JNK/SAPK mediates doxorubicin-induced differentiation and apoptosis in MCF-7 breast cancer cells

Glycyrrhetinic acid remodels the tumor microenvironment and synergizes with doxorubicin for breast cancer treatment in a murine model

We aimed to combine glycyrrhetinic acid with doxorubicin to prepare, characterize and evaluate a drug delivery nano-system with REDOX sensitivity for the treatment of breast cancer. M-DOX-GA NPs prepared by nano sedimentation were spherical, with a particle size of 181 nm. And the maximum encapsulation efficiency and drug loading in M-DOX-GA NPs were 89.28% and 18.22%, respectively. Cytotoxicity and cellular uptake experiments of nanoparticles to KC cells, Cal-27 cells and 4T1 cells were studied by the CCK-8 method. The result indicated that M-DOX-GA NPs could accurately release the drug into the tumor cells, thus achieving the targeted release of the drug. Comparing the survival rate of the above three cells, it was found that M-DOX-GA NPs had a good tumor selectivity and had a more significant therapeutic effect on breast cancer. A 4T1-bearing mouse model was established, and the tumor inhibition rate was 77.37% after injection of nanoparticle solution for 14 d. Normal tissue H&E stained sections and TUNEL assay were verified M-DOX-GA NPs have excellent tumor suppressive effect, and can efficiently reduce the toxic side effects on normal organisms, and effectively avoided 4T1 cells metastasis. Immunofluorescence detection and Western-blot analysis figured a decline in both CUGBP1 and α-SMA, which verifying the TME remodeling induced by glycyrrhetinic acid. Collectively, the combination of doxorubicin and glycyrrhetinic acid is an effective and safe strategy for remodeling fibrotic TME by improving the therapeutic outcome for breast cancer.

Histone deacetylase SIRT6 regulates chemosensitivity in liver cancer cells via modulation of FOXO3 activity

Liver cancer is the leading cause of cancer-related mortality worldwide and its incidence is increasing. Considerable effort has been made in recent decades to improve the diagnosis and treatment of liver cancer. Advanced liver cancer often exhibits a poor response to chemotherapy and poor prognosis due to acquired chemoresistance and tumor recurrence. Understanding the precise molecular mechanisms that are responsible for chemotherapeutic drug-induced cell death could potentially identify novel therapeutic targets and improve liver cancer treatment. In the present study, it was demonstrated that in response to doxorubicin, the most frequently used chemical compound for liver cancer treatment, histone deacetylase sirtuin 6 (SIRT6) is specifically downregulated. This enables forkhead box O3 (FOXO3) upregulation, translocation into the nucleus and increased expression of its target genes p27 and Bim, which further induce apoptosis. Overexpression of SIRT6, but not enzyme-inactivated mutants, prevents FOXO3 translocation into the nucleus and doxorubicin-induced cell death. SIRT6 interacts with FOXO3 and this interaction increases FOXO3 ubiquitination and decreases its stability. Finally, it was identified that the effect of SIRT6 in preventing doxorubicin-induced cell death requires FOXO3. Overexpression of SIRT6 could not prevent doxorubicin-induced cell death in FOXO3-knockdown cells. Therefore, it was concluded that SIRT6 plays a central role in determining doxorubicin-induced cell death via modulation of FOXO3 activity. Therapeutic targeting of SIRT6 and/or FOXO3 may offer novel strategies for treatment of liver cancer.

Reversible permeabilization of the mitochondrial membrane promotes human cardiomyocyte differentiation from embryonic stem cells

Cell death and differentiation appear to share similar cellular features. In this study, we aimed to investigate whether differentiation and mitochondrial cell death use a common pathway. We assessed the hallmarks of apoptosis during cardiomyocyte differentiation of human embryonic stem cells and found remarkable changes in P53, reactive oxygen species, apoptotic protease-activating factor 1, poly[ADP-ribose]polymerase 1, cellular adenosine triphosphate, and mitochondrial complex I activity. Furthermore, we observed reversible mitochondrial membrane permeabilization during cardiomyocyte differentiation accompanied by reversible loss of mitochondrial membrane potential, and these changes coincided with the fluctuating patterns of cytosolic cytochrome c accumulation and subsequent caspase-9 and -3/7 activation. Moreover, the use of apoptosis inhibitors (BCL2-associated X protein [BAX] inhibitor and caspase-3/7 inhibitor) during differentiation impaired cardiomyocyte development, resulting in substantial downregulation of T, MESP1, NKX2.5, and α-MHC. Additionally, although the expression of specific differentiation markers (T, MESP1, NKX2.5, MEF2C, GATA4, and SOX17) was enhanced in doxorubicin-induced human embryonic stem cells, the stemness-specific markers (OCT4 and NANOG) showed significant downregulation. With increasing doxorubicin concentration (0.03-0.6 µM; IC50  = 0.5 µM), we observed a marked increase in the expression of mesoderm and endoderm markers. In summary, we suggest that reversible mitochondrial outer membrane permeabilization promotes cardiomyocyte differentiation through an attenuated mitochondria-mediated apoptosis-like pathway.

