Cell-cycle arrest, micronucleus formation, and cell death in growth inhibition of MCF-7 breast cancer cells by tamoxifen and cisplatin

Favipiravir, an antiviral drug, in combination with tamoxifen exerts synergistic effect in tamoxifen-resistant breast cancer cells via hTERT inhibition

Tamoxifen (TAM) is one of the most successful treatments for breast cancer; however, TAM resistance continues to be a significant barrier. TAM resistance has been reported to be associated with increased expression of human telomerase reverse transcriptase (hTERT). This enzyme shares structural similarity with RNA-dependent RNA polymerase (RdRp) enzyme of RNA viruses, suggesting that RdRp inhibitors may also inhibit hTERT. Favipiravir (FAV) is an antiviral drug that inhibits RdRp of RNA viruses. Thus, we propose that FAV may also elicit an antitumor effect by suppressing hTERT. This study aimed to investigate the effect of FAV and TAM on TAM-resistant breast cancer (TAMR-1). The cell viabilities were determined. The levels of CDK1/ hTERT, in addition to regulators of hTERT-targeted signaling pathways were measured. Apoptosis, migration, and cell cycle distribution were also determined. Our data revealed that the combination of TAM and FAV suppressed cell proliferation synergistically (CI < 1) and resulted in a significant change in cell migration and apoptosis. Indeed, this was associated with reduced levels of hTERT and CDK1 and shift in the cell cycle distribution. Our findings suggest that the TAM/FAV combination exhibits synergistic effects against TAMR-1 human breast cancer cells by targeting hTERT.

Small change - big consequence: The impact of C15-C16 double bond in a D‑ring of estrone on estrogen receptor activity

Estrogen receptor alpha (ER) is a key biomarker for breast cancer, and the presence or absence of ER in breast and other hormone-dependent cancers decides treatment regimens and patient prognosis. ER is activated after ligand binding - typically by steroid. 2682 steroid compounds were used in a molecular docking study to identify novel ligands for ER and to predict compounds that may show anticancer activity. The effect of the most promising compounds was determined by a novel luciferase reporter assay. Two compounds, 7 and 12, showing ER inhibitory activity comparable to clinical inhibitors such as tamoxifen or fulvestrant were selected. We propose that the inhibitory effect of compounds 7 and 12 on ER is related to the presence of a double bond in their D-ring, which may protect against ER activation by reducing the electron density of the keto group, or may undergo metabolism leading to an active compound. Western blotting revealed that compound 12 decreased the level of ER in the breast cancer cell line MCF7, which was associated with reduced expression of both isoforms of the progesterone receptor, a well-known downstream target of ER. However, compound 12 has a different mechanism of action from fulvestrant. Furthermore, we found that compound 12 interferes with mitochondrial functions, probably by disrupting the electron transport chain, leading to induction of the intrinsic apoptotic pathway even in ER-negative breast cancer cells. In conclusion, the combination of computational and experimental methods shown here represents a rapid approach to determine the activity of compounds towards ER. Our data will not only contribute to research focused on the regulation of ER activity but may also be useful for the further development of novel steroid receptor-targeted drugs applicable in clinical practice.

Tumor Cells Transmit Drug Resistance via Cisplatin-Induced Extracellular Vesicles

Cisplatin is a first-line clinical agent used for treating solid tumors. Cisplatin damages the DNA of tumor cells and induces the production of high levels of reactive oxygen species to achieve tumor killing. Tumor cells have evolved several ways to tolerate this damage. Extracellular vesicles (EVs) are an important mode of information transfer in tumor cells. EVs can be substantially activated under cisplatin treatment and mediate different responses of tumor cells under cisplatin treatment depending on their different cargoes. However, the mechanism of action of tumor-cell-derived EVs under cisplatin treatment and their potential cargoes are still unclear. This review considers recent advances in cisplatin-induced release of EVs from tumor cells, with the expectation of providing a new understanding of the mechanisms of cisplatin treatment and drug resistance, as well as strategies for the combined use of cisplatin and other drugs.

Synergistic Cytotoxicity between Elephantopus scaber and Tamoxifen on MCF-7-Derived Multicellular Tumor Spheroid

Elephantopus scaber Linn, a traditional herb, exhibited anticancer properties, and it was cytotoxic against the monolayer estrogen receptor-positive breast cancer cell line, MCF-7, in the previous study. In order to determine the potential of E. scaber as a complementary medicine for breast cancer, this study aimed to evaluate the synergism between E. scaber and tamoxifen in cytotoxicity using MCF-7 in the form of 3-dimensional multicellular tumor spheroid (MCTS) cultures. MCTS represents a more reliable model for studying drug penetration as compared to monolayer cells due to its greater resemblance to solid tumor. Combination of E. scaber ethanol extract and tamoxifen, which were used in concentrations lower than their respective IC₅₀ values, had successfully induced apoptosis on MCTS in this study. The combinatorial treatment showed >58% increase of lactate dehydrogenase release in cell media, cell cycle arrest at the S phase, and 1.3 fold increase in depolarization of mitochondrial membrane potential. The treated MCTS also experienced DNA fragmentation; this had been quantified by TUNEL-positive assay, which showed >64% increase in DNA damaged cells. Higher externalization of phospatidylserine and distorted and disintegrated spheroids stained by acridine orange/propidium iodide showed that the cell death was mainly due to apoptosis. Further exploration showed that the combinatorial treatment elevated caspases-8 and 9 activities involving both extrinsic and intrinsic pathways of apoptosis. The treatment also upregulated the expression of proapoptotic gene HSP 105 and downregulated the expression of prosurvival genes such as c-Jun, ICAM1, and VEGF. In conclusion, these results suggested that the coupling of E. scaber to low concentration of tamoxifen showed synergism in cytotoxicity and reducing drug resistance in estrogen receptor-positive breast cancer.

Colchicine: Isolation, LC-MS QTof Screening, and Anticancer Activity Study of Gloriosa superba Seeds

Colchicine was extracted from Gloriosa superba seeds using the Super Critical Fluid (CO2) Extraction (SCFE) technology. The seeds were purified upto 99.82% using column chromatography. Colchicine affinity was further investigated for anticancer activity in six human cancer cell lines, i.e., A549, MCF-7, MDA-MB231, PANC-1, HCT116, and SiHa. Purified colchicine showed the least cell cytotoxicity and antiproliferation and caused no G2/M arrest at clinically acceptable concentrations. Mitotic arrest was observed in only A549 and MDA-MB231 cell lines at 60nM concentration. Our finding indicated the possible use of colchicine at a clinically acceptable dose and provided insight into the science behind microtubule destabilization. However, more studies need to be conducted beforethese findings could be established.

Galectin-3 Targeting in Thyroid Orthotopic Tumors Opens New Ways to Characterize Thyroid Cancer

Preoperative characterization of thyroid nodules is challenging since thyroid scintigraphy fails to distinguish between benign and malignant lesions. Galectin-3 (gal-3) is expressed in well-differentiated and in undifferentiated thyroid cancer types but not in normal thyrocytes and benign thyroid lesions. Herein, we aimed to validate gal-3 targeting as a specific method to detect non-radioiodine-avid thyroid cancer in thyroid orthotopic tumor models. Methods: Papillary (BcPAP) and anaplastic (CAL62 and FRO82-1) thyroid carcinoma cell lines were characterized via Western blot and polymerase chain reaction for gal-3 and sodium-iodide symporter (NIS) expression. An ⁸⁹Zr-labeled F(ab')₂ antigal-3 was generated and characterized for binding versus ¹²⁵I on 2- and 3-dimensional cell cultures. The thyroid carcinoma cells were inoculated into the left thyroid lobe of athymic nude mice, and the orthotopic tumor growth was monitored via ultrasound and fluorescence molecular tomography. Head-to-head PET/CT comparison of ¹²⁴I versus ⁸⁹Zr-deferoxamine (DFO)-F(ab')₂ antigal-3 was performed, followed by biodistribution studies and immunohistochemical analysis for gal-3 and NIS expression. Results: The thyroid carcinoma cells investigated were invariably gal-3-positive while presenting low or lost NIS expression. ⁸⁹Zr-DFO-F(ab')₂ antigal-3 tracer showed high affinity to gal-3 (dissociation constant, ∼3.9 nM) and retained immunoreactivity (>75%) on 2-dimensional cell cultures and on tumor spheroids. ¹²⁵I internalization in FRO82-1, BcPAP, and CAL62 was directly dependent on NIS expression, both in 2-dimensional and tumor spheroids. PET/CT imaging showed ⁸⁹Zr-DFO-F(ab')₂ antigal-3 signal associated with the orthotopically implanted tumors only; no signal was detected in the tumor-free thyroid lobe. Conversely, PET imaging using ¹²⁴I showed background accumulation in tumor-infiltrated lobe, a condition simulating the presence of non-radioiodine-avid thyroid cancer nodules, and high accumulation in normal thyroid lobe. Imaging data were confirmed by tracer biodistribution studies and immunohistochemistry. Conclusion: A specific and selective visualization of thyroid tumor by targeting gal-3 was demonstrated in the absence of radioiodine uptake. Translation of this method into the clinical setting promises to improve the management of patients by avoiding the use of unspecific imaging methodologies and reducing unnecessary thyroid surgery.

