Inhibition of extracellular signal-regulated protein kinase or c-Jun N-terminal protein kinase cascade, differentially activated by cisplatin, sensitizes human ovarian cancer cell line

Arsenic compounds induce apoptosis by activating the MAPK and caspase pathways in FaDu oral squamous carcinoma cells

For a number of years, oral cancer has remained in the top ten most common types of cancer, with an incidence rate that is steadily increasing. In total, ~75% oral cancer cases are associated with lifestyle factors, including uncontrolled alcohol consumption, betel and tobacco chewing, and the excessive use of tobacco. Notably, betel chewing is highly associated with oral cancer in Southeast Asia. Arsenic is a key environmental toxicant; however, arsenic trioxide has been used as a medicine for the treatment of acute promyelocytic leukemia, highlighting its anticancer properties. The present study aimed to investigate the role of arsenic compounds in the treatment of cancer, using FaDu oral squamous carcinoma cells treated with sodium arsenite (NaAsO₂) and dimethyl arsenic acid (DMA). The results demonstrated that FaDu cells exhibited membrane blebbing phenomena and high levels of apoptosis following treatment with 10 µM NaAsO₂ and 1 mM DMA for 24 h. The results of cell viability assay demonstrated that the rate of FaDu cell survival was markedly reduced as the concentration of arsenic compounds increased from 10 to 100 µM NaAsO₂, and 1 to 100 mM DMA. Moreover, flow cytometry was carried out to further examine the effects of arsenic compounds on FaDu cell cycle regulation; the results revealed that treatment with NaAsO₂ and DMA led to a significant increase in the percentage of FaDu cells in the sub‑G1 and G2/M phases of the cell cycle. An Annexin V/PI double staining assay was subsequently performed to verify the levels of FaDu cell apoptosis following treatment with arsenic compounds. Furthermore, the results of the western blot analyses revealed that the expression levels of caspase‑8, ‑9 and ‑3, and poly ADP‑ribose polymerase, as well the levels of phosphorylated JNK and ERK1/2 were increased following treatment with NaAsO₂ and DMA in the FaDu cells. On the whole, the results of the present study revealed that treatment with NaAsO₂ and DMA promoted the apoptosis of FaDu oral cancer cells, by activating MAPK pathways, as well as the extrinsic and intrinsic apoptotic pathways.

DCBLD2 Mediates Epithelial-Mesenchymal Transition-Induced Metastasis by Cisplatin in Lung Adenocarcinoma

Growing evidence suggests that cisplatin and other chemotherapeutic agents promote tumor metastasis while inhibiting tumor growth, which is a critical issue for certain patients in clinical practices. However, the role of chemotherapeutics in promoting tumor metastasis and the molecular mechanism involved are unclear. Here, we investigated the roles of cisplatin in promoting tumor metastasis in lung adenocarcinoma (LUAD). We demonstrated that cisplatin promoted epithelial-mesenchymal transition (EMT), cell motility, and metastasis in vitro and in vivo. The bioinformatic analysis and molecular biology approaches also indicated that DCBLD2 (Discoidin, CUB and LCCL domain containing 2) is a key gene that mediates cisplatin-induced metastasis. DCBLD2 stabilizes β-catenin by phosphorylating GSK3β and transporting accumulated β-catenin to the nucleus to promote the expression of EMT-related transcriptional factors (TFs), ultimately resulting in tumor metastasis. We also identified that cisplatin enhanced DCBLD2 expression by phosphorylating ERK and hence the AP-1-driven transcription of DCBLD2. Furthermore, DCBLD2-specific siRNAs encapsulated by nanocarriers prominently inhibit cisplatin-induced metastasis in vivo. Therefore, DCBLD2 plays a key role in cisplatin-induced metastasis in LUAD and is a potential target for preventing chemotherapy-induced metastasis in vivo.

Advances in Our Understanding of the Molecular Mechanisms of Action of Cisplatin in Cancer Therapy

Cisplatin and other platinum-based chemotherapeutic drugs have been used extensively for the treatment of human cancers such as bladder, blood, breast, cervical, esophageal, head and neck, lung, ovarian, testicular cancers, and sarcoma. Cisplatin is commonly administered intravenously as a first-line chemotherapy for patients suffering from various malignancies. Upon absorption into the cancer cell, cisplatin interacts with cellular macromolecules and exerts its cytotoxic effects through a series of biochemical mechanisms by binding to Deoxyribonucleic acid (DNA) and forming intra-strand DNA adducts leading to the inhibition of DNA synthesis and cell growth. Its primary molecular mechanism of action has been associated with the induction of both intrinsic and extrinsic pathways of apoptosis resulting from the production of reactive oxygen species through lipid peroxidation, activation of various signal transduction pathways, induction of p53 signaling and cell cycle arrest, upregulation of pro-apoptotic genes/proteins, and down-regulation of proto-oncogenes and anti-apoptotic genes/proteins. Despite great clinical outcomes, many studies have reported substantial side effects associated with cisplatin monotherapy, while others have shown substantial drug resistance in some cancer patients. Hence, new formulations and several combinational therapies with other drugs have been tested for the purpose of improving the clinical utility of cisplatin. Therefore, this review provides a comprehensive understanding of its molecular mechanisms of action in cancer therapy and discusses the therapeutic approaches to overcome cisplatin resistance and side effects.

Flow-induced Shear Stress Confers Resistance to Carboplatin in an Adherent Three-Dimensional Model for Ovarian Cancer: A Role for EGFR-Targeted Photoimmunotherapy Informed by Physical Stress

A key reason for the persistently grim statistics associated with metastatic ovarian cancer is resistance to conventional agents, including platinum-based chemotherapies. A major source of treatment failure is the high degree of genetic and molecular heterogeneity, which results from significant underlying genomic instability, as well as stromal and physical cues in the microenvironment. Ovarian cancer commonly disseminates via transcoelomic routes to distant sites, which is associated with the frequent production of malignant ascites, as well as the poorest prognosis. In addition to providing a cell and protein-rich environment for cancer growth and progression, ascitic fluid also confers physical stress on tumors. An understudied area in ovarian cancer research is the impact of fluid shear stress on treatment failure. Here, we investigate the effect of fluid shear stress on response to platinum-based chemotherapy and the modulation of molecular pathways associated with aggressive disease in a perfusion model for adherent 3D ovarian cancer nodules. Resistance to carboplatin is observed under flow with a concomitant increase in the expression and activation of the epidermal growth factor receptor (EGFR) as well as downstream signaling members mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK) and extracellular signal-regulated kinase (ERK). The uptake of platinum by the 3D ovarian cancer nodules was significantly higher in flow cultures compared to static cultures. A downregulation of phospho-focal adhesion kinase (p-FAK), vinculin, and phospho-paxillin was observed following carboplatin treatment in both flow and static cultures. Interestingly, low-dose anti-EGFR photoimmunotherapy (PIT), a targeted photochemical modality, was found to be equally effective in ovarian tumors grown under flow and static conditions. These findings highlight the need to further develop PIT-based combinations that target the EGFR, and sensitize ovarian cancers to chemotherapy in the context of flow-induced shear stress.

Transcriptional Activation of Gstp1 by MEK/ERK Signaling Confers Chemo-Resistance to Cisplatin in Lung Cancer Stem Cells

Lung cancer management remains a challenge due to its asymptomatic and late presentation when it is metastatic. The clinical response to the first-line platinum-based chemotherapy in patients with advanced lung cancer is disappointing due to the development of chemoresistance. Chemoresistance is a complex phenomenon. Mechanistic research using experimental models has yielded limited clinical results to help increase understanding for overcoming resistance. While the role of lung CSCs in conferring multidrug resistance has been postulated, experimental evidence remains associative and lacks in depth mechanistic inquisition. In the present study, using mouse and human lung adenocarcinoma cell lines and their respective paired CSC derivative cell lines that we generated, we identified cancer stem cell component of lung adenocarcinoma as the source that confers multidrug resistance phenotype. Mechanistically, Gstp1 confers cisplatin resistance in mouse and human lung CSC models, both in vitro and in vivo. Further, transcriptional activation of Gstp1 expression by MEK/ERK signaling underlies cisplatin resistance in lung CSC cells. Moreover, we show that GSTP1 expression is a poor diagnostic and prognostic marker for human lung adenocarcinoma, thus is of high clinical relevance. Taken together, we have provided mechanistic understanding of the lung CSC in mediating chemoresistance.

Cyclosporine A sensitizes lung cancer cells to crizotinib through inhibition of the Ca2+/calcineurin/Erk pathway

Background

Crizotinib has potent anti-tumor activity in patients with advanced MET-amplified non-small cell lung cancer (NSCLC). However, the therapeutic effect is still not satisfying. Thus, developing approaches that improve the efficacy of crizotinib remains a significant challenge.

