[Show abstract][Hide abstract] ABSTRACT: Background
Glioblastoma multiforme stem cells display a highly chemoresistant phenotype, whose molecular basis is poorly known. We aim to clarify this issue and to investigate the effects of temozolomide on chemoresistant stem cells.MethodsA panel of human glioblastoma cultures, grown as stem cells (neurospheres) and adherent cells, was used.ResultsNeurospheres had a multidrug resistant phenotype compared with adherent cells. Such chemoresistance was overcome by apparently noncytotoxic doses of temozolomide, which chemosensitized glioblastoma cells to doxorubicin, vinblastine, and etoposide. This effect was selective for P-glycoprotein (Pgp) substrates and for stem cells, leading to an investigation of whether there was a correlation between the expression of Pgp and the activity of typical stemness pathways. We found that Wnt3a and ABCB1, which encodes for Pgp, were both highly expressed in glioblastoma stem cells and reduced by temozolomide. Temozolomide-treated cells had increased methylation of the cytosine-phosphate-guanine islands in the Wnt3a gene promoter, decreased expression of Wnt3a, disrupted glycogen synthase-3 kinase/β-catenin axis, reduced transcriptional activation of ABCB1, and a lower amount and activity of Pgp. Wnt3a overexpression was sufficient to transform adherent cells into neurospheres and to simultaneously increase proliferation and ABCB1 expression. On the contrary, glioblastoma stem cells silenced for Wnt3a lost the ability to form neurospheres and reduced at the same time the proliferation rate and ABCB1 levels.Conclusions
Our work suggests that Wnt3a is an autocrine mediator of stemness, proliferation, and chemoresistance in human glioblastoma and that temozolomide may chemosensitize the stem cell population by downregulating Wnt3a signaling.
[Show abstract][Hide abstract] ABSTRACT: Low delivery of many anticancer drugs across the blood-brain barrier (BBB) is a limitation to the success of chemotherapy in glioblastoma. This is because of the high levels of ATP-binding cassette transporters like P-glycoprotein (Pgp/ABCB1), which effluxes drugs back to the bloodstream. Temozolomide is one of the few agents able to cross the BBB; its effects on BBB cells permeability and Pgp activity are not known. We found that temozolomide, at therapeutic concentration, increased the transport of Pgp substrates across human brain microvascular endothelial cells and decreased the expression of Pgp. By methylating the promoter of Wnt3 gene, temozolomide lowers the endogenous synthesis of Wnt3 in BBB cells, disrupts the Wnt3/glycogen synthase kinase 3/β-catenin signaling, and reduces the binding of β-catenin on the promoter of mdr1 gene, which encodes for Pgp. In co-culture models of BBB cells and human glioblastoma cells, pre-treatment with temozolomide increases the delivery, cytotoxicity, and antiproliferative effects of doxorubicin, vinblastine, and topotecan, three substrates of Pgp that are usually poorly delivered across BBB. Our work suggests that temozolomide increases the BBB permeability of drugs that are normally effluxed by Pgp back to the bloodstream. These findings may pave the way to new combinatorial chemotherapy schemes in glioblastoma.
Cellular and Molecular Life Sciences CMLS 06/2013; 71(3). DOI:10.1007/s00018-013-1397-y · 5.86 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Durable tumor cell eradication by chemotherapy is challenged by the development of multidrug-resistance (MDR) and the failure to induce immunogenic cell death. The aim of this work was to investigate whether MDR and immunogenic cell death share a common biochemical pathway eventually amenable to therapeutic intervention. We found that mevalonate pathway activity, Ras and RhoA protein isoprenylation, Ras- and RhoA-downstream signalling pathway activities, Hypoxia Inducible Factor-1alpha activation were significantly higher in MDR+ compared with MDR- human cancer cells, leading to increased P-glycoprotein expression, and protection from doxorubicin-induced cytotoxicity and immunogenic cell death. Zoledronic acid, a potent aminobisphosphonate targeting the mevalonate pathway, interrupted Ras- and RhoA-dependent downstream signalling pathways, abrogated the Hypoxia Inducible Factor-1alpha-driven P-glycoprotein expression, and restored doxorubicin-induced cytotoxicity and immunogenic cell death in MDR+ cells. Immunogenic cell death recovery was documented by the ability of dendritic cells to phagocytise MDR+ cells treated with zoledronic acid plus doxorubicin, and to recruit anti-tumor cytotoxic CD8+ T lymphocytes. These data indicate that MDR+ cells have an hyper-active mevalonate pathway which is targetable with zoledronic acid to antagonize their ability to withstand chemotherapy-induced cytotoxicity and escape immunogenic cell death.