Cell cycle-dependent force transmission in cancer cells

The generation of traction forces and their transmission to the extracellular environment supports the disseminative migration of cells from a primary tumor. In cancer cells, the periodic variation of nuclear stiffness during the cell cycle provides a functional link between efficient translocation and proliferation. However, the mechanical framework completing this picture remains unexplored. Here, the Fucci2 reporter was expressed in various human epithelial cancer cells to resolve their cell cycle phase transition. The corresponding tractions were captured by a recently developed reference-free confocal traction-force microscopy platform. The combined approach was conducive to the analysis of phase-dependent force variation at the level of individual integrin contacts. Detected forces were invariably higher in the G1 and early S phases than in the ensuing late S/G2, and locally colocalized with high levels of paxillin phosphorylation. Perturbation of paxillin phosphorylation at focal adhesions, obtained through the biochemical inhibition of focal adhesion kinase (FAK) or the transfection of nonphosphorylatable or phosphomimetic paxillin mutants, significantly diminished the force transmitted to the substrate. These data demonstrate a reproducible modulation of force transmission during the cell cycle progression of cancer cells, instrumental to their invasion of dense environments. In addition, they delineate a model in which paxillin phosphorylation supports the mechanical maturation of adhesions relaying forces to the substrate.

Tamoxifen-Induced Apoptosis of MCF-7 Cells via GPR30/PI3K/MAPKs Interactions: Verification by ODE Modeling and RNA Sequencing

Tamoxifen (Nolvadex) is one of the most widely used and effective therapeutic agent for breast cancer. It benefits nearly 75% of patients with estrogen receptor (ER)-positive breast cancer that receive this drug. Its effectiveness is mainly attributed to its capacity to function as an ER antagonist, blocking estrogen binding sites on the receptor, and inhibiting the proliferative action of the receptor-hormone complex. Although, tamoxifen can induce apoptosis in breast cancer cells via upregulation of pro-apoptotic factors, it can also promote uterine hyperplasia in some women. Thus, tamoxifen as a multi-functional drug could have different effects on cells based on the utilization of effective concentrations or availability of specific co-factors. Evidence that tamoxifen functions as a GPR30 (G-Protein Coupled Receptor 30) agonist activating adenylyl cyclase and EGFR (Epidermal Growth Factor Receptor) intracellular signaling networks, provides yet another means of explaining the multi-functionality of tamoxifen. Here ordinary differential equation (ODE) modeling, RNA sequencing and real time qPCR analysis were utilized to establish the necessary data for gene network mapping of tamoxifen-stimulated MCF-7 cells, which express the endogenous ER and GPR30. The gene set enrichment analysis and pathway analysis approaches were used to categorize transcriptionally upregulated genes in biological processes. Of the 2,713 genes that were significantly upregulated following a 48 h incubation with 250 μM tamoxifen, most were categorized as either growth-related or pro-apoptotic intermediates that fit into the Tp53 and/or MAPK signaling pathways. Collectively, our results display that the effects of tamoxifen on the breast cancer MCF-7 cell line are mediated by the activation of important signaling pathways including Tp53 and MAPKs to induce apoptosis.

Synergistic effect of black tea polyphenol, theaflavin-3,3'-digallate with cisplatin against cisplatin resistant human ovarian cancer cells

Theaflavin-3, 3'-digallate (TF3) is a phenolic compound extracted from black tea. We previously demonstrated that TF3 selectively inhibited ovarian cancer cells. Ovarian cancer has high death rate because of acquired cisplatin resistance. We aimed to investigate the synergistic effect of TF3 and cisplatin (CDDP) against cisplatin resistant ovarian cancer cells. In the present study, combination treatment with TF3 and CDDP showed a synergistic cytotoxic effect in A2780/CP70 and OVCAR3 cells. Combination treatment showed a synergistic pro-apoptotic effect and synergistically induced G1/S phase cell cycle arrest. Synergistic apoptosis was accompanied by regulating protein expression of cleaved caspase 3/7, cytochrome c, Bax and Bcl-2. Combination treatment induced G1/S phase cell cycle arrest via regulating protein expression of cyclin A2, cyclin D1, cyclin E1 and CDK2/4. Combination treatment could synergistically down-regulate Akt phosphorylation in both cell lines. TF3 may be used as an adjuvant for the treatment of advanced ovarian cancer.

C3G shows regulated nucleocytoplasmic exchange and represses histone modifications associated with euchromatin

C3G (RapGEF1), essential for mammalian embryonic development, shows dynamic nucleocytoplasmic exchange. Nuclear localization is regulated by NLSs, NES, and phosphorylation. C3G translocates to the nucleus in response to physiological stimuli and regulates chromatin modifications and gene expression.

C3G (RapGEF1) is a ubiquitously expressed guanine nucleotide exchange factor that functions in signaling pathways regulating cell proliferation, apoptosis, and actin reorganization. It is essential for differentiation and early embryonic development in mice. Overexpressed C3G shows predominant cytoplasmic localization, but endogenous C3G is a component of nuclear fractions in a variety of cell types. Coexpression of importin-α and inhibition of nuclear export by leptomycin B resulted in predominant nuclear localization of C3G. Functional NLSs, NES, and GSK3-β–dependent phosphorylation regulate its dynamic nuclear localization. C3G translocates to the nucleus in response to myogenic differentiation and sublethal dose of cisplatin. C3G is associated with chromatin and nuclear matrix fractions. Cells with C3G localized in the nucleus showed peripheralization of heterochromatin and reduced histone modifications associated with euchromatin. Short hairpin RNA–mediated depletion of C3G in epithelial cells resulted in reduced expression of CDK inhibitors and the histone demethylase KDM5A. Myoblast clones with CRISPR/Cas9-mediated knockout of C3G failed to show repression of histone marks and did not show up-regulation of myosin heavy chain and myotube formation when grown in differentiation medium. Our results document regulated nucleocytoplasmic exchange of C3G in response to physiological stimuli and provide insights into nuclear functions for C3G.

Thymoquinone Could Increase The Efficacy of Tamoxifen Induced Apoptosis in Human Breast Cancer Cells: An In Vitro Study

Objective

Thymoquinone (TQ), as the main component of Nigella Sativa plant, shows anticancer properties. This study was aimed to evaluate the combined effect of TQ and Tamoxifen (TAM) on viability and apoptosis of human breast cancer cell lines.

Materials and Methods

In this experimental study, estrogen positive MCF-7 and estrogen negative MDA-MB-231 human breast cancer cell lines were induced by TAM (2 µM) or different doses of TQ (50, 75, 100, 150 µM), individually or in combination. Cell viability and apoptosis were investigated by MTT assay and TdT-mediated deoxy-uracil nick end labeling (TUNEL) assay; Acridine orange (AO)/Ethidium bromide (EB) staining respectively. Data were analyzed by one way ANOVA and P<0.05 was considered significant.

