Phorbol ester TPA modulates chemoresistance in the drug sensitive breast cancer cell line MCF-7 by inducing expression of drug efflux transporter ABCG2

Recent studies have indicated a link between levels of cyclooxygenase-2 (COX-2) and development of the multidrug resistance (MDR) phenotype. The ATP-binding cassette sub-family G member 2 (ABCG2) is a major MDR-related transporter protein that is frequently overexpressed in cancer patients. In this study, we aimed to evaluate any positive correlation between COX-2 and ABCG2 gene expression using the COX-2 inducer 12-O-tetradecanoylphorbol-13-acetate (TPA) in human breast cancer cell lines. ABCG2 mRNA and protein expression was studied using real-time RT-PCR and flow cytometry, respectively. A significant increase of COX-2 mRNA expression (up to 11-fold by 4 h) was induced by TPA in MDA-MB-231 cells, this induction effect being lower in MCF-7 cells. TPA caused a considerable increase up to 9-fold in ABCG2 mRNA expression in parental MCF-7 cells, while it caused a small enhancement in ABCG2 expression up to 67 % by 4 h followed by a time-dependent decrease in ABCG2 mRNA expression in MDA-MB-231 cells. TPA treatment resulted in a slight increase of ABCG2 protein expression in MCF-7 cells, while a time-dependent decrease in ABCG2 protein expression was occurred in MDA-MB-231 cells. In conclusion, based on the observed effects of TPA in MDA-Mb-231 cells, it is proposed that TPA up-regulates ABCG2 expression in the drug sensitive MCF-7 breast cancer cell line through COX-2 unrelated pathway

Celecoxib up regulates the expression of drug efflux transporter ABCG2 in breast cancer cell lines

Elevated expression of the drug efflux transporter ABCG2 seems to correlate with multidrug resistance of cancer cells. Specific COX-2 inhibitor celecoxib has been shown to enhance the sensitivity of cancer cells to anticancer drugs. To clarify whether ABCG2 inhibition is involved in the sensitizing effect of celecoxib, we investigated whether the expression of ABCG2 in breast cancer cell lines, could be modulated by celecoxib. The expression of the multidrug resistant gene (ABCG2) at mRNA and protein level was detected by real-time quantitative reverse transcription-polymerase chain reaction and flow cytometry analysis, respectively. Among three human breast cancer cell lines ABCG2 and COX-2 were highly expressed in MCF7-MX and MDA-MB-231 cells, respectively. The COX-2 inhibitor celecoxib up-regulated the expression of ABCG2 mRNA in MCF-7 and MCF7-MX cells, which was accompanied by increased ABCG2 protein expression. While celecoxib was able to block the 12-O-tetradecanoylphorbol-13-acetate (TPA)-mediated increase in COX-2 expression in MDA-MB-231 cells, it increased the expression of ABCG2 up to 4.27 times to the control level at mRNA level and with less intensity at protein level. Our findings provide evidence that celecoxib up-regulates ABCG2 expression in human breast cancer cells and proposed that ABCG2 is not involved in chemosensitizing effects of celecoxib

Characterisation of the gerP spore germination operon of Bacillus cereus

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN025042 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Potential role of cyclooxygenase-2 on the regulation of the drug efflux transporter ABCG2 in breast cancer cell lines

ABCG2 (BCRP) implicated as a member of the multidrug resistance (MDR) proteins in tumors, mediating efflux of a wide spectrum of anticancer drugs. In recent years, there has been an increasing tendency toward the exploring of the potential link between cyclooxygenase-2 (COX-2) expression and development of multidrug resistance phenotype in patients with cancer. The aim of this study was to investigate the role of the COX-2 in modulating drug efflux by ABCG2 in a group of breast cancer cell lines. The cytotoxicity of COX-2 inducer (TPA, tetradecanoyl phorbol acetate) and its inhibitor (celecoxib) was determined by an MTT assay. ABCG2 activity was measured by flow cytometric mitoxantrone efflux assay. TPA exhibited very little inhibitory activity in all cell lines, while long-term treatment with celecoxib significantly inhibited the growth of all cell lines. Furthermore, using mitoxantrone efflux assay was shown that TPA could increase ABCG2 activity in all the cell lines with the greatest stimulatory effects in MCF7-MX (more than 6 times the control level). It seemed that celecoxib inverted the effects of TPA on ABCG2 activity. This was more obvious in MCF7-MX. The results suggest a probable causal link between COX-2 and ABCG2 activity. The use of celecoxib for adjuvant therapy in cancer treatment may contribute to decreased resistance to chemotherapeutic drugs transported by ABCG2 Potential role of cyclooxygenase-2 on the regulation of the drug efflux transporter ABCG2 in breast cancer cell lines. Available from: https://www.researchgate.net/publication/43346615_Potential_role_of_cyclooxygenase-2_on_the_regulation_of_the_drug_efflux_transporter_ABCG2_in_breast_cancer_cell_lines [accessed Dec 11 2017]

