Role of specific apoptotic pathways in the restoration of paclitaxel-induced apoptosis by valspodar in doxorubicin-resistant MCF-7 breast cancer cells

Psoralen-loaded polymeric lipid nanoparticles combined with paclitaxel for the treatment of triple-negative breast cancer

Background: Chemotherapeutic drugs are associated with toxic effects. Metastasis is the leading cause of death in breast cancer patients. Aim: To evaluate the antitumor effect of paclitaxel (PTX) combined with psoralen-loaded polymeric lipid nanoparticles (PSO-PLNs) in triple-negative breast cancer. Methods: After treatment of samples, cell viability, apoptosis, migration, invasion, expression of proteins in the IRAK1/NF-κB/FAK signal pathway, biodistribution and pathological characteristics were detected. Results: Compared with the control group, the PTX + PSO-PLNs group showed increased apoptosis and reduced migration, invasion and expression of phosphorylated IRAK1 and NF-κB, with significant inhibition of tumor growth and lung metastases and no obvious toxicity. Conclusion: Combined administration of PTX and PSO-PLNs exerted a synergistic effect and significantly inhibited the growth and metastasis of triple-negative breast cancer.

Enhancement of Tumor Cell Death by Combining gef Gene Mediated Therapy and New 1,4-Benzoxazepin-2,6-Dichloropurine Derivatives in Breast Cancer Cells

New treatment modalities are urgently needed to better manage advanced breast cancer. Combination therapies are usually more effective than monotherapy. In this context, the use of cyclic and acyclic O,N-acetals derivative compounds in combination with the suicide gef gene shown a potent anti-tumor activity and represent a new generation of anticancer agents. Here, we evaluate the use of the gef gene to promote and increase the anti-tumor effect of cyclic and acyclic O,N-acetals purine derivatives and elucidate their mechanisms of action. Among all compounds tested, those with a nitro group and a cyclic pattern structures (FC-30b2, FC-29c, and bozepinib) are the most benefited from the gef gene effect. These compounds, in combination with gef gene, were able to abolish tumor cell proliferation with a minimal dose leading to more effective and less toxic chemotherapy. The effect of this combined therapy is triggered by apoptosis induction which can be found deregulated in the later stage of breast cancer. Moreover, the combined therapy leads to an increase of cell post-apoptotic secondary necrosis that is able to promote the immunogenicity of cancer cells leading to a successful treatment. This data suggests that this novel combination therapy represents a promising candidate for breast cancer treatment.

TRPM2 channel-mediated regulation of autophagy maintains mitochondrial function and promotes gastric cancer cell survival via the JNK-signaling pathway

A lack of effective treatment is one of the main factors contributing to gastric cancer-related death. Discovering effective targets and understanding their underlying anti-cancer mechanism are key to achieving the best response to treatment and to limiting side effects. Although recent studies have shown that the cation channel transient receptor potential melastatin-2 (TRPM2) is crucial for cancer cell survival, the exact mechanism remains unclear, limiting its therapeutic potential. Here, using molecular and functional assays, we investigated the role of TRPM2 in survival of gastric cancer cells. Our results indicated that TRPM2 knockdown in AGS and MKN-45 cells decreases cell proliferation and enhances apoptosis. We also observed that the TRPM2 knockdown impairs mitochondrial metabolism, indicated by a decrease in basal and maximal mitochondrial oxygen consumption rates and ATP production. These mitochondrial defects coincided with a decrease in autophagy and mitophagy, indicated by reduced levels of autophagy- and mitophagy-associated proteins (i.e. ATGs, LC3A/B II, and BNIP3). Moreover, we found that TRPM2 modulates autophagy through a c-Jun N-terminal kinase (JNK)-dependent and mechanistic target of rapamycin-independent pathway. We conclude that in the absence of TRPM2, down-regulation of the JNK-signaling pathway impairs autophagy, ultimately causing the accumulation of damaged mitochondria and death of gastric cancer cells. Of note, by inhibiting cell proliferation and promoting apoptosis, the TRPM2 down-regulation enhanced the efficacy of paclitaxel and doxorubicin in gastric cancer cells. Collectively, we provide compelling evidence that TRPM2 inhibition may benefit therapeutic approaches for managing gastric cancer.

A simple reduction-sensitive micelles co-delivery of paclitaxel and dasatinib to overcome tumor multidrug resistance

Multidrug resistance (MDR) is one of the major obstacles in successful chemotherapy. The combination of chemotherapy drugs and multidrug-resistant reversing agents for treating MDR tumor is a good strategy to overcome MDR. In this work, we prepared the simple redox-responsive micelles based on mPEG-SS-C18 as a co-delivery system to load the paclitaxel (PTX) and dasatinib (DAS) for treatment of MCF-7/ADR cells. The co-loaded micelles had a good dispersity and a spherical shape with a uniform size distribution, and they could quickly disassemble and rapidly release drugs under the reduction environment. Compared with MCF-7 cells, the DAS and PTX co-loaded redox-sensitive micelle (SS-PDNPs) showed stronger cytotoxicity and a more improving intracellular drug concentration than other drug formulations in MCF-7/ADR cells. In summary, the results suggested that the simple co-delivery micelles of PTX and DAS possessed significant potential to overcome drug resistance in cancer therapy.