Results

In 24 hours treatment, TAM and all doses of TQ, solely or in combination, significantly reduced cell viability of both cell lines, except in MCF-7 cells treated with 50 µM TQ, and MDA-MB-231 cells treated with 50 or 75 µM TQ (P<0.01). After 48 hours treatment, cell viability of both cell lines was reduced in all treated groups (P<0.05). Remarkable apoptotic index was observed in combination treatment of MCF-7 or MDA-MB-231 cell lines with TAM and TQ (P<0.001).

Conclusion

The synergistic effect of TQ and TAM on human breast cancer cell lines showed cell viability reduction as well as apoptosis induction, independent to estrogen.

Endocrine resistance in breast cancer--An overview and update

Tumors that express detectable levels of the product of the ESR1 gene (estrogen receptor-α; ERα) represent the single largest molecular subtype of breast cancer. More women eventually die from ERα+ breast cancer than from either HER2+ disease (almost half of which also express ERα) and/or from triple negative breast cancer (ERα-negative, progesterone receptor-negative, and HER2-negative). Antiestrogens and aromatase inhibitors are largely indistinguishable from each other in their abilities to improve overall survival and almost 50% of ERα+ breast cancers will eventually fail one or more of these endocrine interventions. The precise reasons why these therapies fail in ERα+ breast cancer remain largely unknown. Pharmacogenetic explanations for Tamoxifen resistance are controversial. The role of ERα mutations in endocrine resistance remains unclear. Targeting the growth factors and oncogenes most strongly correlated with endocrine resistance has proven mostly disappointing in their abilities to improve overall survival substantially, particularly in the metastatic setting. Nonetheless, there are new concepts in endocrine resistance that integrate molecular signaling, cellular metabolism, and stress responses including endoplasmic reticulum stress and the unfolded protein response (UPR) that provide novel insights and suggest innovative therapeutic targets. Encouraging evidence that drug combinations with CDK4/CDK6 inhibitors can extend recurrence free survival may yet translate to improvements in overall survival. Whether the improvements seen with immunotherapy in other cancers can be achieved in breast cancer remains to be determined, particularly for ERα+ breast cancers. This review explores the basic mechanisms of resistance to endocrine therapies, concluding with some new insights from systems biology approaches further implicating autophagy and the UPR in detail, and a brief discussion of exciting new avenues and future prospects.

NADH-linked metabolic plasticity of MCF-7 breast cancer cells surviving in a nutrient-deprived microenvironment

Characteristic of the tumor microenvironment are fluctuating gradients of reduced nutrient levels and released lactate. A fundamental issue is how tumor cells modulate their metabolic activity when both glucose and glutamine levels become limiting in the presence of high exogenous lactate. For functional analyses, the activities of pyruvate kinase, lactate dehydrogenase (LDH) and plasma membrane NADH oxidase (NOX) as well as cell growth were measured in breast cancer MCF-7 cells cultured in medium containing various concentrations of these metabolites. After 3 days at glucose concentrations below 2.5 mM, cell number was higher with 0.1 mM than with 1.0 mM glutamine, indicating that the glucose/glutamine balance is important for growth. On the other hand, NOX activity increased with increasing glucose >2.5 mM, but only with low glutamine (0.1 mM). Pyruvate kinase activity also increased, with LDH activity remaining 2-3-fold lower. Here NOX could have a complementary role in reoxidizing NADH for glycolysis. Exogenous lactate supported cell survival at limiting concentrations of glucose and glutamine while increasing NOX and pyruvate kinase activities as well as NADH levels. It is proposed that lactate supports cell survival by fuelling gluconeogenesis and/or the TCA cycle in mitochondria, from where NADH could be shuttled to the cytosol and reoxidized by NOX. Cell survival and the metabolic phenotype are thus interrelated to the dynamics of NADH and plasma membrane NOX activity, which are regulated by the balance of glucose/glutamine levels, in conjunction with lactate in a precarious tumor microenvironment.

Synergistic Inhibitory Effects of Cetuximab and Cisplatin on Human Colon Cancer Cell Growth via Inhibition of the ERK-Dependent EGF Receptor Signaling Pathway

The purpose of this study was to evaluate the anticancer efficacy of cetuximab combined with cisplatin (combination treatment) on colon cancer growth, as well as its underlying action mechanism. Combination treatment synergistically potentiated the effect of cetuximab on cell growth inhibition and apoptosis induction in HCT116 and SW480 cells. Combination treatment further suppressed the expression of the activated form of epidermal growth factor receptor (EGFR) and MAP kinase (p-ERK and p-p38) and also significantly inhibited the activity of activator protein-1 (AP-1) and nuclear factor kappa B (NF-κB). Additionally, the expression of cyclooxygenase-2 (COX-2) and interleukin-8 (IL-8) mRNA was significantly reduced by the combination treatment as compared to the expression seen for treatment with cetuximab or cisplatin alone. We found that the synergistic inhibitory effects of cetuximab and cisplatin on AP-1 and NF-κB activation, as well as on cell viability, were reversed by pretreatment with an ERK inhibitor. Results demonstrate that combined treatment with cetuximab and cisplatin exerts synergistic anticancer effects on colon cancer cells and also suggest that the ERK pathway plays a critical role in these effects via the suppression of the EGFR signaling pathway, along with the inhibition of COX-2, IL-8, and AP-1 and NF-κB.

Lipid nanocarriers of a lipid-conjugated estrogenic derivative inhibit tumor growth and enhance cisplatin activity against triple-negative breast cancer: pharmacokinetic and efficacy evaluation

Breast cancer is the leading cause of malignancies among women globally. The triple negative breast cancer (TNBC) subtype is the most difficult to treat and accounts for 15% of all cases. Targeted therapies have been developed for TNBC but come short of clinical translation due to acquired tumor resistance. An effective therapy against TNBC must combine properties of target specificity, efficient tumor killing, and translational relevance. The objective of this study was to formulate a nontoxic, cationic, lipid-conjugated estrogenic derivative (ESC8), with demonstrated anticancer activity, for oral delivery in mice bearing triple negative breast cancer (TNBC) as xenograft tumors. The in vitro cell viability, Caco-2 permeability, and cell cycle dynamics of ESC8-treated TNBC cells were investigated. ESC8 was formulated as liposomes, solid lipid nanoparticles (SLNs), and nanostructured lipid carriers (NLCs) and characterized for size, zeta potential, entrapment efficiency, size stability, and tumor biodistribution. Pharmacokinetic modeling of plasma concentration-time course data was carried out following intravenous and oral administration in Sprague-Dawley rats. In vivo efficacy investigation of ESC8-SLNC was carried out in Nu/Nu mice bearing MDA-MB-231 TNBC as xenograft tumors, and the molecular dynamics modulating tumor growth inhibition was analyzed by Western blot. In vitro ESC8 inhibited TNBC and non-TNBC cell viability with IC50 ranging from 1.81 to 3.33 μM. ESC8 was superior to tamoxifen and Cisplatin in inhibiting MDA-MB-231 cell viability; and at 2.0 μM ESC8 enhanced Cisplatin cytotoxicity 16-fold. Intravenous ESC8 (2.0 mg/kg) was eliminated at a rate of 0.048 ± 0.01 h(-1) with a half-life of 14.63 ± 2.95 h in rats. ESC8 was orally bioavailable (47.03%) as solid lipid nanoparticles (ESC8-SLN). ESC8-SLN (10 mg/kg/day, ×14 days, p.o.) inhibited breast tumor growth by 74% (P < 0.0001 vs control) in mice bearing MDA-MB-231 cells as xenografts; and when given in combination with Cisplatin (2.0 mg/kg/biweekly, ×2 weeks, IV), tumor growth was inhibited by 87% (P = 0.0002, vs ESC8-SLN; 10 mg/kg/day, ×14 days, p.o). ESC8-SLN tumor growth inhibition was associated with increased expression of p21 and Caspase-9; as well as by inhibition of EGFR, Slug, p-Akt1, Vimentin, NFkβ, and IKKγ. These results show the promise of ESC8 as an oral adjuvant or neoadjuvant against triple negative breast cancer.