PLoS ONE 04/2013; 8(4):e60975. DOI:10.1371/journal.pone.0060975 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The role of Vγ9Vδ2 T cells in chronic lymphocytic leukemia (CLL) is unexplored, although these cells have a natural inclination to react against B-cell malignancies. Proliferation induced by zoledronic acid was used as a surrogate of γδ TCR-dependent stimulation to functionally interrogate Vγ9Vδ2 T cells in 106 untreated CLL patients. This assay permitted the identification of responder and low-responder (LR) patients. The LR status was associated with greater baseline counts of Vγ9Vδ2 T cells and to the expansion of the effector memory and terminally differentiated effector memory subsets. The tumor immunoglobulin heavy chain variable region was more frequently unmutated in CLL cells of LR patients, and the mevalonate pathway, which generates Vγ9Vδ2 TCR ligands, was more active in unmutated CLL cells. In addition, greater numbers of circulating regulatory T cells were detected in LR patients. In multivariate analysis, the LR condition was an independent predictor of shorter time-to-first treatment. Accordingly, the time-to-first treatment was significantly shorter in patients with greater baseline numbers of total Vγ9Vδ2 T cells and effector memory and terminally differentiated effector memory subpopulations. These results unveil a clinically relevant in vivo relationship between the mevalonate pathway activity of CLL cells and dys-functional Vγ9Vδ2 T cells.
[Show abstract][Hide abstract] ABSTRACT: Cardioactive glycosides exert positive inotropic effects on cardiomyocytes through the inhibition of Na+/K+-ATPase. We showed previously that in human hepatoma cells, digoxin and ouabain increase the rate of the mevalonate cascade and therefore have Na+/K+-ATPase-independent effects. In the present study we found that they increase the expression and activity of 3-hydroxy-3 methylglutaryl-CoA reductase and the synthesis of cholesterol in cardiomyocytes, their main target cells. Surprisingly this did not promote intracellular cholesterol accumulation. The glycosides activated the liver X receptor transcription factor and increased the expression of ABCA1 (ATP-binding cassette protein A1) transporter, which mediates the efflux of cholesterol and its delivery to apolipoprotein A-I. By increasing the synthesis of ubiquinone, another derivative of the mevalonate cascade, digoxin and ouabain simultaneously enhanced the rate of electron transport in the mitochondrial respiratory chain and the synthesis of ATP. Mice treated with digoxin showed lower cholesterol and higher ubiquinone content in their hearts, and a small increase in their serum HDL (high-density lipoprotein) cholesterol. The results of the present study suggest that cardioactive glycosides may have a role in the reverse transport of cholesterol and in the energy metabolism of cardiomyocytes.
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND AND PURPOSE The passage of drugs across the blood–brain barrier (BBB) limits the efficacy of chemotherapy in brain tumours. For instance, the anticancer drug doxorubicin, which is effective against glioblastoma in vitro, has poor efficacy in vivo, because it is extruded by P-glycoprotein (Pgp/ABCB1), multidrug resistance-related proteins and breast cancer resistance protein (BCRP/ABCG2) in BBB cells. The aim of this study was to convert poorly permeant drugs like doxorubicin into drugs able to cross the BBB.
EXPERIMENTAL APPROACH Experiments were performed on primary human cerebral microvascular endothelial hCMEC/D3 cells, alone and co-cultured with human brain and epithelial tumour cells.
KEY RESULTS Statins reduced the efflux activity of Pgp/ABCB1 and BCRP/ABCG2 in hCMEC/D3 cells by increasing the synthesis of NO, which elicits the nitration of critical tyrosine residues on these transporters. Statins also increased the number of low-density lipoprotein (LDL) receptors exposed on the surface of BBB cells, as well as on tumour cells like human glioblastoma. We showed that the association of statins plus drug-loaded nanoparticles engineered as LDLs was effective as a vehicle for non-permeant drugs like doxorubicin to cross the BBB, allowing its delivery into primary and metastatic brain tumour cells and to achieve significant anti-tumour cytotoxicity.