The role of individual caspases in cell death induction by taxanes in breast cancer cells

Background

In previous study we showed that caspase-2 plays the role of an apical caspase in cell death induction by taxanes in breast cancer cells. This study deals with the role of other caspases. We tested breast cancer cell lines SK-BR-3 (functional caspase-3) and MCF-7 (nonfunctional caspase-3).

Methods and results

Using western blot analysis we demonstrated the activation of initiator caspase-8 and -9 as well as executioner caspase-6 and -7 in both tested cell lines after application of taxanes (paclitaxel, SB-T-1216) at death-inducing concentrations. Caspase-3 activation was also found in SK-BR-3 cells. Employing specific siRNAs after taxane application, suppression of caspase-3 expression significantly increased the number of surviving SK-BR-3 cells. Inhibition of caspase-7 expression also increased the number of surviving SK-BR-3 and MCF-7 cells. On the other hand, suppression of caspase-8 and caspase-9 expression had no significant effect on cell survival. However, caspase-9 seemed to be involved in the activation of caspase-3 and caspase-7. Caspase-3 and caspase-7 appeared to activate mutually. Furthermore, we observed a significant decrease in mitochondrial membrane potential (flow cytometric analysis) and cytochrome c release (confocal microscopy, western blot after cell fractionation) from mitochondria in SK-BR-3 cells. No such changes were observed in MCF-7 cells after taxane treatment.

Conclusion

We conclude that the activation of apical caspase-2 results in the activation of caspase-3 and -7 without the involvement of mitochondria. Caspase-9 can be activated directly via caspase-2 or alternatively after cytochrome c release from mitochondria. Subsequently, caspase-9 activation can also lead to caspase-3 and -7 activations. Caspase-3 and caspase-7 activate mutually. It seems that there is also a parallel pathway involving mitochondria that can cooperate in taxane-induced cell death in breast cancer cells.

Systematic expression analysis of genes related to multidrug-resistance in isogenic docetaxel- and adriamycin-resistant breast cancer cell lines

Docetaxel (Doc) and adriamycin (Adr) are two of the most effective chemotherapeutic agents in the treatment of breast cancer. However, their efficacy is often limited by the emergence of multidrug resistance (MDR). The purpose of this study was to investigate MDR mechanisms through analyzing systematically the expression changes of genes related to MDR in the induction process of isogenic drug resistant MCF-7 cell lines. Isogenic resistant sublines selected at 100 and 200 nM Doc (MCF-7/100 nM Doc and MCF-7/200 nM Doc) or at 500 and 1,500 nM Adr (MCF-7/500 nM Adr and MCF-7/1,500 nM) were developed from human breast cancer parental cell line MCF-7, by exposing MCF-7 to gradually increasing concentrations of Doc or Adr in vitro. Cell growth curve, flow cytometry and MTT cytotoxicity assay were preformed to evaluate the MDR characteristics developed in the sublines. Some key genes on the pathways related to drug resistance (including drug-transporters: MDR1, MRP1 and BCRP; drug metabolizing-enzymes: CYP3A4 and glutathione S-transferases (GST) pi; target genes: topoisomerase II (TopoIIα) and Tubb3; apoptosis genes: Bcl-2 and Bax) were analyzed at RNA and protein expression levels by real time RT-qPCR and western blot, respectively. Compared to MCF-7/S (30.6 h), cell doubling time of MCF-7/Doc (41.6 h) and MCF-7/Adr (33.8 h) were both prolonged, and the cell proportion of resistant sublines in G1/G2 phase increased while that in S-phase decreased. MCF-7/100 nM Doc and MCF-7/200 nM Doc was 22- and 37-fold resistant to Doc, 18- and 32-fold to Adr, respectively. MCF-7/500 nM Adr and MCF-7/1,500 nM Adr was 61- and 274-fold resistant to Adr, three and 12-fold to Doc, respectively. Meantime, they also showed cross-resistance to the other anticancer drugs in different degrees. Compared to MCF-7/S, RT-qPCR and Western blot results revealed that the expression of MDR1, MRP1, BCRP, Tubb3 and Bcl-2 were elevated in both MCF-7/Doc and MCF-7/Adr, and TopoIIα, Bax were down-regulated in both the sublines, while CYP3A4, GST pi were increased only in MCF-7/Doc and MCF-7/Adr respectively. Furthermore, the changes above were dose-dependent. The established MCF-7/Doc or MCF-7/Adr has the typical MDR characteristics, which can be used as the models for resistance mechanism study. The acquired process of MCF-7/S resistance to Doc or Adr is gradual, and is complicated with the various pathways involved in. There are some common resistant mechanisms as well as own drug-specific changes between both the sublines.

Role of aldo-keto reductases and other doxorubicin pharmacokinetic genes in doxorubicin resistance, DNA binding, and subcellular localization

Background

Since proteins involved in chemotherapy drug pharmacokinetics and pharmacodynamics have a strong impact on the uptake, metabolism, and efflux of such drugs, they likely play critical roles in resistance to chemotherapy drugs in cancer patients.