A hypoxia efficient imidazole-based Ru(ii) arene anticancer agent resistant to deactivation by glutathione

[Ru^II(η⁶-p-cym)(L)Cl](PF₆) is slow to hydrolyze and shows better anticancer activity in hypoxia with strong resistance to deactivation by l-glutathione.

The effects of 56MESS on mitochondrial and cytoskeletal proteins and the cell cycle in MDCK cells

BACKGROUND

56MESS has been shown to be cytotoxic but the mode of this action is unclear. In order to probe the mechanism of action for 56MESS, MDCK cells were utilised to investigate the effect on treated cells.

RESULTS

IC50 values for 56MESS and cisplatin in the MDCK cell line, determined by a SRB assay, were 0.25 ± 0.03 and 18 ± 1.2 μM respectively. In a preliminary study, cells treated with 56MESS displayed no caspase-3/7 activity, suggesting that the mechanism of action is caspase independent. Protein expression studies revealed an increase the expression in the MTC02 protein associated with mitochondria in cells treated with 56MESS and cisplatin. Non-synchronised 56MESS-treated cells caused an arrest in the G2/M phase of the cell cycle, in comparison to the S phase arrest of cisplatin. In G0/G1 synchronised cells, both 56MESS and cisplatin both appeared to arrest within the S phase.

CONCLUSIONS

these results suggest that 56MESS is capable of causing cell-cycle arrest, and that mitochondrial and cell cycle proteins may be involved in the mode of action of cytotoxicity of 56MESS.

Therapeutic targeting of CPT-11 induced diarrhea: a case for prophylaxis

CPT-11 (irinotecan), a DNA topoisomerase I inhibitor is one of the main treatments for colorectal cancer. The main dose limiting toxicities are neutropenia and late onset diarrhea. Though neutropenia is manageable, CPT-11 induced diarrhea is frequently severe, resulting in hospitalizations, dose reductions or omissions leading to ineffective treatment administration. Many potential agents have been tested in preclinical and clinical studies to prevent or ameliorate CPT-11 induced late onset diarrhea. It is predicted that prophylaxis of CPT-11 induced diarrhea will reduce sub-therapeutic dosing as well as hospitalizations and will eventually lead to dose escalations resulting in better response rates. This article reviews various experimental agents and strategies employed to prevent this debilitating toxicity. Covered topics include schedule/dose modification, intestinal alkalization, structural/chemical modification, genetic testing, anti-diarrheal therapies, transporter (ABCB1, ABCC2, BCRP2) inhibitors, enzyme (β-glucuronidase, UGT1A1, CYP3A4, carboxylesterase, COX-2) inducers and inhibitors, probiotics, antibiotics, adsorbing agents, cytokine and growth factor activators and inhibitors and other miscellaneous agents.

Equol enhances tamoxifen's anti-tumor activity by induction of caspase-mediated apoptosis in MCF-7 breast cancer cells

BACKGROUND

Soy phytoestrogens, such as daidzein and its metabolite equol, have been proposed to be responsible for the low breast cancer rate in Asian women. Since the majority of estrogen receptor positive breast cancer patients are treated with tamoxifen, the basic objective of this study is to determine whether equol enhances tamoxifen's anti-tumor effect, and to identify the molecular mechanisms involved.

METHODS

For this purpose, we examined the individual and combined effects of equol and tamoxifen on the estrogen-dependent MCF-7 breast cancer cells using viability assays, annexin-V/PI staining, cell cycle and western blot analysis.

RESULTS

We found that equol (>50 μM) and 4-hydroxy-tamoxifen (4-OHT; >100 nM) significantly reduced the MCF-7 cell viability. Furthermore, the combination of equol (100 μM) and 4-OHT (10 μM) induced apoptosis more effectively than each compound alone. Subsequent treatment of MCF-7 cells with the pan-caspase inhibitor Z-VAD-FMK inhibited equol- and 4-OHT-mediated apoptosis, which was accompanied by PARP and α-fodrin cleavage, indicating that apoptosis is mainly caspase-mediated. These compounds also induced a marked reduction in the bcl-2:bax ratio, which was accompanied by caspase-9 and caspase-7 activation and cytochrome-c release to the cytosol. Taken together, these data support the notion that the combination of equol and tamoxifen activates the intrinsic apoptotic pathway more efficiently than each compound alone.

CONCLUSIONS

Consequently, equol may be used therapeutically in combination treatments and clinical studies to enhance tamoxifen's effect by providing additional protection against estrogen-responsive breast cancers.

Gene rearrangements in hormone receptor negative breast cancers revealed by mate pair sequencing

Background

Chromosomal rearrangements in the form of deletions, insertions, inversions and translocations are frequently observed in breast cancer genomes, and a subset of these rearrangements may play a crucial role in tumorigenesis. To identify novel somatic chromosomal rearrangements, we determined the genome structures of 15 hormone-receptor negative breast tumors by long-insert mate pair massively parallel sequencing.

Results

We identified and validated 40 somatic structural alterations, including the recurring fusion between genes DDX10 and SKA3 and translocations involving the EPHA5 gene. Other rearrangements were found to affect genes in pathways involved in epigenetic regulation, mitosis and signal transduction, underscoring their potential role in breast tumorigenesis. RNA interference-mediated suppression of five candidate genes (DDX10, SKA3, EPHA5, CLTC and TNIK) led to inhibition of breast cancer cell growth. Moreover, downregulation of DDX10 in breast cancer cells lead to an increased frequency of apoptotic nuclear morphology.

Conclusions

Using whole genome mate pair sequencing and RNA interference assays, we have discovered a number of novel gene rearrangements in breast cancer genomes and identified DDX10, SKA3, EPHA5, CLTC and TNIK as potential cancer genes with impact on the growth and proliferation of breast cancer cells.

Proteomic identification of E6AP as a molecular target of tamoxifen in MCF7 cells

Tamoxifen (Tam) is most widely used selective estrogen receptor modulator (SERM) for treatment of hormone-responsive breast cancer. Despite being regularly used in clinical therapy for breast cancer since 1971, the mechanism of Tam action remains largely unclear. In order to gain insights into Tam-mediated antibreast cancer actions, we applied 2DE and MS based proteomics approach to identify target proteins of Tam. We identified E6-associated protein, i.e. E6AP (UBE3A) among others to be regulated by Tam that otherwise is upregulated in breast tumors. We confirmed our 2DE finding by immunoblotting and further show that Tam leads to inhibition of E6AP expression presumably by promoting its autoubiquitination, which is coupled with nuclear export and subsequent proteasome-mediated degradation. Furthermore, we show that Tam- and siE6AP-mediated inhibition of E6AP leads to enhanced G0-G1 growth arrest and apoptosis, which is also evident from significant upregulation of cytochrome-c, Bax, p21, and PARP cleavage. Taken together, our data suggest that, Tam-targeted E6AP inhibition is in fact required for Tam-mediated antibreast cancer actions. Thus, E6AP may be a therapeutic target in breast cancer.

Ubiquitin ligase c-Cbl is involved in tamoxifen-induced apoptosis of MCF-7 cells by downregulating the survival signals

BACKGROUND

Tamoxifen (TAM) is a nonsteroidal antiestrogen that has been widely used in the treatment of breast cancer through its anti-estrogen activity. Recent studies show that TAM is cytotoxic to both estrogen receptor (ER)-positive and ER-negative cells via the induction of apoptosis. However, the molecular mechanisms of this effect are not well understood. In the present study, we investigated the roles of c-Src, ERK, AKT and c-Cbl ubiquitin ligases during TAM-induced apoptosis of MCF-7 cells.

MATERIAL AND METHODS

MCF-7 cell proliferation and apoptosis were measured by 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, and flow cytometry, respectively. c-Cbl expression, and the activity of c-Src, ERK, AKT were assayed by Western blotting. Overexpression of the wild and the dominant-negative type of c-Cbl (70Z/Cbl) were achieved by transient transfection of plasmids encoding c-Cbl and 70Z/Cbl, respectively, and were confirmed by Western blotting. Statistical analysis was performed using the t-test, and a p-value <0.05 was considered to be statistically significant.

