Celecoxib enhanced the sensitivity of cancer cells to anticancer drugs by inhibition of the expression of P-glycoprotein through a COX-2-independent manner

Perspectives of the Application of Non-Steroidal Anti-Inflammatory Drugs in Cancer Therapy: Attempts to Overcome Their Unfavorable Side Effects

Non-steroidal anti-inflammatory drugs (NSAIDs) express anti-tumoral activity mainly by blocking cyclooxygenase-2 involved in the synthesis of prostaglandins. Therefore, in the last few decades, many have attempted to explore the possibilities of applying this group of drugs as effective agents for the inhibition of neoplastic processes. This review summarizes the evidence presented in the literature regarding the anti-tumoral actions of NSAIDs used as monotherapies as well as in combination with conventional chemotherapeutics and natural products. In several clinical trials, it was proven that combinations of NSAIDs and chemotherapeutic drugs (CTDs) were able to obtain suitable results. The combination with phospholipids may resolve the adverse effects of NSAIDs and deliver derivatives with increased antitumor activity, whereas hybrids with terpenoids exhibit superior activity against their parent drugs or physical mixtures. Therefore, the application of NSAIDs in cancer therapy seems to be still an open chapter and requires deep and careful evaluation. The literature's data indicate the possibilities of re-purposing anti-inflammatory drugs currently approved for cancer treatments.

The crucial role of epigenetic regulation in breast cancer anti-estrogen resistance: Current findings and future perspectives

Breast cancer (BC) cell de-sensitization to Tamoxifen (TAM) or other selective estrogen receptor (ER) modulators (SERM) is a complex process associated with BC heterogeneity and the transformation of ER signalling. The most influential resistance-related mechanisms include modifications in ER expression and gene regulation patterns. During TAM/SERM treatment, epigenetic mechanisms can effectively silence ER expression and facilitate the development of endocrine resistance. ER status is efficiently regulated by specific epigenetic tools including hypermethylation of CpG islands within ER promoters, increased histone deacetylase activity in the ER promoter, and/or translational repression by miRNAs. Over-methylation of the ER α gene (ESR1) promoter by DNA methyltransferases was associated with poor prognosis and indicated the development of resistance. Moreover, BC progression and spreading were marked by transformed chromatin remodelling, post-translational histone modifications, and expression of specific miRNAs and/or long non-coding RNAs. Therefore, targeted inhibition of histone acetyltransferases (e.g. MYST3), deacetylases (e.g. HDAC1), and/or demethylases (e.g. lysine-specific demethylase LSD1) was shown to recover and increase BC sensitivity to anti-estrogens. Indicated as a powerful molecular instrument, the administration of epigenetic drugs can regain ER expression along with the activation of tumour suppressor genes, which can in turn prevent selection of resistant cells and cancer stem cell survival. This review examines recent advances in the epigenetic regulation of endocrine drug resistance and evaluates novel anti-resistance strategies. Underlying molecular mechanisms of epigenetic regulation will be discussed, emphasising the utilization of epigenetic enzymes and their inhibitors to re-program irresponsive BCs.

Drugs repurposed: An advanced step towards the treatment of breast cancer and associated challenges

Breast cancer (BC) is mostly observed in women and is responsible for huge mortality in women subjects globally. Due to the continued development of drug resistance and other contributing factors, the scientific community needs to look for new alternatives, and drug repurposing is one of the best opportunities. Here we light upon the drug repurposing with a major focus on breast cancer. BC is a division of cancer known as the leading cause of death of 2.3 million women globally, with 685,000 fatalities. This number is steadily rising, necessitating the development of a treatment that can extend survival time. All available treatments for BC are very costly as well as show side effects. This unfulfilled requirement of the anti-cancer drugs ignited an enthusiasm for drug repositioning, which means finding out the anti-cancer use of already marketed drugs for other complications. With the advancement in proteomics, genomics, and computational approaches, the drug repurposing process hastens. So many drugs are repurposed for the BC, including alkylating agents, antimetabolite, anthracyclines, an aromatase inhibitor, mTOR, and many more. The drug resistance in breast cancer is rising, so reviewing how the challenges in breast cancer can be combated with drug repurposing. This paper provides the updated information on all the repurposed drugs candidates for breast cancer with the molecular mechanism responsible for their anti-tumor activity. Additionally, all the challenges that occur during the repurposing of the drugs are discussed.