Methods

To investigate this hypothesis, we conducted a whole genome microarray study to identify difference in the expression of genes between isogenic doxorubicin-sensitive and doxorubicin-resistant MCF-7 breast tumour cells. We then assessed the degree of over-representation of doxorubicin pharmacokinetic and pharmacodynamic genes in the dataset of doxorubicin resistance genes.

Results

Of 27,958 Entrez genes on the array, 7.4 per cent or 2,063 genes were differentially expressed by ≥ 2-fold between wildtype and doxorubicin-resistant cells. The false discovery rate was set at 0.01 and the minimum p value for significance for any gene within the “hit list” was 0.01. Seventeen and 43 per cent of doxorubicin pharmacokinetic genes were over-represented in the hit list, depending upon whether the gene name was identical or within the same gene family, respectively. The most over-represented genes were within the 1C and 1B families of aldo-keto reductases (AKRs), which convert doxorubicin to doxorubicinol. Other genes convert doxorubicin to other metabolites or affect the influx, efflux, or cytotoxicity of the drug. In further support of the role of AKRs in doxorubicin resistance, we observed that, in comparison to doxorubicin, doxorubincol exhibited dramatically reduced cytotoxicity, reduced DNA-binding activity, and strong localization to extra nuclear lysosomes. Pharmacologic inhibition of the above AKRs in doxorubicin-resistant cells increased cellular doxorubicin levels, restored doxorubicin cytotoxicity and re-established doxorubicin localization to the nucleus. The properties of doxorubicinol were unaffected.

Conclusions

These findings demonstrate the utility of using curated pharmacokinetic and pharmacodynamic knowledge bases to identify highly relevant genes associated with doxorubicin resistance. The induction of one or more of these genes was found to be correlated with changes in the drug’s properties, while inhibiting one specific class of these genes (the AKRs) increased cellular doxorubicin content and restored drug DNA binding, cytotoxicity, and subcellular localization.

Systemic therapy options in BRCA mutation-associated breast cancer

BRCA mutation-associated breast cancers are characterized by deficient homologous recombination of DNA, and 80 % of BRCA1-associated breast cancers display the basal-like molecular subtype. Traditionally, BRCA carriers have received conventional systemic chemotherapy based on their baseline tumor characteristics, and it is generally accepted that after the appropriate treatment the prognosis of a mutation carrier is equivalent to that of a patient with sporadic breast cancer. However, with the growing understanding of the functions of BRCA1/2 proteins in homologous DNA repair, it is recognized that BRCA-associated breast cancer tumors may have distinct biochemical characteristics and thus require tailored treatment strategies. Tumors arising in patients with BRCA mutations were shown to be particularly sensitive to platinum compounds or inhibitors of poly(ADP-ribose) polymerase. In addition, BRCA1-mutation carriers seem to benefit from anthracycline-taxane-containing regimens as much as sporadic triple-negative breast cancers do. In this article, we review the functions of the BRCA1 and BRCA2 genes, and their differential chemosensitivity in both the preclinical and clinical settings. The optimal chemotherapy regimen for this subset of patients still remains to be determined.

Novel drug delivery system based on docetaxel-loaded nanocapsules as a therapeutic strategy against breast cancer cells

In the field of cancer therapy, lipid nanocapsules based on a core-shell structure are promising vehicles for the delivery of hydrophobic drugs such as docetaxel. The main aim of this work was to evaluate whether docetaxel-loaded lipid nanocapsules improved the anti-tumor effect of free docetaxel in breast cancer cells. Three docetaxel-loaded lipid nanocapsules were synthesized by solvent displacement method. Cytotoxic assays were evaluated in breast carcinoma (MCF-7) cells treated by the sulforhodamine B colorimetric method. Cell cycle was studied by flow cytometry and Annexin V-FITC, and apoptosis was evaluated by using propidium iodide assays. The anti-proliferative effect of docetaxel appeared much earlier when the drug was encapsulated in lipid nanoparticles than when it was free. Docetaxel-loaded lipid nanocapsules significantly enhanced the decrease in IC₅₀ rate, and the treated cells evidenced apoptosis and a premature progression of the cell cycle from G(1) to G(2)-M phase. The chemotherapeutic effect of free docetaxel on breast cancer cells is improved by its encapsulation in lipid nanocapsules. This approach has the potential to overcome some major limitations of conventional chemotherapy and may be a promising strategy for future applications in breast cancer therapy.

The selective cytotoxic activity in breast cancer cells by an anthranilic alcohol-derived acyclic 5-fluorouracil O,N-acetal is mediated by endoplasmic reticulum stress-induced apoptosis

Advance in the knowledge of molecular biology has thrown light on many aspects of apoptosis regulation mechanisms. This has allowed a change in anti-cancer therapy trends, from classic cytotoxic strategies to the development of new non-harmful therapies which target the apoptosis response selectively only in tumour cells. We have selected an anthranilic alcohol-derived acyclic 5-fluorouracil O,N-acetal (5) to carry out the anti-cancer studies. This compound shows activity as a potent growth inhibitor of the tumour cell line MCF-7 at a very low concentration. Moreover, when this compound was administered to the non-neoplastic cell line, MCF-10A displayed less toxicity resulting in lower rates of apoptosis. Further studies by microarray hybridization, real-time PCR and western blot showed that when administered to human breast cancer cells, MCF-7, 5 had no activity against classic pro-apoptotic genes such as p53, and even induced the down-regulation of anti-apoptotic genes such as Bcl-2. In contrast, several pro-apoptotic genes related with the endoplasmic reticulum (ER)-stress-induced apoptosis, such as BBC3 and Noxa, appeared up-regulated. These results seem to show that the mechanism of action and selectivity of 5 was via the activation of the ER stress-induced apoptosis. The selective activity of this compound against tumour cells via the ER stress-induced apoptosis supposes a great advantage for future therapeutic use.