RESULTS

A high concentration of TAM (25 μM) induced a time-dependent apoptosis of MCF-7 cells. ERK1/2 and AKT were activated during TAM-induced apoptosis. The ERK1/2 inhibitor PD98059, the PI3K/Akt inhibitor LY294002, and the c-Src inhibitor PP2 all enhanced TAM action. Moreover, the ubiquitin ligase c-Cbl was up-regulated during this process. Over-expression of c-Cbl significantly enhanced the apoptosis-inducing effects of TAM, while 70Z/Cbl suppressed the apoptosis-inducing effects of TAM. Further investigation revealed that, overexpression of c-Cbl significantly downregulated the c-Src protein levels and TAM-induced AKT activity. But 70Z/Cbl significantly upregulated TAM-induced ERK and AKT activity.

CONCLUSIONS

This study demonstrates that c-Src, ERK, and AKT played a protective role during TAM-induced apoptosis, and that c-Cbl sensitized MCF-7 cells to TAM by modulating the expression of c-Src, and TAM-induced ERK and AKT activity.

Pineapple bromelain induces autophagy, facilitating apoptotic response in mammary carcinoma cells

Bromelain, from pineapple, possesses potent anticancer effects. We investigated autophagic phenomenon in mammary carcinoma cells (estrogen receptor positive and negative) under bromelain treatment and also illustrated the relationship between autophagy and apoptosis in MCF-7 cells. MCF-7 cells exposed to bromelain showed delayed growth inhibitory response and induction of autophagy, identified by monodansylcadaverine localization. It was succeeded by apoptotic cell death, evident by sub-G1 cell fraction and apoptotic features like chromatin condensation and nuclear cleavage. 3-Methyladenine (MA, autophagy inhibitor) pretreatment reduced the bromelain-induced autophagic level, also leading to decline in apoptotic population, indicating that here autophagy facilitates apoptosis. However, addition of caspase-9 inhibitor Z-LEHD-FMK augmented the autophagy levels, inhibited morphological apoptosis but did not prevent cell death. Next, we found that bromelain downregulated the phosphorylation of extracellular signal-regulated kinase ½ (ERK½), whereas that of c-jun N-terminal kinase (JNK) and p38 kinase were upregulated. Also, MA had no influence on bromelain-suppressed ERK½ activation, yet, it downregulated JNK and p38 activation. Also, addition of mitogen-activated protein kinase (MAPK) inhibitors enhanced the autophagic ratios, which suggested the role of MAP kinases in bromelain-induced autophagy. All three MAPKs were seen to be constantly activated over the time. Bromelain was seen to induce the expressions of autophagy-related proteins, light chain 3 protein B II (LC3BII), and beclin-1. Using ERK½ inhibitor, expressions of LC3BII and beclin-1 increased, whereas p38 and JNK inhibitors decreased this protein expression, indicating that bromelain-induced autophagy was positively regulated by p38 and JNK but negatively regulated by ERK½. Autophagy-inducing property of bromelain can be further exploited in breast cancer therapy.

Tamoxifen Induction of CCAAT Enhancer-binding Protein α Is Required for Tamoxifen-induced Apoptosis

Low concentrations of tamoxifen or its active metabolite 4-hydroxytamoxifen (OHT) induce estrogen receptor alpha (ERalpha)-dependent apoptosis. To analyze the pathway of OHT-ERalpha-induced apoptosis, we developed stably transfected lines of HeLa cells expressing wild-type ER and an inactive mutant ERalpha unable to bind estrogen response elements. HeLa cells expressing the mutant ERalpha and HeLa cells expressing wild-type ERalpha in which the ER was knocked down with an ER-specific small interfering RNA were not killed by Tam or OHT, suggesting that estrogen response element-mediated transcription is required for Tam- and OHT-induced apoptosis. Microarray analysis to identify a gene(s) whose expression is important in OHT-ER-mediated apoptosis identified 19 mRNAs that OHT up-regulated by >1.6-fold and 15 down-regulated mRNAs. Gene function and the time course of induction by OHT-ERalpha led us to further investigate CCAAT enhancer-binding protein alpha (C/EBPalpha), which has roles in cell cycle progression and apoptosis, and p21. Quantitative reverse transcription-PCR, Western blot analysis, and RNA interference knockdown suggest that cell cycle arrest resulting from OHT-ERalpha induction of p21 may facilitate apoptosis. OHT-ERalpha, but not E2-ERalpha, induced C/EBPalpha mRNA and protein. RNA interference knockdown of C/EBPalpha nearly abolished OHT-ERalpha-induced apoptosis. We isolated stable cell lines that were resistant to OHT-induced apoptosis, contain full-length functional ERalpha, and undergo apoptosis in response to etoposide. In these OHT-resistant cell lines both before and after OHT treatment, C/EBPalpha levels are much lower than in OHT-sensitive cells. These studies establish a novel molecular site responsible for Tam- and OHT-ERalpha-induced apoptosis of cancer cells.

Andrographolide induces cell cycle arrest at G2/M phase and cell death in HepG2 cells via alteration of reactive oxygen species

The cytotoxicity of andrographolide to HepG2 human hepatoma cells was investigated in the present study. Growth of HepG2 cells was affected in the presence of andrographolide with an IC(50) of 40.2 microM after 48 h treatment. Flow cytometric analysis and DNA fragmentation assay revealed that andrographolide induced cell cycle arrest at G2/M phase and a late apoptosis of the cells. The occurrence of cell cycle arrest was accompanied by the collapse of mitochondrial membrane potential (MMP) and an intracellular increase of hydrogen peroxide (H(2)O(2)) but a decrease of superoxide radicals (O(2)(-)) and reduced glutathione. In the treated cells, expression of Bax as well as the transcriptional controller of this pro-apoptotic gene, p53, was upregulated but not other apoptotic proteins such as Bad, Bcl-2 and Bcl-X(L). Although the activity of caspase-3, which has direct effect on apoptosis, was also enhanced by the presence of andrographolide, cell death of HepG2 could neither be prevented by a specific inhibitor of capsase-3 nor the pan-caspase inhibitor-zVAD (Val-Ala-Asp), indicating that it was a caspase-independent cell death. Since the overall percentage of apoptotic cells was relatively small throughout the experimental studies, we conclude that the cytotoxic effect of andrographolide on HepG2 cells is primary attributed to the induction of cell cycle arrest via the alteration of cellular redox status.

Tamoxifen-induced rapid death of MCF-7 breast cancer cells is mediated via extracellularly signal-regulated kinase signaling and can be abrogated by estrogen

Tamoxifen (Tam) is widely used in chemotherapy of breast cancer. It inhibits proliferation and induces apoptosis of breast cancer cells by estrogen receptor (ER)-dependent modulation of gene expression. In addition, recent reports have shown that Tam also has nongenomic effects. We previously reported induction of a rapid mitochondrial death program in breast cancer cells at pharmacological concentrations of Tam. Here we studied the upstream signaling events leading to mitochondrial disruption by Tam. We observed that 5 mum Tam rapidly induced sustained activation of ERK1/2 in ER-positive breast cancer cell lines (MCF-7 and T47D) and that PD98059 (inhibitor of ERK activation) was able to protect MCF-7 cells against Tam-induced death. These data suggest that activation of ERK has a primary role in the acute death response of the cells. In addition, inhibition of epidermal growth factor receptor (EGFR) opposed both Tam-induced ERK1/2 phosphorylation and cell death, which suggests that EGFR-associated mechanisms are involved in Tam-induced death. ERK1/2 phosphorylation was associated with a prolonged nuclear localization of ERK1/2 as determined by fluorescence microscopy with ERK2-green fluorescent protein construct. 17beta-Estradiol was shown to exert a different kind of temporal pattern of ERK nuclear localization in comparison with Tam. Moreover, 17beta-estradiol was found to oppose the rapid effects of Tam in MCF-7 and T47D cells but not in MDA-MB-231 cells, which implies a role for estrogen receptors in the protective effect of estrogen. The pure antiestrogen ICI182780 could not, however, prevent Tam-induced ERK1/2 phosphorylation, suggesting that the Tam-induced rapid cell death is primarily ER-independent or mediated by ICI182780 insensitive nongenomic mechanisms.

