Enhanced in vitro invasiveness and drug resistance with altered gene expression patterns in a human lung carcinoma cell line after pulse selection with anticancer drugs

Evaluation of ABT-751, a novel anti-mitotic agent able to overcome multi-drug resistance, in melanoma cells

PURPOSE

Drug efflux transporter associated multi-drug resistance (MDR) is a potential limitation in the use of taxane chemotherapies for the treatment of metastatic melanoma. ABT-751 is an orally bioavailable microtubule-binding agent capable of overcoming MDR and proposed as an alternative to taxane-based therapies.

METHODS

This study compares ABT-751 to taxanes in vitro, utilizing seven melanoma cell line models, publicly available gene expression and drug sensitivity databases, a lung cancer cell line model of MDR drug efflux transporter overexpression (DLKP-A), and drug efflux transporter ATPase assays.

RESULTS

Melanoma cell lines exhibit a low but variable protein and RNA expression of drug efflux transporters P-gp, BCRP, and MDR3. Expression of P-gp and MDR3 correlates with sensitivity to taxanes, but not to ABT-751. The anti-proliferative IC50 profile of ABT-751 was higher than the taxanes docetaxel and paclitaxel in the melanoma cell line panel, but fell within clinically achievable parameters. ABT-751 IC50 was not impacted by P-gp-overexpression in DKLP-A cells, which display strong resistance to the P-gp substrate taxanes compared to DLKP parental controls. The addition of ABT-751 to paclitaxel treatment significantly decreased cell proliferation, suggesting some reversal of MDR. ATPase activity assays suggest that ABT-751 is a potential BCRP substrate, with the ability to inhibit P-gp ATPase activity.

CONCLUSION

Our study confirms that ABT-751 is active against melanoma cell lines and models of MDR at physiologically relevant concentrations, it inhibits P-gp ATPase activity, and it may be a BCRP and/or MDR3 substrate. ABT-751 warrants further investigation alone or in tandem with other drug efflux transporter inhibitors for hard-to-treat MDR melanoma.

PepAnalyzer: predicting peptide properties using its sequence

Peptides are short linear molecules consisting of amino acids that play an essential role in most biological processes. They can treat diseases by working as a vaccine or antimicrobial agent and serves as a cancer molecule to deliver the drug to the target site for the treatment of cancer. They have the potential to solve the drawbacks of current medications and can be industrially produced in large quantities at low cost. However, poor chemical and physical stability, short circulating plasma half-life, and solubility are some issues that need solutions before they can be used as therapeutics. PepAnalyzer tool is a user-friendly tool that predicts 15 different properties such as binding potential, half-life, transmembrane patterns, test tube stability, charge, isoelectric point, molecular weights, and molar extinction coefficients only using the sequence. The tool is designed using BioPython utility and has even results with standard tools, such as Expasy, EBI, Genecorner, and Geneinfinity. The tool assists students, researchers, and the pharmaceutical sector. The PepAnalyzer tool's online platform is accessible at the link: http://www.iksmbrlabdu.in/peptool .

New Insights into the Role of Endoplasmic Reticulum Stress in Breast Cancer Metastasis

Cellular stress severely disrupts endoplasmic reticulum (ER) function, leading to the abnormal accumulation of unfolded or misfolded proteins in the ER and subsequent development of endoplasmic reticulum stress (ERS). To accommodate the occurrence of ERS, cells have evolved a highly conserved, self-protecting signal transduction pathway called the unfolded protein response. Notably, ERS signaling is involved in the development of a variety of diseases and is closely related to tumor development, particularly in breast cancer. This review discusses recent research regarding associations between ERS and tumor metastasis. The information presented here will help researchers elucidate the precise mechanisms underlying ERS-mediated tumor metastasis and provide new directions for tumor therapies.

Mitomycin C treatment induces resistance and enhanced migration via phosphorylated Akt in aggressive lung cancer cells

Since 1984, mitomycin C (MMC) has been applied in the treatment of non-small-cell lung cancer (NSCLC). MMC-based chemotherapeutic regimens are still under consideration owing to the efficacy and low cost as compared with other second-line regimens in patients with advanced NSCLC. Hence, it is important to investigate whether MMC induces potential negative effects in NSCLC. Here, we found that the malignant lung cancer cells, CL1-2 and CL1-5, were more resistant to MMC than were the parental CL1-0 cells and pre-malignant CL1-1 cells. CL1-2 and CL1-5 cells consistently showed lower sub-G1 fractions post MMC treatment. DNA repair-related proteins were not induced more in CL1-5 than in CL1-0 cells, but the levels of endogenous and MMC-induced phosphorylated Akt (p-Akt) were higher in CL1-5 cells. Administering a p-Akt inhibitor reduced the MMC resistance, demonstrating that p-Akt is important in the MMC resistance of CL1-5 cells. Furthermore, we revealed that cell migration was enhanced by MMC but lowered by a p-Akt inhibitor in CL1-5 cells. This study suggests that in CL1-5 cells, the activity of p-Akt, rather than DNA repair mechanisms, may underlie the resistance to MMC and enhance the cells' migration abilities after MMC treatment.

