Search

Background/aim: Malignant diseases present a significant public health burden worldwide and their treatment is further complicated by the phenomenon of multidrug resistance. Derivatives of imidazopyridine exhibit several remarkable pharmacological activities and they could reverse the multidrug resistance of cancer cells due to overexpressing P-glycoprotein., Materials and Methods: A series of novel imidazo[4,5-b]pyridine derivatives were synthesized and their biological activities were evaluated in vitro using parental (PAR) and multidrug resistant (MDR; ABCB1-overexpressing) mouse T-lymphoma cells. The cytotoxic activity and selectivity of the tested compounds were assessed by the thiazolyl blue tetrazolium bromide (MTT) assay, the ABCB1 modulating activity was measured by rhodamine 123 accumulation assay using flow cytometry., Results: Six compounds ( b, c, d, f, h and i ) showed moderate-to-high cytotoxic activity on the tested cell lines, while derivative i presented with promising selectivity towards the MDR cell line. Derivatives a, d, f, g and i were proven to be effective modulators of the ABCB1 multidrug efflux pump, with two compounds showing efflux pump modulatory activity at 2 μM concentration., Conclusion: Based on our experimental results, compounds that showed potent activity are those with a short carbon side chain; a methoxy group on the benzene ring; a heterocyclic (triazole) side chain and the presence of an alkylated N-atom at position 4., (Copyright© 2018, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: (-)-Epigallocatechin-3-gallate (EGCG) has been indicated to regulate the function of P-glycoprotein (P-gp), which is a drug transporter encoded by the MDR1 (ABCB1) gene. P-gp expression is induced by doxorubicin (DOX). We aimed to clarify the mechanisms and inhibitory effects of EGCG on DOX-induced P-gp expression in HepG2 cells., Materials and Methods: Rhodamine 123 (Rho123) was used for P-gp substrate. Western blotting and polymerase chain reactions (PCRs) were conducted using specific antibodies and primer sets., Results: The DOX-pretreated cells accumulated a significantly decreased amount of Rho123), than control cells; however, the cells pretreated with EGCG and DOX, in combination, accumulated Rho123 more than DOX-pretreated cells. DOX induced the overexpression of MDR1 mRNA and increased the phosphorylation of Akt, ERK1/2, p38 MAPK and JNK. EGCG significantly inhibited the phosphorylation of Akt and ERK. The DOX-induced P-gp overexpression was partially suppressed by an inhibitor of MEK1/2 (U0126), but not by a PI3K inhibitor (LY294002). Interestingly, the expression of P-gp was synergistically inhibited by combined treatment of U0126 with LY294002 and also inhibited by an mTORC1 inhibitor, rapamycin., Conclusion: EGCG inhibited DOX-induced overexpression of P-gp through the coordinate inhibitory action on MEK/ERK and PI3K/Akt signaling pathways., (Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background: Phenothiazines have anticancer properties and are able to reverse the multidrug resistance of neoplastic cells by inhibiting the ATP-binding cassette, sub-family B (MDR/TAP), member 1 protein (ABCB1 or P-glycoprotein) activity., Materials and Methods: A series of new phenothiazine derivatives was investigated regarding their ABCB1-modulating effect on multidrug resistant mouse T-lymphoma cells by rhodamine 123 accumulation assay and real-time ethidium bromide accumulation assay., Results: The phenothiazine derivatives exhibited a potent anticancer effect on the parental cell line and on its multidrug-resistant mouse T-lymphoma subline overexpressing the ABCB1 transporter. The inhibition of the ABCB1 transporter in the presence of the newly-developed phenothiazines was greater than that for the known ABCB1 inhibitors thioridazine and verapamil., Conclusion: Based on the chemical structures and biological activity, compounds with bivalent sulfur atom in the phenothiazine ring demonstrated marked ABCB1-modulating effect, however, other derivatives with halogen or amide substitutions were ineffective.

Background: One of the major causes of failure in chemotherapy for patients with acute lymphoblastic leukemia (ALL) is the acquisition of multidrug resistance (MDR). Predominant mechanisms for MDR acquisition include the overexpression of efflux pumps. In the present study, the regulation of the expression of two genes that encode efflux pumps, ATP-binding cassette, sub-family B, member 1 (ABCB1) and ABCG2, through mitogen-activated protein kinase (MAPK) pathways was examined., Materials and Methods: ABCB1 and ABCG2 mRNAs were quantified in a T-ALL cell line, CCRF-HSB-2 and a B-ALL cell line, YAMN90 using real-time RT-PCR. Changes in the mRNA amounts of these genes were examined after activation or inhibition of MAPK/extracellular signal-regulated kinase (ERK) pathway and c-Jun NH2-terminal kinase (JNK) pathway., Results: Activation of MAPK/ERK pathway up-regulated ABCB1 expression but down-regulated ABCG2 expression. Activation of JNK pathway up-regulated ABCG2 gene expression., Conclusion: The expressions of ABCB1 and ABCG2 genes were regulated through MAPK/ERK and JNK pathways in the human ALL cell lines.