Inhibition of deoxyribonuclease I by actin is to protect cells from premature cell death

Deoxyribonuclease I (Dnase1) is the major extracellular endonuclease. It is secreted by digestive glands into the alimentary tract and into the plasma, lacrimal fluid and urine by hepatocytes, lacrimal glands and renal proximal tubular cells, respectively. In many species the activity of Dnase1 is inhibited by monomeric actin. However, the biological significance of this high affinity interaction is unknown. We generated a Dnase1 mutant with extremely reduced actin binding capacity. EGFP-constructs of wild-type and mutant Dnase1 were transfected into MCF-7 breast cancer cells and apoptosis or necrosis was induced by staurosporine or oxidative stress. During apoptosis faster chromatin fragmentation occurred in cells transfected with mutant Dnase1. When wt (wild-type)- or mutated Dnase1 were added to cells after induction of necrosis, faster chromatin degradation occurred in the presence of mutant Dnase1. Inclusion of actin under these conditions inhibited chromatin degradation by wt- but not by mutated Dnase1. Thus, inhibition of Dnase1 by actin may serve as a self-protection mechanism against premature DNA degradation during cell damage.

The role of tamoxifen in combination with cisplatin on oral squamous cell carcinoma cell lines

The purpose of this study was to evaluate the effect of tamoxifen (TAM) when used in combination with cisplatin on oral squamous cell carcinoma (OSCC). For this, the relation between estrogen receptor (ER) expression level and the cytotoxic effect of TAM, the apoptotic effect and its molecular mechanisms of TAM were investigated using OSCC cell lines. Combination treatment demonstrated a superior cytotoxic and apoptotic effect on OSCC cell lines. Considerable amount of ER was detected in some OSCC cell lines, but there were no significant differences of cytotoxic effect of TAM. TAM inhibited PKC activity and up-regulated TGF-beta1 secretion.

Morphological and growth altering effects of Cisplatin in C. albicans using fluorescence microscopy

Changes in morphology and growth curve of Candida albicans in response to treatment by Cisplatin has been studied using fluorescence staining with ethidium bromide. Treatment with Cisplatin was found to markedly inhibit hyphae and ovoid growth as revealed by ethidium bromide staining of drug treated cells. These changes were concomitant with inhibitory effects on the growth curve with respect to untreated cells

Presence of Cisplatin not only caused suppression in the limiting values in the growth curve, but also caused a slight left shift in the EC50 values. Some of the ovoid cells undergoing poisoning with cisplatin were found to be unusually enlarged before undergoing their natural fate thus suggesting formation of similar cytotoxic end products with DNA.

Analysis of Drug Action on Tumor Cell Metabolism Using Electronic Sensor Chips

Chemotherapeutic drugs affect the metabolism of tumor cells regardless of the specific target of action. Basic parameters of cell metabolism are extrusion of acids into the microenvironment and oxygen consumption. To analyze these changes on living cells in real-time, a test system based on multiparametric chips with an array of sensors for monitoring pH and O(2) as well as electric impedance has been developed. Cells are cultivated on these chips and supplied with medium by a fluid perfusion set-up which mimics microphysiological conditions and allows for drug addition and removal. Human colon carcinoma cells LS174T were used as a model to test the effect of drugs. Cells growing on chips were monitored for 24 h and longer. Untreated cells showed a continuous increase in the rate of acidification, while the rate of respiration remained fairly constant. Addition of chloroacetaldehyde (50 microM) rapidly attenuated O(2) consumption with a gradual decrease in acidification following. In contrast, with cisplatin (16.7 microM) a delayed and gradual decrease in both the rates of acidification and respiration effect occurred over 2-3 days. These results provide insights to the mechanisms of action of these drugs, which are coherent with those already known. Thus, multiparametric sensor chips provide elementary information on drug action.

Tamoxifen inhibits cell proliferation via mitogen-activated protein kinase cascades in human ovarian cancer cell lines in a manner not dependent on the expression of estrogen receptor or the sensitivity to cisplatin

Although tamoxifen (TAM), which is widely used in the treatment of breast cancer, also has a beneficial effect on cisplatin-refractory ovarian cancer, the biological mechanism of this effect has remained obscure. TAM, besides its action as an antiestrogen, also inhibits cell proliferation of estrogen receptor (ER)-negative cells by an unknown mechanism. Therefore, we examined the roles of the MAPK family in the antiproliferative effect of TAM on cisplatin-resistant Caov-3, which expresses ER and cisplatin-sensitive A2780, which does not express ER. The number of viable cells was reduced by TAM dose-dependently. TAM induced the activation of ERK, c-Jun N-terminal protein kinase (JNK), and p38 with different time courses. PD98059 canceled the reduction of the number of viable cells by 1 microM TAM and inhibited the TAM-induced cell-cycle arrest at the G(1) phase and dephosphorylation of the retinoblastoma protein. Either expression of dominant-negative JNK or pretreatment with SB203580 canceled the reduction of the number of viable cells by 5 microM TAM and inhibited the apoptotic nuclear changes and the cleavage of poly (ADP-ribose) polymerase induced by TAM. These results provide evidence that whereas the ERK cascade is involved in the induction of cell-cycle arrest at the G(1) phase by lower concentrations of TAM, the JNK or p38 cascade is involved in the induction of apoptosis by higher concentrations of TAM in both types of cells.

Tamoxifen induces suppression of cell viability and apoptosis in the human hepatoblastoma cell line HepG2 via down-regulation of telomerase activity

BACKGROUND/AIMS

Antiproliferative action of tamoxifen in the estrogen receptor-alpha-negative human hepatoblastoma cell line HepG2 was investigated.

METHODS

HepG2 cells, seeded at different densities (4000-36 000 cells/cm(2)), were incubated with tamoxifen (1, 10, or 20 microM) or the telomerase inhibitor 3'-azido-3'-deoxythymidine (AZT) (0.6-3.0 mM) up to 72 h. Cell viability was assessed (MTT-test), flow cytometric analysis was performed, and telomerase activity was measured (telomeric repeat amplification protocol assay).

RESULTS

Ten or 20 microM tamoxifen induced a reduction of cell viability. Basically reduction of viability was related to an increase in the fraction of G0/1-phase. When tamoxifen was present at higher concentration (20 microM) or at low cell density (4000/cm(2)) an additional increase of the rate of apoptotic cells occurred with a delay, aggravating the effect of tamoxifen on cell viability substantially. When apoptosis was induced a significant suppression of telomerase activity preceded regularly. Direct inhibition of telomerase activity with AZT resulted in a decrease of cell viability and apoptosis.

CONCLUSION

The tamoxifen-induced reduction of cell viability in HepG2 cells depends on drug concentration and cell density and is due to cytostatic and cytocide effects. The latter may be mediated by a down-regulation of telomerase activity.

Biochemical studies of apoptosis induced by tamoxifen in estrogen receptor positive and negative breast cancer cell lines

OBJECTIVES

Tamoxifen has been reported to show an efficacy in the treatment of breast cancer. Apoptosis could be a major mechanism of its antitumor effect. Therefore, this study has been designed to investigate the biochemical mechanisms of tamoxifen-induced apoptosis in both ER(+) MCF-7 and ER(-) MDA-MB468 breast cancer cell lines.

METHODS

Trypan blue dye exclusion test, Annexin V-Fluorescein/PI flow cytometry, MTT assay and Hoechst 33258 staining were used to detect cytotoxicity and apoptosis. The activation of caspase-3 was assayed by colorimetric assay kit. Bcl-2 and Bax proteins were estimated by western immunoblotting method.

RESULTS

Tamoxifen induced apoptosis in both cell lines (chi-square test, p < 0.05). Unlike the MCF-7 cells, which responded to the low concentration (1 microM), the treated MDA-MB468 cells have mainly been affected at a higher dose (20 microM) at which a significant increase was also obtained in the caspase-3 activity (chi-square test, p < 0.05). Interestingly, tamoxifen at doses higher than 2.5 microM increased cell proliferation in the MCF-7 cells. The levels of Bcl-2 and Bax remained unchanged.