Taxane resistance in breast cancer: a closed HER2 circuit?

Microtubule inhibitors, such as the taxanes docetaxel and paclitaxel, are commonly used drugs for the treatment of breast cancer. Although highly active in a large fraction of individuals a considerable number of patients show poor response due to either intrinsic or acquired drug resistance. Extensive research in the past identified several taxane resistance-related mechanisms being activated by pathologically altered single gene function. To date, however, a clinically relevant predictive biomarker for taxanes has not been derived yet from this knowledge, most likely due to the manifold of resistance mechanisms that may combine in one tumor, thereby fostering escape from taxane cytotoxicity. Here, we aimed to comprehensively review the current literature on taxane resistance mechanisms in breast cancer. Interestingly, besides altered microtubule physiology we identified the HER2 signaling cascade as a major dominator influencing several routes of cytotoxicity escape, such as cell survival, apoptosis, drug efflux, and drug metabolism. Furthermore, the transcription factor YBX-1, activated by HER2, facilitates a sustaining HER2 signaling feedback loop contributing to the establishment of cellular survival detours. In conclusion, taxane resistance in breast cancer follows a multiplex establishment of drug cytotoxicity escape routes, which may be most efficiently therapeutically targeted by interference with their mutually governing signaling nodes.

New (RS)-benzoxazepin-purines with antitumour activity: The chiral switch from (RS)-2,6-dichloro-9-[1-(p-nitrobenzenesulfonyl)-1,2,3,5-tetrahydro-4,1-benzoxazepin-3-yl]-9H-purine

Completing an SAR study, a series of (RS)-6-substituted-7- or 9-(1,2,3,5-tetrahydro-4,1-benzoxazepine-3-yl)-7H or 9H-purines has been prepared under microwave-assisted conditions. Their antiproliferative activities on MCF-7 and MDA-MB-231 cancerous cell lines are presented, being the majority of the IC(50) values below 1μM. The most active compound (RS)-2,6-dichloro-9-[1-(p-nitrobenzenesulfonyl)-1,2,3,5-tetrahydro-4,1-benzoxazepin-3-yl]-9H-purine (14) presents an IC(50) of 0.166μM against the human cancerous cell line MDA-MB-231. Compound 14 was the most selective against the human breast adenocarcinoma MCF-7 and MDA-MB-231 cancer cell lines (Therapeutic Indexes, TIs=5.1 and 11.0, respectively) in relation to the normal one MCF-10A. (RS)-14 was resolved into its enantiomers. Both enantiomers are equally potent, but more potent than the corresponding racemic mixture. (R)-14 induces apoptosis against MCF-7 up to 52.50% of cell population after 48h, being more potent than the clinical-used drug paclitaxel (43%). (RS)-14 induces no acute toxicity in mice after two weeks of treatment.

Selective targeting of death receptor 5 circumvents resistance of MG-63 osteosarcoma cells to TRAIL-induced apoptosis

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a tumor necrosis factor superfamily member, targets death receptors and selectively kills malignant cells while leaving normal cells unaffected. However, unlike most cancers, many osteosarcomas are resistant to TRAIL. To investigate this resistance, we characterized the response of MG-63 osteosarcoma cells and hPOB-tert osteoblast-like cells to TRAIL and agonist antibodies to death receptor 4 (DR4) and death receptor 5 (DR5). We found that MG-63 osteosarcoma cells and hPOB-tert osteoblast-like cells show no or very little response to TRAIL or a DR4 agonist, but MG-63 cells undergo apoptosis in response to a DR5 agonist. Analysis of TRAIL receptor expression showed that normal osteoblastic and osteosarcoma cells express a variety of TRAIL receptors but this does not correlate to TRAIL responsiveness. Production of the soluble decoy receptor osteoprotegerin also could not explain TRAIL resistance. We show that TRAIL activates the canonical caspase-dependent pathway, whereas treatment with cycloheximide increases the sensitivity of MG-63 cells to TRAIL and anti-DR5 and can also sensitize hPOB-tert cells to both agents. Proapoptotic and antiapoptotic protein expression does not significantly differ between MG-63 and hPOB-tert cells or change following treatment with TRAIL or anti-DR5. However, sequencing the death domain of DR4 in several osteoblast-like cells showed that MG-63 osteosarcoma cells are heterozygous for a dominant-negative mutation, which can confer TRAIL resistance. These results suggest that although the dominant-negative form of the receptor may block TRAIL-induced death, an agonist antibody to the active death receptor can override cellular defenses and thus provide a tailored approach to treat resistant osteosarcomas.