Chemotherapy Resistance in Lung Cancer

Despite a growing interest in development of non-cytotoxic targeted agents, systemic chemotherapy is still the mainstay of treatment for both non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). However, chemotherapy resistance limits our ability to effectively treat advanced lung cancer. Some lung tumors are intrinsically resistant to chemotherapy, and in virtually all cases, even the initial responders rapidly develop acquired resistance. While targeting histology could result in enhanced tumor sensitivity to a particular chemotherapeutic agent, better understanding of molecular determinants of chemotherapy sensitivity/resistance would be critically important. Development of predictive biomarkers to personalize chemotherapeutic agents and combining novel agents targeting specific resistance pathways with standard chemotherapy could be some promising strategies to overcome chemotherapy resistance in lung cancer. In this chapter, we will discuss some key mechanisms of resistance for commonly used chemotherapeutic agents in lung cancer.

Elevated STAT3 Signaling-Mediated Upregulation of MMP-2/9 Confers Enhanced Invasion Ability in Multidrug-Resistant Breast Cancer Cells

The development of multidrug resistance greatly impedes effective cancer therapy. Recent advances in cancer research have demonstrated that acquisition of multidrug resistance by cancer cells is usually accompanied by enhanced cell invasiveness. Several lines of evidence indicated that cross activation of other signaling pathways during development of drug resistance may increase invasive potential of multidrug-resistant (MDR) cancer cells. However, the accurate mechanism of this process is largely undefined. In this study, to better understand the associated molecular pathways responsible for cancer progression induced by drug resistance, a MDR human breast cancer cell line SK-BR-3/EPR with P-glycoprotein overexpression was established using stepwise long-term exposure to increasing concentration of epirubicin. The SK-BR-3/EPR cell line exhibited decreased cell proliferative activity, but enhanced cell invasive capacity. We showed that the expression of metastasis-related matrix metalloproteinase (MMP)-2/9 was elevated in SK-BR-3/EPR cells. Moreover, SK-BR-3/EPR cells showed elevated activation of STAT3. Activation of STAT3 signaling is responsible for enhanced invasiveness of SK-BR-3/EPR cells through upregulation of MMP-2/9. STAT3 is a well-known oncogene and is frequently implicated in tumorigenesis and chemotherapeutic resistance. Our findings augment insight into the mechanism underlying the functional association between MDR and cancer invasiveness.

Influence of multidrug resistance and drug transport proteins on chemotherapy drug metabolism

INTRODUCTION

Chemotherapy involving the use of anticancer drugs remains an important strategy in the overall management of patients with metastatic cancer. Acquisition of multidrug resistance remains a major impediment to successful chemotherapy. Drug transporters in cell membranes and intracellular drug metabolizing enzymes contribute to the resistance phenotype and determine the pharmacokinetics of anticancer drugs in the body.

AREAS COVERED

ATP-binding cassette (ABC) transporters mediate the transport of endogenous metabolites and xenobiotics including cytotoxic drugs out of cells. Solute carrier (SLC) transporters mediate the influx of cytotoxic drugs into cells. This review focuses on the substrate interaction of these transporters, on their biology and what role they play together with drug metabolizing enzymes in eliminating therapeutic drugs from cells.

EXPERT OPINION

The majority of anticancer drugs are substrates for the ABC transporter and SLC transporter families. Together, these proteins have the ability to control the influx and the efflux of structurally unrelated chemotherapeutic drugs, thereby modulating the intracellular drug concentration. These interactions have important clinical implications for chemotherapy because ultimately they determine therapeutic efficacy, disease progression/relapse and the success or failure of patient treatment.

Carboplatin and taxol resistance develops more rapidly in functional BRCA1 compared to dysfunctional BRCA1 ovarian cancer cells