Methods

MET-amplified NSCLC cell lines were treated with crizotinib and cyclosporine A (CsA). Cell viability was determined by MTS assay. The changes of apoptosis, cell cycle and calcineurin-Erk pathways were assessed by western blot. Xenograft mouse model, primary human NSCLC cells and hollow fiber assays were utilized to confirm the effects of CsA.

Findings

We demonstrated that CsA significantly increased the anti-tumor effect of crizotinib on multiple MET-amplified NSCLC cells in vitro and in vivo. Mechanistically, crizotinib treatment led to the activation of Ca²⁺-calcineurin (CaN)-Kinase suppressor of Ras 2 (KSR2) signaling, resulting in Erk1/2 activation and enhanced survival of cancer cells. CsA effectively blocked CaN-KSR2-Erk1/2 signaling, promoting crizotinib-induced apoptosis and G2/M arrest. Similarly, pharmacologic or genetic inhibition of Erk1/2 also enhanced crizotinib-induced growth inhibition in vitro. Xenograft studies further confirmed that CsA or Erk1/2 inhibitor PD98059 enhanced the anti-cancer activity of crizotinib through inhibition of CaN-Erk1/2 axis. The results were also validated by primary human NSCLC cells in vitro and hollow fiber assays in vivo.

Interpretation

This study provides preclinical evidences that combination therapy of CsA and crizotinib is a promising approach for targeted treatment of MET-amplified lung cancer patients.

Fund

This work was supported by the National Natural Science Foundation of China, the Key Projects of Natural Foundation of Zhejiang Province, the Ten thousand plan youth talent support program of Zhejiang Province, the Zhejiang Natural Sciences Foundation Grant, and the Zhejiang medical innovative discipline construction project-2016.

Effect of CXCR4 silencing with shRNA on MAPK signaling in ovarian cancer

Our previous study demonstrated that short hairpin RNA (shRNA) targeting of C-X-C chemokine receptor type 4 (CXCR4) significantly inhibited cell proliferation, metastasis and invasion. On the basis of these results, the aim of the present study was to determine the effects of shRNA-CXCR4 silencing on mitogen-activated protein kinase (MAPK) signaling in human SW626 ovarian cancer cells. Following silencing the CXCR4 gene with shRNA, the mRNA expression of apoptosis signal-regulating kinase 1 (ASK1) was determined using the reverse transcription-quantitative polymerase chain reaction, whereas the protein expression of extracellular-signal-regulated kinase (ERK)1/2 and phosphorylated (p)-c-Jun were determined using immunocytochemistry and western blotting. SW626 cells transfected with shRNA-CXCR4 exhibited significantly increased ASK1 mRNA expression (P<0.05), significantly increased p-c-Jun protein expression (P<0.05), and significantly decreased ERK1/2 protein expression (P<0.05). Silencing the CXCR4 gene with shRNA significantly inhibited cell proliferation, promoted cell apoptosis and may be mediated by the MAPK signaling pathway.

Inhibition of lysine-specific demethylase 1 prevents proliferation and mediates cisplatin sensitivity in ovarian cancer cells

Lysine-specific demethylase 1 (LSD1) functions as a transcriptional coregulator by modulating histone methylation and has been associated with numerous high-risk cancers. Previously, our group and others identified LSD1 as an upregulated gene in ovarian cancer, and reported that the upregulation of LSD1 was associated with poor prognosis of patients with ovarian cancer. However, the role of LSD1 in ovarian cancer requires further investigation. The present study revealed that the overexpression of LSD1 significantly promoted the proliferation of SKOV3 ovarian cancer cells, while knockdown of LSD1 markedly inhibited cell proliferation and potentiated cisplatin-induced cell apoptosis, supporting LSD1 as an oncogenic protein in ovarian cancer. Mechanistic studies have indicated that LSD1 modulates the expression of cyclin dependent kinase inhibitor 1, Survivin, B-cell lymphoma-2 (Bcl-2) and Bcl-2-associated X genes, which are known regulators of cell proliferation. Furthermore, LSD1 knockdown plus cisplatin synergistically impaired cell migration via the induction of the epithelial marker E-cadherin and inhibition of the mesenchymal markers, snail family transcriptional repressor 1 and Vimentin. These data of the present study indicated LSD1 as a potential regulator of ovarian cancer cell progression and suggested an unfavorable role of LSD1 in cisplatin-based regimens.

Cisplatin based therapy: the role of the mitogen activated protein kinase signaling pathway

Cisplatin is a widely used chemotherapeutic agent for treatment of various cancers. However, treatment with cisplatin is associated with drug resistance and several adverse side effects such as nephrotoxicity, reduced immunity towards infections and hearing loss. A Combination of cisplatin with other drugs is an approach to overcome drug resistance and reduce toxicity. The combination therapy also results in increased sensitivity of cisplatin towards cancer cells. The mitogen activated protein kinase (MAPK) pathway in the cell, consisting of extracellular signal regulated kinase, c-Jun N-terminal kinase, p38 kinases, and downstream mediator p90 ribosomal s6 kinase (RSK); is responsible for the regulation of various cellular events including cell survival, cell proliferation, cell cycle progression, cell migration and protein translation. This review article demonstrates the role of MAPK pathway in cisplatin based therapy, illustrates different combination therapy involving cisplatin and also shows the importance of targeting MAPK family, particularly RSK, to achieve increased anticancer effect and overcome drug resistance when combined with cisplatin.

Hexokinase 2 confers resistance to cisplatin in ovarian cancer cells by enhancing cisplatin-induced autophagy

The high mortality rate of ovarian cancer is connected with the development of acquired resistance to multiple cancer drugs, especially cisplatin. Activation of cytoprotective autophagy has been implicated as a contributing mechanism for acquired cisplatin resistance in ovarian cancer cells. Hexokinase 2 (HK2) phosphorylates glucose to generate glucose-6-phosphate, the rate-limiting step in glycolysis. Higher HK2 expression has been associated with chemoresistance in ovarian cancer. However, whether HK2 functionally contributes to cisplatin resistance in ovarian cancer is unclear. In this study, we investigated the role of HK2 in regulating ovarian cancer cisplatin resistance. Increased HK2 levels were detected in drug-resistant human ovarian cancer cells and tissues. Cisplatin downregulated HK2 in cisplatin-sensitive but not in resistant ovarian cancer cells. HK2 knockdown sensitized resistant ovarian cancer cells to cisplatin-induced cell death and apoptosis. Conversely, HK2 overexpression in cisplatin-sensitive cells induced cisplatin resistance. Mechanistically, cisplatin increased ERK1/2 phosphorylation as well as autophagic activity. Blocking autophagy with the autophagy inhibitor 3-MA sensitized resistant ovarian cancer cells to cisplatin. HK2 overexpression enhanced cisplatin-induced ERK1/2 phosphorylation and autophagy while HK2 knockdown showed the opposite effects. Blocking the MEK/ERK pathway using the MEK inhibitor U0126 prevented cisplatin-induced autophagy enhanced by HK2 overexpression. Furthermore, HK2 knockdown sensitized resistance ovarian tumor xenografts to cisplatin in vivo. In conclusion, our data supported that HK2 promotes cisplatin resistance in ovarian cancer by enhancing drug-induced, ERK-mediated autophagy. Therefore, targeting HK2 may be a new therapeutic strategy to combat chemoresistance in ovarian cancer.

Discovering drugs to overcome chemoresistance in ovarian cancers based on the cancer genome atlas tumor transcriptome profile

Ovarian cancer accounts for the highest mortality among gynecologic cancers, mainly due to intrinsic or acquired chemoresistance. While mechanistic-based methods have been used to identify compounds that can overcome chemoresistance, an effective comprehensive drug screening has yet to be developed. We applied a transcriptome based drug sensitivity prediction method, to the Cancer Genome Atlas (TCGA) ovarian cancer dataset to impute patient tumor response to over 100 different drugs. By stratifying patients based on their predicted response to standard of care (SOC) chemotherapy, we identified drugs that are likely more sensitive in SOC resistant ovarian tumors. Five drugs (ABT-888, BIBW2992, gefitinib, AZD6244 and lenalidomide) exhibit higher efficacy in SOC resistant ovarian tumors when multi-platform of transcriptome profiling methods were employed. Additional in vitro and clinical sample validations were carried out and verified the effectiveness of these agents. Our candidate drugs hold great potential to improve clinical outcome of chemoresistant ovarian cancer.