Protective effects of curcumin against doxorubicin-induced toxicity and resistance: A review

Doxorubicin (DOX)-induced toxicity and resistance are major obstacles in chemotherapeutic approaches. Despite effective in the treatment of numerous malignancies, some clinicians have voiced concern that DOX has the potential to cause debilitating consequences in organ tissues, especially the heart. The mechanisms of toxicity and resistance are respectively related to induction of reactive oxygen species (ROS) and up-regulation of ATP-binding cassette (ABC) transporter. Curcumin (CUR) with several biological and pharmacological properties is expected to restore DOX-mediated impairments to tissues. This review is intended to address the current knowledge on DOX adverse effects and CUR protective actions in the heart, kidneys, liver, brain, and reproductive organs. Coadministration of CUR and DOX is capable of ameliorating DOX toxicity pertained to antioxidant, apoptosis, autophagy, and mitochondrial permeability.

Cellular effects of a turmeric root and rosemary leaf extract on canine neoplastic cell lines

BACKGROUND

The use of nutraceuticals is gaining in popularity in human and canine oncology with a relatively limited understanding of the effects in the vastly different tumor types seen in canine oncology. We have previously shown that turmeric root (TE) and rosemary leaf (RE) extracts can work synergistically to reduce neoplastic cell growth, but the mechanisms are poorly understood and require further elucidation.

RESULTS

Three different canine cell lines (C2 mastocytoma, and CMT-12 mammary carcinoma, D17 osteosarcoma) were treated with 6.3 μg mL^-1 extract individually, or 3.1 μg mL^-1 of each extract in combination based on studies showing synergy of these two extracts. Apoptosis, antioxidant effects, cellular accumulation of curcumin, and perturbation of signaling pathways were assessed. The TE + RE combination treatment resulted in Caspase 3/7 activation and apoptosis in all cell lines, beyond the effects of TE alone with the CMT-12 cell line being most susceptible. Both extracts had antioxidant effects with RE reducing reactive oxygen species (ROS) by 40-50% and TE reducing ROS by 80-90%. In addition RE treatment enhanced the c-jun N-terminal kinase (JNK) activity in the C2 cell line and TE + RE exposure increased activated JNK by 4-5 times in the CMT-12 cell line. Upon further examination, it was found that RE treatment caused a significant increase in the cellular accumulation of curcumin by approximately 30% in the C2 and D17 cell lines, and by 4.8-fold in the CMT-12 cell line. This increase in intracellular curcumin levels may play a role in the synergy exhibited when using TE and RE in combination.

CONCLUSIONS

The use of RE in combination with TE induces a synergistic response to induce apoptosis which is better than either extract alone. This appears to be related to a variable increased TE uptake in cells and activation of pathways involved in the apoptotic response.

c-Jun N-Terminal Kinase Inactivation by Mitogen-Activated Protein Kinase Phosphatase 1 Determines Resistance to Taxanes and Anthracyclines in Breast Cancer

MAPK phosphatase-1 (MKP-1) is overexpressed during malignant transformation of the breast in many patients, and it is usually associated with chemoresistance through interference with JNK-driven apoptotic pathways. Although the molecular settings of the mechanism have been documented, details about the contribution of MKP-1 to the failure of chemotherapeutic interventions are unclear. Transient overexpression of MKP-1 and treatment with JNK-modulating agents in breast carcinoma cells confirmed the mediation of MKP-1 in the resistance to taxanes and anthracyclines in breast cancer, through the inactivation of JNK1/2. We next assessed MKP-1 expression and JNK1/2 phosphorylation status in a large cohort of samples from 350 early breast cancer patients treated with adjuvant anthracycline-based chemotherapy. We detected that MKP-1 overexpression is a recurrent event predominantly linked to dephosphorylation of JNK1/2 with an adverse impact on relapse of the tumor and overall and disease-free survival. Moreover, MKP-1 and p-JNK1/2 determinations in 64 locally advanced breast cancer patients treated with neoadjuvant taxane-based chemotherapy showed an inverse correlation between MKP-1 overexpression (together with JNK1/2 inhibition) and the pathologic response of the tumors. Our results emphasize the importance of MKP-1 as a potential predictive biomarker for a subset of breast cancer patients with worse outcome and less susceptibility to treatment. Mol Cancer Ther; 15(11); 2780-90. ©2016 AACR.