CONCLUSIONS AND IMPLICATIONS We suggest that our ‘Trojan horse’ approach, based on the administration of statins plus a LDL receptor-targeted liposomal drug, might have potential applications in the pharmacological therapy of different brain diseases for which the BBB represents an obstacle.
British Journal of Pharmacology 07/2012; 167(7). DOI:10.1111/j.1476-5381.2012.02103.x · 4.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Invasive micropapillary carcinoma (IMPC) of the breast is a distinct and aggressive variant of luminal type B breast cancer that does not respond to neoadjuvant chemotherapy. It is characterized by small pseudopapillary clusters of cancer cells with inverted cell polarity. To investigate whether hypoxia-inducible factor-1 (HIF-1) activation may be related to the drug resistance described in this tumor, we used MCF7 cancer cells cultured as 3-D spheroids, which morphologically simulate IMPC cell clusters.
HIF-1 activation was measured by EMSA and ELISA in MCF7 3-D spheroids and MCF7 monolayers. Binding of HIF-1α to MDR-1 gene promoter and modulation of P-glycoprotein (Pgp) expression was evaluated by ChIP assay and FACS analysis, respectively. Intracellular doxorubicin retention was measured by spectrofluorimetric assay and drug cytotoxicity by annexin V-FITC measurement and caspase activity assay.
In MCF7 3-D spheroids HIF-1 was activated and recruited to participate to the transcriptional activity of MDR-1 gene, coding for Pgp. In addition, Pgp expression on the surface of cells obtained from 3-D spheroids was increased. MCF7 3-D spheroids accumulate less doxorubicin and are less sensitive to its cytotoxic effects than MCF7 cells cultured as monolayer. Finally, HIF-1α inhibition either by incubating cells with 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (a widely used HIF-1α inhibitor) or by transfecting cells with specific siRNA for HIF-1α significantly decreased the expression of Pgp on the surface of cells and increased the intracellular doxorubicin accumulation in MCF7 3-D spheroids.
MCF7 breast cancer cells cultured as 3-D spheroids are resistant to doxorubicin and this resistance is associated with an increased Pgp expression in the plasma membrane via activation of HIF-1. The same mechanism may be suggested for IMPC drug resistance.
BMC Cancer 01/2012; 12(1):4. DOI:10.1186/1471-2407-12-4 · 3.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Asbestos is a naturally occurring fibrous silicate, whose inhalation is highly related to the risk of developing malignant mesothelioma (MM), and crocidolite is one of its most oncogenic types. The mechanism by which asbestos may cause MM is unclear. We have previously observed that crocidolite in human MM (HMM) cells induces NF-κB activation and stimulates the synthesis of nitric oxide by inhibiting the RhoA signaling pathway. In primary human mesothelial cells (HMCs) and HMM cells exposed to crocidolite asbestos, coincubated or not with antioxidants, we evaluated cytotoxicity and oxidative stress induction (lipid peroxidation) and the effect of asbestos on the RhoA signaling pathway (RhoA GTP binding, Rho kinase activity, RhoA prenylation, hydroxy-3-methylglutharyl-CoA reductase activity). In this paper we show that the reactive oxygen species generated by the incubation of crocidolite with primary HMCs and three HMM cell lines mediate the inhibition of 3-hydroxy-3-methylglutharyl-CoA reductase (HMGCR). The coincubation of HMCs and HMM cells with crocidolite together with antioxidants, such as Tempol, Mn-porphyrin, and the association of superoxide dismutase and catalase, prevented the cytotoxicity and lipoperoxidation caused by crocidolite alone as well as the decrease of HMGCR activity and restored the RhoA/RhoA-dependent kinase activity and the RhoA prenylation. The same effect was observed when the oxidizing agent menadione was administrated to the cells in place of crocidolite. Such a mechanism could at least partly explain the effects exerted by crocidolite fibers in mesothelial cells.