Transporter-Mediated Interaction Between Platinum Drugs and Sorafenib at the Cellular Level

Combining the multikinase inhibitor sorafenib with the platinum-based chemotherapy of solid tumors was expected to improve treatment outcome. However, in many clinical trials, no benefit from sorafenib addition to the platinum-containing regimen could be demonstrated. Moreover, in some studies, decreased survival of ovarian cancer patients as well as non-small cell lung cancer patients with squamous cell histology was observed. The aim of this study was to investigate the cellular mechanisms of the pharmacological interaction between platinum drugs and sorafenib in different cancer cell lines. The interaction was characterized by combination index analysis, platinum accumulation and DNA platination were determined using flameless atomic absorption spectrometry, and protein expression was assessed with Western blot. In the sensitive A2780 ovarian carcinoma and H520 squamous cell lung carcinoma cell lines, sorafenib induced downregulation of Na⁺,K⁺-ATPase. In A2780 cells, the kinase inhibitor also decreased the expression of copper transporter 1 (CTR1). As a result, sorafenib treatment led to a diminished cellular accumulation of cisplatin and carboplatin and to a decrease in DNA platination in these cell lines. This was not the case in the cisplatin-resistant A2780cis ovarian carcinoma and H522 lung adenocarcinoma cell lines featuring lower basal expression of the above-mentioned transporters. In all cell lines studied, an antagonistic interaction between platinum drugs and sorafenib was found. Our results suggest that sorafenib impairs cisplatin and carboplatin uptake through downregulation of CTR1 and/or Na⁺,K⁺-ATPase resulting in reduction of DNA platination. This effect is not observed in cancer cells with defects in platinum accumulation.

Relationship between apoptosis and survival molecules in human cumulus cells as markers of oocyte competence

To select from a single patient the best oocytes able to reach the blastocyst stage, we searched for valuable markers for oocytes competence. We evaluated the DNA fragmentation index (DFI) and the level of some survival molecules, such as AKT, pAKT and pERK1/2, in individual cumulus cell-oocyte complexes (COC). The study included normo-responder women. The average age of the patients was 34.3. DFI in cumulus cells was evaluated using the terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labelling (TUNEL) assay in situ. AKT, pAKT and pERK1/2 were measured by immunological assay and densitometric analysis of fluorescent signals using NIS-Elements BR 3.10 image software. Statistical analysis was performed using STATA SE/14.1. The study focused on 53 patients involved after informed consent. Out of 255 MII oocytes, 197 were fertilized and the derived embryos had the following evolution: 117 completed the development to blastocyst and were transferred to uterus; 57 were vitrified at the blastocyst stage; and 23 were arrested during in vitro culture at different stages of cleavage. We found a significant statistical difference between the DFI of cumulus cells of the arrested embryos and the transferred blastocysts (P = 0.004), confirming that DFI could be considered as a valuable marker of oocyte competence. In addition, the pAKT/DFI ratio was higher in cumulus cells of oocytes able to produce blastocysts, indicating that DFI is significantly lower when pAKT is higher (P = 0.043). This study demonstrates for the first time that the relationship between apoptosis and survival molecules can be used as a marker to select the best oocytes.

VRK1 promotes cisplatin resistance by up-regulating c-MYC via c-Jun activation and serves as a therapeutic target in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a common malignant disease characterized by poor prognosis. Chemoresistance remains a major cause of ESCC relapse. Vaccinia-related kinase 1 (VRK1) has previously been identified as a cancer-related gene. However, there is little research demonstrating an association between VRK1 and ESCC. In this study, we show that VRK1 is overexpressed in ESCC primary tumor samples and cell lines. VRK1 expression was significantly correlated with clinical characteristics and predicted poor outcomes in ESCC patients. Functionally, knockdown of VRK1 inhibited ESCC cell proliferation, survival, migration and invasion; conversely, VRK1 overexpression produced the opposite effects. Furthermore, we found that up-regulation of VRK1 promoted cisplatin (CDDP) resistance in ESCC both in vitro and in vivo, whereas knockdown of VRK1 reduced this resistance. Further studies verified that VRK1 phosphorylated c-Jun and that the VRK1/c-Jun pathway contributed to CDDP resistance in ESCC. Mechanistically, a dual luciferase reporter assay revealed that c-Jun transcriptionally activated the expression of c-MYC. Silencing c-MYC abolished the c-Jun-mediated CDDP resistance of ESCC cells. A Kaplan-Meier analysis indicated that c-MYC is a potential prognostic factor in ESCC. Finally, luteolin, a VRK1 inhibitor, attenuated the malignant biological behaviors and CDDP resistance in ESCC cells. Collectively, we conclude that VRK1 promotes CDDP resistance through c-MYC by activating c-Jun and potentiating a malignant phenotype in ESCC. Our studies provide novel insight into the role of VRK1 in carcinogenesis and indicate that VRK1 can serve as a potential therapeutic target in ESCC.

Inhibition of the PI3K/AKT Pathway Sensitizes Oral Squamous Cell Carcinoma Cells to Anthracycline-Based Chemotherapy In Vitro

Anthracycline-based chemotherapy, such as doxorubicin (Dox), while effective against many solid tumors, is not widely used for head and neck cancers. In this study, we evaluated the efficacy of Dox, and its derivative AD198 in human, canine, and feline oral squamous cell carcinomas cells (OSCC) in vitro. Dox and AD198 had significant an anti-proliferative effect on human, canine, and feline OSCC cells in dose-dependent manner. AD198 inhibited cell proliferation more effectively than Dox in tested OSCC cells. In the human oral squamous cell carcinoma SCC25 cells, Dox and AD198 increased the production of reactive oxygen species and subsequently increased apoptosis through activation of caspase signaling pathway. Dox and AD198 increased activation of AKT, ERK1/2, and p38 MAPK signaling pathways in tested OSCC cells by dose-dependent manner. The efficacy of Dox and AD198 treatments in inhibition of cell proliferation was increased in tested OSCC when combined with PI3K/AKT inhibitor, LY294002 treatment. Inhibition of PI3K/AKT reduced Dox- and AD198-induced activation of ERK1/2 and further increased Dox- and AD198-induced phosphorylation of p38 MAPK in OSCC. Our results suggest that the anthracycline therapies, such as Dox or AD198, can be more effective for treatment of OSCC when combined with inhibitors of the PI3K/AKT pathway. J. Cell. Biochem. 118: 2615-2624, 2017. © 2016 Wiley Periodicals, Inc.

Activation of estrogen receptor α by estradiol and cisplatin induces platinum-resistance in ovarian cancer cells

Activation of Estrogen receptor (ER) α (α) promotes cell growth and influences the response of cancer cell to chemotherapeutic agents. However, the mechanism by which ERα activation antagonizes cells to chemotherapy-induced cytotoxicity remains unclear. Here, we investigated the effect of cisplatin on ERα activation. In addition, we examined whether down-regulation of ERα modulate cisplatin-mediated cytotoxicity using 2 human ovarian cancer cells (Caov-3 and Ovcar-3) transduced with ERα short hairpin RNA (shRNA). The proliferation assay showed that 17β-estradiol (E2) induced cell proliferation via activation of Akt and extracellular signal-regulated kinase (ERK) cascades, while shRNA mediated downregulation of ERα inhibited the cell proliferation. Immunoblot analysis revealed that cisplatin induced the phosphorylation of ERα at serine 118 via ERK cascade. Luciferase assay showed that cisplatin increases transcriptional activity of estrogen-responsive element (ERE). The E2-stimulated ERα activation attenuated cisplatin-induced cytotoxicity. Meanwhile, down-regulation of ERα inhibited E2-induced protective effect on cisplatin toxicity as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Moreover, Pretreatment with E2 followed by cisplatin decreased the expression of cleaved PARP, and increased the expression of anti-apoptotic protein Bcl-2. Collectively, our findings suggest that activation of ERα by E2 and cisplatin can induce platinum-resistance by increasing the expression of anti-apoptotic protein in ovarian cancer cells. Therefore, our findings provide valuable information that ERα might be a promising therapeutic target for platinum-resistant ovarian cancer.

Tetrathiomolybdate mediates cisplatin-induced p38 signaling and EGFR degradation and enhances response to cisplatin therapy in gynecologic cancers

Cisplatin and its analogs are among the most widely used chemotherapeutic agents against various types of cancer. It is known that cisplatin can activate epidermal growth factor receptor (EGFR), which may provide a survival benefit in cancers. Tetrathiomolybdate (TM) is a potent anti-cancer and anti-angiogenic agent and has been investigated in a number of clinical trials for cancer. In this study, we explore the therapeutic potential of TM on cisplatin-mediated EGFR regulation. Our study shows that TM is not cytotoxic, but exerts an anti-proliferative effect in ECC-1 cells. However, TM treatment prior to cisplatin markedly improves cisplatin-induced cytotoxicity. TM suppressed cisplatin-induced activation of EGFR while potentiating activation of p38; the activation of p38 signaling appeared to promote cisplatin-induced EGFR degradation. These results are in contrast to what we saw when cells were co-treated with cisplatin plus an EGFR tyrosine kinase inhibitor, where receptor activation was inhibited but receptor degradation was also blocked. Our current study is in agreement with previous findings that TM may have a therapeutic benefit by inhibiting EGFR activation. We furthermore provide evidence that TM may provide an additional benefit by potentiating p38 activation following cisplatin treatment, which may in turn promote receptor degradation by cisplatin.