Involvement of caspase-8 in chemotherapy-induced apoptosis of patient derived leukemia cell lines independent of the death receptor pathway and downstream from mitochondria

Resistance of leukemic cells to chemotherapy frequently occurs in patients with acute leukemia, which may be caused by alterations in common apoptotic pathways. Controversy exists whether cytostatic agents induce the mitochondrial or death receptor pathway of apoptosis. In the mitochondrial pathway cytochrome C release and caspase-9 activation play a central role in the induction of apoptosis, while formation of a Death Inducing Signaling Complex (DISC) and caspase-8 activation have been reported to be essential in death receptor-induced apoptosis. Here, we show in human derived myeloid and lymphoblastic leukemia cell lines that caspase-8 plays a more important role than previously expected in apoptosis mediated via the mitochondrial pathway. We demonstrated in these malignant cells chemotherapy-induced apoptosis independent of the death receptor pathway, since blocking this pathway using a retroviral construct encoding Flice inhibitory protein (FLIP) did not inhibit drug-induced apoptosis or caspase-8 activation, while overexpression of Bcl-2 completely inhibited both events. Furthermore, we showed that activation of caspase-8 by cytostatic agents occurred downstream from mitochondria. Since caspase-8 plays a central role in both death receptor- and chemotherapy-induced apoptosis of malignant cells from patients with acute leukemia, therapeutic strategies focusing at modulation and activation of caspase-8 may be successful in the treatment of drug-resistant malignancies.

Contributing factors of temozolomide resistance in MCF-7 tumor xenograft models

Vasculature mediated drug resistance in tumors was studied in female SCID mice bearing wild type MCF-7 and adriamycin resistant MCF-7/ADR xenograft using temozolomide (TMZ). A strong tumor growth inhibitory effect of TMZ treatment was observed in MCF-7 tumors during the initial treatment phase with subsequent relapse, but not in MCF-7/ADR tumors. Non-invasive MRI measurements of tumor vascular volume and vascular permeability-surface area product (PS) demonstrated significant reduction of PS in long-term treated MCF-7, but not in MCF-7/ADR tumors. O(6)-Methylguanine-DNA methyltransferase (MGMT) mRNA, and VEGF expression was analyzed using real-time RT-PCR and ELISA, respectively. No significant changes in MGMT mRNA and VEGF expression were observed in either MCF-7 or MCF-7/ADR tumors. However, in vitro incubation of MCF-7 cells with TMZ did induce the expression of MGMT mRNA. In addition, p53 and p21 levels were scored by immunoblotting. Exposure of cells to TMZ did not affect either the p21 or the p53 expression in both MCF-7 and MCF-7/ADR cells. The absence of these molecular responses to TMZ treatment in MCF-7 tumors in vivo supports the possibility that the onset of cancer drug resistance is associated with reduced PS, which can decrease delivery of the drug to cancer cells.

Paclitaxel induced apoptosis in breast cancer cells requires cell cycle transit but not Cdc2 activity

PURPOSE

Paclitaxel (PTX) is a widely used chemotherapy agent and may cause cell death by apoptosis subsequent to microtubule (MT) disruption. In this paper, we have investigated whether cell cycle transit and or Cdc2 (Cdk1) activity is required for the apoptosis induced by PTX.

METHODS

Cell cycle was analyzed by flow cytometry, Cdc2 was assayed bio chemically. Cdc2 activity was decreased by siRNA and dominant negative (dn) Cdc2 expression. Cells were arrested by chemical or biological inhibitors in a G1 or S phase. Apoptosis was measured by DNA fragmentation and examination of nuclei by microscopy. JNK and AKT activations were assessed as well.

RESULTS

Cell cycle inhibition was highly effective in decreasing PTX induced apoptosis. MT morphology was not altered by these inhibitors. PTX induced JNK activity or AKT mediated BAD phosphorylation was unaffected by cell cycle inhibitors. Abrogation of Cdc 2 activity was without effect on PTX induced apoptosis.

CONCLUSIONS

While cell cycle transit is required for PTX induced apoptosis; Cdc2 activity is not required.

cDNA microarray analysis of isogenic paclitaxel- and doxorubicin-resistant breast tumor cell lines reveals distinct drug-specific genetic signatures of resistance

cDNA microarray analysis is a highly useful tool for the classification of tumors and for prediction of patient prognosis to specific cancers based on this classification. However, to date, there is little evidence that microarray approaches can be used to reliably predict patient response to specific chemotherapy drugs or regimens. This is likely due to an inability to differentiate between genes affecting patient prognosis and genes that play a role in response to specific drugs. Thus, it would be highly useful to identify genes whose expression correlates with tumor cell sensitivity to specific chemotherapy agents in a drug-specific manner. Using cDNA microarray analysis of wildtype MCF-7 breast tumor cells and isogenic paclitaxel-resistant (MCF-7(TAX)) or doxorubicin-resistant (MCF-7(DOX)) derivative cell lines, we have uncovered drug-specific changes in gene expression that accompany the establishment of paclitaxel or doxorubicin resistance. These changes in gene expression were confirmed by quantitative reverse transcription polymerase chain reaction and immunoblotting experiments, with a confirmation rate of approximately 91-95%. The genes identified may prove highly useful for prediction of response to paclitaxel or doxorubicin in patients with breast cancer. To our knowledge this is the first report of drug-specific genetic signatures of resistance to paclitaxel or doxorubicin, based on a comparison of gene expression between isogenic wildtype and drug-resistant tumor cell lines. Moreover, this study provides significant insight into the wide variety of mechanisms through which resistance to these agents may be acquired in breast cancer.