COX-2 promotes mammary adipose tissue inflammation, local estrogen biosynthesis, and carcinogenesis in high-sugar/fat diet treated mice

Obesity is a major risk factor for breast cancer, especially in post-menopausal women. In the breast tissue of obese women, cyclooxygenase-2 (COX-2)-dependent prostaglandin E2 (PGE2) production has been correlated with inflammation and local estrogen biosynthesis via aromatase. Using a mouse model of 7,12-dimethylbenz[a]anthracene/medroxyprogesterone-acetate (DMBA/MPA)-induced carcinogenesis, we demonstrated that an obesogenic diet promotes mammary tissue inflammation and local estrogen production, and accelerates mammary tumor formation in a COX-2-dependent manner. High-sugar/fat (HSF) diet augmented the levels of the pro-inflammatory mediators MCP-1, IL-6, COX-2, and PGE2 in mammary tissue, and this was accompanied by crown-like structures of breast (CLS-B) formation and aromatase/estrogen upregulation. Treatment with a COX-2 selective inhibitor, etoricoxib, decreased PGE2, IL-6, MCP-1, and CLS-B formation as well as reduced aromatase protein and estrogen levels in the mammary tissue of mice fed a HSF diet. Etoricoxib-treated mice showed increased latency and decreased incidence of mammary tumors, which resulted in prolonged animal survival when compared to HSF diet alone. Inhibition of tumor angiogenesis also seemed to account for the prolonged survival of COX-2 inhibitor-treated animals. In conclusion, obesogenic diet-induced COX-2 is sufficient to trigger inflammation, local estrogen biosynthesis, and mammary tumorigenesis.

Doxorubicin uptake in ascitic lymphoma model: resistance or curability is governed by tumor cell density and prolonged drug retention

Background/Aims: Chemotherapy resistance of malignancies is a universal phenomenon which unfavorably affects therapeutic results. Genetic adaptations as well as epigenetic factors can play an important role in the development of multidrug resistance. Cytotoxic drug content in plasma of cancer patients is known to variate up to one hundred-fold regardless of the same dose injected per m² body surface. The relationship between plasma concentrations, tissue uptake, and chemotherapy response is not completely understood. The main objective of this study was to investigate how the identical dose of Doxorubicin (Dox) can result in a different therapeutic response pattern depending on tumor size. Study Design: The study was performed on ascitic EL4 lymphoma in an exponential growth phase focusing on the rapidly changing tumor susceptibility to the Dox treatment. Well distinguishable tumor response patterns (curability, remission-relapse, resistance) were selected to unveil Dox intratumoral uptake and drug tissue persistence. Intratumoral Dox content within peritoneal cavity (PerC) in conjunction with systemic toxicity and plasma pharmacokinetics, were monitored at several time points following Dox injection in tumor bearing mice (TBM) with differing patterns of response. Results: Following intraperitoneal (i.p.) transplantation of 5x10⁴ EL4 lymphoma cells rapid exponential proliferation with ascites volume and animal mass increase resulted in median survival of 14.5 days. The increase in tumor cell mass in PerC between day 3 and day 9 was 112.5-fold (0.2±0.03 mg vs 22.5±0.31 mg respectively). However, tumors at this time interval (day 3 to day 9 post-transplantation) were relatively small and constituted less than 0.05% of animal weight. An identical dose of Dox (15 mg/kg) injected intravenously (i.v.) on Day 3 lead to a cure whereas a TBM injected on day 9 exhibited resistance with a median survival time no different from the untreated TBM control. Injection of Dox resulted in noticeable differences of cellular uptake in PerC between all three groups of TBM ("cure", relapse", "resistance"). Larger tumors were consistently taking up less Dox 60 min after the 15 mg/kg i.v. bolus injection. Higher initial uptake resulted also in longer retention of drug in PerC cells. The area under the concentration curve in PerC cells AUC_0-10d was 8.2±0.57 µg/g x h, 4.6±0.27 µg/g x h and 1.6±0.02 µg/g x h in "cure", "relapse" and "resistance" TBM respectively (p<0.05 "relapse" vs "cure" and p<0.001 "resistance" vs "cure"). No differences in plasma Dox pharmacokinetics or systemic hematological effects were observed in TBM following a single i.v. Dox push. Hematologic nadir was tested on day 2 and subsequent hematologic recovery was evaluated on day 10 following Dox administration. Hematologic recovery on day 10 coincided with complete drug efflux from PerC and rising tumor cell numbers in PerC of "relapse" TBM. Myelosuppression and hematological recovery patterns were identical in all surviving animal groups regardless of the tumor size on the day of Dox injection. Conclusions: Within a few days of exponential tumor growth, an identical dose of Dox produced dramatically different responses in the TBM with increasing resistance. Systemic toxicity and plasma pharmacokinetics were indistinguishable between all TBM groups. Initial uptake in tumor cells was found to be consistently lower in larger tumors. Drug uptake in tumor cells was regulated locally - a phenomenon known as inoculum effect in vitro. The duration of drug retention in cells was directly related to initial cellular uptake. The magnitude of Dox cellular retention could potentially play a role in determining tumor remission and relapse.

