Mediated Multidrug Resistance Phenotype Research Articles

Osthole shows the potential to overcome P-glycoprotein‑mediated multidrug resistance in human myelogenous leukemia K562/ADM cells by inhibiting the PI3K/Akt signaling pathway.

P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) has been reported to play a pivotal role in tumorchemotherapy failure. Study after study has illustrated that the phosphoinositide 3-kinase (PI3K)/Akt signaling cascade is involved in the MDR phenotype and is correlated with P-gp expression in many human malignancies. In the present study, osthole, an O-methylated coumarin, exhibited potent reversal capability of MDR in myelogenous leukemia K562/ADM cells. Simultaneously, the uptake and efflux of Rhodamine-123 (Rh-123) and the accumulation of doxorubicin assays combined with flow cytometric analysis suggested that osthole could increase intracellular drug accumulation. Furthermore, osthole decreased the expression of multidrug resistance gene1 (MDR1) at both the mRNA and protein levels. Further experiments elucidated that osthole could suppress P-gp expression by inhibiting the PI3K/Akt signaling pathway which might be the main mechanism accounting for the reversal potential of osthole in the MDR in K562/ADM cells. In conclusion, osthole combats MDR and could be a promising candidate for the development of novel MDR reversal modulators.

Perifosine downregulates MDR1 gene expression and reverses multidrug-resistant phenotype by inhibiting PI3K/Akt/NF-κB signaling pathway in a human breast cancer cell line

P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) is the major clinical impediment to chemotherapy of breast cancers. Down-regulation of PI3K/Akt pathway has been described as related to reversal of MDR in cancer cells. Here, we investigated the reversal effect on MDR phenotype of perifosine, a new Akt inhibitor, in breast cancer cell lines. In this study, MCF-7/ADM cells and MCF-7 cells were treated with different concentrations of perifosine. Our results suggested that perifosine reversed MDR partially by downregulation of P-gp expression and inhibition of PI3K/Akt/NF-κB pathway in the MCF-7/ADM cell line. The novel Akt inhibitor perifosine may be a promising new drug due to its ability to reverse MDR in human breast cancer cells.

Complete In Vivo Reversal of the Multidrug Resistance Phenotype by Jet-injection of Anti-MDR1 Short Hairpin RNA-encoding Plasmid DNA

Triggering the RNA interference (RNAi) pathway by inducing the expression of short hairpin RNA (shRNA) molecules has become a promising tool for efficient silencing of a given gene in gene therapy applications. In this study, shRNA encoding DNA was utilized to reverse the classical MDR1/P-glycoprotein (MDR1/P-gp)-mediated multidrug resistance (MDR) phenotype in vivo. For the first time, the nonviral jet-injection technology was applied for delivering naked shRNA-vector constructs for direct intratumoral in vivo transfer. The highly efficient anti-MDR1 shRNA expression vectors were applied twice in the human MDR1/P-gp overexpressing MaTu/ADR cancer xenograft-bearing mice, and twice in the corresponding drug-sensitive parental MaTu tumor xenograft bearing mice as well. Two days after anti-MDR1 shRNA vector injection, the expression level of the MDR1 messenger RNA (mRNA) was decreased by more than 90% and the corresponding MDR1/P-gp protein was no longer detectable in the tumors. Two jet-injections of anti-MDR1 shRNA vectors into the tumors, combined with two intravenous (IV) administrations of doxorubicin, were sufficient to achieve complete reversal of the drug-resistant phenotype. The data show that jet-injection delivery of shRNA-expressing vectors is effective in reversing MDR1/P-gp-mediated MDR in vivo, and is therefore a promising strategy for making tumors with an MDR1/Pgp-dependent MDR phenotype revert to a drug-sensitive state.

Clinical Relevance of Spontaneous Apoptosis Is Independent from Multidrug Resistance in Acute Myeloid Leukemia (AML).