CONCLUSION

Since tamoxifen has induced apoptosis in both cell lines by different mechanisms, it might be concluded that there exists ER(+) and ER(-) pathways for the induction of apoptosis.

Role of proliferation and apoptosis in net growth rates of human breast cancer cells (MCF-7) treated with oestradiol and/or tamoxifen

Studies on growth regulation in vitro to a large extent rely on comparison of growth curves. However, these do not discriminate between the relative contributions of the mitotic rate and the apoptotic rate to the net growth rate. In the present study, differential effects of 17beta-oestradiol (E2, 10(-8) M) and/or tamoxifen (TAM, 10(-6) M) on proliferation and apoptosis have been examined and related to growth curves of a subline of the human breast cancer cell line MCF-7 adapted to grow at low serum concentrations. Counting of cells and scoring of labelling and apoptotic indices were performed at the start of the experiment and 3, 6 and 9 days after changing the experimental media. The results demonstrate that apoptosis in this subline is constitutively expressed, that E2 protects (at least partly) against apoptosis and stimulates proliferation, resulting in an increased (net) growth rate, and final cell pool size, and that TAM has a weak cytostatic effect and stimulates apoptosis strongly, resulting in a decreased (net) growth rate and final cell pool size. When E2 and TAM are added simultaneously to the medium, the cytotoxic effect of TAM is partly counterbalanced by the protective role of E2, resulting in a reduced apoptotic rate that, however, is at a higher level than in cultures grown with E2 only. As the cytostatic role of TAM is partly abolished by E2, the combined effect of E2 and TAM results in a final (net) growth rate and cell pool size intermediary to cells grown with E2 or TAM alone.

Nuclear apoptosis detection by flow cytometry: influence of endogenous endonucleases

Nuclear apoptosis is characterized by chromatin condensation and progressive DNA cleavage into high-molecular-weight fragments and oligonucleosomes. These complex phenomena can be mediated by the activation of a multiplicity of enzymes, characterized by specific patterns of cation dependance, pH requirement, and mode of activation. The significance of this multiplicity of enzymes that cleave genomic DNA has been attributed to the need of death effector pathways specific for cell types/tissues, the level of cell differenciation, and the nature of the apoptotic stimuli. The activation of these factors contributes to the development of alterations that can be detected specifically by flow cytometric assays, namely, propidium iodide assays, acridine orange/ethidium bromide double staining, the TUNEL and ISNT techniques, and the assays of DNA sensitivity to denaturation. Although applicable to a wide spectrum of cell types, an increasing body of literature indicates that these techniques cannot be universally applied to all cell lines and apoptotic conditions: The requirement of a particular mediator(s) of nuclear apoptosis or the absence of endonuclease activity can limit the relevance of certain techniques. Finally, endonucleases recruited during primary necrosis can introduce nuclear alterations detected by some assays and raise the problem of their specificity. This review underlines the need for strategies to accurately detect and quantify nuclear apoptosis by flow cytometry when new cell systems and apoptotic conditions are considered.

A novel lipid compound, epolactaene, induces apoptosis: its action is modulated by its side chain structure

A novel lipid compound, epolactaene, was isolated from the culture supernatant of Penicillium sp. 1689-P and it has already been reported that it induced neurite outgrowth in a human neuroblastoma cell line. In this study, we first investigated the effects of epolactaene on a human leukemia B-cell line, BALL-1 cells, and clarified that epolactaene induces apoptosis in BALL-1 cells in a dose- and time-dependent manner. Furthermore, we focused on the side chain structure of epolactaene, and chemically synthesized epolactaene derivatives. One derivative, which has a straight long alkyl chain as its side chain, induced apoptosis more effectively than epolactaene. On the other hand, other derivatives with a short alkyl side chain had weaker apoptosis-inducing actions. A good correlation was found between the apoptosis-inducing action of these compounds and their octanol/water partition coefficients (log P). These results suggested that the apoptosis-inducing activities of epolactaene and its derivatives were related to the hydrophobicity of these compounds; so that side chain structure of epolactaene is very important for its apoptosis-inducing activities. These apoptosis-inducing actions of epolactaene and its derivatives were also observed in various blood tumor cell lines and normal lymphocytes.

Using mRNA expression profiling to determine anticancer drug efficacy

Pharmacogenomics is a fast-growing field of investigations that aims to further elucidate the inherited nature of interindividual differences in drug disposition and effects, with the ultimate goal of providing a stronger scientific basis for selecting the optimal drug therapy. Providing the right drug for the right patient is an important problem in the treatment of cancer. This is mainly due to the lack of information about the sensitivity of the tumor for a specific treatment modality, such as either chemotherapy or radiation treatment. This presentation highlights two approaches to identify responsiveness to treatment. Both approaches are based on the identification of expression profiles. The first approach concentrates on drug resistance and the second on the signaling pathways leading up to the death of the cell. Both approaches provide expression profiles; however, the more dynamic expression profiling as used to determine the signaling in damage cells promises to be a better determinant for the pharmacogenomic changes in expression profiles and, consequently, a potential better determinant for drug efficacy.

Effects of heat shock protein 70 (Hsp70) on arsenite-induced genotoxicity

Arsenic, a human carcinogen, is genotoxic, although its mechanism(s) of action for tumorigenesis is not well understood. Among the toxicity-related properties of this chemical are its clastogenic and aneugenic activities, as well as its capacity for inducing stress-response in the form of elevated heat shock protein (HSP) expression. In the present study, we evaluated the effects of Hsp70 expression on arsenite (As)-induced structural and numerical chromosome anomalies in human cells. Human MCF-7 Tet-off cells stably transfected with a pTRE/Hsp70-1 transgene construct were used to regulate Hsp70 levels prior to in vitro As exposures. Separate cultures of relatively high vs. low Hsp70-expressing cells were established. A cytokinesis block micronucleus assay with kinetochore immunostaining was used to detect micronuclei (MN) derived from chromosome breakage (K-MN) or loss (K+MN). These studies demonstrated significant increases in micronucleus frequencies in response to As following either a long exposure (5 or 10 microM for 46 hr), or short exposure (10 or 40 microM for 8 hr) protocol. Overall, the long protocol was more efficient in producing K+MN and cells with multiple MN. Overexpressing Hsp70 resulted in significant reductions in the percent of cells positive for MN for both the long and short As exposure protocols. Both K+ and K- types of As-induced MN were lower in cells with elevated Hsp70 as compared to cells without overexpression of Hsp70. We conclude that the dose and duration of As exposure influence the type as well as amount of chromosomal alteration produced and that inducible Hsp70 protects against both the clastogenic and aneugenic effects of this chemical.

Induction of apoptosis in the blue mussel Mytilus galloprovincialis by tri-n-butyltin chloride

Induction of apoptosis by tri-n-butyltin (TBT) in gill tissue of the mussel Mytilus galloprovincialis was investigated. The terminal dUTP nick-end labeling technique (TUNEL) was used to detect cells displaying DNA fragmentation within gill structures. Genomic DNA fragmentation was detected as characteristically ladder-like pattern of DNA fragments induced by single injection of different doses of TBT (1-5 microg/g) below the mantle, directly into the pallial fluid, after 24 h of incubation. DNA degradation of higher order DNA structure, as well as reduced G(0)/G(1) cell cycle region (the sub-G(1) region) was detectable after 1.5 h of TBT incubation. Presence of apoptotic cells in mussels' gills was indicated by the selective loss of G(2)/M cells concomitant with the appearance of cells with decreased DNA content in S and G(0)/G(1) cell cycle regions. The effect of the TBT on cell cycle in a mussel gill was a dose related and exposure time depending. The possible mechanism of induction of apoptosis in vivo in gill tissue of mussel treated with TBT is discussed.