Time-staggered inhibition of JNK effectively sensitizes chemoresistant ovarian cancer cells to cisplatin and paclitaxel

Ovarian cancer is the most lethal gynecological malignancy, for which platinum- and taxane-based chemotherapy plays a major role. Chemoresistance of ovarian cancer poses a major obstacle to the successful management of this devastating disease; however, effective measures to overcome platinum and taxane resistance are yet to be established. In the present study, while investigating the mechanism underlying the chemoresistance of ovarian cancer, we found that JNK may have a key role in the resistance of ovarian cancer cells to cisplatin and paclitaxel. Importantly, whereas simultaneous application of a JNK inhibitor and either of the chemotherapeutic agents had contrasting effects for cisplatin (enhanced cytotoxicity) and paclitaxel (decreased cytotoxicity), JNK inhibitor treatment prior to chemotherapeutic agent application invariably enhanced the cytotoxicity of both drugs, suggesting that the basal JNK activity is commonly involved in the chemoresistance of ovarian cancer cells to cisplatin and paclitaxel in contrast to drug‑induced JNK activity which may have different roles for these two drugs. Furthermore, we confirmed using non-transformed human and rodent fibroblasts that sequential application of the JNK inhibitor and the chemotherapeutic agents did not augment their toxicity. Thus, our findings highlight for the first time the possible differential roles of the basal and induced JNK activities in the chemoresistance of ovarian cancer cells and also suggest that time‑staggered JNK inhibition may be a rational and promising strategy to overcome the resistance of ovarian cancer to platinum- and taxane-based chemotherapy.

MAPK1 of Leishmania donovani modulates antimony susceptibility by downregulating P-glycoprotein efflux pumps

Emergence of resistance to pentavalent antimonials has become a severe obstacle in the treatment of visceral leishmaniasis (VL) in the Indian subcontinent. Mitogen-activated protein kinases (MAPKs) are well-known mediators of signal transduction of eukaryotes, regulating important processes, like proliferation, differentiation, stress response, and apoptosis. In Leishmania, MAPK1 has been shown to be consistently downregulated in antimony-resistant field isolates, suggesting that it has a role in antimony resistance. The present work investigates the molecular mechanism of MAPK1 in antimony resistance in Leishmania donovani. The L. donovani MAPK1 (LdMAPK1) single-allele replacement mutants exhibited increased resistance to Sb(III) (5.57-fold) compared to wild-type promastigotes, while overexpressing parasites became much more susceptible to antimony. The LdMAPK1-mediated drug sensitivity was directly related to antimony-induced apoptotic death of the parasite, as was evidenced by a 4- to 5-fold decrease in cell death parameters in deletion mutants and a 2- to 3-fold increase in MAPK1-overexpressing cells. LdMAPK1-underexpressing parasites also exhibited increased P-glycoprotein (P-gp)-mediated efflux pump activity, while a significant decrease in pump activity was observed in overexpressing cells. This change in efflux pump activity was directly related to expression levels of P-gp in all cell lines. However, episomal complementation of the gene restored normal growth, drug sensitivity, P-gp expression, and efflux pump activity. The data indicate that LdMAPK1 negatively regulates the expression of P-glycoprotein-type efflux pumps in the parasite. The decrease in efflux pump activity with an increase in LdMAPK1 expression may result in increased antimony accumulation in the parasite, making it more vulnerable to the drug.

Synergistic growth inhibition by sorafenib and cisplatin in human osteosarcoma cells

Molecular-targeted therapy has shown promise as a treatment for advanced osteosarcoma (OS). Sorafenib (SOR), a multikinase inhibitor, is the approved systemic drug of choice for OS, but has demonstrated limited benefits due to its toxicity and other adverse effects. Therapy strategies for reducing toxicity include using lower doses of SOR in combination with other complementary agents. Cisplatin (CDDP) has been shown to be a promising anticancer drug against various types of cancer including OS. In the present study, SOR was combined with CDDP to determine whether this combinatorial treatment suppressed tumor growth thereby simultaneously reducing doses of the two drugs for the treatment of OS. Human Saos-2 OS cells were treated with SOR and CDDP, alone and in combination, and the effect of these treatments on cell proliferation, colony formation, cell cycle, apoptosis, migration, and invasion, and involvement in receptor signaling, as well as tumor growth ability in nude mice was determined. It was found that the combination of low concentrations of SOR and CDDP significantly suppressed the cell proliferation, colony formation, migration and invasion, and induced cell apoptosis and cell cycle arrest in the G0/G1 stage, and suppressed tumor growth in a nude mouse model compared to the actions of either agent alone. The results also showed that SOR in combination with CDDP significantly suppressed the phosphorylation of extracellular signal-regulated kinase (ERK), which may contribute to the inhibition of tumor growth. These results suggested that SOR in combination with CDDP acts synergistically in the treatment of OS.

Cisplatin in cancer therapy: molecular mechanisms of action

Cisplatin, cisplatinum, or cis-diamminedichloroplatinum (II), is a well-known chemotherapeutic drug. It has been used for treatment of numerous human cancers including bladder, head and neck, lung, ovarian, and testicular cancers. It is effective against various types of cancers, including carcinomas, germ cell tumors, lymphomas, and sarcomas. Its mode of action has been linked to its ability to crosslink with the purine bases on the DNA; interfering with DNA repair mechanisms, causing DNA damage, and subsequently inducing apoptosis in cancer cells. However, because of drug resistance and numerous undesirable side effects such as severe kidney problems, allergic reactions, decrease immunity to infections, gastrointestinal disorders, hemorrhage, and hearing loss especially in younger patients, other platinum-containing anti-cancer drugs such as carboplatin, oxaliplatin and others, have also been used. Furthermore, combination therapies of cisplatin with other drugs have been highly considered to overcome drug-resistance and reduce toxicity. This comprehensive review highlights the physicochemical properties of cisplatin and related platinum-based drugs, and discusses its uses (either alone or in combination with other drugs) for the treatment of various human cancers. A special attention is paid to its molecular mechanisms of action, and its undesirable side effects.

Differential sensitivity of p44/p42-MAPK- and PI3K/Akt-targeted neuroblastoma subtypes to arsenic trioxide

PI3K/Akt and MAPK/ERK pathways are differentially activated in neuroblastoma (NB) cell types. In an effort to enhance the effectiveness of the NB treatment, we designed experiments to evaluate the effects of ATO in combination with PI3K and MEK1/2 specific inhibitors, LY29004 and U0126, respectively, in SK-N-MC and SK-N-BE(2) cell lines. The results indicated that specific inhibition of PI3K and MEK1/2 significantly enhanced antiproliferative and proapoptotic effects of ATO in SK-N-BE(2), but not in SK-N-MC. Furthermore, in SK-N-BE(2), NF-κB activation was significantly suppressed by LY29004+ATO treatments as compared with ATO alone, indicating that inhibition of PI3K may enhance anti-neoplastic properties of ATO in I-type NB cells through suppression of NF-κB. Moreover, expressions of c-Myc, Bad, Bax and ATM in SK-N-BE(2) cell line were significantly increased by U0126+ATO treatment as compared to treatment with ATO alone. Expression of telomerase hTERT was almost depleted by U0126+ATO treatment. Regarding the fact that activation of PI3K and MAPK in SK-N-BE(2) is higher than in other NB subtypes, we hypothesize that growth of SK-N-BE(2) cell line is highly dependent on these pathways and inhibition of these pathways may has promise for the treatment of multi-drug resistant I-type NB cells by ATO. However, for successful strategies for the treatment of this heterogeneous tumor, other combinations approaches need to be considered to simultaneously target other NB cells.

Compartmentalized Ras signaling differentially contributes to phenotypic outputs

Ras isoforms are membrane bound proteins that differentially localize to the plasma membrane and subcellular compartments within the cell. Whilst the cell surface is the main site for Ras activity the extent to which intracellular pools contribute to Ras function is debated. We have generated Ras chimeras targeting Ras to the ER, Golgi, mitochondria and endosomes to compare the capacity of each of these locations to support activity equivalent to normal Ras function. We find that all locations are capable of regulating the MAP kinase and Akt pathways. Furthermore, whilst endomembranous Ras pools show location-specific competence to support proliferation and transformation, Golgi-Ras is as potent as N-Ras.