P-glycoprotein (PGP)-mediated multidrug resistance (MDR) and anti-apoptotic proteins overexpression represent key mechanisms explaining the high rate of treatment failure in AML. Expression profiling studies have identified genes involved in drug resistance (Vey N, 2004) and in apoptosis block (Kern W, 2004) as discriminator genes for a poor prognosis. The availability of third-generation PGP inhibitors and bcl-2 targeting drugs prompted us to evaluate the impact of a MDR phenotype and apoptosis on AML prognosis. Therefore, a large series of 355 de novo AML pts, except FABM3, treated with intensive chemotherapy regimens, was tested. The principal aims of our study were: 1) to correlate spontaneous apoptosis (bax/bcl-2 ratio) with a MDR phenotype (PGP) and 2) to demonstrate that apoptosis and MDR are clinically relevant and independent events. PGP, bcl-2 and bax proteins were determined by multicolor flow cytometry. Two hundred-three pts (57%) were bax/bcl-2 ratio positive (>0.3) and 229/355 (64.5%) were PGP positive (>20%). There was a close correlation between MDR positivity and higher CD71 (167/225; p<0.00001), showing that a MDR phenotype is strictly linked to an increased proliferation. Only a slight correlation was found between a higher bax/bcl-2 ratio and a higher PGP (141/229; p=0.025). A lower complete remission (CR) rate was found in pts with lower bax/bcl-2 ratio (42% vs 71%, p<0.00001) or higher PGP (49% vs 71%, p=0.0003). Overall survival (OS) was shorter either in pts with lower bax/bcl-2 ratio (0% vs 14% at 3.5 years; p<0.00001) or higher PGP (2% vs 13% at 7 years; p=0.0008). A longer disease free survival (DFS) was observed either in pts with higher bax/bcl-2 ratio (10% vs 0% at 2.7 years; p=0.0002) or lower PGP (12% vs 0% at 3.9 years; p=0.002). Bax/bcl-2 ratio and PGP showed additive prognostic properties, since higher bax/bcl-2 ratio plus lower PGP identified a subset at better prognosis with regard to CR (85% vs 33%; p<0.00001), OS (31% vs 0% at 2.4 years; p<0.00001) and DFS (50% vs 0% at 1.2 years; p=0.00002). In order to establish the independent prognostic value of bax/bcl-2 ratio from PGP, we investigated MDR + (229 pts) and MDR - (126 pts) subgroups. As a matter of fact, a lower CR rate was found in pts with lower bax/bcl-2 ratio either within MDR+ (32% vs 65%, p=0.00002) or within MDR- subset (56% vs 87%, p=0.0003). Lower bax/bcl-2 ratio was associated both with a shorter OS and DFS in MDR+ (0% vs 7% at 2.4 years, p=0.005; 0% vs 13% at 1.2 years, p=0.01) and, more significantly, in MDR- (0% vs 30% at 3.5 years, p<0.00001; 0% vs 31% at 2.7 years, p=0.0008) pts. On the contrary, PGP was not able to distinguish pts at different prognosis within the lower bax/bcl-2 ratio subgroup. The independent prognostic value of bax/bcl-2 ratio was confirmed in multivariate analysis with regard to CR (p=0.00002), OS (p=0.000007) and DFS (p=0.00001). In conclusion, the lack of an important correlation between bax/bcl-2 ratio and MDR confirms the independence of apoptosis from MDR. The capacity of bax/bcl-2 ratio of clearly identifying pts at different prognosis within the MDR+ and MDR- subgroups implies that apoptosis has an intrinsic more relevant clinical significance. That has to be considered focusing future strategies on apoptosis inducers and effectors in order to improve outcome in AML (Reed JC, 2005).

P-Glycoprotein - Implications of Metabolism of Neoplastic Cells and Cancer Therapy

Multidrug resistance (MDR) of neoplastic tissues is a major obstacle in cancer chemotherapy. The predominant cause of MDR is the overexpression and drug transport activity of P-glycoprotein (P-gp, a product of the MDR gene). P-gp is a member of the ATP binding cassette (ABC) transporters family, with broad substrate specificity for several substances including anticancer drugs, linear and cyclic peptides, inhibitors of HIV protease, and several other substances. The development of P-gp-mediated MDR is often associated with several changes in cell structure and metabolism of resistant cells. In the present review are discussed the relations between glucosylceramide synthase activity, Pregnane X receptor and development of P-gp mediated MDR phenotype. Attention is also focused on the changes in protein kinase systems (mitogen-activated protein kinases, protein kinase C, Akt kinase) that are associated with the development of MDR phenotype and to the possible role of these kinase cascades in modulation of P-gp expression and function. The overexpression of P-gp may be associated with changes in metabolism of sugars as well as energy production. Structural and ultrastructural characteristics of multidrug resistant cells expressing P-gp are typical for cells engaged in a metabolically demanding process of protein synthesis and transport. P-gp mediated MDR phenotype is often also associated with alterations in cytoskeletal elements, microtubule and mitochondria distribution, Golgi apparatus, chromatin texture, vacuoles and caveolae formation. The current review also aims at bringing some state-of-the-art information on interactions of P-glycoprotein with various substances. To capture and transport the numerous unrelated substances, P-gp should contain site(s) able to bind compounds with a molecular weight of several hundreds and comprising hydrophobic and/or base regions that are protonated under physiological conditions. Drug binding sites that are able to recognize substances with different chemical structures may have a complex architecture in which different parts are responsible for binding of different drugs. For P-gp substrates and inhibitors, a pharmacophore-based model has been described. The pharmacophores have to contain parts with hydrophobic and aromatic characteristics and functional groups that can act as hydrogen-bond donors and/or acceptors. Several drugs are known to be P-glycoprotein antagonizing agents. They represent a large group of structurally unrelated substances that can act via direct interaction with P-gp and inhibition of its transport activity, or via possible modulation of processes (such as phosphorylation) regulating P-gp transport activity. Effects of MDR reversal agents on the P-gp expression have also been reported. Function and expression of P-gp can be affected indirectly as well, e.g. through cyclooxygenase-2 or carbonic anhydrase-IX expression and effects.