Combined effect of papuamine and doxorubicin in human breast cancer MCF-7 cells

Our previous study reported that an extract of an Indonesian marine sponge, Haliclona sp., showed potent cytotoxicity and induced apoptosis. The major cytotoxic chemical compound was identified as papuamine, which caused reduction of cell survival through activation of c-Jun N-terminal kinase (JNK) in human breast cancer MCF-7 cells. Doxorubicin (DOX), a Streptomyces metabolite, is used in chemotherapy against a wide range of cancers, including breast cancer. The present study examined the combined effect of papuamine and DOX on MCF-7 cells. The effect of these reagents on cell growth was assessed by a colony formation assay. Incubation with either of the reagents alone resulted in concentration-dependent decreases in the colony formation of the MCF-7 cells. Incubation with the reagents together at sub-cytotoxic concentrations resulted in significant decreases in colony formation. The phosphorylation of JNK, the activated form of the protein, was elevated in a concentration-dependent manner upon co-incubation with papuamine and DOX. Fluorescence intensity analysis demonstrated that papuamine caused a small, but non-significant, decrease in cellular accumulation of DOX. These results indicate that the combinatory effect of papuamine and DOX is not associated with changes in the cellular accumulation of DOX, and may instead reflect additive effects on JNK activation. This study indicates that papuamine may represent a novel type of modulator for DOX chemotherapy.

Delay in apoptosome formation attenuates apoptosis in mouse embryonic stem cell differentiation

Differentiation is an inseparable process of development in multicellular organisms. Mouse embryonic stem cells (mESCs) represent a valuable research tool to conduct in vitro studies of cell differentiation. Apoptosis as a well known cell death mechanism shows some common features with cell differentiation, which has caused a number of ambiguities in the field. The research question here is how cells could differentiate these two processes from each other. We have investigated the role of the mitochondrial apoptotic pathway and cell energy level during differentiation of mESCs into the cardiomyocytes and their apoptosis. p53 expression, cytochrome c release, apoptosome formation, and caspase-3/7 activation are observed upon induction of both apoptosis and differentiation. However, remarkable differences are detected in time of cytochrome c appearance, apoptosome formation, and caspase activity upon induction of both processes. In apoptosis, apoptosome formation and caspase activity were observed rapidly following the cytochrome c release. Unlike apoptosis, the release of cytochrome c upon differentiation took more time, and the maximum caspase activity was also postponed for 24 h. This delay suggests that there is a regulatory mechanism during differentiation of mESCs into cardiomyocytes. The highest ATP content of cells was observed immediately after cytochrome c release 6 h after apoptosis induction and then decreased, but it was gradually increased up to 48 h after differentiation. These observations suggest that a delay in the release of cytochrome c or delay in ATP increase attenuate apoptosome formation, and caspase activation thereby discriminates apoptosis from differentiation in mESCs.

Synergistic apoptotic effect of Doxil ® and aminolevulinic acid-based photodynamic therapy on human breast adenocarcinoma cells

BACKGROUND

5-Aminolevulinic acid (ALA) is a natural heme precursor metabolized into protoporphyrin IX (PpIX). PpIX preferentially accumulates in tumor cells resulting in the formation of singlet oxygen upon exposure to visible light. Doxil(®), an active agent against breast and ovarian cancer, is a nano-formulation of doxorubicin. This study aimed to investigate in vitro synergistic cytotoxic effect of low doses of combined chemotherapy and ALA/PDT to human breast adenocarcinoma cells (MCF-7) compared to high doses of each individual therapy.

METHODS

MCF-7 cells were pretreated with Doxil(®) (48 h) followed by ALA/PDT (4h). The cell viability was evaluated by trypan blue assay and PpIX production was measured spectrofluorometrically. Alkaline phosphatase was determined as a marker for cellular differentiation. Apoptosis and necrosis were evaluated by fluorescence stains. The apoptosis cell death pathways were investigated: detection of mitochondrial membrane potential (ΔΨm) and percent of DNA fragmentation, malondialdehyde, histone deacetylase (HDAC) activity, caspase-3 and death receptors (DR4 and DR5). Vascular endothelial growth factor (VEGF) was determined by ELISA, as an angiogenic mediator.

RESULTS

There was a higher reduction in cell viability in Doxil(®)+ALA/PDT-treated cells compared with their individual effect. The combined therapy showed enhanced apoptosis with a significant increase in the loss of ΔΨm, DNA fragmentation %, caspase-3, DR4, DR5 and lipid peroxides and inhibited HDAC. Pretreatment with Doxil(®) resulted in a twofold increase in the intracellular PpIX, by increasing the PDT killing of MCF-7 cells.

CONCLUSION

The combined therapy using 50% of IC50 of ALA/PDT and Doxil(®) possessed a synergistic apoptotic effect on MCF-7 cells compared to 100% of IC50 of each therapy through enhancing both intrinsic and extrinsic apoptotic pathways, thus may minimize side effects of Doxil(®) and ALA.