Background: Hydantoin derivatives are very promising candidates to improve the efficacy of anticancer chemotherapy. Previously, we demonstrated that eight hydantoin derivatives inhibited the P-glycoprotein (ABCB1) efflux pump of mouse T-lymphoma cells, as well as acting synergistically with the anticancer drug doxorubicin., Materials and Methods: The activity of the hydantoin derivatives were investigated in another MDR cancer model, namely Colo 205/S sensitive and Colo 320/R resistant colon carcinoma cells respectively, having normal or overexpressed ABCB1 systems., Results: Among the hydantoin derivatives evaluated, BS-1, MN-3 and JH-63 were the most effective ABCB1 transporter inhibitors at the concentration of 4 mg/l on the Colo 320/R cells, compared to the positive control, verapamil., Conclusion: The derivatives did not induce apoptosis of Colo 320/R resistant colon carcinoma cells, indicating that these hydantoin compounds are potent efflux pump inhibitors (EPI) without affecting the signalling pathways that regulate apoptosis.

Background: We used the CellScan, a novel static cytometer, to monitor changes induced by anti-neoplastic drugs in the fluorescence intensity and polarization of fluorescently-labeled tumor cells., Materials and Methods: T47D and T80 human breast cancer cell lines were exposed to navelbine and to 5-fluorouracil and the fluorescence properties of the treated cells, stained with fluorescein diacetate and rhodamine 123, were measured by the CellScan., Results: A strong correlation was found between the inhibition of cell growth induced by the two drugs, as estimated from cell counts, and the resulting changes in fluorescence intensity and polarization, as monitored by the CellScan. Fluorescence hyperpolarization of the labeled cells occurred in conjunction with AnnexinV binding and propidium iodide exclusion, indicating that such hyperpolarization, resulting from drug action, reflects an early stage of apoptosis, as previously proposed., Conclusion: The system presented here could serve as the basis for assessing drug sensitivity or resistance of cancer cells derived from small biopsies of solid human tumors, thus eliminating prior tumor culturing and time-consuming assays.

Eleven 4-phenyl-3,5-diacetyl-1,4-dihydropyridines (AcDHPs) [G1-11] substituted at the phenyl ring were synthesized and compared for their cytotoxic activity and multidrug resistance (MDR)-reversing activity in in vitro assay systems. Among them, compound [G7] showed the highest cytotoxic activity against human promyelocytic leukemia HL-60 and human squamous cell carcinoma HSC-2 cells. However, no compounds tested produced radicals at pH 7.4-12.5. The activity of P-glycoprotein (Pgp) responsible for MDR in tumor cells was reduced by compounds [G2, 3, 6, 5, 8, 1, 11], verapamil [VP] and nifedipine [NP]. However, compounds [G4, 7, 10] were hardly active while G9 did not show a MDR reversing effect at 2.0-20.0 micrograms/mL. These data show a relationship between chemical structures and MDR-reversing effect on tumor cells.

Didemnin B (DB), a marine natural product, has very encouraging biological activity in vitro (Antineoplastic, immunosuppressive, antiviral). To learn more about its intracellular effects and targets, videomicrofluorometry on single living cells and a protocol of multiple labeling: Hoechst 342 for nuclear DNA, Rhodamine 123 for mitochondria and Nile Red for plasma membrane, have been used. DB behaves differently from Adriamycin, inducing at its IC50 dose of (20 nM) an accumulation of the CEM-WT lymphoblasts in the S phase of the cell cycle while we observed a 50% decrease of the mitochondrial labeling by R123, showing a decrease of the mitochondrial energetic state. Cytostatic dose of DB (250 nM) confirms these observations. However the treatment with a dose reported as apoptotic (1000 nM) induces a much faster effect (corresponding to that of 72 hours at the IC50 dose), 24 hours incubation induced a drastic decrease of nuclear DNA content as well as of the mitochondria energetic state. The evolution of NAD(P)H cellular content exhibited an increase that seems to indicate that the decrease of mitochondrial energetic state was dependent on inhibition of the mitochondrial activity due to an effect of DB at the mitochondrial level, either direct or mediated. Furthermore, the decrease of mitochondrial labeling appears as a very early event in the mechanisms leading to apoptosis.

Sophoraflavanone, kurarinone (GS08), norkurarinol (GS11), kurarinol (GS12) and kushenol K are cytotoxic flavonoids isolated from Sophora flavescens. In this study, we tested the cytotoxicity of those flavonoids to human cancer cells including P-glycoprotein (Pgp)-expressing HCT15 cells and its multidrug resistant subline, HCT15/CL02 cells. HCT15/CL02 cells revealed resistance to GS08, GS11 and GS12 about 2 fold in comparison with HCT15 cells. Nonetheless, verapamil, a Pgp inhibitor, could not increase the cytotoxicity of all the flavonoids tested. We also investigated that the flavonoids could modulate the Pgp action. At nontoxic concentrations, the flavonoids could not effect on the cytotoxicity of paclitaxel, a well-known Pgp-substrate. The flavonoids also had no effects on the accumulation of rhodamine 123 in all the cells tested at 10 microM. From the results, we concluded that Pgp had no effect on the cytotoxicity of the flavonoids, and the flavonoids also had no effect on the action of Pgp. Our results also suggested that HCT15/CL02 cells had additional mechanisms for drug resistance distinct from Pgp overexpression.