Reduction of expression of the multidrug resistance protein (MRP)1 in glioma cells by antisense phosphorothioate oligonucleotides.

The tumor cells' acquisition of resistance to multiple drugs due to overexpression of the multidrug resistance protein (MPRP)1 gene is one of major obstacles in cancer chemotherapy. We have attempted to reverse the multidrug resistance (MDR) phenotype by treating etoposide resistant glioma cell lines (T98G-VP and Gli36-VP) with RP1 antisense oligonucleotides. 20-mer phosphorothioate oligodeoxynucleotide (0.3 microM), complementary to the coding region in the MRP cDNA sequence, could significantly inhibit the growth of multidrug resistant cell lines, T98G-VP and Gli36-VP, cultured in etoposide containing medium. No such effect was observed for the parental T98G and Gli36 cell lines. Further investigations by the reverse transcription-polymerase chain reaction and immunoblotting revealed that antisense oligomer could result in a reduction in the level of MRP1 mRNA, probably through hindering MRP1 gene transcription. This study demonstrates that the antisense oligonucleotides can increase the sensitivity of the tumor cells to the anticancer drug by decreasing the expression of the MRP gene. This strategy may be applicable to cure cancer patients with MRP mediated MDR phenotype.

Multiple gene expression analysis reveals distinct differences between G2 and G3 stage breast cancers, and correlations of PKC eta with MDR1, MRP and LRP gene expression.

A possible link between protein kinase C (PKC) and P-glycoprotein (P-gp)-mediated-multidrug resistance (MDR) was assumed from studies on MDR cell lines selected in vitro. The functional relevance of PKC for the MDR phenotype remains unclear, and the involvement of a particular PKC isozyme in clinically occurring drug resistance is not known. Recently, we have demonstrated significant correlations between the expression levels of the PKC eta isozyme and the MDR1 or MRP (multidrug resistance-associated protein) genes in blasts from patients with acute myelogenous leukaemia (AML) and in ascites cell aspirates from ovarian cancer patients. To extend these findings to further types of human tumours we analysed specimens from 64 patients with primary breast cancer for their individual expression levels of several MDR-associated genes (MDR1, MRP, LRP (lung cancer resistance-related protein), topoisomerase (Topo) II alpha/IIbeta, cyclin A and the PKC isozyme genes (alpha, beta1, beta2, eta, theta, and mu) by a cDNA-PCR approach. We found significantly enhanced mean values for MRP, LRP and PKC eta gene expression, but significantly decreased Topo II alpha and cyclin A gene expression levels in G2 tumours compared with G3. Remarkably, significant positive correlations between the MDR1, MRP or LRP gene expression levels and PKC eta were determined: MDR1/PKC eta (rs = +0.6451, P < 0.0001) n = 62; MRP/PKC eta (rs = +0.5454, P < 0.0001) n = 63; LRP/PKC eta (rs = +0.5436, P < 0.0001) n = 62; MRP/LRP (rs = +0.7703, P < 0.0001) and n = 62, MDR1/MRP (rs = +0.5042, P < 0.0001) n = 62. Our findings point to the occurrence of a multifactorial MDR in the clinics and to PKC eta as a possible key regulatory factor for up-regulation of a series of MDR-associated genes in different types of tumours.