[Antimitochondrial agents: a new class of anticancer agents]

Over the last 2 decades, the role of apoptosis in anticancer agent cytotoxicity has become clear. Defects in the regulation of apoptosis (programmed cell death) make important contributions to the pathogenesis and progression of most cancers and leukemias. Apoptosis defects also have a key role in cell resistance to chemotherapy. Mitochondria play a central part in cell death in response to anticancer agents. Most of these agents target mitochondria via caspases or other regulator elements of the apoptotic machinery. Nevertheless, some anticancer agents, already in clinical use (paclitaxel, vinblastine, lonidamine, etoposide, arsenic trioxide) or in pre-clinical development (betulinic acid, MT21), directly target and permeabilize mitochondria. The acknowledgement of mitochondria as a new target for anticancer agents provides a new way to bypass cancer cell chemoresistance.

Antitumoural properties of benzannelated seven-membered 5-fluorouracil derivatives and related open analogues. Molecular markers for apoptosis and cell cycle dysregulation

Attention is increasingly being focussed on the cell cycle and apoptosis as potential targets for therapeutic intervention in cancer. We prepared a series of bioisosteric benzannelated seven-membered 5-FU O,N-acetals to test them against the MCF-7 human breast cancer cell line. Benzo-fused seven-membered O,O-acetals or their acyclic analogues led to the expected 5-FU O,N-acetals (or aminals), in addition to six- and 14-membered aminal structures and acyclic compounds. All the cyclic aminals provoked a G0/G1-phase cell cycle arrest, whereas Ftorafur, a known prodrug of 5-FU, and 1-[2-(2-hydroxymethyl-4-nitrophenoxy)-1-methoxyethyl]-5-fluorouracil (11) induced an S-phase cell cycle arrest. Although breast cancer is most often treated with conventional cytotoxic agents it has proved difficult to induce apoptosis in breast cancer cells, but improved clinical responses may be obtained by identifying therapies that are particularly effective in activating apoptosis. 1-(2,3-Dihydrobenzoxepin-2-yl)-5-fluorouracil (5) may be particularly useful in stimulating apoptosis in breast cancer.

Antitumor mechanism of evodiamine, a constituent from Chinese herb Evodiae fructus, in human multiple-drug resistant breast cancer NCI/ADR-RES cells in vitro and in vivo

Drug resistance is one of the main obstacles to the successful treatment of cancer. The availability of agents that are highly effective against drug-resistant cancer cells is therefore essential. The present study was performed to examine the anticancer effects of evodiamine, a major constituent of the Chinese herb Evodiae fructus, in adriamycin-resistant human breast cancer NCI/ADR-RES cells. Evodiamine inhibited the proliferation of NCI/ADR-RES cells in a concentration-dependent manner with a GI50 of 0.59 +/- 0.11 microM. This agent also caused a substantial apoptosis at 1 microM. FACScan flow cytometric analysis of cell cycle progression revealed that a G2/M arrest was initiated after a 12-h exposure to the drug. Evodiamine increased tubulin polymerization as determined by the immunocytochemical and in vivo tubulin polymerization analyses. In a time- and concentration-dependent manner, evodiamine also promoted the phosphorylations of Raf-1 kinase and Bcl-2. The phosphorylation site of Raf-1 kinase was identified to be serine338. The in vivo anticancer effects of evodiamine were evaluated in Balb-c/nude mice following a tumor xenograft implantation of NCI/ADR-RES cells. The antitumor activity of evodiamine against the human multiple-drug resistant tumor xenograft was found to be superior to that of paclitaxel. Evodiamine therefore represents a highly promising chemotherapeutic agent in the treatment of human multiple-drug resistant cancer cells.

Paclitaxel treatment of breast cancer cell lines modulates Fas/Fas ligand expression and induces apoptosis which can be inhibited through the CD40 receptor

OBJECTIVE

Cytotoxic chemotherapy of advanced breast cancer is frequently complicated by drug resistance. Our goal was to define the role of the apoptosis-regulating receptors Fas (CD95) and CD40 in the chemosensitivity of breast cancer.

METHODS

The sensitivity of four breast cancer cell lines to paclitaxel and mitoxantrone was evaluated using an ATP-based cell viability assay. After verification of apoptosis by annexin V staining and TUNEL assay, cell lines were characterized regarding their constitutive expression of both surface and soluble (s)Fas (CD95) and Fas ligand (Fas-L). The role of the Fas/Fas-L system and different caspases was assessed by blocking drug-mediated apoptosis with specific antibodies. Finally, the paclitaxel sensitivity of the CD40-negative cell line KS was compared to that of its CD40-positive transfectant KS-CD40.

