dose effective against 50% of the cells (ED50) was calculated for each cell line. In vivo experiments were performed on adult female C3HeB/FeJ mice, which were injected i.p. with 10(5) MOT cells and varying amounts of Bullatacin given either in a single dose or in 5 subsequent doses over 72 h. All mice were observed for survival relative to that of the control groups, which were injected either with 10(5) MOT cells with or without serial injections of vehicle or with vehicle only. All four epithelial ovarian cancer cell lines displayed sensitivity to Bullatacin. The relative cytotoxic effects were very heterogeneous, with the ED50 value ranging between 10(-7) micrograms/ml for OC-194 and 4 micrograms/ml for the cisplatin-resistant cell line OVCAR-3 in a 72-h MTT cytotoxicity assay. All mice that had been injected i.p. with 10(5) MOT cells and 1.4 mg/kg or more of Bullatacin died within the first 24 h after injection, whereas all mice that had received 600 micrograms/kg of Bullatacin or less survived equally as long as the controls that had been injected with MOT only (21.1 +/- 0.9 days). Mice that had received Bullatacin at a dose ranging from 600 micrograms/kg to 1.4 mg/kg either died during the 1st day postinjection or survived, but not longer than the MOT control group. Serial i.p. injections of Bullatacin again either led to death of the mice within 24-48 h of the last dose of Bullatacin or did not have any effect on the survival of the mice as compared with the respective control groups, which had been injected with the tumor and serial injections of vehicle (22.5 +/- 2.2 days). In summary, Bullatacin showed no effect on MOT-caused animal death in C3HeB/FeJ mice at nonlethal dose ranges, whether it was given as a single i.p. dose or serially over 72 h. In vitro, however, it proved to be a very potent cytotoxic agent in a variety of ovarian cancer cell lines.(ABSTRACT TRUNCATED AT 400 WORDS)

Chemosensitivity testing of human mouth carcinoma cell line

The chemosensitivity of KB cells derived from oral epidermal carcinoma to various antitumor agents was analyzed using the MTT[3-(4,5-dimethyl-2-thiazoyl)-2,5-diphenyl-2H tetrazolium bromide] assay. Optical density (OD) for MTT assay was measured with dual wavelengths. The chemosensitivity of the drugs was evaluated by the 50% OD (OD50) of each drug concentration in the control group. Five platinum (Pt) drugs and 3 anthracycline (AC) drugs were used in this study. The chemosensitivity differed among the 5 Pt drugs. No significant difference was observed among the 3 AC drugs. A linear increase in OD corresponding to an increase in number of cells was observed. When 0.1 M sodium succinate (S.S.) was added to 0.4% MTT, the sensitivity increased five-fold compared to the control group without S.S. The MTT assay is a precise, rapid, easy and inexpensive experimental system useful for evaluation of antitumor drug sensitivity on tumor cell lines.