Differential regulation of c-Jun protein plays an instrumental role in chemoresistance of cancer cells

The chemotherapeutic drug cisplatin (cis-diamminedichloroplatinum(II) (CDDP)) is widely used in the treatment of human cancers. However, the mechanism underlying intrinsic tumor resistance to CDDP remains elusive. Here, we demonstrate that treatment with CDDP resulted in down-regulation of c-Jun expression via caspase-9-dependent cleavage of c-Jun at Asp-65 and MEKK1-mediated ubiquitylation and degradation of c-Jun in CDDP-sensitive cancer cells. In contrast, activation of JNK2 (but not JNK1) phosphorylated and up-regulated the expression of c-Jun in CDDP-resistant cells. Activated c-Jun bound to the promoter regions of the MDR1 gene and promoted the expression of MDR1. Expression of a cleavage-resistant c-Jun mutant (D65A) suppressed CDDP-induced apoptosis of CDDP-sensitive cells, whereas depletion of JNK2, c-Jun, or MDR1 in CDDP-resistant cancer cells promoted apoptosis upon CDDP treatment. In addition, mammary gland tumors induced by polyomavirus middle T antigen in JNK2(-/-) mice were more sensitive to CDDP compared with those in JNK2(+/+) mice. These findings highlight the instrumental role of c-Jun in the resistance of tumors to treatment with CDDP and indicate that c-Jun is a molecular target for improving cancer therapy.

Notch3 induces epithelial-mesenchymal transition and attenuates carboplatin-induced apoptosis in ovarian cancer cells

OBJECTIVE

Notch3 is implicated in chemoresistance of ovarian cancer, yet the molecular mechanism underlying Notch3-mediated drug resistance remains to be elucidated. Here, we investigated the role of Notch3 in carboplatin-induced apoptosis in ovarian cancer cells.

METHODS

Ovarian cancer cell line OVCA429 cells were stably transduced with an empty vector or a retroviral vector expressing the Notch3 intracellular domain (NICD3, the constitutively active form of Notch3) to generate OVCA429/vector and OVCA429/NICD3 cells. Epithelial-mesenchymal transition (EMT) was determined by morphological change and expression of the EMT markers. Carboplatin-induced cytotoxicity was determined by the neutral red uptake assay. Apoptosis was determined by Annexin V staining and Western blotting. Carboplatin-induced phosphorylation of extracellular signal-regulated kinase (ERK) was identified by a phospho-kinase array and confirmed by Western blotting.

RESULTS

Activation of Notch3 in OVCA429 cells causes a spindle and fibroblast-like morphology, induces the expression of smooth muscle α-actin, Slug and Snail, but decreases the expression of E-cadherin, indicating that Notch3 activation induces EMT in OVCA429 cells. Furthermore, Notch3 activation renders OVCA429 cells more resistant to carboplatin-induced cytotoxicity and attenuates carboplatin-induced apoptosis in these cells. Our results indicate that phosphorylation of ERK is a positive regulator of carboplatin-induced apoptosis in OVCA429 cells. Interestingly, carboplatin-induced ERK phosphorylation is inhibited by Notch3 activation.

CONCLUSIONS

Notch3 activation induces EMT and attenuates carboplatin-induced apoptosis in OVCA429 cells. ERK phosphorylation plays a pro-apoptotic role in carboplatin-induced apoptosis in OVCA429 cells. Interestingly, Notch3 activation attenuates carboplatin-induced ERK phosphorylation in these cells.

Inorganic phosphate enhances sensitivity of human osteosarcoma U2OS cells to doxorubicin via a p53-dependent pathway

Osteosarcoma is the most common malignant primary bone tumor in children and adolescents. The clinical outcome for osteosarcoma remains discouraging despite aggressive surgery and intensive radiotherapy and chemotherapy regimens. Thus, novel therapeutic approaches are needed. Previously, we have shown that inorganic phosphate (Pi) inhibits proliferation and aggressiveness of human osteosarcoma U2OS cells identifying adenylate cyclase, beta3 integrin, Rap1, ERK1/2 as proteins whose expression and function are relevantly affected in response to Pi. In this study, we investigated whether Pi could affect chemosensitivity of osteosarcoma cells and the underlying molecular mechanisms. Here, we report that Pi inhibits proliferation of p53-wild type U2OS cells (and not of p53-null Saos and p53-mutant MG63 cells) by slowing-down cell cycle progression, without apoptosis occurrence. Interestingly, we found that Pi strongly enhances doxorubicin-induced cytotoxicity in U2OS, and not in Saos and MG63 cells, by apoptosis induction, as revealed by a marked increase of sub-G1 population, Bcl-2 downregulation, caspase-3 activation, and PARP cleavage. Remarkably, Pi/doxorubicin combination-induced cytotoxicity was accompanied by an increase of p53 protein levels and of p53 target genes mdm2, p21 and Bax, and was significantly reduced by the p53 inhibitor pifithrine-alpha. Moreover, the doxorubicin-induced cytotoxicity was associated with ERK1/2 pathway inhibition in response to Pi. Altogether, our data enforce the evidence of Pi as a novel signaling molecule capable of inhibiting ERK pathway and inducing sensitization to doxorubicin of osteosarcoma cells by p53-dependent apoptosis, implying that targeting Pi levels might represent a rational strategy for improving osteosarcoma therapy.

Activation of the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase pathway overcomes cisplatin resistance in ovarian carcinoma cells

OBJECTIVE

This study was aimed to elucidate the roles of the mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) and phosphatidylinositol 3'-kinase (PI3K)/Akt pathways in regulating cytotoxicity induced by cisplatin (CDDP) in ovarian carcinoma cells.

METHODS

We treated 7 ovarian cancer cell lines with CDDP alone or with CDDP and either a PI3K inhibitor (LY294002), a MEK inhibitor (PD98059), or a MEK/ERK activator (phorbol 12-myristate 13-acetate [PMA]) and assessed cell viability, expression of MEK/ERK and PI3K/Akt, cell cycle distribution, and apoptosis. We also investigated the effect of combination treatment on survival in a xenograft model.

RESULTS

The cell lines showed half-maximal inhibitory concentrations (IC50) of CDDP from 2.4 to 26.9 μmol/L. KFr, a CDDP-resistant cell line developed from KF cells, showed an IC50 of CDDP of 9.6 μmol/L. Five of the cell lines with IC50 values of 9.6 μmol/L or greater were defined as CDDP-resistant. Cisplatin and LY294002 had an additive effect on inhibiting cell growth, and CDDP and PD98059 had and antagonistic effect on cell growth in all cell lines. In CDDP-resistant cells, CDDP and PMA dramatically suppressed the cell growth, up-regulated the expression of phosphorylated ERK and cleaved caspase-9, down-regulated the expression of checkpoint kinases, and increased the proportion of cells in the synthesis-phase fraction and apoptotic cells. The treatment of nude mice with CDDP and PMA prolonged survival in an ovarian cancer xenograft model.

CONCLUSIONS

The present study indicates that further study is warranted to determine the effectiveness of combination treatment with CDDP and PMA for platinum-resistant ovarian carcinoma.

Alterations of microRNA expression patterns in human cervical carcinoma cells (Ca Ski) toward 1'S-1'-acetoxychavicol acetate and cisplatin

The aims of this study were to investigate the combined effects of a natural compound 1'S-1'-acetoxychavicol acetate (ACA) with cisplatin (CDDP) on HPV-positive human cervical carcinoma cell lines (Ca Ski-low cisplatin sensitivity and HeLa-high cisplatin sensitivity), and to identify microRNAs (miRNAs) modulated in response toward ACA and/or CDDP. It was revealed that both ACA and CDDP induced dose- and time-dependent cytotoxicity when used as a stand-alone agent, while synergistic effects were observed when used in combination with a combination index (CI) value of 0.74 ± 0.01 and 0.85 ± 0.01 in Ca Ski and HeLa cells, respectively. A total of 25 miRNAs were found to be significantly differentially expressed in response to ACA and/or CDDP. These include hsa-miR-138, hsa-miR-210, and hsa-miR-744 with predicted gene targets involved in signaling pathways regulating apoptosis and cell cycle progression. In conclusion, ACA acts as a chemosensitizer which synergistically potentiates the cytotoxic effect of CDDP in cervical cancer cells. The altered miRNA expression upon administration of ACA and/or CDDP suggests that miRNAs play an important role in anticancer drug responses, which can be manipulated for therapeutic purposes.