RESULTS AND CONCLUSION

While the cytotoxic effect of mitoxantrone did not correlate with Fas expression, the results presented here suggest some involvement of the Fas/Fas-L system in paclitaxel-induced apoptosis. Cell lines with constitutive expression of Fas/sFas demonstrated a higher sensitivity to paclitaxel than Fas-negative cells. Incubation with paclitaxel led to a measurable downregulation of the expression of both soluble and surface Fas receptor in these cells. Interestingly, stimulation of the CD40 receptor inhibited paclitaxel-induced apoptosis in the transfected cell line KS-CD40, suggesting a role of this receptor in the modulation of chemosensitivity.

Cross-resistance studies of isogenic drug-resistant breast tumor cell lines support recent clinical evidence suggesting that sensitivity to paclitaxel may be strongly compromised by prior doxorubicin exposure

Less than half of breast cancer patients respond to second-line chemotherapy with paclitaxel after failing treatment with anthracyclines such as doxorubicin. A recent clinical trial by Paridaens et al. [J. Clin. Oncol. 18 : 724-733, 2000] examined whether patients may derive a better clinical benefit if paclitaxel was administered before doxorubicin. While overall survival was similar regardless of the order of drug administration, a >4-fold reduction in the response rate to paclitaxel was observed after late crossover from doxorubicin, compared to the response rate to doxorubicin after late crossover from paclitaxel. This may be related to differences in the ability of the drugs to induce cross-resistance to each other. To test this hypothesis, we examined whether isogenic breast tumor cells selected for resistance to doxorubicin exhibit greater cross-resistance to paclitaxel and other drugs than identical cells selected for resistance to paclitaxel. We found that cells selected for resistance to paclitaxel showed strong resistance (>/=40-fold) to paclitaxel and docetaxel, with little cross-resistance (4-fold) to doxorubicin. In contrast, cells selected for resistance to doxorubicin exhibited 50-fold resistance to doxorubicin and a dramatic 4700-fold and 14,600-fold cross-resistance to paclitaxel and docetaxel, respectively. Doxorubicin-resistant cells exhibited higher P-glycoprotein and breast cancer resistance protein (BCRP) levels than paclitaxel-resistant cells. In addition, procaspase-9 was strongly downregulated in doxorubicin-resistant cells but not in paclitaxel-resistant cells. These differences may account for the contrasting cross-resistance profiles observed for the two cell lines and may help to explain why treatment of breast cancer patients with paclitaxel appears to be compromized by prior doxorubicin exposure.

Effet radiosensibilisateur de l'acide linoléique conjugué chez les cellules cancéreuses du sein MCF-7 et MDA-MB-231

Apoptotic pathways in breast cancer cells are frequently altered, reducing the efficiency of radiotherapy. Conjugated linoleic acid (CLA), known to trigger apoptosis, was tested as radiosensitizer in breast cancer cells MCF-7 and MDA-MB-231. The CLA-mix, made up of the isomers CLA-9cis 11trans and CLA-10trans 12cis, was compared to three purified isomers, i.e., the CLA-9cis 11cis, CLA-9cis 11trans, and CLA-10trans 12cis. Using the apoptotic marker YO-PRO®-1, the CLA-9cis 11cis at 50 µmol/L turned out to be the best apoptotic inducer leading to a 10-fold increase in MCF-7 cells and a 2,5-fold increase in MDA-MB-231 cells, comparatively to the CLA-mix. Contrary to previous studies on colorectal and prostate cancer cells, CLA-10trans 12cis does not lead to an apoptotic response on breast cancer cell lines MCF-7 and MDA-MB-231. Our results also suggest that the main components of the CLA-mix (CLA-9cis 11trans and CLA-10trans 12cis) are not involved in the induction of apoptosis in the breast cancer cells studied. A dose of 5 Gy did not induce apoptosis in MCF-7 and MDA-MB-231 cells. The addition of CLA-9cis 11cis or CLA-mix has allowed us to observe a radiation-induced apoptosis, with the CLA-9cis 11cis being about 8-fold better than the CLA-mix. CLA-9cis 11cis turned out to be the best radiosensitizer, although the isomers CLA-9cis 11trans and CLA-10trans 12cis have also reduced the cell survival following irradiation, but using a mechanism not related to apoptosis. In conclusion, the radiosensitizing property of CLA-9cis 11cis supports its potential as an agent to improve radiotherapy against breast carcinoma.Key words: breast cancer, conjugated linoleic acid (CLA), radiotherapy, apoptosis.

Potent Killing of Paclitaxel- and Doxorubicin-resistant Breast Cancer Cells by Calphostin C Accompanied by Cytoplasmic Vacuolization