Inhibition Growth of Multidrug Resistant KBV200Cells by MDR1 Antisense RNA

Acquisition of resistance to multiple drugs of tumor cell caused by overexpression of the MDR1 gene is one of major obstacles in cancer chemotherapy. We have attempted to reverse the multidrug resistance (MDR) phenotype by treating vincristine (VCR) and adriamycin (ADM) resistant KBV200cells with MDR1 antisense RNA. Retroviral vector expressing the antisense RNA was transfected into KBV200. In the transfected cells, a stable expression of antisense RNA and a reduction of cellular MDR1 mRNA could be detected by RT-PCR, and a reduction of MDR1 specific P-glycoprotein (P-gp) was also detected by Western blot, whereas an increase of the drug concentration in the cells was detected by FACS. The IC50of transfected cells to VCR and ADM was reduced by 65 and 47%. This study demonstrates that antisense RNA can increase the sensitivity of tumor cells to anticancer drug by decreasing the expression of the MDR1 gene. This strategy may be applicable to cure cancer patients with P-gp mediated MDR phenotype.

Polyaromatic alkaloids from marine invertebrates as cytotoxic compounds and inhibitors of multidrug resistance caused by P-glycoprotein.

The effects of several members of the family of lamellarins, polyaromatic alkaloids isolated from tunicates belonging to the genus Didemnum, on the growth of several tumour cell lines and on P-glycoprotein (P-gp)-mediated multidrug resistance (MDR), were investigated. Cytotoxicity experiments of lamellarins were performed on a panel of tumour cell lines, including two multidrug-resistant cell lines. Some lamellarins showed good anti-tumour activity, with similar levels of cytotoxicity against both the resistant and their corresponding parental cell lines. Two lamellarins displayed a high potency against lung carcinoma cells. Studies of the resistance modifier activity of the different lamellarins at non-toxic concentrations were also carried out in cells exhibiting MDR, and lamellarin I was selected for the highest chemosensitising activity. At non-toxic doses, verapamil and lamellarin I effectively increased the cytotoxicity of doxorubicin, vinblastine and daunorubicin in a concentration-dependent manner in multidrug-resistant cells, but the potency of lamellarin I as a MDR modulator was 9- to 16-fold higher than that of verapamil. In vitro measurements of rhodamine 123 accumulation in the multidrug-resistant Lo Vo/Dx cells suggest that lamellarin I reverses MDR by directly inhibiting the P-gp-mediated drug efflux. This work underscores the possibility of using these marine-derived compounds as a potential new source of anti-tumoral drugs active on resistant cells as well as of non-toxic modulators of the MDR phenotype.

Reversal by a Dihydropyridine Derivative of Non-P-Glycoprotein-Mediated Multidrug Resistance in Etoposide-Resistant Human Prostatic Cancer Cell Line

Purpose We have isolated etoposide-resistant prostatic cancer cell lines, P/VP10 and P/VP20, to investigate the multidrug resistance (MDR) mechanism and to find MDR reversal agents. Materials and Methods We examined expression of MDR-related genes and screened reversal agents of MDR in P/VP20 cells. Results These cells demonstrated a non-P-glycoprotein (P-gp)-mediated MDR phenotype with overexpression of MDR-associated protein (MRP) mRNA due to MRP DNA amplification. A 1,4-dihydropyridine derivative, bis(4-pyridylmethyl)4-[2-(3-methyl-5,6- dihydro-1,4-dithiinyl)]-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate (NIK250), was found to overcome MDR in P/VP20 cells. Conclusions NIK250 might be useful in reversing MDR, which often develops during chemotherapy of advanced or hormone-resistant prostatic cancer.

Novel dithiane analogues of tiapamil with high activity to overcome multidrug resistance in vitro

Dithiane analogues of tiapamil are highly active as modifiers of P-glycoprotein mediated multidrug resistance (MDR) in vitro. In an assay using the P-glycoprotein over-expressing cell line KB-8-5, the most active analogues for decreasing vincristine resistance were the racemate Ro 11-5160 and its two enantiomers, Ro 44-5911 (R) and Ro 44-5912 (S). In the KB-8-5 assay, the resistance modification index (RMI) of Ro 11-5160 was approximately 12-fold higher than those of the most active reference compounds tested, dipyridamole, cepharanthine, reserpine and cyclosporin A, when compared at concentrations equal to one-tenth of the ic 50 of each compound (RMI 0.1). The enantiomers have similar resistance modifying activities, but the (S) enantiomer Ro 44-5912 is somewhat more active, fully reverting the vincristine sensitivity of KB-8-5 cells to the level of the parental KB-3-1 cells at a concentration of 2 μM. The (R) enantiomer attained this level of modification at a concentration of 3.5 μM. These concentrations are both well below their ic 50 values for KB-8-5 cells (150 μM). The enantiomers appear to interact with P-glycoprotein because they inhibited [ 3H]azidopine and [ 3H]-vinblastine binding to plasma membrane fractions prepared from resistant K562/ADR cells. However, in addition to their resistance modifying activities with KB-8-5 cells, these compounds also decreased the ic 50 values of vincristine and doxorubicin with KB-3-1 cells that do not express detectable levels of P-glycoprotein. Ro 44-5911 overcame doxorubicin and vincristine resistance in three colorectal cancer cell lines (DLD-1, WiDr and COLO 201) that express P-glycoprotein. No effect was seen with the 3 colorectal cell lines on the ic 50 values of three drugs not related to the MDR phenotype, 5-fluorouracil, 5′-deoxy-5-fluorouridine and cis-diaminodichloroplatinum(II). The in vitro vasodilatory activity of these dithianes, measured with strips of rat aorta contracted with KCl, was about 5% of that of verapamil. These results suggest that dithianes could be useful agents for MDR modification in vivo.