Fresh Garlic Extract Induces Growth Arrest and Morphological Differentiation of MCF7 Breast Cancer Cells

Consumption of diets rich in fruits and vegetables is often associated with a reduced risk of developing cancer, particularly breast cancer. Considering that 1 in 8 women in the United States will develop breast cancer in the course of her lifetime, dietary manipulation could have a major impact on the incidence of breast cancer. We report here that fresh extracts of garlic (not boiled) arrested the growth and altered the morphology of MCF7 breast cancer cells. Deregulated levels of E-cadherin, cytokeratin8/18, and β-catenin correlated with the altered phenotype. We propose that early down-regulation of cyclin D1, reduced phosphorylation of ERK1, and increased phosphorylation of eIF2-α triggered the phenotypical changes. Reduced expression of hsp27 and sam68 and elevated levels of Rb and p21 further contributed to the sustained growth reduction. These findings provide a better understanding of the cellular responses to dietary supplements and provide potential options to treat breast cancer.

Growth hormone receptor blockade inhibits growth hormone-induced chemoresistance by restoring cytotoxic-induced apoptosis in breast cancer cells independently of estrogen receptor expression

CONTEXT

GH and IGF-I play a role in breast cancer (BC) development. We previously demonstrated that GH protects the estrogen receptor (ER) positive BC-derived MCF7 cell line toward the cytotoxic effects of doxorubicin (D), independently of IGF-I. This issue may be important in ER negative BC cells that are more aggressive and more likely to develop chemoresistance.

AIM OF THE STUDY

The aim of this study was to evaluate whether GH may impact chemoresistance phenotype of ER-negative BC-derived MDA-MB-231 cell line and investigate the possible mechanisms implicated in the protective action of GH toward the cytotoxic effects of D in both ER-positive and ER-negative BC-derived cell lines.

RESULTS

GH protects ER-negative MDA-MB-231 cells from the cytotoxic effects of D and GH receptor antagonist pegvisomant reduces GH-induced DNA synthesis also in these cells. In both MDA-MB-231 and MCF7 cells, GH does not revert D-induced G2/M accumulation but significantly reduces basal and D-induced apoptosis, an effect blocked by pegvisomant. Glutathione S-transferase activity is not implicated in the protective effects of GH, whereas D-induced apoptosis depends on c-Jun N terminal kinase (JNK) activation. GH reduces both basal and D-stimulated JNK transcriptional activity and phosphorylation.

CONCLUSIONS

In human BC cell lines, GH directly promotes resistance to apoptosis induced by chemotherapeutic drugs independently of ER expression by modulating JNK, further broadening the concept that GH excess may hamper cytotoxic BC treatment. These findings support the hypothesis that blocking GH receptor may be viewed as a potential new therapeutic approach to overcome chemoresistance, especially in ER-negative BC.

Therapeutic resistance resulting from mutations in Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR signaling pathways

Chemotherapy remains a commonly used therapeutic approach for many cancers. Indeed chemotherapy is relatively effective for treatment of certain cancers and it may be the only therapy (besides radiotherapy) that is appropriate for certain cancers. However, a common problem with chemotherapy is the development of drug resistance. Many studies on the mechanisms of drug resistance concentrated on the expression of membrane transporters and how they could be aberrantly regulated in drug resistant cells. Attempts were made to isolate specific inhibitors which could be used to treat drug resistant patients. Unfortunately most of these drug transporter inhibitors have not proven effective for therapy. Recently the possibilities of more specific, targeted therapies have sparked the interest of clinical and basic researchers as approaches to kill cancer cells. However, there are also problems associated with these targeted therapies. Two key signaling pathways involved in the regulation of cell growth are the Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR pathways. Dysregulated signaling through these pathways is often the result of genetic alterations in critical components in these pathways as well as mutations in upstream growth factor receptors. Furthermore, these pathways may be activated by chemotherapeutic drugs and ionizing radiation. This review documents how their abnormal expression can contribute to drug resistance as well as resistance to targeted therapy. This review will discuss in detail PTEN regulation as this is a critical tumor suppressor gene frequently dysregulated in human cancer which contributes to therapy resistance. Controlling the expression of these pathways could improve cancer therapy and ameliorate human health.