Celecoxib in breast cancer prevention and therapy

Breast cancer has a high incidence worldwide. The results of substantial studis reveal that inflammation plays an important role in the initiation, development, and aggressiveness of many malignancies. The use of celecoxib, a novel NSAID, is repetitively associated with the reduced risk of the occurrence and progression of a number of types of cancer, particularly breast cancer. This observation is also substantiated by various meta-analyses. Clinical trials have been implemented on integration treatment of celecoxib and shown encouraging results. Celecoxib could be treated as a potential candidate for antitumor agent. There are, nonetheless, some unaddressed questions concerning the precise mechanism underlying the anticancer effect of celecoxib as well as its activity against different types of cancer. In this review, we discuss different mechanisms of anticancer effect of celecoxib as well as preclinical/clinical results signifying this beneficial effect.

Interaction of WBP2 with ERα increases doxorubicin resistance of breast cancer cells by modulating MDR1 transcription

BACKGROUND

Surgery combined with new adjuvant chemotherapy is the primary treatment for early stage invasive and advanced stage breast cancer. Growing evidence indicates that patients with ERα-positive breast cancer show poor response to chemotherapeutics. However, ERα-mediated drug-resistant mechanisms remain unclear.

METHODS

Levels of WW domain-binding protein 2 (WBP2) and drug-resistant gene were determined by western blotting and RT-PCR, respectively. Cell viability was measured by preforming MTT assay. CD243 expression and apoptosis rate were evaluated by flow cytometry. Interactions of WBP2/ERα and ERα/MDR1 were detected by co-immunoprecipitation and chromatin immunoprecipitation (ChIP) assay, respectively.

RESULTS

There was an intrinsic link between WBP2 and ERα in drug-resistant cancer cells. Upregulation of WBP2 in MCF7 cells increased the chemoresistance to doxorubicin, while RNAi-mediated knockdown of WBP2 in MCF7/ADR cells sensitised the cancer cells to doxorubicin. Further investigation in in vitro and in vivo models demonstrated that WBP2 expression was directly correlated with MDR1, and WBP2 could directly modulate MDR1 transcription through binding to ERα, resulting in increased chemotherapy drug resistance.

CONCLUSIONS

Our finding provides a new mechanism for the chemotherapy response of ERα-positive breast tumours, and WBP2 might be a key molecule for developing new therapeutic strategies to treat chemoresistance in breast cancer patients.

Fusion peptide functionalized hybrid nanoparticles for synergistic drug delivery to reverse cancer drug resistance

A facile self-assembly strategy was developed to decorate polymer/inorganic hybrid nano-sized drug delivery systems with functional peptides. To enhance drug delivery efficacy and overcome tumor drug resistance, a functional fusion peptide containing an RGD sequence for tumor targeting and an R₈ sequence for cell penetration was introduced onto the surface of biotinylated carboxymethyl chitosan/CaCO₃ (BCMC/CaCO₃) hybrid nanoparticles through biotin-avidin interaction to obtain peptide functionalized nanoparticles (PNP). The peptide functionalization results in improved delivery efficiency and effective inhibition for drug resistant tumor cells. Co-delivery of an anti-cancerous drug (doxorubicin hydrochloride, DOX) and a cyclooxygenase-2 inhibitor (celecoxib, CXB) by PNP can further improve the therapeutic efficiency by effectively down-regulating P-gp expression to reduce P-gp mediated drug efflux and increase intracellular drug accumulation.

Lipid–polymer hybrid nanoparticles for synergistic drug delivery to overcome cancer drug resistance

Co-delivery of a chemotherapeutic drug and a drug resistance inhibitor by lipid–polymer hybrid nanoparticles can effectively overcome tumor drug resistance.