Serum withdrawal induces a redistribution of intracellular gelsolin towards F-actin in NIH 3T3 fibroblasts preceding apoptotic cell death

The intracellular distribution of gelsolin in NIH 3T3 cells was examined by immunostaining using affinity-purified polyclonal gelsolin antibodies before and after induction of apoptosis by serum withdrawal. Serum deprivation induced detachment of an increasing number of NIH 3T3 cells, but also apoptosis in attached cells as verified morphologically by chromatin condensation, nuclear fragmentation and labelling of their periphery by FITC-annexin V. Ongoing apoptosis was also demonstrated by activation of caspase-3 activity and chromatin cleavage into high-molecular-mass fragments, although no internucleosomal chromatin degradation (DNA-ladder formation) was detected. When cells were maintained in the presence of 10% foetal calf serum, gelsolin immunoreactivity was evenly distributed in the cytoplasm. No obvious co-localisation of gelsolin and the actin-containing stress fibres was detected under these conditions. At day one after serum withdrawal, a redistribution of gelsolin to actin filaments was detected within a few attached cells by double fluorescence staining. The number of cells exhibiting this redistribution increased at days two to four. In addition, the stress fibres increased in thickness and their length was continuously reduced. At day four, many cells contained shortened stress fibres, which had lost their longitudinal orientation. Additionally, the cytoplasm of a number of attached cells was highly condensed around their nuclei and a homogenous distribution of both gelsolin and actin was detected in the remaining cytoplasmic rim. Up to day two, these effects were reversible after re-addition of serum to attached cells. A similar redistribution of gelsolin immunore-activity was observed after induction of apoptosis by cycloheximide, but not after initiation of necrosis by hydrogen peroxide. In NIH 3T3 cells no alteration in the expression of gelsolin at the level of protein (Western blot) or specific mRNA (Northern blot) was observed after serum withdrawal. Using Western blotting, no proteolysis of gelsolin was detected up to day 4, although caspase-3 activity was found to have increased fivefold after serum withdrawal. These results suggested that in these cells F-actin severing might occur in the absence or advance of gelsolin cleavage by caspases. Intact gelsolin on its own may be sufficient for the dissolution of the microfilaments, since micro-injection of gelsolin into primary bovine lens cells led to a transient disappearance of the stress fibres and to a reduction of their attachment area to the substratum. In NIH 3T3 cells similar effects of micro-injected gelsolin were only observed at day one after serum withdrawal.

Autophagic and apoptotic types of programmed cell death exhibit different fates of cytoskeletal filaments

Programmed cell death comprises several subtypes, as revealed by electron microscopy. Apoptosis or type I programmed cell death is characterized by condensation of cytoplasm and preservation of organelles, essentially without autophagic degradation. Autophagic cell death or type II programmed cell death exhibits extensive autophagic degradation of Golgi apparatus, polyribosomes and endoplasmatic reticulum, which precedes nuclear destruction. In the present study, we analysed the fate of cytokeratin and F-actin during autophagic cell death in the human mammary carcinoma cell line MCF-7 because recent studies suggest that an intact cytoskeleton is necessary for autophagocytosis. Programmed cell death was induced by 10(-)(6) M tamoxifen. For quantitative light microscopic analysis, autophagic vacuoles were visualized by monodansyl cadaverin, which stains autophagic vacuoles as distinct dot-like structures. In control cultures, the number of monodansylcadaverin-positive cells did not exceed 2%. Tamoxifen induced a dramatic increase 2–4 days after treatment to a maximum of 60% monodansylcadaverin-positive cells between days 5 and 7. Cell death, as indicated by nuclear condensation, increased more gradually to about 18% of all cells on day 7. In cells with pyknotic nuclei cytokeratin appeared disassembled but retained its immunoreactivity; actin was still polymerized to filaments, as demonstrated by its reaction with phalloidin. Western blot analysis showed no significant cleavage of the monomeric cytokeratin fraction. For comparison, apoptotic or type I cell death was studied using the human colon cancer cell HT29/HI1 treated with the tyrosine kinase inhibitor tyrphostin A25 as a model. Cleavage of cytokeratin was already detectable in early morphological stages of apoptosis. F-actin was found to depolymerize; its globular form could be detected by antibodies; western blot analysis revealed no products of proteolytic cleavage. In conclusion, in our model of apoptosis, early stages are associated with depolymerization of actin and degradation of intermediate filaments. In contrast, during autophagic cell death intermediate and microfilaments are redistributed, but largely preserved, even beyond the stage of nuclear collapse. The present data support the concept that autophagic cell death is a separate entity of programmed cell death that is distinctly different from apoptosis.

Gamma-rays-induced death of human cells carrying mutations of BRCA1 or BRCA2

There is now evidence to suggest that BRCA1 and BRCA2 are involved in the response of cells to DNA damage and cell cycle checkpoint control. This report examines the death pathways of human cells with various BRCA1 and BRCA2 genotypes after exposure to gamma-rays. A lack of functional BRCA1 and BRCA2 led to defective repair of DNA double-strand breaks in irradiated cells. This impairment resulted in a relaxation of cell cycle checkpoints, production of micronuclei, and a loss of proliferative capacity. Heterozygous BRCA1 and BRCA2 mutations also led to enhanced radiosensitivity, with an impaired proliferative capacity after irradiation. The existence of a phenotype related to radiosensitivity in BRCA1+/- and BRCA2+/- cells raises the question of the response of heterozygous women to radiation.

Changes in vascularization of human breast cancer xenografts responding to antiestrogen therapy

To elucidate the previously suggested vascular effect(s) of antiestrogen therapy, we studied the effect of estrogen withdrawal and tamoxifen on 1) vascular resistance, 2) glucose and oxygen consumption, and 3) vascular density in a perfused breast cancer line (ZR75-1). Furthermore, we examined ZR75-1 tumors by functional CT-scanning (fCT) to determine changes in parameters related to tumor capillary transfer constants and vascular volume fraction in response to antiestrogenic manipulations. The vascular resistance decreased significantly from 42.7 to 20.8 mmHg x min x g x ml(-1) (P< .03) on day 9 after estrogen withdrawal, but not after 9 days of tamoxifen treatment. The estrogen-depleted tumors were significantly smaller than controls on day 9. There was no difference in nutrient consumption or vascular density in any of the experimental groups compared to controls. fCT showed an increase (P < .03) in vascular volume fraction during tumor growth, and this parameter was significantly lower after estrogen withdrawal when compared to controls (P < .05). Vascular resistance correlated with tumor size (R = 0.7, P < .0001), indicating that vascular resistance increases during tumor growth. The changes in vascular parameters after estrogen withdrawal indicate a vascular remodeling effect. This inhibition of vascular development by hormone deprivation may have important implications for future planning of multimodal treatment regimens.

Comparison of methods based on annexin-V binding, DNA content or TUNEL for evaluating cell death in HL-60 and adherent MCF-7 cells

HL-60 and MCF-7 cells were treated with 0.15 microM camptothecin (CPT) or with the solvent dimethylsulfoxide (DMSO) for the controls, for 2, 3 and 4 h or for 24, 48 and 72 h, respectively. The apoptotic index (AI) was then evaluated in parallel by the following flow cytometric methods: (1) double staining of unfixed cells with fluoresceinated annexin V and propidium iodide (PI), this after detachment by trypsinization in the case of MCF-7 cultures; (2) prefixation in 70% ethanol, extraction of degraded, low molecular weight DNA with 0.2 M phosphatecitrate buffer and analysis of the DNA content stained with PI; (3) TUNEL, i.e. labelling of DNA strand breaks with biotin-dUTP, followed by staining with streptavidin-fluorescein and counterstaining with PI. In HL-60 cells, the three methods gave similar results for the AI (3-4% in the controls and at 2 h of CPT treatment, and 35-43% at 3 and 4 h after CPT). This indicates that CPT-induced membrane alteration and DNA fragmentation occurred concomitantly in those cells. For MCF-7 cells, CPT-induced apoptosis developed more slowly, the AI, whether based on annexin V or on DNA content, remained unchanged at 24 h, then was increasing to 8% at 48 h and to 25% at 72 h of treatment. In these cells, the TUNEL index did not increase prior to 72 h, and the increase was minor (up to 9% vs. 2-3% in the controls) at 72 h of the treatment. This indicates that in MCF-7 cells DNA strand breaks cannot be effectively labelled, which may be due to inaccessibility of 3'-OH ends in the breaks to exogenous terminal deoxynucleotidyl transferase. The mechanism of endonucleolytic DNA fragmentation thus may be different, depending on the cell type.