Amelioration of doxorubicin-induced cardiotoxicity by an anticancer-antioxidant dual-function compound, HO-3867

Doxorubicin (DOX) is a drug commonly used for the treatment of cancer. The development of resistance to DOX is common, and high cumulative doses cause potentially lethal cardiac side effects. HO-3867 (3,5-bis(4-fluorobenzylidene)-1-[(2,2,5,5-tetramethyl-2,5-dihydro-1-hydroxy-pyrrol-3-yl)methyl]piperidin-4-one), a synthetic curcumin analog, has been shown to exhibit both anticancer and cardioprotective effects. However, its cardioprotection in the setting of a conventional cancer therapy has not been established. This work investigated the use of HO-3867 and DOX to achieve a complementary outcome, i.e., increased toxicity toward cancer cells, and reduced cardiac toxicity. Combination treatment was investigated using DOX-resistant MCF-7 breast cancer cells [MCF-7 multidrug-resistant (MDR)] and BALB/c mice. Lower doses of HO-3867 and DOX (5 and 2.5 μM, respectively) reduced viability of MCF-7 MDR cells to an extent significantly greater than that when either drug was used alone, an effect equivalent to that induced by exposure to 50 μM DOX. In normal cardiac cells, the loss of viability from combination treatment was significantly lower than that induced by 50 μM DOX. Increases in apoptotic markers, e.g., cleaved caspase-3, and decreases in fatty acid synthase and pAkt expressions were observed by Western blotting. Mice treated with both HO-3867 and DOX showed significant improvement in cardiac functional parameters compared with mice treated with DOX alone. Reduced expression of Bcl-2 and pAkt was observed in mice treated with DOX alone, whereas mice given combination treatment showed levels similar to control. The study indicates that combination treatment of HO-3867 and DOX is a viable option for treatment of cancer with reduced cardiotoxic side effects.

Tetrathiomolybdate induces doxorubicin sensitivity in resistant tumor cell lines

OBJECTIVE

Doxorubicin is a potent anti-cancer agent with efficacy against a broad range of tumors, including endometrial cancer. Doxorubicin produces reactive oxygen species (ROS) resulting in cytotoxicity. Tetrathiomolybdate (TM), a copper-chelating agent, is known to target a cellular antioxidant enzyme copper/zinc-superoxide dismutase. This study tests the hypothesis that TM can modulate antioxidants in tumor cells and render doxorubicin resistant tumor cells sensitive to doxorubicin.

METHODS

The anti-cancer activities of doxorubicin and TM, as single agents and in combination, were assessed. Flow cytometric and immunoblot analysis were conducted to investigate the induction of apoptosis and changes in apoptotic signaling pathways.

RESULTS

Doxorubicin-induced growth inhibition was observed in each endometrial cancer cell line (ECC-1, AN3CA, and KLE) tested with cell specificity. ECC-1 and KLE cells were found to have increased resistance to doxorubicin than AN3CA cells. Moreover, doxorubicin mediated apoptosis was greater in the AN3CA cell line than ECC-1 and KLE. The combination of doxorubicin with a sub-cytotoxic level of TM was significantly more effective at inducing apoptosis in doxorubicin resistant cell lines.

CONCLUSION

Our results highlight the therapeutic potential of TM to sensitize tumor cells to doxorubicin for endometrial cancer treatment.

Targeting the translational apparatus to improve leukemia therapy: roles of the PI3K/PTEN/Akt/mTOR pathway

It has become apparent that regulation of protein translation is an important determinant in controlling cell growth and leukemic transformation. The phosphoinositide 3-kinase (PI3K)/phosphatase and tensin homologue deleted on chromosome ten (PTEN)/Akt/mammalian target of rapamycin (mTOR) pathway is often implicated in sensitivity and resistance to therapy. Dysregulated signaling through the PI3K/PTEN/Akt/mTOR pathway is often the result of genetic alterations in critical components in this pathway as well as mutations at upstream growth factor receptors. Furthermore, this pathway is activated by autocrine transformation mechanisms. PTEN is a critical tumor suppressor gene and its dysregulation results in the activation of Akt. PTEN is often mutated, silenced and is often haploinsufficient. The mTOR complex1 (mTORC1) regulates the assembly of the eukaryotic initiation factor4F complex, which is critical for the translation of mRNAs that are important for cell growth, prevention of apoptosis and transformation. These mRNAs have long 5'-untranslated regions that are G+C rich, rendering them difficult to translate. Elevated mTORC1 activity promotes the translation of these mRNAs via the phosphorylation of 4E-BP1. mTORC1 is a target of rapamycin and novel active-site inhibitors that directly target the TOR kinase activity. Although rapamycin and novel rapalogs are usually cytostatic and not cytotoxic for leukemic cells, novel inhibitors that target the kinase activities of PI3K and mTOR may prove more effective for leukemia therapy.