Evaluation of indomethacin and dexamethasone effects on BCRP-mediated drug resistance in MCF-7 parental and resistant cell lines.

Breast cancer resistance protein is a member of the ATP-binding cassette transporter G family that extrudes xenotoxins from cells, mediating drug resistance, and has been recognized as a major cause of failure of various carcinoma chemotherapies. In this study, the modulatory effects of dexamethasone and indomethacin on the cell cytotoxicity of mitoxantrone and on the BCRP protein activity in breast cancer cell lines were examined. MCF cells were seeded at 1 x 10(4) cells per well in 96-well flat-bottomed microplates for 48 hours and treated with increasing doses of dexamethasone, indomethacin, and novobiocin alone or preincubated with increasing doses of the drugs and then coexposed to mitoxantrone. Cell viability was measured after 1-4 days, using the MTT assay. BCRP activity was determined flow cytometrically by measuring mitoxantrone accumulation in the absence and presence of the inhibitor, novobiocin. Cotreatment of mitoxantrone with different concentrations of dexamethasone and indomethacin sensitized parental and resistant MCF-7 cells to mitoxantrone cytotoxicity. Dexamethasone increased the accumulation of mitoxantrone in the MCF-7/MX cell line, indicating an inhibition of BCRP. In spite of increased levels of mitoxantrone cytotoxicity in the presence of indomethacin, the accumulation of mitoxantrone was not increased in indomethacin-treated MCF cells

Dexamethasone downregulates BCRP mRNA and protein expression in breast cancer cell lines.

It is hypothesized that anti-inflammatory drugs regulate breast cancer resistance protein (BCRP) expression. Hence, we examined the effects of indomethacin and dexamethasone on BCRP expression in MCF cells. For evaluation of BCRP mRNA expression, relative quantitative PCR and comparative C1 method was exploited. BCRP protein expression was measured flow cytometrically with the monoclonal antibody (mAb) BXP-21. Dexamethasone showed a dose-independent and a time-dependent effect on decreasing the mRNA level of BCRP gene in comparison with control in MCF-7 and MCF-7/MX breast cancer cell lines, whereas no changes were noted in the presence of indomethacin. The level of BCRP protein, expressed as a ratio of the corresponding control, was decreased in dexamethasone-treated MCF-7/MX cells. These results could be of great importance when combination therapy protocols with cytotoxic agents and dexamethasone regimens are considered in breast cancer patients

ANTIVIRAL ACTIVITY OF EUPHORBIA MICROSCIADIA EXTRACT

In traditional medicine, the extracts of different species of Euphorbia have been successfully used for the treatment of skin diseases. Therefore, the antiviral effects of Euphorbia microsciadia extracts were investigated using a plaque reduction assay. Plant material was collected, dried and ground and extracted either with methanol using a Soxhlet apparatus or by maceration in methanol. After applying several enriching stages of phage CP51, phage titration was performed to determine the phage concentration in phage lysate for specifying the dilution factor of the phage to be used as negative control for the next working stages. Then IC50 of trifluridine, as a positive control, for phage CP51 was determined. The MIC of the extracts for Bacillus cereus was determined as 1.25 and 0.5 mg/ml for Soxhlet and maceration extracts, respectively, To determine whether the extracts have the ability to inhibit the adsorption of virus to host cell, it was pre-incubated with phage CP51 for 30 min at 25ºC. The growth and reproduction of phage was inhibited by more than 50% at concentration of 1 and 0.25 mg/ml, respectively. In order to test the effects of extract on the transcription process, Bacillus cereus, phage CP51 and extract were incubated together. The growth and reproduction of phage was inhibited by more than 50% at concentration of 0.75 and 0.125 mg/ml for Soxhlet and macerated extracts, respectively. These results indicated that both extracts of E. microsciadia have considerable antiviral activity