American Journal of Respiratory Cell and Molecular Biology 09/2011; 45(3):625-31. DOI:10.1165/rcmb.2010-0089OC · 4.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Vγ9Vδ2 T cells play a major role as effector cells of innate immune responses against microbes, stressed cells, and tumor cells. They constitute <5% of PBLs but can be expanded by zoledronic acid (ZA)-treated monocytes or dendritic cells (DC). Much less is known about their ability to act as cellular adjuvants bridging innate and adaptive immunity, especially in patients with cancer. We have addressed this issue in multiple myeloma (MM), a prototypic disease with several immune dysfunctions that also affect γδ T cells and DC. ZA-treated MM DC were highly effective in activating autologous γδ T cells, even in patients refractory to stimulation with ZA-treated monocytes. ZA inhibited the mevalonate pathway of MM DC and induced the intracellular accumulation and release into the supernatant of isopentenyl pyrophosphate, a selective γδ T cell activator, in sufficient amounts to induce the proliferation of γδ T cells. Immune responses against the tumor-associated Ag survivin (SRV) by MHC-restricted, SRV-specific CD8(+) αβ T cells were amplified by the concurrent activation of γδ T cells driven by autologous DC copulsed with ZA and SRV-derived peptides. Ancillary to the isopentenyl pyrophosphate-induced γδ T cell proliferation was the mevalonate-independent ZA ability to directly antagonize regulatory T cells and downregulate PD-L2 expression on the DC cell surface. In conclusion, ZA has multiple immune modulatory activities that allow MM DC to effectively handle the concurrent activation of γδ T cells and MHC-restricted CD8(+) αβ antitumor effector T cells.
The Journal of Immunology 08/2011; 187(4):1578-90. DOI:10.4049/jimmunol.1002514 · 5.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The widely used anticholesterolemic drugs statins decrease the synthesis of cholesterol and the isoprenylation and activity of small G-proteins such as Ras and Rho, the effectors of which are often critical in cell proliferation. Thanks to this property, it has been hypothesized that statins may have anti-tumor activities. We investigated this issue in BALB-neuT mice, which developed Her2/neu-positive mammary cancers with 100% penetrance, and in TUBO cells, a cell line established from these tumors. Contrary to the mammary glands of BALB/c mice, the tumor tissue from BALB-neuT animals had constitutively activated Ras and ERK1/2. These were reduced by the oral administration of atorvastatin, but the statin did not prevent tumor growth in mice nor reduce the proliferation of TUBO cells, although it lowered the activity of mevalonate pathway and Ras/ERK1/2 signaling. By decreasing the mevalonate pathway-derived metabolite geranylgeranyl pyrophosphate and the RhoA/RhoA kinase signaling, atorvastatin activated NF-κB, that sustained cell proliferation. Unexpectedly Her2-positive cells were much more sensitive to the inhibition of RhoA-dependent pathways than to the suppression of Ras-dependent pathways elicited by atorvastatin. Only the simultaneous inhibition of RhoA/RhoA-kinase/NF-κB and Ras/ERK1/2 signaling allowed the statin to decrease tumor cell proliferation. Our study demonstrates that Her2-positive mammary cancers have redundant signals to sustain their proliferation and shows that statins simultaneously reduce the pro-proliferative Ras/ERK1/2 axis and activate the pro-proliferative RhoA/RhoA-kinase/NF-κB axis. The latter event dissipates the antitumor efficacy that may arise from the former one. Only the association of statins and NF-κB-targeted therapies efficiently decreased proliferation of tumor cells.
[Show abstract][Hide abstract] ABSTRACT: The anticancer drug doxorubicin induces the synthesis of nitric oxide, a small molecule that enhances the drug cytotoxicity and reduces the drug efflux through the membrane pump P-glycoprotein (Pgp). Doxorubicin also induces the translocation on the plasma membrane of the protein calreticulin (CRT), which allows tumour cells to be phagocytized by dendritic cells. We have shown that doxorubicin elicits nitric oxide synthesis and CRT exposure only in drug-sensitive cells, not in drug-resistant ones, which are indeed chemo-immunoresistant. In this work, we investigate the mechanisms by which nitric oxide induces the translocation of CRT and the molecular basis of this chemo-immunoresistance. In the drug-sensitive colon cancer HT29 cells doxorubicin increased nitric oxide synthesis, CRT exposure and cells phagocytosis. Nitric oxide promoted the translocation of CRT in a guanosine monophosphate (cGMP) and actin cytoskeleton-dependent way. CRT translocation did not occur in drug-resistant HT29-dx cells, where the doxorubicin-induced nitric oxide synthesis was absent. By increasing nitric oxide with stimuli other than doxorubicin, the CRT exposure was obtained also in HT29-dx cells. Although in sensitive cells the CRT translocation was followed by the phagocytosis, in drug-resistant cells the phagocytosis did not occur despite the CRT exposure. In HT29-dx cells CRT was bound to Pgp and only by silencing the latter the CRT-operated phagocytosis was restored, suggesting that Pgp impairs the functional activity of CRT and the tumour cells phagocytosis. Our work suggests that the levels of nitric oxide and Pgp critically modulate the recognition of the tumour cells by dendritic cells, and proposes a new potential therapeutic approach against chemo-immunoresistant tumours.