Involvement of stress activated protein kinases (JNK and p38) in 1,25 dihydroxyvitamin D3-induced breast cell death

It has been previously demonstrated that 1,25 dihydroxyvitamin D(3) (1,25-D(3)) exerts inhibitory effects in breast cancer cells. The aim of this study was to determine whether mitogen-activated protein kinase (MAPK) pathways are associated with 1,25-D(3)-induced cell death in breast cancer. We used three breast cell lines which have different sensitivities to 1,25-D(3) treatment. Non-malignant MCF-12A cells were more sensitive to 1,25-D(3) treatment than malignant MCF-7 cells (growth inhibition IC(50) 75 nM vs. 100 nM, p<0.001) while malignant MDA-MB-231 cells were resistant. Moreover, 1,25-D(3)-induced apoptosis was caspase-dependent in MCF-12A cells and caspase-independent in MCF-7 cells. Following MAPK activation analysis, we found a significant activation of JNK in MCF-12A cells and malignant MCF-7 cells in response to 1,25-D(3) treatment. Furthermore, 1,25-D(3) treatment stimulated p38 activity in MCF-12A cells and in MCF-7 cells. ERK1/2 activity was unaffected by 1,25-D(3) treatment in all breast cells. Importantly, no increased MAPK activity was observed in MDA-MB-231 breast cancer cells which displayed resistance to 1,25-D(3)-induced apoptosis. Utilising specific pharmacological inhibitors of JNK and p38, it was demonstrated that MCF-12A and MCF-7 cells were protected from death induced by 1,25-D(3). These results implicate JNK and p38 signalling in 1,25-D(3)-induced cancer breast cell death.

Sporadic epithelial ovarian cancer: clinical relevance of BRCA1 inhibition in the DNA damage and repair pathway

Among the most promising pathways for molecular targets in sporadic epithelial ovarian cancer (SEOC) are those involving the BRCA1 protein. Because somatic mutations in BRCA1 are rare in SEOC, it was originally postulated that BRCA1 plays a limited role in the pathogenesis of this disease. However, inactivation of BRCA1 through various mechanisms is a relatively frequent event in ovarian cancer. This is important because BRCA1 is involved in the cellular response to DNA damage and repair and has an essential role in the maintenance of genomic stability. The BRCA1 tumor suppressor protein is known to interact with genes and proteins known collectively as the BRCA1 pathway, and defects in this pathway are believed to be a driving force for cancer progression. As a result, there is compelling evidence to suggest that the dysfunction of BRCA1 may be a central mechanism in all ovarian carcinogenesis, and this has clinical and molecular significance beyond the management of patients with hereditary ovarian cancer. The aim of this review is to evaluate the evidence for BRCA1 dysfunction in SEOC and to link this dysfunction to a defective DNA repair pathway and ultimately the promotion of genomic instability and tumorigenesis. Furthermore, we advocate the continued need to study BRCA1 and its pathway by prospectively correlating clinicopathologic data with molecular aberrations. This will determine whether BRCA1 has relevance as a predictive and prognostic marker in SEOC and whether aberrations in the BRCA1 pathway warrant further study as potential therapeutic targets.

Doxorubicin activates FOXO3a to induce the expression of multidrug resistance gene ABCB1 (MDR1) in K562 leukemic cells

Using the doxorubicin-sensitive K562 cell line and the resistant derivative lines KD30 and KD225 as models, we found that acquisition of multidrug resistance (MDR) is associated with enhanced FOXO3a activity and expression of ABCB1 (MDR1), a plasma membrane P-glycoprotein that functions as an efflux pump for various anticancer agents. Furthermore, induction of ABCB1 mRNA expression on doxorubicin treatment of naive K562 cells was also accompanied by increased FOXO3a activity. Analysis of transfected K562, KD30, and KD225 cells in which FOXO3a activity can be induced by 4-hydroxytamoxifen showed that FOXO3a up-regulates ABCB1 expression at protein, mRNA, and gene promoter levels. Conversely, silencing of endogenous FOXO3a expression in KD225 cells inhibited the expression of this transport protein. Promoter analysis and chromatin immunoprecipitation assays showed that FOXO3a regulation of ABCB1 expression involves binding of this transcription factor to the proximal promoter region. Moreover, activation of FOXO3a increased ABCB1 drug efflux potential in KD30 cells, whereas silencing of FOXO3a by siRNA significantly reduced ABCB1 drug efflux ability. Together, these findings suggest a novel mechanism that can contribute towards MDR, involving FOXO3a as sensor for the cytotoxic stress induced by anticancer drugs. Although FOXO3a may initially trigger a program of cell cycle arrest and cell death in response to doxorubicin, sustained FOXO3a activation promotes drug resistance and survival of cells by activating ABCB1 expression.