A major risk factor for ovarian cancer is germline mutations of BRCA1/2. It has been found that (80%) of cellular models with acquired platinum or taxane resistance display an inverse resistance relationship, that is collateral sensitivity to the other agent. We used a clinically relevant comparative selection strategy to develop novel chemoresistant cell lines which aim to investigate the mechanisms of resistance that arise from different exposures of carboplatin and taxol on cells having BRCA1 function (UPN251) or dysfunction (OVCAR8). Resistance to carboplatin and taxol developed quicker and more stably in UPN251 (BRCA1-wildtype) compared to OVCAR8 (BRCA1-methylated). Alternating carboplatin and taxol treatment delayed but did not prevent resistance development when compared to single-agent administration. Interestingly, the sequence of drug exposure influenced the resistance mechanism produced. UPN251-6CALT (carboplatin first) and UPN251-6TALT (taxol first) have different profiles of cross resistance. UPN251-6CALT displays significant resistance to CuSO4 (2.3-fold, p=0.004) while UPN251-6TALT shows significant sensitivity to oxaliplatin (0.6-fold, p=0.01). P-glycoprotein is the main mechanism of taxol resistance found in the UPN251 taxane-resistant sublines. UPN251 cells increase cellular glutathione levels (3.0-fold, p=0.02) in response to carboplatin treatment. However, increased glutathione is not maintained in the carboplatin-resistant sublines. UPN251-7C and UPN251-6CALT are low-level resistant to CuSO4 suggesting alterations in copper metabolism. However, none of the UPN251 sublines have alterations in the protein expression of ATP7A or CTR1. The protein expression of BRCA1 and MRP2 is unchanged in the UPN251 sublines. The UPN251 sublines remain sensitive to parp inhibitors veliparib and CEP8983 suggesting that these agents are candidates for the treatment of platinum/taxane resistant ovarian cancer patients.

P-glycoprotein associates with Anxa2 and promotes invasion in multidrug resistant breast cancer cells

Several recent studies have suggested that the acquisition of the multidrug resistance (MDR) phenotype is associated with elevated invasion and metastasis of tumor cells. P-glycoprotein (P-gp), the major determinant in the generation of the MDR phenotype, was reported to be correlated with a more aggressive phenotype and poor prognosis in many forms of malignancies. However, a clear understanding of the association is still lacking. We previously showed that Anxa2, a calcium-dependent phospholipid-binding protein, interacts with P-gp and contributes to the invasiveness of MDR breast cancer cells. In the present study, a strong positive correlation between MDR1 and Anxa2 mRNA expression in invasive breast cancer tissues during cancer progression was observed. In addition, exposure to adriamycin significantly enhanced motility in breast cancer cells and increased levels of P-gp and Anxa2. Moreover, inhibition of P-gp activity, using selective P-gp modulators, was found to significantly inhibit the invasive capacity of MCF-7/ADR cells without affecting the interaction and co-localization between P-gp and Anxa2. However, suppression of P-gp pump activity and knockdown of MDR1 expression both disrupted adriamycin-induced Anxa2 phosphorylation. Interestingly, P-gp was further demonstrated to interact with Src, a tyrosine kinase upstream of Anxa2. Taken together, our results indicate that P-gp may promote the invasion of MDR breast cancer cells by modulating the tyrosine phosphorylation of Anxa2. The interaction between Anxa2 and P-gp is possibly, at least in part, responsible for the association between MDR and invasive potential in breast cancer cells.

Myxoma virus infection promotes NK lysis of malignant gliomas in vitro and in vivo

Myxoma virus (MYXV) is a well-established oncolytic agent against different types of tumors. MYXV is also known for its immunomodulatory properties in down-regulating major histocompatibility complex (MHC) I surface expression (via the M153R gene product, a viral E3-ubiquitin ligase) and suppressing T cell killing of infected target cells. MHC I down-regulation, however, favors NK cell activation. Brain tumors including gliomas are characterized by high MHC I expression with impaired NK activity. We thus hypothesized that MYXV infection of glioma cells will promote NK cell-mediated recognition and killing of gliomas. We infected human gliomas with MYXV and evaluated their susceptibility to NK cell-mediated cytotoxicity. MYXV enhanced NK cell-mediated killing of glioma cells (U87 cells, MYXV vs. Mock: 51.73% vs. 28.63%, P = .0001, t test; U251 cells, MYXV vs. Mock: 40.4% vs. 20.03%, P .0007, t test). Using MYXV M153R targeted knockout (designated vMyx-M153KO) to infect gliomas, we demonstrate that M153R was responsible for reduced expression of MHC I on gliomas and enhanced NK cell-mediated antiglioma activity (U87 cells, MYXV vs. vMyx-M153KO: 51.73% vs. 25.17%, P = .0002, t test; U251 cells, MYXV vs. vMyx-M153KO: 40.4% vs. 19.27, P = .0013, t test). Consequently, NK cell-mediated lysis of established human glioma tumors in CB-17 SCID mice was accelerated with improved mouse survival (log-rank P = .0072). These results demonstrate the potential for combining MYXV with NK cells to effectively kill malignant gliomas.