Cell death triggered by synthetic flavonoids in human leukemia cells is amplified by the inhibition of extracellular signal-regulated kinase signaling

A new class of methyl esters of flavonoids, with different substituents on the B ring were synthesized and evaluated for their antiproliferative activity against the human leukemia cell line HL-60. The presence of either a methyl group (1f) or a chlorine atom (1o) at position 2' of the B ring played an important role in affecting antiproliferative activity. The cytotoxic effects of these compounds were accompanied by the concentration- and time-dependent appearance of DNA- and nuclear-fragmentation, increase in the percentage of sub-G(1) cells, and processing of multiple caspases and poly(ADP-ribose)polymerase cleavage. Pretreatment of cells with the specific mitogen-activated extracellular kinases (MEK) 1/2 inhibitor PD98059, together with 1f and 1o, resulted in an important enhancement of cell death, which might have clinical implications for the use of both compounds in combination with MEK 1/2 inhibitors as potential therapeutic agents.

On the discovery, biological effects, and use of Cisplatin and metallocenes in anticancer chemotherapy

The purpose of this paper is to summarize mode of action of cisplatin on the tumor cells, a brief outlook on the metallocene compounds as antitumor drugs as well as the future tendencies for the use of the latter in anticancer chemotherapy. Molecular mechanisms of cisplatin interaction with DNA, DNA repair mechanisms, and cellular proteins are discussed. Molecular background of the sensitivity and resistance to cisplatin, as well as its influence on the efficacy of the antitumor immune response was evaluated. Furthermore, herein are summarized some metallocenes (titanocene, vanadocene, molybdocene, ferrocene, and zirconocene) with high antitumor activity.

Inhibition of JNK-1 by small interfering RNA induces apoptotic signaling in PC-3 prostate cancer cells

Previous studies have shown that c-Jun-N-terminal kinase-1 (JNK-1) is involved in the transformation of primary fibroblasts and plays a role in tumor cell growth. A number of observations suggest that JNK-1 is a growth promoting factor in prostate cancer cells and blocking its function may induce apoptosis. To test this further, we used a small interfering RNA (siRNA) against JNK-1 mRNA that efficiently inhibits JNK-1 expression in the prostate cancer cell line, PC-3. The application of siRNA against JNK-1 decreased the expression of JNK-1 and affected the expression of p21, XIAP and Bcl-2, but had no effect on the expression of VEGF. In contrast, a control scramble siRNA did not affect the expression of the above indicated proteins. The downregulation of JNK-1 expression at both the mRNA and protein levels was detected by reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis. Cell proliferation inhibition rates were determined by the MTT assay. The effect of JNK-1-siRNA on cell cycle distribution and cell apoptosis was determined by flow cytometry, DNA fragmentation and caspase activity. Our data showed that siRNA against JNK-1 mRNA, could efficiently suppress the expression of JNK-1 in PC-3 cells. After 5 days of transfection, the cell death rate was 52%, the apoptotic rate 26% and the viability rate 22%. In conclusion, downregulation of JNK-1 expression by siRNA against JNK-1 mRNA induces apoptotic signaling in prostate cancer PC-3 cells. The use of siRNA against JNK-1 as a novel approach to cancer therapy deserves further investigation.

Mifepristone prevents repopulation of ovarian cancer cells escaping cisplatin-paclitaxel therapy

Background

Advanced ovarian cancer is treated with cytoreductive surgery and combination platinum- and taxane-based chemotherapy. Although most patients have acute clinical response to this strategy, the disease ultimately recurs. In this work we questioned whether the synthetic steroid mifepristone, which as monotherapy inhibits the growth of ovarian cancer cells, is capable of preventing repopulation of ovarian cancer cells if given after a round of lethal cisplatin-paclitaxel combination treatment.

Methods

We established an in vitro approach wherein ovarian cancer cells with various sensitivities to cisplatin or paclitaxel were exposed to a round of lethal doses of cisplatin for 1 h plus paclitaxel for 3 h. Thereafter, cells were maintained in media with or without mifepristone, and short- and long-term cytotoxicity was assessed.

Results

Four days after treatment the lethality of cisplatin-paclitaxel was evidenced by reduced number of cells, increased hypodiploid DNA content, morphological features of apoptosis, DNA fragmentation, and cleavage of caspase-3, and of its downstream substrate PARP. Short-term presence of mifepristone either enhanced or did not modify such acute lethality. Seven days after receiving cisplatin-paclitaxel, cultures showed signs of relapse with escaping colonies that repopulated the plate in a time-dependent manner. Conversely, cultures exposed to cisplatin-paclitaxel followed by mifepristone not only did not display signs of repopulation following initial chemotherapy, but they also had their clonogenic capacity drastically reduced when compared to cells repopulating after cisplatin-paclitaxel.

Conclusions

Cytostatic concentrations of mifepristone after exposure to lethal doses of cisplatin and paclitaxel in combination blocks repopulation of remnant cells surviving and escaping the cytotoxic drugs.

Gefitinib (ZD1839) increases the efficacy of cisplatin in ovarian cancer cells

We examined the effect of gefitinib (ZD1839), a selective epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor, on cytotoxicity to cisplatin, EGFR downstream signaling, apoptosis and the association between the inhibition of DNA repair by gefitinib and the expression of DNA-dependent protein kinase (DNA-PK) using three ovarian cancer cell lines. In the presence of gefitinib, cisplatin-induced growth inhibition and apoptosis were significantly enhanced in Caov-3 and RMG-1 cells, which express EGFR, and in A2780, which lacks EGFR but expresses HER-2. Gefitinib significantly inhibited the cisplatin-induced ERK and Akt activation in Caov-3 and RMG-1 cells but not in A2780 cells. In all three cell lines, there was delayed repair of DNA intrastrand cross-links damaged by cisplatin used in combination with gefitinib, compared with cisplatin alone. The reduction in DNA-PK levels persisted when cells were exposed to combinations of cisplatin and gefitinib in all cell lines. Moreover, the delayed repair was cancelled by anti-HER2 small-interfering RNA transfection in A2780 cells. These results suggest that combination therapy with cisplatin and gefitinib may increase the therapeutic efficacy of cisplatin by blocking EGFR downstream signaling and/or inhibiting DNA repair in ovarian cancer.

Combined experimental and computational analysis of DNA damage signaling reveals context-dependent roles for Erk in apoptosis and G1/S arrest after genotoxic stress

Following DNA damage, cells display complex multi-pathway signaling dynamics that connect cell-cycle arrest and DNA repair in G1, S, or G2/M phase with phenotypic fate decisions made between survival, cell-cycle re-entry and proliferation, permanent cell-cycle arrest, or cell death. How these phenotypic fate decisions are determined remains poorly understood, but must derive from integrating genotoxic stress signals together with inputs from the local microenvironment. To investigate this in a systematic manner, we undertook a quantitative time-resolved cell signaling and phenotypic response study in U2OS cells receiving doxorubicin-induced DNA damage in the presence or absence of TNFα co-treatment; we measured key nodes in a broad set of DNA damage signal transduction pathways along with apoptotic death and cell-cycle regulatory responses. Two relational modeling approaches were then used to identify network-level relationships between signals and cell phenotypic events: a partial least squares regression approach and a complementary new technique which we term 'time-interval stepwise regression.' Taken together, the results from these analysis methods revealed complex, cytokine-modulated inter-relationships among multiple signaling pathways following DNA damage, and identified an unexpected context-dependent role for Erk in both G1/S arrest and apoptotic cell death following treatment with this commonly used clinical chemotherapeutic drug.

Autocrine production of interleukin-8 confers cisplatin and paclitaxel resistance in ovarian cancer cells

It has been widely reported that interleukin-8 (IL-8) is overexpressed in ovarian cyst fluid, ascites, serum, and tumor tissue from ovarian cancer (OVCA) patients, and elevated IL-8 expression correlates with a poor final outcome and chemosensitivity. However, the role of IL-8 expression in the acquisition of the chemoresistance phenotype and the underlining mechanisms of drug resistance in OVCA cells are not yet fully understood. Here we show that both exogenous (a relatively short period of treatment with recombination IL-8) and endogenous IL-8 (by transfecting with plasmid encoding for sense IL-8) induce cisplatin and paclitaxel resistance in non-IL-8-expressing A2780 cells, while deleting of endogenous IL-8 expression in IL-8-overexpressing SKOV-3 cells (by transfecting with plasmid encoding for antisense IL-8) promotes the sensitivity of these cells to anticancer drugs. IL-8-mediated resistance of OVCA cells exhibits decreased proteolytic activation of caspase-3. Meanwhile, the further study demonstrates that the chemoresistance caused by IL-8 is associated with increased expression of both multidrug resistance-related genes (MDR1) and apoptosis inhibitory proteins (Bcl-2, Bcl-xL, and XIAP), as well as activation of PI3K/Akt and Ras/MEK/ERK signaling. Therefore, modulation of IL-8 expression or its related signaling pathway may be a promising strategy of treatment for drug-resistant OVCA.