Novel retinoic acid metabolism blocking agents have potent inhibitory activities on human breast cancer cells and tumour growth

Antitumour effects of retinoids are attributed to their influence on cell proliferation, differentiation, apoptosis and angiogenesis. In our effort to develop useful agents for breast cancer therapy, we evaluated the effects of four representative retinoic acid metabolism blocking agents (RAMBAs, VN/14-1, VN/50-1, VN/66-1 and VN/69-1) on growth inhibition of oestrogen receptor positive (ER +ve, MCF-7 and T-47D) and oestrogen receptor negative (ER −ve, MDA-MB-231) human breast cancer cells. Additionally, we investigated the biological effects/molecular mechanism(s) underlying their growth inhibitory properties as well as their antitumour efficacies against MCF-7 and MCF-7Ca tumour xenografts in nude mice. We also assessed the effect of combining VN/14-1 and all-trans-retinoic acid (ATRA) on MCF-7 tumuor xenografts. The ER +ve cell lines were more sensitive (IC₅₀ values between 3.0 and 609 nM) to the RAMBAs than the ER −ve MDA-MB-231 cell line (IC₅₀=5.6–24.0 μM). Retinoic acid metabolism blocking agents induced cell differentiation as determined by increased expression of cytokeratin 8/18 and oestrogen receptor-α (ER-α). Similar to ATRA, they also induced apoptosis via activation of caspase 9. Cell cycle analysis indicated that RAMBAs arrested cells in the G1 and G2/M phases and caused significant downregulation (>80%) of cyclin D1 protein. In vivo, the growth of MCF-7 mammary tumours was dose-dependently and significantly inhibited (92.6%, P<0.0005) by VN/14-1. The combination of VN/14-1 and ATRA also inhibited MCF-7 breast tumour growth in vivo (up to 120%) as compared with single agents (P<0.025). VN/14-1 was also very effective in preventing the formation of MCF-7Ca tumours and it significantly inhibited the growth of established MCF-7Ca tumours, being as effective as the clinically used aromatase inhibitors, anastrozole and letrozole. Decrease in cyclin D1 and upregulation of cytokeratins, Bad and Bax with VN/14-1 may be responsible for the efficacy of this compound in inhibiting breast cancer cell growth in vitro and in vivo. Our results suggest that our RAMBAs, especially VN/14-1 may be useful novel therapy for breast cancer.

Ursodeoxycholic acid modulates histone acetylation and induces differentiation and senescence

Agents that can modulate colonic environment and control dysregulated signaling are being evaluated for their chemopreventive potential in colon cancer. Ursodeoxycholate (UDCA) has shown chemopreventive potential in preclinical and animal models of colon cancer, but the mechanism behind it remains unknown. Here biological effects of UDCA were examined to understand mechanism behind its chemoprevention in colon cancer. Our data suggests that UDCA can suppress growth in a wide variety of cancer cell lines and can induce low level of apoptosis in colon cancer cells. We also found that UDCA treatment induces alteration in morphology, increased cell size, upregulation of cytokeratin 8, 18 and 19 and E-cadherin, cytokeratin remodeling and accumulation of lipid droplets, suggesting that UDCA induces differentiation in colon carcinoma cells. Our results also suggest significant differences in UDCA and sodium butyrate induced functional differentiation. We also report for the first time that UDCA can induce senescence in colon cancer cells as assessed by flattened, spread out and vacuolated morphology as well as by senescence marker beta-galactosidase staining. We also found that UDCA inhibits the telomerase activity. Surprisingly, we found that UDCA is not a histone deacytylase inhibitor but instead induces hypoacetylation of histones unlike hyperacetylation induced by sodium butyrate. Our results also suggest that, although UDCA induced senescence is p53, p21 and Rb independent, HDAC6 appears to be important in UDCA induced senescence. In summary, our data shows that UDCA modulates chromatin by inducing histone hypoacetylation and induces differentiation and senescence in colon cancer cells.

Apoptosis induced by chemotherapeutic agents involves c-Jun N-terminal kinase activation in sarcoma cell lines

Molecular mechanisms underlying chemotherapeutic agent-induced apoptosis in sarcoma cells are not well known. Induction of apoptosis is regulated by several components including mitogen-activated protein kinases (MAPKs) comprising ERK, p38MAPKs, and c-Jun N-terminal kinase (JNK). In the present study, we examined whether activation of JNK is induced by the chemotherapeutic agents cis-diaminedichloroplatinum (cisplatin, CDDP) or doxorubicin (DXR), and whether the ectopic expression of constitutively active (MKK7-JNK1) or dominant-negative form of JNK (dnJNK) influenced apoptosis in response to the CDDP or DXR in sarcoma cell lines MG-63 and SaOS-2. The CDDP or DXR induced JNK activation in the both cell lines, as assessed by Western blotting using phosphospecific antibodies. A transient expression of the activated form of JNK sensitized the MG-63 and SaOS-2 cells to the drug-induced apoptosis, while dnJNK1 reduced the proportion of apoptotic cell death. Apoptosis was determined by flow cytometry using annexin-V Cy5. Collectively, our results indicate that JNK activation is involved in apoptotic cell death in sarcoma cell lines following stimulation with CDDP or DXR.