Suppression of endoplasmic reticulum stress-induced invasion and migration of breast cancer cells through the downregulation of heparanase

Tumor metastasis is the ultimate stage of cancer, and the primary cause of mortality in patients. Tumor cells breaking through the natural barrier consisting of the basement membrane (BM) and extracellular matrix (ECM) is the a crucial step in tumor invasion and metastasis. Thus, protecting this barrier is the key to reducing mortality. Heparanase is a mammalian endo-β-glucuronidase which has been found to promote the cleavage of heparan sulfate (HS), and plays a significant role in tumor cell invasion and metastasis. Although chemotherapeutic reagents have a strong antitumor activity, they may promote the invasion and migration of cancer cells, as has been observed during clinical treatment. Chemotherapeutic reagents can induce endoplasmic reticulum (ER) stress; in this study, we used adriamycin (ADM) and a classical ER stress inducer, tunicamycin (TM). We report that the activation of ER stress is involved in the enhanced invasion and migration ability of breast cancer cells and we hypothesized that this effect is associated with the activation of heparanase. In support of this, we used the heparanase inhibitor, OGT2115, and low molecular weight heparin (LMWH) to inhibit the expression and activity of heparanase, and we found that the invasion and migration ability of the cells was suppressed. Our findings demonstrate that heparanase inhibitors suppress breast cancer cell invasion and migration induced by ER stress, and provide a strong rationale for the development of heparanase-based therapeutics for the prevention of metastasis induced by chemotherapeutic reagents.

Potentiation of anticancer drugs: effects of pentoxifylline on neoplastic cells

The drug efflux activity of P-glycoprotein (P-gp, a product of the mdr1 gene, ABCB1 member of ABC transporter family) represents a mechanism by which tumor cells escape death induced by chemotherapeutics. In this study, we investigated the mechanisms involved in the effects of pentoxifylline (PTX) on P-gp-mediated multidrug resistance (MDR) in mouse leukemia L1210/VCR cells. Parental sensitive mouse leukemia cells L1210, and multidrug-resistant cells, L1210/VCR, which are characterized by the overexpression of P-gp, were used as experimental models. The cells were exposed to 100 μmol/L PTX in the presence or absence of 1.2 μmol/L vincristine (VCR). Western blot analysis indicated a downregulation of P-gp protein expression when multidrug-resistant L1210/VCR cells were exposed to PTX. The effects of PTX on the sensitization of L1210/VCR cells to VCR correlate with the stimulation of apoptosis detected by Annexin V/propidium iodide apoptosis necrosis kit and proteolytic activation of both caspase-3 and caspase-9 monitored by Western blot analysis. Higher release of matrix metalloproteinases (MMPs), especially MMP-2, which could be attenuated by PTX, was found in L1210/VCR than in L1210 cells by gelatin zymography in electrophoretic gel. Exposure of resistant cells to PTX increased the content of phosphorylated Akt kinase. In contrast, the presence of VCR eliminated the effects of PTX on Akt kinase phosphorylation. Taken together, we conclude that PTX induces the sensitization of multidrug-resistant cells to VCR via downregulation of P-gp, stimulation of apoptosis and reduction of MMPs released from drug-resistant L1210/VCR cells. These facts bring new insights into the mechanisms of PTX action on cancer cells.

Discovery of IL-18 as a novel secreted protein contributing to doxorubicin resistance by comparative secretome analysis of MCF-7 and MCF-7/Dox

Background

Resistance to chemotherapy is the major cause of failure in breast cancer treatment. Recent studies suggest that secreted proteins may play important roles in chemoresistance. We sought to systematically characterize secreted proteins associated with drug resistance, which may represent potential serum biomarkers or novel drug targets.

Methodology/Principal Findings

In the present work, we adopted the proteomic strategy of one-dimensional gel electrophoresis followed by liquid chromatography-tandem mass spectrometry to compare the secretome of MCF-7 and doxorubicin-resistant MCF-7/Dox. A total of 2,084 proteins were identified with at least two unique peptides in the conditioned media of two cell lines. By quantification with label-free spectral counting, 89 differentially expressed secreted proteins (DESPs) between the two cell lines were found. Among them, 57 DESPs were first found to be related to doxorubicin resistance in this work, including 24 extracellular matrix related proteins, 2 cytokines and 31 unclassified proteins. We focused on 13 novel DESPs with confirmed roles in tumor metastasis. Among them, the elevated expression of IL-18 in doxorubicin-resistant cell lines and breast tumor tissues was validated and its role in doxorubicin resistance was further confirmed by cell viability experiments in the presence or absence of this protein.

Conclusions/Significance

Comparative analysis of the secretome of MCF-7 and MCF-7/Dox identified novel secreted proteins related to chemotherapy resistance. IL-18 was further validated to contribute to doxorubicin resistance, in addition to its confirmed role in breast cancer metastasis. Due to its dual roles in both drug resistance and tumor metastasis, IL-18 may represent a useful drug target for breast cancer therapy.