Co-delivery of multiple drug resistance inhibitors by polymer/inorganic hybrid nanoparticles to effectively reverse cancer drug resistance

To effectively reverse multiple drug resistance (MDR) in tumor treatments, a functional nano-sized drug delivery system with active targeting function and pH sensitivity was prepared for the co-delivery of multiple drug resistance inhibitors. Buthionine sulfoximine (BSO) to inhibit GSH synthesis and celecoxib (CXB) to down-regulate P-gp expression were co-loaded in polymer/inorganic hybrid nanoparticles to form buthionine sulfoximine/celecoxib@biotin-heparin/heparin/calcium carbonate/calcium phosphate nanoparticles (BSO/CXB@BNP). To investigate the reversal of MDR, the drug resistant cells (MCF-7/ADR) were pretreated by the dual-inhibitor loaded nanoparticles (BSO/CXB@BNP) followed by the treatment of doxorubicin (DOX) loaded nanoparticles (DOX@BNP). The dual-inhibitor loaded nanoparticles (BSO/CXB@BNP) exhibited greatly enhanced efficiency in down-regulation of GSH and P-gp since BSO and CXB had combined effects on the reduction of GSH and P-gp in drug resistant tumor cells. As a result, BSO/CXB@BNP exhibited a significantly improved capability in reversal of MDR compared with mono-inhibitor loaded nanoparticles (CXB@BNP and BSO@BNP). As compared with free drug resistance inhibitors, delivery of drug resistance inhibitors by functional nanocarriers could obviously improve the therapeutic efficiency due to enhanced cellular uptake and increased intracellular drug accumulation. The study on immunostimulatory effects of different treatments showed that BSO/CXB@BNP treatment resulted in the lowest concentration of interleukin 10, a cytokine related to tumor development. These results suggest the nanoparticulate drug delivery platform developed in this study has promising applications in multiple drug delivery to overcome drug resistance in tumor treatments.

Potency of non-steroidal anti-inflammatory drugs in chemotherapy

Cancer cell resistance, particularly multidrug resistance (MDR), is the leading cause of chemotherapy failure. A number of mechanisms involved in the development of MDR have been described, including the overexpression of ATP-dependent membrane-bound transport proteins. The enhanced expression of these proteins, referred to as ATP-binding cassette (ABC) transporters, results in an increased cellular efflux of the cytotoxic drug, thereby reducing its intracellular concentration to an ineffective level. Non-steroidal anti-inflammatory drugs (NSAIDs) are the most frequently consumed drugs worldwide. NSAIDs are mainly used to treat pain, fever and inflammation. Numerous studies suggest that NSAIDs also show promise as anticancer drugs. NSAIDs have been shown to reduce cancer cell proliferation, motility, angiogenesis and invasiveness. In addition to these effects, NSAIDs have been shown to induce apoptosis in a wide variety of cancer types. Moreover, several studies have indicated that NSAIDs may sensitise cancer cells to the antiproliferative effects of cytotoxic drugs by modulating ABC transporter activity. Therefore, combining specific NSAIDs with chemotherapeutic drugs may have clinical applications. Such treatments may allow for the use of a lower dose of cytotoxic drugs and may also enhance the effectiveness of therapy. The objective of this review was to discuss the possible role of NSAIDs in the modulation of antitumour drug cytotoxicity. We particularly emphasised on the use of COX-2 inhibitors in combination with chemotherapy and the molecular and cellular mechanisms underlying the alterations in outcome that occur in response to this combination therapy.

Emerging EGFR antagonists for breast cancer

INTRODUCTION

The EGFR has been associated with the pathogenesis and progression of breast cancer. Treatment based on an EGFR target is emerging as a promising option, especially in combination with conventional therapies. Unfortunately, there are no validated predictor biomarkers, and combinatorial treatments are meeting new resistance.

AREAS COVERED

The purpose of this review is to summarize the existing treatments and the current research based on targeting the EGFR pathway.

EXPERT OPINION

The existing EGFR treatments in breast cancer have shown limited benefit. The combination of the monoclonal antibody cetuximab and platinum salts achieves a 15 - 20% response rate. The effectiveness of tyrosine kinase inhibitors is not completely clear, showing modest or no benefits. Gefitinib treatment has offered some promising results in estrogen receptor + breast cancer. However, it has not been identified as a predictive factor for the appropriate selection of patients. Radioimmunotherapy with anti-EGFR radiolabeled antibodies is a promising strategy in BRCA-mutated breast cancer, but it still requires clinical confirmation. Nevertheless, the crosstalk between pathways frequently leads to treatment resistance. Current research is focused on increasing knowledge about the mechanisms of response and the discovery of predictive markers. Targeting several pathways simultaneously and a correct selection of patients seem essential.