P-Glycoprotein mediated resistance to 5′-nor-anhydro-vinblastine (Navelbine®)

Navelbine (NVB, vinorelbine tartrate) is a semisynthetic Vinca alkaloid in which the catharanthine moiety contains an eight-membered ring in place of the nine-membered ring that is present in all naturally occurring members of the vinblastine group. This modification selectively reduces interaction with anoxal vs mititotic microtubules and may account for the lower neurotoxicity with improved antitumor activity that has been observed in clinical trials with breast, lung and ovarian cancer. We were interested in whether the structural modification in NVB would also alter the drug resistance profile. Specifically, our aim was to determine whether NVB, like vinblastine (VBL), participates in P-glycoprotein (P-gp)-mediated multidrug resistance (MDR). NVB-resistant, murine P388 cells (P388/NVB), were derived in vivo and used in conjunction with a battery of drug-resistant P388 cell lines in vivo and murine and human tumor cell lines in vitro to develop a resistance profile for NVB. P388/NVB bells were cross-resistant to drugs involved in MDR (doxorubicin, etoposide, amsacrine, vinblastine, vincristine and actinomycin D), but not to the alkylating agents, cyclophosphamide, carmustine, and cisplatin, or to the antimetabolites, 5-fluorouracil and methotrexate. P388/NVB cellular resistance to NVB was stable without drug pressure during continuous passage in vivo for more than ten weeks and in vitro for at least five weeks. These cells exhibited increased expression of P-gp, and a 30-fold level of resistance of NVB in vitro, which was completely reversable with verapamil. The MDR phenotype was confirmed in other tumor models. P388 tumors resistant to vinblastine, vincristine, doxorubicin, and etoposide were cross-resistant to NVB in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Reversal of multidrug resistance in friend leukemia cells by dexniguldipine-HCl

Dexniguldipine-HCl (DNIG)--a prospective clinical modulator of p170-glycoprotein (pgp170)-mediated multidrug resistance (MDR)--was evaluated in a drug-accumulation assay in MDR murine leukemia cell strain F4-6RADR expressing pgp170. The compound elevated low accumulation of either doxorubicin (DOX), daunorubicin (DNR), or mitoxantrone (MITO) in resistant F4-6RADR cells to the very levels observed in drug-sensitive F4-6 precursor cells. In parallel with the increase in DNR content (F4-6RADR, solvent: 303 +/- 27 pmol/mg protein; DNIG (3.3 mumol/l): 1,067 +/- 174 pmol/mg protein; F4-6P, solvent: 948 +/- 110 pmol/mg protein; n = 8-9, SEM), the amount of DNR tightly bound to the acid precipitate pellet obtained from F4-6RADR (i.e., protein, DNA, RNA) increased 3.9-times to the levels observed in sensitive F4-6 cells. The main pyridine metabolite of DNIG displayed similar activity. Concentration-response analysis revealed that DNIG and R,S-verapamil (VER) induced 100% reversal of the DNR accumulation shortage associated with the MDR phenotype but DNIG was 8 times more potent than VER (50% inhibitory concentration (IC50), 0.73 vs 5.4 mumol/l). In keeping with the accumulation assay, DNIG was about 10 times more potent than VER in sensitizing F4-6RADR cells to the cytostatic and cytotoxic effects of DNR in proliferation assays. In conclusion, DNIG is a potent in vitro modulator, improving (a) the accumulation of anthracycline-like cytostatics, (b) drug access to cellular binding sites, and (c) the cytostatic action of DNR in F4-6RADR leukemia cells of the MDR phenotype.