Tumor and host factors that may limit efficacy of chemotherapy in non-small cell and small cell lung cancer

While chemotherapy provides useful palliation, advanced lung cancer remains incurable since those tumors that are initially sensitive to therapy rapidly develop acquired resistance. Resistance may arise from impaired drug delivery, extracellular factors, decreased drug uptake into tumor cells, increased drug efflux, drug inactivation by detoxifying factors, decreased drug activation or binding to target, altered target, increased damage repair, tolerance of damage, decreased proapoptotic factors, increased antiapoptotic factors, or altered cell cycling or transcription factors. Factors for which there is now substantial clinical evidence of a link to small cell lung cancer (SCLC) resistance to chemotherapy include MRP (for platinum-based combination chemotherapy) and MDR1/P-gp (for non-platinum agents). SPECT MIBI and Tc-TF scanning appears to predict chemotherapy benefit in SCLC. In non-small cell lung cancer (NSCLC), the strongest clinical evidence is for taxane resistance with elevated expression or mutation of class III beta-tubulin (and possibly alpha tubulin), platinum resistance and expression of ERCC1 or BCRP, gemcitabine resistance and RRM1 expression, and resistance to several agents and COX-2 expression (although COX-2 inhibitors have had minimal impact on drug efficacy clinically). Tumors expressing high BRCA1 may have increased resistance to platinums but increased sensitivity to taxanes. Limited early clinical data suggest that chemotherapy resistance in NSCLC may also be increased with decreased expression of cyclin B1 or of Eg5, or with increased expression of ICAM, matrilysin, osteopontin, DDH, survivin, PCDGF, caveolin-1, p21WAF1/CIP1, or 14-3-3sigma, and that IGF-1R inhibitors may increase efficacy of chemotherapy, particularly in squamous cell carcinomas. Equivocal data (with some positive studies but other negative studies) suggest that NSCLC tumors with some EGFR mutations may have increased sensitivity to chemotherapy, while K-ras mutations and expression of GST-pi, RB or p27kip1 may possibly confer resistance. While limited clinical data suggest that p53 mutations are associated with resistance to platinum-based therapies in NSCLC, data on p53 IHC positivity are equivocal. To date, resistance-modulating strategies have generally not proven clinically useful in lung cancer, although small randomized trials suggest a modest benefit of verapamil and related agents in NSCLC.

Is resistance useless? Multidrug resistance and collateral sensitivity

When cancer cells develop resistance to chemotherapeutics, it is frequently conferred by the ATP-dependent efflux pump P-glycoprotein (MDR1, P-gp, ABCB1). P-gp can efflux a wide range of cancer drugs; its expression confers cross-resistance, termed "multidrug resistance" (MDR), to a wide range of drugs. Strategies to overcome this resistance have been actively sought for more than 30 years, yet clinical solutions do not exist. A less understood aspect of MDR is the hypersensitivity of resistant cancer cells to other drugs, a phenomenon known as "collateral sensitivity" (CS). This review highlights the extent of this effect for the first time, and discusses hypotheses (e.g. generation of reactive oxygen species) to account for the underlying generality of this phenomenon, and proposes exploitation of CS as a strategy to improve response to chemotherapy.

Enhanced invasiveness of drug-resistant acute myeloid leukemia cells through increased expression of matrix metalloproteinase-2

The acquired drug resistance as well as extramedullary tissue infiltration of leukemic cells is a major obstacle in leukemia treatment. Excessive egress of leukemia cell blasts results in invasion into various organs or tissues, which is facilitated by the catalytic activities of matrix metalloproteinases (MMPs). However, the migration of chemoresistant leukemia cells remains unclear. Here, we generated drug-resistant variants of the human acute myeloid leukemia cell line (AML-2/WT) by stepwise exposure to anticancer drugs and evaluated the level of MMP-2 in the drug-resistant variants, along with their invasiveness. Each of the drug-resistant cell variants demonstrated predominant increases in the expression and gelatinolytic activity of MMP-2 as well as in invasiveness, which were significantly suppressed by both a MMP-2 inhibitor and a blocking antibody. Knockdown experiments using MMP-2 short hairpin RNA also indicated that its upregulation was strongly associated with the cells' increased invasive properties. Importantly, elevated levels of MMP-2 activity and invasiveness were observed in ex vivo mononuclear cell of bone marrow from patients with poor responses to chemotherapy. These findings suggest that advanced malignancy due to acquired drug resistance is responsible for the progressive invasiveness of leukemia cells via MMP-2.

Inhibition of P-glycoprotein-mediated docetaxel efflux sensitizes ovarian cancer cells to concomitant docetaxel and SN-38 exposure