Journal of Cellular and Molecular Medicine 07/2011; 15(7):1492-504. DOI:10.1111/j.1582-4934.2010.01137.x · 3.70 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: How anti-neoplastic agents induce MDR (multidrug resistance) in cancer cells and the role of GSH (glutathione) in the activation of pumps such as the MRPs (MDR-associated proteins) are still open questions. In the present paper we illustrate that a doxorubicin-resistant human colon cancer cell line (HT29-DX), exhibiting decreased doxorubicin accumulation, increased intracellular GSH content, and increased MRP1 and MRP2 expression in comparison with doxorubicin-sensitive HT29 cells, shows increased activity of the PPP (pentose phosphate pathway) and of G6PD (glucose-6-phosphate dehydrogenase). We observed the onset of MDR in HT29 cells overexpressing G6PD which was accompanied by an increase in GSH. The G6PD inhibitors DHEA (dehydroepiandrosterone) and 6-AN (6-aminonicotinamide) reversed the increase of G6PD and GSH and inhibited MDR both in HT29-DX cells and in HT29 cells overexpressing G6PD. In our opinion, these results suggest that the activation of the PPP and an increased activity of G6PD are necessary to some MDR cells to keep the GSH content high, which is in turn necessary to extrude anticancer drugs out of the cell. We think that our data provide a new further mechanism for GSH increase and its effects on MDR acquisition.
[Show abstract][Hide abstract] ABSTRACT: The most frequent drawback of doxorubicin is the onset of drug resistance, due to the active efflux through P-glycoprotein (Pgp). Recently formulations of liposome-encapsulated doxorubicin have been approved for the treatment of tumors resistant to conventional anticancer drugs, but the molecular basis of their efficacy is not known. To clarify by which mechanisms the liposome-encapsulated doxorubicin is effective in drug-resistant cancer cells, we analyzed the effects of doxorubicin and doxorubicin-containing anionic liposomal nanoparticles ("Lipodox") on the drug-sensitive human colon cancer HT29 cells and on the drug-resistant HT29-dx cells. Interestingly, we did not detect any difference in drug accumulation and toxicity between free doxorubicin and Lipodox in HT29 cells, but Lipodox was significantly more effective than doxorubicin in HT29-dx cells, which are rich in Pgp. This effect was lost in HT29-dx cells silenced for Pgp and acquired by HT29 cells overexpressing Pgp. Lipodox was less extruded by Pgp than doxorubicin and inhibited the pump activity. This inhibition was due to a double effect: the liposome shell per se altered the composition of rafts in resistant cells and decreased the lipid raft-associated amount of Pgp, and the doxorubicin-loaded liposomes directly impaired transport and ATPase activity of Pgp. The efficacy of Lipodox was not increased by verapamil and cyclosporin A and was underwent interference by colchicine. Binding assays revealed that Lipodox competed with verapamil for binding Pgp and hampered the interaction of colchicine with this transporter. Site-directed mutagenesis experiments demonstrated that glycine 185 is a critical residue for the direct inhibitory effect of Lipodox on Pgp. Our work describes novel properties of liposomal doxorubicin, investigating the molecular bases that make this formulation an inhibitor of Pgp activity and a vehicle particularly indicated against drug-resistant tumors.