Phenethyl isothiocyanate sensitizes human cervical cancer cells to apoptosis induced by cisplatin

SCOPE

Naturally-occurring chemopreventive agent phenethyl isothiocyanate (PEITC), derived primarily from watercress, has been shown to inhibit cell growth and induce apoptosis in cancer cells. In this study, we examined the potential of PEITC in enhancing cisplatin-induced apoptosis in cervical cancer cells and its mechanisms.

METHODS AND RESULTS

HeLa cells were exposed to PEITC, cisplatin or both. Pretreatment of cells with PEITC strongly enhanced cisplatin-induced cytotoxicity. PEITC activated the mitogen-activated protein kinases, including c-Jun N-terminal kinase (JNK), extracellular signal-related kinase (ERK), and p38. Caspase-3 activity assay demonstrated that the synergistic induction of apoptosis was significantly attenuated by MEK1/2 inhibitor U0126, but not by JNK or p38 inhibitor, suggesting that ERK activation is responsible for the synergistic effect. We found that NF-κB signaling pathway is not involved in the synergistic effect. Sulforaphane and benzyl isothiocyanate, two other members of the isothiocyanate family, also sensitize HeLa cells to apoptosis induced by cisplatin. Furthermore, we found that the synergistic effect was also observed in cervical cancer C33A and breast cancer MCF-7 cells but not in normal mammary epithelial MCF-10A cells. Finally, we demonstrated that Noxa induction was associated with apoptosis induced by PEITC plus cisplatin.

CONCLUSION

Taken together, this study shows that PEITC can sensitize cancer cells to apoptosis induced by cisplatin and this effect is mediated through ERK activation, suggesting the potential of PEITC to be used as an adjuvant with cisplatin in combination therapeutic treatments.

Up-regulation of extracellular signal-regulated kinase 1/2-dependent thymidylate synthase and thymidine phosphorylase contributes to cisplatin resistance in human non-small-cell lung cancer cells

Chemotherapy for advanced human non-small-cell lung cancer (NSCLC) includes platinum-containing compound such as cisplatin in combination with a second- or third-generation cytotoxic agent. 5-Fluorouracil (5-FU) belongs to antimetabolite chemotherapeutics, and its mechanism of cytotoxicity is involved in the inhibition of thymidylate synthase (TS). TS and thymidine phosphorylase (TP) are key enzymes of the pyrimidine salvage pathway. In this study, we have examined the molecular mechanism of TS and TP in regulating drug sensitivity to cisplatin in NSCLC cell lines. Cisplatin could increase the phosphorylation of mitogen-activated protein kinase kinase 1/2 (MKK1/2)-extracellular signal-regulated kinase 1/2 (ERK1/2) and the protein levels of TS and TP through enhancing the protein stability in A549 and H1975 cells. Blocking ERK1/2 activation by MKK1/2 inhibitor [U0126; 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)butadiene)] decreased TS and TP protein levels in both cell lines treated with cisplatin. Depletion of endogenous TS or TP expression by specific small interfering RNA transfection significantly increased cisplatin-induced cell death and growth inhibition. Combined treatment with 5-FU could decrease cisplatin-induced ERK1/2 activation and the induction of TS and TP, which subsequently resulted in synergistic cytotoxic effects. Enforced expression of constitutive active MKK1/2 vectors rescued the protein levels of phospho-ERK1/2, TS, and TP, and the cell viability that were decreased by cisplatin and 5-FU combination. In contrast, U0126 enhanced drug sensitivity to cisplatin and/or 5-FU in lung cancer cells. In conclusion, the up-regulation of ERK1/2-dependent TS and TP can protect human lung cancer cells from cisplatin-induced cytotoxicity.

Role of JNK/ATF-2 pathway in inhibition of thrombospondin-1 (TSP-1) expression and apoptosis mediated by doxorubicin and camptothecin in FTC-133 cells

Our previous studies have shown that camptothecin and doxorubicin triggered ceramide accumulation via de novo synthesis pathway. De novo ceramide generation was responsible for the drug-induced apoptosis through a caspase-3-dependent pathway and a decrease of thrombospondin-1 expression in human thyroid carcinoma FTC-133 cells. Here, we demonstrate that Jun N-terminal kinases play a critical role in camptothecin- and doxorubicin-induced down-regulation of thrombospondin-1 expression: i) de novo ceramide synthesis pathway activates Jun N-terminal kinase 1/2 resulting in activating transcription factor 2 phosphorylation; ii) cell treatment by SP600125, a Jun N-terminal kinase specific inhibitor, strongly reduced activating transcription factor 2 phosphorylation and completely abolished camptothecin and doxorubicin effects; and iii) activating transcription factor 2 expression silencing greatly attenuated camptothecin- and doxorubicin-induced down-regulation of thrombospondin-1 expression and apoptosis. The set of our data established that camptothecin- and doxorubicin-induced activation of Jun N-terminal kinase/activating transcription factor 2 pathway via de novo ceramide synthesis down-regulates thrombospondin-1 expression and apoptosis in human thyroid carcinoma FTC-133 cells. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.

Reactive oxygen species mediate lysophosphatidic acid induced signaling in ovarian cancer cells

Lysophosphatidic acid (LPA) is produced by tumor cells and is present in the ascites fluid of ovarian cancer patients. To determine the role of endogenous LPA in the ovarian cancer cell line SKOV3, we treated cells with the LPA receptor antagonist VPC32183 and found that it inhibited cell growth and induced apoptosis. Exogenous LPA further stimulated ERK and Akt phosphorylation and NF-κB activity. To determine if reactive oxygen species (ROS), which have been implicated as second messengers in cell signaling, were also involved in LPA signaling, we treated cells with the NADPH oxidase inhibitor diphenyleneiodonium (DPI), and antioxidants N-acetyl cysteine, EUK-134 and curcumin, and showed that all blocked LPA-dependent NF-κB activity and cell proliferation. DPI and EUK-134 also inhibited Akt and ERK phosphorylation. LPA was shown to stimulate dichlorofluorescein fluorescence, though not in the presence of DPI, apocynin (an inhibitor of NADPH oxidase), VPC32183, or PEG-catalase. Akt phosphorylation was also inhibited by PEG-catalase and apocynin. These data indicate that NADPH oxidase is a major source of ROS and H(2)O(2) is critical for LPA-mediated signaling. Thus, LPA acts as a growth factor and prevents apoptosis in SKOV3 cells by signaling through redox-dependent activation of ERK, Akt, and NF-κB-dependent signaling pathways.

Cellular responses to Cisplatin-induced DNA damage

Cisplatin is one of the most effective anticancer agents widely used in the treatment of solid tumors. It is generally considered as a cytotoxic drug which kills cancer cells by damaging DNA and inhibiting DNA synthesis. How cells respond to cisplatin-induced DNA damage plays a critical role in deciding cisplatin sensitivity. Cisplatin-induced DNA damage activates various signaling pathways to prevent or promote cell death. This paper summarizes our current understandings regarding the mechanisms by which cisplatin induces cell death and the bases of cisplatin resistance. We have discussed various steps, including the entry of cisplatin inside cells, DNA repair, drug detoxification, DNA damage response, and regulation of cisplatin-induced apoptosis by protein kinases. An understanding of how various signaling pathways regulate cisplatin-induced cell death should aid in the development of more effective therapeutic strategies for the treatment of cancer.

Modulation of cell sensitivity to antitumor agents by targeting survival pathways

The advent of drugs targeting tumor-associated prosurvival alterations of cancer cells has changed the interest of antitumor drug development from cytotoxic drugs to target-specific agents. Although single-agent therapy with molecularly targeted agents has shown limited success in tumor growth control, a promising strategy is represented by the development of rational combinations of target-specific agents and conventional antitumor drugs. Activation of survival/antiapoptotic pathways is a common feature of cancer cells that converge in the development of cellular resistance to cytotoxic agents. The survival pathways implicated in cellular response to drug treatment are primarily PI3K/Akt and Ras/MAPK, which also mediate the signalling activated by growth factors and play a role in the regulation of critical processes including cell proliferation, metabolism, apoptosis and angiogenesis. Inhibitors of PI3K, Akt and mTOR have been shown to sensitize selected tumor cells to cytotoxic drugs through multiple downstream effects. Moreover, the MAPK pathway, also implicated in the regulation of gene expression in response to stress stimuli, can interfere with the chemotherapy-induced proapoptotic signals. Targeting Hsp90, which acts as a molecular chaperone for survival factors including Akt, may have the potential advantage to simultaneously block multiple oncogenic pathways. Overall, the available evidence supports the interest of rationally designed approaches to enhance the efficacy of conventional antitumor treatments through the inhibition of survival pathways and the notion that the concomitant targeting of multiple pathways may be a successful strategy to deal with tumor heterogeneity and to overcome drug resistance of tumor cells.