ERα directly activated the MDR1 transcription to increase paclitaxel-resistance of ERα-positive breast cancer cells in vitro and in vivo

Chemotherapy is commonly used to treat early-stage invasive and advanced-stage breast cancer either before or after surgery. Increasing evidence from clinical analysis and in vitro studies has shown that ER-positive breast cancer cells are insensitive to chemotherapy. Complete understanding of how ERα mediates drug resistance is prerequisite to improvement of the chemotherapeutic efficacy. Over-expression of P-glycoprotein (P-gp) encoded by MDR1 gene is one of the major causes of drug resistance. The association between ERα and MDR1 in breast cancer is still unclear and the limited reports are conflict. This study systematically explored intrinsic link between ERα and the P-gp over-expression in paclitaxel-resistant ERα(+) breast cancer cell lines and mouse model in molecular details. Our data showed that ERα activated the MDR1 transcription in MCF-7/PTX breast cancer cells by binding to ERE1/2 and interacting with Sp1 that bridged to the downstream CG-rich element within the MDR1 promoter. Knockdown of MDR1 restrained the effect of ERα in MCF-7 cells and sensitized the cells to paclitaxel. Treatment of ICI 182,780 that selectively suppressed ERα significantly decreased the MDR1 expression and increased the sensitivity of drug resistant breast cancer cells and xenograft tumors to paclitaxel. Our data strongly demonstrated that ERα was able to increase drug resistance of breast cancer cells through activating MDR1 transcription. This novel mechanism provides new insight to how the ERα signaling regulates response of ERα(+) breast tumors to chemotherapy, which may be exploited for developing novel therapeutic strategies for breast cancer in the future.

Expression and significance of cyclooxygenase-2 mRNA in benign and malignant ascites

AIM: To investigate the mRNA expression of cyclooxygensae-2 (COX-2) in benign and malignant ascites, and to explore the difference in COX-2 mRNA expression among different diseases.

METHODS: A total of 36 samples were collected from the Fifth Affiliated Hospital of Sun Yat-Sen University and divided into two experimental groups: benign ascites (n = 21) and malignant ascites (n = 15). Benign ascites included cirrhotic ascites (n = 10) and tuberculous ascites (n = 5). Malignant ascites included oophoroma (n = 7), cancer of colon (n = 5), cancer of the liver (n = 6), gastric cancer (n = 2), and bladder carcinoma (n = 1). The mRNA expression of COX-2 in ascites was examined with reverse transcriptase polymerase chain reaction (RT-PCR) technology, and the positive rate of COX-2 mRNA was compared between different diseases.

RESULTS: The positive rate of COX-2 mRNA in malignant ascites was 42.9% (9/21), which was significantly higher than in benign ascites, 6.7% (1/15), difference being significant between these two groups (χ² = 4.051, P = 0.044). The proportion of the positive rate in the malignant ascites was as follows: ovarian cancers 57.1% (4/7), colon cancer 40.0% (2/5), liver cancer 33.3% (2/6), gastric cancer 50.0% (1/2), and bladder cancer 0.00% (0/1). However, there was no significant difference in COX-2 mRNA expression among various tumors with malignant ascites (χ² = 1.614, P = 0.806). Among the benign ascites, COX-2 mRNA levels were different between the tuberculous ascites (0/5) and cirrhotic ascites (1/10), but there was no significant difference (P = 1.000).

CONCLUSION: COX-2 mRNA, detected by RT-PCR, is useful in the differential diagnosis of benign and malignant ascites, which also has potential value in the clinical diagnosis of tumors.

Selective cyclooxygenase inhibitors increase paclitaxel sensitivity in taxane-resistant ovarian cancer by suppressing P-glycoprotein expression

Objective

The purpose of this study was to investigate whether selective cyclooxygenase (COX) inhibitors promote paclitaxel-induced apoptosis in taxane-resistant ovarian cancer cells by suppressing MDR1/P-glycoprotein (P-gp) expression.