The first-line treatment of ovarian cancer is based on cytoreductive surgery and the use of anticancer drugs. The main disadvantage in the usage of anticancer drugs is the wide capacity of cancer cells to acquire a resistance to chemotherapeutic agents and therefore new treatment strategies have to be developed and tested. In this study, the responses of seven ovarian carcinoma cell lines to docetaxel and a camptothecin derivative, SN-38, were evaluated. We further studied the expression of P-glycoprotein (P-gp), the best described mechanism of drug resistance, in these cells and the effect of treatment with a specific P-gp inhibitor (PGP-4008). Simultaneous treatment with docetaxel and SN-38 (docetaxel+SN-38) had an antagonistic growth effect that was not dependent on the administration schedule. Both drugs alone or in combination induced G2M cell cycle arrest. Docetaxel was a more potent inducer of apoptosis than SN-38, but simultaneous treatment with docetaxel+SN-38 decreased the proportion of apoptotic cells to the same level observed after exposure to SN-38 alone. SN-38 increased P-gp expression in all cell lines. PGP-4008 enhanced docetaxel-mediated growth inhibition and apoptosis, but it did not have an effect when used simultaneously with SN-38. When cells were treated with docetaxel, SN-38, and PGP-4008 simultaneously, the growth was inhibited more efficiently and the proportion of apoptotic cells was higher than that without PGP-4008. Thus, treatment of ovarian cancer cells with docetaxel+SN-38 may have antagonistic effects. The simultaneous administration of a P-gp inhibitor may prevent docetaxel efflux, thereby sensitizing cells to docetaxel and other chemotherapeutic agents.

Resistance to cytarabine induces the up-regulation of NKG2D ligands and enhances natural killer cell lysis of leukemic cells

Prolonged treatment of leukemic cells with chemotherapeutic agents frequently results in development of drug resistance. Moreover, selection of drug-resistant cell populations may be associated with changes in malignant properties such as proliferation rate, invasiveness, and immunogenicity. In the present study, the sensitivity of cytarabine (1-beta-D-arabinofuranosylcytosine, araC)-resistant and parental human leukemic cell lines (T-lymphoid H9 and acute T-lymphoblastic leukemia Molt-4) to natural killer (NK) cell-mediated killing was investigated. The results obtained demonstrate that araC-resistant H9 and Molt-4 (H9(r)ARAC(100) and Molt-4(r)ARAC(100)) cell lines are more sensitive to NK cell-mediated lysis than their respective parental cell lines. This increased sensitivity was associated with a higher surface expression of ligands for the NK cell-activating receptor NKG2D, notably UL16 binding protein-2 (ULBP-2) and ULBP-3 in H9(r)ARAC(100) and Molt-4(r)ARAC(100) cell lines. Blocking ULBP-2 and ULBP-3 or NKG2D with monoclonal antibody completely abrogated NK cell lysis. Constitutive phosphorylated extracellular signal-regulated kinase (ERK) but not pAKT was higher in araC-resistant cells than in parental cell lines. Inhibition of ERK using ERK inhibitor PD98059 decreased both ULBP-2/ULBP-3 expression and NK cell cytotoxicity. Furthermore, overexpression of constitutively active ERK in H9 parental cells resulted in increased ULBP-2/ULBP-3 expression and enhanced NK cell lysis. These results demonstrate that increased sensitivity of araC-resistant leukemic cells to NK cell lysis is caused by higher NKG2D ligand expression, resulting from more active ERK signaling pathway.

MDR1/P-gp and VEGF synergistically enhance the invasion of Hep-2 cells with multidrug resistance induced by taxol

BACKGROUND

Tumor invasion/metastasis and multidrug resistance (MDR) are the main causes of treatment failure and high mortality in all kinds of cancer patients. The relationship between the two factors is still unclear. The aim of this study is to investigate the association between MDR and invasion, especially the role of multidrug resistance 1/P-glycoprotein (MDR1/P-gp) and vascular endothelial growth factor (VEGF) during the invasion.

METHODS

Multidrug resistance 1 (MDR1) and VEGF receptor 2 (VEGFR-2) were detected with real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR) and Western blotting at the levels of messenger RNA (mRNA) and protein, respectively. RNA interference was applied to inhibit the expression of MDR1. The invasive assays were performed with the CHEMICON cell invasion assay kit.

RESULTS

The MDR cell line induced by Taxol (Hep-2T cell) was more invasive than its parent cell line (Hep-2 cell), which was at least in part mediated through the overexpressed MDR1/P-pg. MDR1-targeted RNA interference could effectively inhibit the expression of MDR1 and obviously decrease the invasive ability. Synergistic enhancing effects existed between MDR1/P-gp and VEGF on the invasion of Hep-2T cells. The expression of VEGFR-2 was elevated in Hep-2T cells. SU1498 could significantly decrease the invasion of Hep-2T cells. MDR1-targeted RNA interference and SU1498 had synergistic decreasing effect on the invasion of Hep-2T cells.

CONCLUSIONS

MDR1/P-pg may be a risk predictor for the invasion of laryngeal cancer. MDR1 knock down and VEGFR-2 inhibitor may be two promising treatment regiments for advanced laryngeal carcinoma patients with MDR and invasion/metastasis.