[Show abstract][Hide abstract] ABSTRACT: Products 4 and 5, obtained by conjugation of doxorubicin with nitric oxide (NO) donor nitrooxy and phenylsulfonyl furoxan moieties, respectively, accumulate in doxorubicin-resistant human colon cancer cells (HT29-dx), inducing high cytotoxicity. This behavior parallels the ability of the compounds to generate NO, detected as nitrite, in these cells. Preliminary immunoblotting studies suggest that the mechanism that underlies the cytotoxic effect could involve inhibition of cellular drug efflux due to nitration of tyrosine residues of the MRP3 protein pump.Keywords: Multidrug resistance; doxorubicin; nitric oxide; P-glycoprotein
[Show abstract][Hide abstract] ABSTRACT: Tumor cells in chronic lymphocytic leukemia (CLL) are more prone to apoptosis when cultured ex vivo, because they lack prosurvival signals furnished in vivo via B-cell receptor (BCR)-dependent and -independent pathways. This study compared the susceptibility of unmutated (UM) and mutated (M) CLL B cells to spontaneous apoptosis and prosurvival signals. UM CLL B cells showed a significantly higher rate of spontaneous apoptosis than M CLL B cells. Nuclear factor-kB (NF-kB) was rapidly inactivated, and B-cell leukemia/lymphoma 2 (Bcl-2) expression progressively down-regulated in the UM CLL B cells. CD40-Ligand, interleukin-4 and stromal cells significantly improved their viability and partially recovered Bcl-2, but not NF-kB expression. Peripheral blood mononuclear cells also offered protection of UM CLL B cells, and recovered both NF-kB and Bcl-2 expression. T cells, rather than nurse-like cells, were responsible for protecting UM CLL B cells by means of cell-to-cell contact and soluble factors. Despite their more aggressive features, UM CLL B cells are more susceptible to spontaneous apoptosis and depend from environmental prosurvival signals. This vulnerability of UM CLL B cells can be exploited as a selective target of therapeutic interventions.
Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 03/2011; 25(5):828-37. DOI:10.1038/leu.2011.12 · 9.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cardioactive glycosides, like digoxin, ouabain and related compounds, are drugs that inhibit Na(+)/K(+)-ATPase and have a strong inotropic effect on heart: they cause the Na(+)/Ca(2+) exchanger to extrude Na+ in exchange with Ca(2+) and therefore increase the [Ca(2+)](i) concentration. For this reason, some of these drugs are currently used in the treatment of congestive heart failure and cardiac arrhythmias. Recently it has been discovered that cardiac glycosides exert pleiotropic effects on many aspects of cell metabolism. Na(+)/K(+)-ATPase is not the exclusive target, as they affect the cell response to hypoxia, modulate several signaling pathways involved in cell death and proliferation, regulate the transcription of different genes and modify the pharmacokinetics of other drugs, by altering the expression and activity of drug-metabolizing enzymes. Some of these effects are related to the steroid structure of glycosides, a property which also makes them fine modulators of the synthesis of cholesterol and steroid hormones. Moreover, new endogenously synthesized glycosides have been discovered in the last years: these molecules are involved in the balance of salt and in the control of blood pressure. This review will focus on the recent studies which have demonstrated that exogenous and endogenous glycosides, besides playing a role as inotropic agents, are also important in the pathogenesis and therapy of different human diseases, such as stroke, diabetes, neurological diseases and cancer.
Current Medicinal Chemistry 02/2011; 18(6):872-85. DOI:10.2174/092986711794927685 · 3.85 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Doxorubicin is one of the most employed anticancer drugs, but its efficacy is limited by the onset of adverse effects such as drug resistance, due to the drug efflux via P-glycoprotein (Pgp). Several factors are associated to a high Pgp activity, including the amount of cholesterol in plasma membrane, which is essential to maintain the pump function. In this work we started from the following observations: 1) the drug-resistant colon cancer HT29-dx cells had a higher content of cholesterol in plasma membrane than drug-sensitive HT29 cells and a higher activity of Pgp, which was decreased by the cholesterol-lowering agent β-methyl-cyclodextrin; 2) HT29-dx cells showed a higher synthesis of endogenous cholesterol and a higher expression of the low-density lipoprotein receptor (LDLR); 3) the anti-cholesterolemic drug simvastatin reduced the cholesterol synthesis, increased the synthesis of LDLR and lowered the Pgp activity in resistant cells. In order to circumvent drug resistance we designed a new liposomal doxorubicin, conjugated with a recombinant LDLR-binding peptide from human apoB100: this LDL-masked doxorubicin ("apo-Lipodox") was efficiently internalized by a LDLR-driven endocytosis and induced cytotoxic effects in HT29-dx cells, reversing their drug resistance. Its efficacy was further increased by simvastatin, which up-regulates the LDLR levels and contemporarily reduces the Pgp activity, thus increasing the liposomes uptake and limiting the drug efflux. We propose that the association of liposomal doxorubicin and statins may be a future promising strategy to reverse drug-resistance in human cancer cells.