Methods

Taxane-resistant ovarian cancer cells were cultured with paclitaxel alone or combined with a selective COX inhibitors. The expression patterns of MDR1/P-gp and the ability of COX inhibitors to inhibit growth of taxane-resistant ovarian cancer cells were measured. The efficacy of prostaglandin E₂ (PGE₂) supplementation was measured to evaluate the mechanisms involved in suppressing MDR1 gene expression.

Results

P-gp was upregulated in taxane-resistant ovarian cancer cells compared to paired paclitaxel-sensitive ovarian cancer cells. An 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that selective COX inhibitors significantly enhanced the cytotoxic effects of paclitaxel in taxane-resistant ovarian cancer cells via a prostaglandin-independent mechanism. These increased apoptotic effects were further verified by measuring an increased percentage of cells in sub-G1 stage using flow cytometry. Selective COX inhibitors suppressed MDR1 and P-gp expression. Moreover, combined treatment with paclitaxel and selective COX inhibitors increased poly (ADP-ribose) polymerase (PARP) cleavage in taxane-resistant ovarian cancer cells.

Conclusion

Selective COX inhibitors significantly promote paclitaxel-induced cell death in taxane-resistant ovarian cancer cells in a prostaglandin-independent manner. COX inhibitors could be potent therapeutic tools to promote paclitaxel sensitization of taxane-resistant ovarian cancers by suppressing MDR1/P-gp, which is responsible for the efflux of chemotherapeutic agents.

Crosstalk between HER2 signaling and angiogenesis in breast cancer: molecular basis, clinical applications and challenges

PURPOSE OF REVIEW

Angiogenesis is an essential hallmark of cancer. Targeting angiogenesis has proven its efficacy in the modern therapeutic paradigm. HER2 positive breast cancer, in particular, is a challenging disease in which resistance to standard therapy has been attributed to parallel and downstream signaling cascades including angiogenesis. This review explores the molecular mechanisms underlying crosstalk between HER2 signaling and angiogenesis. It highlights the role of angiogenesis in the emerging resistance to anti-HER2 therapy. It surveys the current repertoire of clinical trials involving use of combination of anti-HER2 and antiangiogenic therapies. Finally, it entertains the hopes and challenges posed by this novel therapeutic approach.

RECENT FINDINGS

HER2 signaling upregulates angiogenesis at different levels and by different mechanisms. A large number of clinical trials were conducted in attempt to exploit the potential benefit of the combination. Results of early phase trials were promising. However, in the late phase clinical trials, the AVEREL trial did not demonstrate a consistent benefit for bevacizumab in the HER2 positive breast cancer patient population. The BETH trial is ongoing and recruiting patients. Safety issues regarding cardiovascular toxicity of the combination have been already raised. Negative experience of dual EGFR and VEGF targeting in colon cancer cannot be overlooked.

SUMMARY

Angiogenesis and HER2 signaling are closely related at the molecular level. Appraisal of efficacy of antiangiogenic therapies requires revisit of the current literature as well as following the results of ongoing trials.

Effects of Jianpi Jiedu Recipe on reversion of P-glycoprotein-mediated multidrug resistance through COX-2 pathway in colorectal cancer

OBJECTIVE

To evaluate the underlying mechanism of Jianpi Jiedu Recipe (, JJR) in the reversion of multidrug resistance concerning colorectal cancer in vitro and in vivo.

METHODS

Mice were treated orally with JJR at a daily 4.25 g/(kg·day) or injected with vinblastine (VCR) 2.5 mg/(kg·day) for 3 weeks after having been inoculated with HCT8/V cells; tumor tissues were assayed by hematoxylin and eosin staining. Firstly, the effects of JJR on the expression of cyclooxygenase-2 (COX-2) were tested by real-time polymerase chain reaction (PCR) technique and COX-2 gene silenced by siRNA. Secondly, the variation of intracellular concentration of oxaliplatin (L-OHP) was evaluated by the inductively coupled plasma mass spectroscopy (ICPMS) in HCT8/V and its COX-2 siRNA cells; the concentration of JJR combined with chemotherapeutic drugs and the reverse effect of multidrug resistance (MDR) in HCT8/V cells was evaluated by the MTT assay. Thirdly, real-time quantitative PCR and Western blot analysis were used to detect the multidrug resistance gene 1 (MDR1) mRNA and P-gp expression.