Chemoprevention by Pyrimethamine

The goal of the current research was to investigate the chemopreventive potency of an antimalaria drug, pyrimethamine, in in vitro conditions. The fibrosarcoma (WEHI-164) cell line was used for evaluating cytotoxicity, matrix metalloproteinase 2 (MMP-2) activity, and apoptosis. Pyrimethamine and methotrexate were used at concentrations of 0-8 microg/ml in triplicate and 2-fold dilutions. MMP-2 activity was assessed using zymoanalysis method. For assessment of apoptosis, the terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) method was used. Cytotoxicity analysis of pyrimethamine showed a greater tolerability than methotrexate at concentrations of 1-8 microg/ml. The dose-dependent inhibitory effect of pyrimethamine on MMP-2 activity was significantly less than that of methotrexate at concentrations of 1-8 microg/ml. Moreover, the rate of apoptosis for pyrimethamine-treated cells at different doses (0.1, 1, and 10 microg/ml) was 3.30%, 9.42%, and 11.32%, respectively. Our data suggest that pyrimethamine enables suppression of MMP-2 activity and induces apoptosis that could be assumed for chemoprevention therapy.

Dichloroacetate induces apoptosis in endometrial cancer cells

PURPOSE

A recent landmark study demonstrated that Dichloroacetate (DCA) treatment promoted apoptosis in lung, breast, and glioblastoma cancer cell lines by shifting metabolism from aerobic glycolysis to glucose oxidation coupled with NFAT-Kv1.5 axis remodeling. The objective of this study was to determine whether DCA induces apoptosis in endometrial cancer cells and to assess apoptotic mechanism.

METHODS

A panel of endometrial cancer cell lines with varying degrees of differentiation was treated with DCA and analyzed for apoptosis via flow cytometry. Biological correlates such as gene expression, intracellular Ca(2+), and mitochondrial membrane potential were examined to assess apoptotic mechanism.

RESULTS

Initiation of apoptosis was observed in five low to moderately invasive cancer cell lines including Ishikawa, RL95-2, KLE, AN3CA, and SKUT1B while treatment had no effect on non-cancerous 293T cells. Two highly invasive endometrial adenocarcinoma cell lines, HEC1A and HEC1B, were found to be resistant to DCA-induced apoptosis. Apoptotic responding cell lines had a significant increase in early and late apoptotis, a decrease in mitochondrial membrane potential, and decreased Survivin transcript abundance, which are consistent with a mitochondrial-regulated mechanism. DCA treatment decreased intracellular calcium levels in most apoptotic responding cell lines which suggests a contribution from the NFAT-Kv1.5-mediated pathway. DCA treatment increased p53 upregulated modulator of apoptosis (PUMA) transcripts in cell lines with an apoptotic response, suggesting involvement of a p53-PUMA-mediated mechanism.

CONCLUSIONS

Dichloroacetate effectively sensitizes most endometrial cancer cell lines to apoptosis via mitochondrial, NFAT-Kv1.5, and PUMA-mediated mechanisms. Further investigation of the cancer therapeutic potential of DCA is warranted.

A systematic review of platinum and taxane resistance from bench to clinic: An inverse relationship

We undertook a systematic review of the pre-clinical and clinical literature for studies investigating the relationship between platinum and taxane resistance. Medline was searched for (1) cell models of acquired drug resistance reporting platinum and taxane sensitivities and (2) clinical trials of platinum or taxane salvage therapy in ovarian cancer. One hundred and thirty-seven models of acquired drug resistance were identified. 68.1% of cisplatin-resistant cells were sensitive to paclitaxel and 66.7% of paclitaxel-resistant cells were sensitive to cisplatin. A similar inverse pattern was observed for cisplatin vs. docetaxel, carboplatin vs. paclitaxel and carboplatin vs. docetaxel. These associations were independent of cancer type, agents used to develop resistance and reported mechanisms of resistance. Sixty-five eligible clinical trials of paclitaxel-based salvage after platinum therapy were identified. Studies of single agent paclitaxel in platinum-resistant ovarian cancer where patients had previously recieved paclitaxel had a pooled response rate of 35.3%, n=232, compared to 22% in paclitaxel naïve patients n=1918 (p<0.01, Chi-squared). Suggesting that pre-treatment with paclitaxel may improve the response of salvage paclitaxel therapy. The response rate to paclitaxel/platinum combination regimens in platinum-sensitive ovarian cancer was 79.5%, n=88 compared to 49.4%, n=85 for paclitaxel combined with other agents (p<0.001, Chi-squared), suggesting a positive interaction between taxanes and platinum. Therefore, the inverse relationship between platinum and taxanes resistance seen in cell models is mirrored in the clinical response to these agents in ovarian cancer. An understanding of the cellular and molecular mechanisms responsible would be valuable in predicting response to salvage chemotherapy and may identify new therapeutic targets.

Chemoresistance induces enhanced adhesion and transendothelial penetration of neuroblastoma cells by down-regulating NCAM surface expression

Background

Drug resistance to chemotherapy is often associated with increased malignancy in neuroblastoma (NB). One explanation for the link between resistance and malignancy might be that resistance facilitates cancer progression and invasion. To investigate this hypothesis, adhesion, transendothelial penetration and NCAM (CD56) adhesion receptor expression of drug-resistant versus drug-sensitive NB tumor cells were evaluated.