Intraperitoneal administration of telomerase-specific oncolytic adenovirus sensitizes ovarian cancer cells to cisplatin and affects survival in a xenograft model with peritoneal dissemination

Despite tremendous development in chemotherapy for ovarian cancer over the past few decades, the prognosis of advanced cases with massive peritoneal dissemination is still unsatisfactory, and novel treatment modalities that can combine with chemotherapy are urgently needed. We recently developed virotherapy for solid tumors using telomerase-specific replication-selective adenoviruses (Telomelysin: OBP-301), in which the human telomerase reverse transcriptase (hTERT) gene promoter has been inserted to direct tumor-specific E1 gene expression. In this study, we investigated the anti-tumor effects of OBP-301, combined with cisplatin (CDDP), on ovarian cancer cells. In vitro treatment of SKOV3 cells with OBP-301 at a multiplicity of infection (MOI) of 0.01–100 induced significant cell death in a dose-dependent manner, with moderate cytotoxicity at an MOI of 1–10 and maximal cytotoxicity at an MOI of 100. In contrast, OBP-301 treatment of normal human cells showed no significant cell death at an MOI of 1–10 and exhibited modest cytotoxicity at an MOI of 100. The effects of low-dose CDDP at 0.5–1 μM, which induced only 20% cell death, were significantly augmented by combination with OBP-301 at an MOI of 1–10, finally achieving 40% cell death. Such enhancement of CDDP sensitivity was also observed in CDDP-resistant ovarian cancer cells. The combinatorial effects were further tested using a xenograft mouse model of SKOV3 with peritoneal dissemination. After intraperitoneal administration of OBP-301, we confirmed that injected OBP-301 fused with the green fluorescent protein (GFP) gene (OBP-401) was preferentially localized to peritoneal disseminations, as determined by fluorescence imaging. Treatment of mice with CDDP at low dose (0.5 mg kg^–1) had modest effects, showing a 10% decrease in disseminations, whereas combination with intraperitoneal administration of OBP-301 at an MOI of 10 led to enhanced effects, achieving an approximately 80% decrease in disseminations. Kaplan–Meier analysis showed improved overall survival of mice treated with CDDP plus OBP-301 compared with CDDP alone. These findings support the therapeutic potential of intraperitoneal administration of OBP-301 to sensitize ovarian cancer cells to CDDP.

Melatonin suppresses cyclosporine A-induced autophagy in rat pituitary GH3 cells

Cyclosporine A (CsA) is a powerful immunosuppressive drug with side effects including the induction of chronic nephrotoxicity including endoplasmic reticulum (ER) stress in tubular cells. Recently, it was reported that autophagy is induced by ER stress and serves to alleviate the associated deleterious effects. In the current study, CsA treatment (0-100 microm) decreased cell survival of rat pituitary GH3 cells in a dose-dependent manner. At concentrations ranging from 1.0 to 10 microm, CsA induced a dose-dependent increase in the expression of microtubule-associated protein 1 light chain 3 (LC3)-I and LC3-II. Cells treated with 2.5 microm CsA exhibited cytoplasmic vacuolation, indicating that CsA induces autophagy in rat pituitary GH3 cells. In the presence of 1.0-10 microm CsA, the expression of catalase decreased while that of the ER stress markers, ER luminal binding protein (BiP) and inositol-requiring enzyme 1 alpha (IRE1alpha), increased as compared those levels in untreated cells. These results suggested that CsA-induced autophagy is dependent on ER stress. To determine whether melatonin would protect cells against CsA-induced autophagy, we treated rat pituitary GH3 cells with melatonin in the presence of CsA. Melatonin treatment (100 and 200 microm) suppressed autophagy induced by 2.5 and 5 microm CsA. Furthermore, co-treatment with 100 microm melatonin inhibited LC3-II expression, and increased catalase and phosphorylated p-ERK levels in the presence of 2.5 and 5 microm CsA. BiP and IRE1alpha expression in melatonin-co-treated cells was superior to that in cells treated with 2.5 and 5 microm CsA alone. Thus, melatonin suppresses CsA-mediated autophagy in rat pituitary GH3 cells.

Autocrine production of interleukin-6 confers cisplatin and paclitaxel resistance in ovarian cancer cells

It has been shown that IL-6 is elevated in the serum and ascites of ovarian cancer patients, and increased IL-6 concentration correlates with poor prognosis and chemoresistance. However, the role of IL-6 expression in the acquisition of the chemoresistance phenotype and the underlining mechanisms of drug resistance in ovarian cancer cells remain unclear. Here we demonstrate that both exogenous (a relatively short period of treatment with recombination IL-6) and endogenous IL-6 (by transfecting with plasmid encoding for sense IL-6) induce cisplatin and paclitaxel resistance in non-IL-6-expressing A2780 cells, while deleting of endogenous IL-6 expression in IL-6-overexpressing SKOV3 cells (by transfecting with plasmid encoding for antisense IL-6) promotes the sensitivity of these cells to anticancer drugs. IL-6-mediated resistance of ovarian cancer cells exhibits decreased proteolytic activation of caspase-3. Meanwhile, the further study demonstrates that the chemoresistance caused by IL-6 is associated with increased expression of both multidrug resistance-related genes (MDR1 and GSTpi) and apoptosis inhibitory proteins (Bcl-2, Bcl-xL and XIAP), as well as activation of Ras/MEK/ERK and PI3K/Akt signaling. Therefore, modulation of IL-6 expression or its related signaling pathway may be a promising strategy of treatment for drug-resistant ovarian cancer.

Melatonin-induced calbindin-D9k expression reduces hydrogen peroxide-mediated cell death in rat pituitary GH3 cells

In this study, we investigated whether calbindin-D9k (CaBP-9k) expression was regulated by melatonin during hydrogen peroxide (H(2)O(2))-induced cell death in rat pituitary GH3 cells. CaBP-9k expression was increased by melatonin in a dose- and time-dependent manner, indicating that CaBP-9k expression is regulated by melatonin. Cell survival was increased approximately 27-30% where H(2)O(2)-treated cells (0.25 or 0.5 mm) were also incubated with 1 mm melatonin, when compared with H(2)O(2) alone or H(2)O(2) plus 0.5 mm melatonin. This result was consistent with 4,6-diamidino-2-phenylindole staining. CaBP-9k expression was also augmented by co-treatment with H(2)O(2) and 1 mm melatonin, suggesting a functional relationship between increased cell death and melatonin-induced CaBP-9k expression during H(2)O(2)-mediated apoptosis. Bcl-2-associated protein expression increased following treatment with H(2)O(2) alone, whereas Bcl-2 expression was elevated following treatment with melatonin alone, or H(2)O(2) plus melatonin. The expression of p53 was depressed by treatment with melatonin alone, or co-treatment with H(2)O(2) plus melatonin. These results correlated with CaBP-9k expression levels and activation of the mitogen-activated protein kinase/extracellular signal-regulated kinase signaling pathway. Knockdown of CaBP-9k expression using a small inhibitory RNA resulted in an elevation of H(2)O(2)-induced cell death, whereas cell survival was increased in cells that overexpressed CaBP-9k, providing additional evidence that the induction of CaBP-9k expression may be associated with survival signaling during H(2)O(2)-mediated oxidative cell death. CaBP-9k appears to interact with p53, suggesting a possible role for this interaction in cell proliferation and cell cycle progression.

Apoptotic and chemotherapeutic properties of iron (III)-salophene in an ovarian cancer animal model

The cytotoxicity of organometallic compounds iron(III)-, cobalt(III)-, manganese(II)-, and copper(II)-salophene (-SP) on platinum-resistant ovarian cancer cell lines was compared. Fe-SP displayed selective cytotoxicity (IC(50) at ~1 muM) against SKOV-3 and OVCAR-3 cell lines while Co-SP caused cytotoxic effects only at higher concentrations (IC(50) at 60 muM) and Cu-SP effects were negligible. High cytotoxicity of Mn-SP (30-60 muM) appeared to be nonspecific because the Mn-chloride salt reduced cell viability similarly. The effect of Fe-SP at 1 muM proved to be ovarian cancer cell selective when compared to a panel of cell lines derived from different tumors. The first irreversible step in the induction of cell death by Fe-SP occurred after 3 hrs as indicated by the mitochondrial transmembrane potential (DeltaPsim) and was mainly linked to apoptotic, not necrotic events. To evaluate the toxicity of Fe-SP in vivo we conducted an acute toxicity study in rats. The LD(50) of Fe-SP is >2000 mg/kg orally and >5.5 mg/kg body weight by intraperitoneal injection. An ovarian cancer animal model showed that the chemotherapeutic relevant dose of Fe-SP in rats is 0.5-1 mg/kg body weight. The present report suggests that Fe-SP is a potential therapeutic drug to treat ovarian cancer.