Drug resistance is a major impediment to the successful treatment of breast cancer using chemotherapy. The photoactivatable drug calphostin C has shown promise in killing select drug-resistant tumor cells lines in vitro. To assess the effectiveness of this agent in killing doxorubicin- or paclitaxel-resistant breast tumor cells and to explore its mode of action, MCF-7 cells were exposed to increasing concentrations of either doxorubicin or paclitaxel until maximum resistance was obtained. This resulted in the creation of isogenic drug-resistant MCF-7TAX and MCF-7DOX cell lines, which were approximately 50- and 65-fold resistant to paclitaxel and doxorubicin, respectively. Interestingly, calphostin C was able to kill MCF-7TAX cells as efficiently as wildtype MCF-7 cells (IC50s were 9.2 and 13.2 nM, respectively), while MCF-7DOX cells required a 5-fold higher concentration of calphostin C to achieve the same killing (IC50 = 64.2 nM). Consistent with their known mechanisms of action, paclitaxel killed tumor cells by inducing mitotic arrest and cell multinucleation, while doxorubicin induced plasma membrane blebbing and decreased nuclear staining with propidium iodide. In contrast, cytoplasmic vacuolization accompanied cell killing by calphostin C in these cell lines, without the induction of caspase-8 or PARP cleavage or the release of cytochrome c from mitochondria. Calphostin C had little effect on the uptake of either paclitaxel or doxorubicin by the cells. Taken together, the above data suggests that calphostin C is able to potently kill drug-resistant breast tumor cells through a mechanism that may involve the induction of cytoplasmic vacuolization, without activation of typical apoptotic pathways. Consequently, calphostin C may prove useful clinically to combat tumor growth in breast cancer patients whose tumors have become unresponsive to anthracyclines or taxanes, particularly in association with photodynamic therapy.

p53 expression and resistance against paclitaxel in patients with metastatic breast cancer

PURPOSE

Paclitaxel is an important agent in the pharmacological treatment of metastatic breast cancer. Despite its efficacy in selected patients, the majority of patients have a resistance against paclitaxel. The aim of this study was to identify the responding patients and hence prevent the other patients from ineffective treatment. Identifying these patients could spare them an ineffective treatment and could in turn characterize a subgroup of patients with a higher response rate.

MATERIAL AND METHODS

Thirty-three patients with metastatic breast cancer received paclitaxel 175 mg/m(2 )either as first- (15 patients) or as second-line (18 patients) treatment. Immunohistochemistry was performed on the blocks of the primary tumors with monoclonal antibodies against p53, HER-2/ neu, P-glycoprotein, Glutathione-S-Transferase-pi, and beta-tubulin II. The expression of those factors was then correlated with the objective response to paclitaxel.

RESULTS

Ten of 33 patients had an objective response to treatment. A significant correlation with the objective response was found for the expression of p53. None of the tumors with p53 expression ( n=11) responded to paclitaxel. In contrast, 10 of the 22 patients without p53 expression showed an objective response ( P=0.013). Expression of HER-2/ neu, P-glycoprotein, Glutathione-S-Transferase-pi, and beta-tubulin II did not show a correlation with the response to paclitaxel.

CONCLUSION

The immunohistochemical detection of p53 characterizes patients with metastatic breast cancer unlikely to respond to paclitaxel.

Acetaminophen induces a caspase-dependent and Bcl-XL sensitive apoptosis in human hepatoma cells and lymphocytes

Acetaminophen is a widely used analgesic and antipyretic drug that exhibits toxicity at high doses to the liver and kidneys. This toxicity has been attributed to cytochrome P-450-generated metabolites which covalently modify target proteins. Recently, acetaminophen, in its unmetabolized form, has been shown to affect a variety of cells and tissues, for instance, testicular and lymphoid tissues and lymphocyte cell lines. The effects on cell viability of acetaminophen at a concentration comparable to that achieved in plasma during acetaminophen toxicity have now been examined with a hepatoma cell line SK-Hep1, primary human peripheral blood lymphocytes and human Jurkat T cells. Acetaminophen reduced cell viability in a time-dependent manner. Staining of cells with annexin-V also revealed that acetaminophen induced, after 8 hr of treatment, a loss of the asymmetry of membrane phospholipids, which is an early event associated with apoptosis. Acetaminophen triggered the release of cytochrome c from mitochondria into the cytosol, activation of caspase-3, 8, and 9, cleavage of poly(ADP-ribose) polymerase, and degradation of lamin B1 and DNA. Whereas cleavage of DNA into internucleosomal fragments was apparent in acetaminophen treated SK-Hep1 and primary lymphocytes, DNA was only degraded to 50-kb fragments in treated Jurkat cells. Overexpression of the antiapoptotic protein Bcl-XL prevented these various apoptotic events induced by acetaminophen in Jurkat cells. Caspase-8 activation was a postmictochondrial event and occurred in a Fas-independent manner. These results demonstrate that acetaminophen induces caspases-dependent apoptosis with mitochondria as a primary target. These results also reiterate the potential role of apoptosis in acetaminophen hepatic and extrahepatic toxicity.

The role of caspase-8 in resistance to cancer chemotherapy

Toxicity of chemotherapeutic agents against cancer cells is mediated through the initiation of programmed cell death. Apoptosis is an evolutionarily conserved cascade of intracellular proteolytic events propagated by a family of cysteine proteases called caspases. Many receptor- and non-receptor-mediated death signals induce apoptosis via activation of caspase-8 (FLICE/MACH). Mechanisms of tumor resistance to cytotoxic drugs through decreased apoptosis may occur by altered expression of caspase-8, upregulation of caspase-8 inhibitors like FLIP (FLICE-like Inhibitory Protein), or sequestration of caspase-8 by Bcl-2. Modulation of caspase-8 and apoptosis may be a therapeutic strategy for sensitization of drug-resistant malignancies to radiation or combination chemotherapy.