RESULTS

JJR had an inhibitory effect on the growth of tumors in vivo, and it, in combination with chemotherapeutic drugs, could reverse the drug-resistance of HCT8/V cells and increase the sensitivity of HCT8/V cells to VCR, DDP, 5-Fu, and THP. ICP-MS results showed that JJR could increase the concentration of drugs in HCT8/V cells (P<0.01). Furthermore, it was shown that JJR could reverse drug resistance of colorectal cancer cells by decreasing MDR1 expression and P-gp level via downregulation of COX-2, which has been represented as one of the major mechanisms that contributes to the MDR phenotype (P<0.01).

CONCLUSION

JJR reversed multidrug resistance and enhanced the sensitivity to chemotherapy, which could be attributed to the down-regulation of COX-2 in MDR1/P-gp-mediated MDR colorectal cancer after chemotherapy.

The dual cyclooxygenase/5-lipoxygenase inhibitor licofelone attenuates p-glycoprotein-mediated drug resistance in the injured spinal cord

There are currently no proven effective treatments that can improve recovery of function in spinal cord injury (SCI) patients. Many therapeutic compounds have shown promise in pre-clinical studies, but clinical trials have been largely unsuccessful. P-glycoprotein (Pgp, Abcb1b) is a drug efflux transporter of the blood-spinal cord barrier that limits spinal cord penetration of blood-borne xenobiotics. Pathological Pgp upregulation in diseases such as cancer causes heightened resistance to a broad variety of therapeutic drugs. Importantly, several drugs that have been evaluated for the treatment of SCI, such as riluzole, are known substrates of Pgp. We therefore examined whether Pgp-mediated pharmacoresistance diminishes delivery of riluzole to the injured spinal cord. Following moderate contusion injury at T10 in male Sprague-Dawley rats, we observed a progressive, spatial spread of increased Pgp expression from 3 days to 10 months post-SCI. Spinal cord uptake of i.p.-delivered riluzole was significantly reduced following SCI in wild type but not Abcb1a-knockout rats, highlighting a critical role for Pgp in mediating drug resistance following SCI. Because inflammation can drive Pgp upregulation, we evaluated the ability of the new generation dual anti-inflammatory drug licofelone to promote spinal cord delivery of riluzole following SCI. We found that licofelone both reduced Pgp expression and enhanced riluzole bioavailability within the lesion site at 72 h post-SCI. This work highlights Pgp-mediated drug resistance as an important obstacle to therapeutic drug delivery for SCI, and suggests licofelone as a novel combinatorial treatment strategy to enhance therapeutic drug delivery to the injured spinal cord.

COX-2 inhibitors block chemotherapeutic agent-induced apoptosis prior to commitment in hematopoietic cancer cells

Enzymatic inhibitors of pro-inflammatory cyclooxygenase-2 (COX-2) possess multiple anti-cancer effects, including chemosensitization. These effects are not always linked to the inhibition of the COX-2 enzyme. Here we analyze the effects of three COX-2 enzyme inhibitors (nimesulide, NS-398 and celecoxib) on apoptosis in different hematopoietic cancer models. Surprisingly, COX-2 inhibitors strongly prevent apoptosis induced by a panel of chemotherapeutic agents. We selected U937 cells as a model of sensitive cells for further studies. Here, we provide evidence that the protective effect is COX-independent. No suppression of the low basal prostaglandin (PG)E(2) production may be observed upon treatment by COX-2 inhibitors. Besides, the non-active celecoxib analog 2,5-dimethyl-celecoxib is able to protect from apoptosis as well. We demonstrate early prevention of the stress-induced apoptotic signaling, prior to Bax/Bak activation. This preventive effect fits with an impairment of the ability of chemotherapeutic agents to trigger apoptogenic stress. Accordingly, etoposide-induced DNA damage is strongly attenuated in the presence of COX-2 inhibitors. In contrast, COX-2 inhibitors do not exert any anti-apoptotic activity when cells are challenged with physiological stimuli (anti-Fas, TNFα or Trail) or with hydrogen peroxide, which do not require internalization and/or are not targeted by chemoresistance proteins. Altogether, our findings show a differential off-target anti-apoptotic effect of COX-2 inhibitors on intrinsic vs. extrinsic apoptosis at the very early steps of intracellular signaling, prior to commitment. The results imply that an exacerbation of the chemoresistance phenomena may be implicated.