Methods

Acquired drug resistance was mimicked by exposing parental UKF-NB-2, UKF-NB-3 or IMR-32 tumor cells to increasing concentrations of vincristine- (VCR) or doxorubicin (DOX) to establish the resistant tumor cell sublines UKF-NB-2^VCR, UKF-NB-2^DOX, UKF-NB-3^VCR, UKF-NB-3^DOX, IMR-32^VCR and IMR-32^DOX. Additionally, the malignant behaviour of UKF-NB-4, which already possessed the intrinsic multidrug resistance (MDR) phenotype, was analyzed. UKF-NB-4 exposed to VCR or DOX were designated UKF-NB-4^VCR or UKF-NB-4^DOX. Combined phase contrast – reflection interference contrast microscopy was used to separately evaluate NB cell adhesion and penetration. NCAM was analyzed by flow cytometry, western blot and RT-PCR.

Results

VCR and DOX resistant tumor sublines showed enhanced adhesion and penetration capacity, compared to their drug naïve controls. Strongest effects were seen with UKF-NB-2^VCR, UKF-NB-3^VCR and IMR-32^DOX. DOX or VCR treatment also evoked increased invasive behaviour of UKF-NB-4. The process of accelerated tumor invasion was accompanied by decreased NCAM surface and protein expression, and down-regulation of NCAM coding mRNA. Transfection of UKF-NB-4^VCR cells with NCAM cDNA led to a significant receptor up-regulation, paralleled by diminished adhesion to an endothelial cell monolayer.

Conclusion

It is concluded that NB cells resistant to anticancer drugs acquire increased invasive capacity relative to non-resistant parental cells, and that enhanced invasion is caused by strong down-regulation of NCAM adhesion receptors.

Carcinogenesis, cancer therapy and chemoprevention

Carcinogenesis and cancer therapy are two sides of the same coin, such that the same cytotoxic agent can cause cancer and be used to treat cancer. This review links carcinogenesis, chemoprevention and cancer therapy in one process driven by cytotoxic agents (carcinoagents) that select either for or against cells with oncogenic alterations. By unifying therapy and cancer promotion and by distinguishing nononcogenic and oncogenic mechanisms of resistance, I discuss anticancer- and chemopreventive agent-induced carcinogenesis and tumor progression and, vice versa, carcinogens as anticancer drugs, anticancer drugs as chemopreventive agents and exploiting oncogene-addiction and drug resistance for chemoprevention and cancer therapy.

Concentration-dependent collateral sensitivity of cisplatin-resistant gastric cancer cell sublines

The cisplatin-resistant gastric cancer cell sublines, SNU-601/Cis2 and /Cis10, were 49 and >530 times more resistant to cisplatin, respectively, compared with the drug-sensitive cells, SNU-601/WT. The SNU-601/Cis2 showed cross-resistance to carboplatin, heptaplatin, doxorubicin, mitomycin C, and 5-fluorouracil compared with the SNU-601/WT whereas the SNU-601/Cis10 displayed collateral sensitivity to these drugs with the exception of cisplatin compared with the SNU-601/Cis2, suggesting that the cross-resistance and collateral sensitivity of cisplatin-resistant gastric cancer cells are dependent upon cisplatin concentrations. Altered expression of the antioxidant and transporter genes (metallothionein, catalase, superoxide dismutases, P-glycoprotein, and the breast cancer resistance protein) was involved in these phenotypes of the cisplatin-resistant gastric cancer cell lines.

Induction of stem cell factor/c-Kit/slug signal transduction in multidrug-resistant malignant mesothelioma cells

Malignant mesothelioma (MM) is strongly resistant to conventional chemotherapy by unclear mechanisms. We and others have previously reported that cytokine- and growth factor-mediated signal transduction is involved in the growth and progression of MM. Here, we identified a pathway that involves stem cell factor (SCF)/c-Kit/Slug in mediating multidrug resistance of MM cells. When we compared gene expression profiles between five MM cells and their multidrug-resistant (MM DX) sublines, we found that MM DX cells expressed both SCF and c-Kit and had higher mRNA levels of Slug. Knockdown of c-Kit or Slug expression with their respective small interfering RNA sensitized MM DX cells to the induction of apoptosis by different chemotherapeutic agents, including doxorubicin, paclitaxel, and vincristine. Transfection of c-Kit in parental MM cells in the presence of SCF up-regulated Slug and increased resistance to the chemotherapeutic agents. Moreover, MM cells expressing Slug showed a similar increased resistance to the chemotherapeutic agents. These results indicate that induction of Slug by autocrine production of SCF and c-Kit activation plays a key role in conferring a broad spectrum chemoresistance on MM cells and reveal a novel signal transduction pathway for pharmacological or genetic intervention of MM patients.