Modulation of mitogen-activated protein kinase cascades by differentiation-1 protein: acquired drug resistance of hormone independent prostate cancer cells

PURPOSE

The inhibitor of differentiation-1 protein (Id-1) is over expressed in multidrug resistance prostate cancer cells. We determined the effect of Id-1 expression and its underlying pathways on the development of multidrug resistance in prostate cancer.

MATERIALS AND METHODS

AT3 cells were transfected with the Id-1 gene or a blank vector. Id-1 mRNA expression was determined by reverse transcriptase-polymerase chain reaction and Id-1 protein content was detected by immunoblot and flow cytometry. Cellular cytotoxicity was determined by MTT (microculture 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay (Sigma Chemical Co., St. Louis, Missouri). The activation and expression of mitogen-activated protein kinase (MAPK) were measured by transactivation assay and Western blotting, respectively.

RESULTS

Id-1 overproduction drove AT3 cells to become resistant to chemotherapeutic agents but did not induce mdr-1 gene expression. The p38MAPK and c-jun N-terminal kinase (JNK) pathways were suppressed, which correlated with increased Id-1 expression. No significant change in extracellular signal-regulated kinase (ERK) activation was observed in Id-1 transfectants compared with that of AT3 or vector control. Treatment of Id-1 expressing cells with p38MAPK and JNK inhibitors resulted in decreased doxorubicin induced apoptosis. In contrast, Id-1 expressing cells treated with ERK inhibitor made cells more sensitive to drug induced apoptosis.

CONCLUSIONS

Up-regulation of Id-1 was found in prostate cancer multidrug resistant cells. Sustained ERK activation, and JNK and p38MAPK inhibition by Id-1 in cells may confer drug resistance. These changes in MAPKs could be a mechanism for the acquisition of multidrug resistance in prostate cancer.

Doxorubicin induces expression of multidrug resistance-associated protein 1 in human small cell lung cancer cell lines by the c-jun N-terminal kinase pathway

Multidrug resistance (MDR) is a major impediment to successful chemotherapy for lung cancer. Overexpression of multidrug resistance-associated protein 1 (MRP1) appears to be involved in MDR development in lung cancer cells. A number of chemotherapeutic agents including doxorubicin (DOX) were reported to induce MRP1 expression in human lung cancer cells. In our study, we investigated the mechanism by which DOX induces MRP1 expression in human small cell lung cancer (SCLC) cell lines, GLC4 and NCI-H82. These cells expressed MRP1 protein at low levels and were sensitive to DOX. Doxorubicin at 50 nM induced a marked increase in MRP1 expression in 24 hr, and stimulated c-jun N-terminal kinase (JNK) activity. Treatment with a JNK inhibitor, SP600125, significantly inhibited MRP1 induction. Furthermore, transfection with JNK1 and JNK2 antisense oligonucleotides markedly inhibited DOX-induced MRP1 expression. Chromatin immunoprecipitation assays revealed an enhanced recruitment of phosphorylated c-jun to the MRP1 promoter containing the AP-1 site upon DOX stimulation, which was inhibited by pretreatment with SP600125. Surprisingly, GLC4 cells exposed to DOX for 24 hr maintained increased MRP1 expression and resistance to DOX for at least 3 weeks. Pretreatment with SP600125 before DOX stimulation blocked the appearance of the MDR phenotype as well as MRP1 induction in GLC4 cells. These findings suggest that JNK activation may play an essential role for the induction of MRP1 protein in human SCLC cells by chemotherapeutic agents and that combined treatment of a JNK inhibitor with anticancer drugs may prevent the development of MDR by the abrogation of MRP1 induction.

Apoptosis induced by penta-acetyl geniposide in C6 glioma cells is associated with JNK activation and Fas ligand induction

In our previous study, penta-acetyl geniposide ((AC)(5)GP) is suggested to induce tumor cell apoptosis through the specific activation of PKCdelta. However, the downstream signal pathway of PKCdelta has not yet been investigated. It was shown that JNK may play an important role in the regulation of apoptosis and could be a possible downstream signal of PKCdelta isoforms. In the present study, we investigate whether JNK is involved in (AC)(5)GP induced apoptosis. The result reveals that (AC)(5)GP induces JNK activation and c-Jun phosphorylation thus stimulating the expression of Fas-L and Fas. Using SP600125 to block JNK activation shows that (AC)(5)GP-mediated apoptosis and related proteins expression are attenuated. Furthermore, we find that the (AC)(5)GP induces apoptosis through the activation of JNK/Jun/Fas L/Fas/caspase 8/caspase 3, a mitochondria-independent pathway. The JNK pathway is suggested to be the downstream signal of PKCdelta, since rottlerin impedes (AC)(5)GP-induced JNK activation. Therefore, (AC)(5)GP mediates cell death via activation of PKCdelta/JNK/FasL cascade signaling.