EGCG enhances 5-fluorouracil-induced cell growth inhibition in human hepatocellular carcinoma cell line BEL-7402

AIM: To investigate whether epigallocatechin-3-gallate (EGCG) enhances 5-fluorouracil (5-FU)-induced cell growth inhibition in human hepatocellular carcinoma cell line BEL-7402 and to explore potential mechanisms involved.

METHODS: MTT assay was used to evaluate cell viability. Western blotting analysis was performed to detect protein expression, and small interfering RNA was used to suppress COX-2 expression. ELISA assay was applied to test the release of prostaglandin E2 (PGE2).

RESULTS: Treatment with different concentrations of EGCG (5, 10, 25, or 50 mmol/L) significantly inhibited the growth of BEL-7402 cells compared with control cells (treated with 0.1% DMSO, all P < 0.05). When cells were treated with 10 mmol/L 5-FU in combination with either 5, 10, 25, or 50 mmol/L EGCG, the percentages of viable cell significantly decreased when compared with cells treated with each drug alone, suggesting a synergistic effect between the two drugs. Moreover, EGCG down-regulated the expression of COX-2 and reduced the release of PGE2 in BEL-7402 cells.

CONCLUSION: EGCG enhances 5-FU-induced cell growth inhibition in human hepatocellular carcinoma cell line BEL-7402 possibly by down-regulating COX-2 expression and inhibiting PGE2 release.

Upregulation of mdr1 gene is related to activation of the MAPK/ERK signal transduction pathway and YB-1 nuclear translocation in B-cell lymphoma

OBJECTIVE

Multidrug resistance (MDR) in human B-cell lymphoma constitutes a major obstacle to the effectiveness of chemotherapy. The aim of this study was to investigate the molecular mechanism of MDR in B-cell lymphoma.

MATERIALS AND METHODS

The B-cell lymphoma MDR sublines were developed by exposing the parental Daudi cells to stepwise increasing concentrations of doxorubicin. Interaction of Y-box binding protein-1 (YB-1) with the Y-box motif of the mdr1 gene promoters was studied by electrophoretic mobility shift assay. The effects of YB-1 on mdr1 promoter activity were examined by luciferase assay. After silencing of YB-1 gene by shRNA, the role of YB-1 nuclear translocation in the formation of induced MDR was examined. Expression of mdr1 and YB-1 was examined further after Daudi cells were pretreated with mitogen-activated protein kinase (MAPK) inhibitor PD98059 for 1 hour.

RESULTS

Doxorubicin-resistant sublines was generated from the Daudi cell line by stepwise selection in doxorubicin. We found that acquisition of MDR is associated with enhanced YB-1 nuclear translocation and MAPK/extracellular signal-regulated kinase (ERK) activity. Electrophoretic mobility shift assay revealed that doxorubicin increased binding of YB-1 to the Y-box of mdr1 promoter. Luciferase reporter assays demonstrated that the Y-box region is essential for YB-1 regulation of mdr1 expression. The introduction of exogenous YB-1 shRNA into Daudi cells resulted in decreased levels of the expression of mdr1 gene and P-glycoprotein induced by doxorubicin. When Daudi cells were pretreated with MAPK inhibitor PD98059, the phosphorylation of ERK was effectively inhibited as well as the nuclear translocation of YB-1 and the expression of mdr1 gene.

CONCLUSION

Doxorubicin can increase expression of mdr1/P-glycoprotein through activating MAPK/ERK transduction pathway, then increasing expression of YB-1, inducing YB-1 nuclear translocation, and enhancing DNA-binding activity of YB-1.

P-Glycoprotein/MDR1 regulates pokemon gene transcription through p53 expression in human breast cancer cells

P-glycoprotein (Pgp), encoded by the multidrug resistance 1 (MDR1) gene, is an efflux transporter and plays an important role in pharmacokinetics. In this study, we demonstrated that the pokemon promoter activity, the pokemon mRNA and protein expression can be significantly inhibited by Pgp. Chromatin immunoprecipitation assay showed that Pgp can bind the pokemon prompter to repress pokemon transcription activity. Furthermore, Pgp regulated pokemon transcription activity through expression of p53 as seen by use of p53 siRNA transfected MCF-7 cells or p53 mutated MDA-MB-231 cells. Moreover, p53 was detected to bind with Pgp in vivo using immunoprecipitation assay. Taken together, we conclude that Pgp can regulate the expression of pokemon through the presence of p53, suggesting that Pgp is a potent regulator and may offer an effective novel target for cancer therapy.