51
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Improved paramagnetic liposomes for MRI visualization of pH triggered release. J Control Release 2011; 154:196-202. [PMID: 21621569 DOI: 10.1016/j.jconrel.2011.05.017] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2010] [Revised: 05/12/2011] [Accepted: 05/16/2011] [Indexed: 11/20/2022]
Abstract
This work aims at assessing the in vitro potential of paramagnetic pH sensitive liposomes as imaging tools for visualizing drug-delivery and release processes by Magnetic Resonance Imaging (MRI). pH sensitive liposomes (pSLs) were formulated using the fusogenic phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), the membrane stabilizer D-α-tocopherol-hemisuccinate (THS), and were loaded with several paramagnetic complexes including the clinically approved Gadoteridol (marketed as ProHance™). The proposed formulation allows the fast and full release of Gadoteridol at pH 5.5. The leakage of the imaging reporter from the vesicles was associated with a relaxivity enhancement that allowed its visualization by MRI. It was observed that the release mechanism implies the protonation of the THS basic sites that leads to vesicle aggregation, thus enabling the expression of the fusogenic property of POPE. Attempts for improving the MRI properties of pSLs were pursued through the encapsulation of imaging agents with higher relaxivity than Gadoteridol, but it was observed that the release kinetic can be significantly affected by the probe size. Aiming at preparing stealth pSLs, PEG chains were conjugated to the external surface of the vesicles via cleavable disulphide bridges. Such nanomedicines do not release their content at acidic pH as long as the coating polymer is not removed from the surface. The results obtained suggest that the liposomal formulation investigated in this work has the potential for visualizing drug-delivery and release processes by in vivo MRI preclinical studies.
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52
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Lammers T, Subr V, Ulbrich K, Peschke P, Huber PE, Hennink WE, Storm G, Kiessling F. HPMA-based polymer therapeutics improve the efficacy of surgery, of radiotherapy and of chemotherapy combinations. Nanomedicine (Lond) 2011; 5:1501-23. [PMID: 21143030 DOI: 10.2217/nnm.10.130] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
To assist intravenously administered anticancer agents in achieving proper circulation times and tumor concentrations, and to thereby improve the balance between their efficacy and their toxicity, a large number of drug delivery systems have been designed and evaluated over the years. Clinically relevant examples of such nanometer-sized carrier materials are liposomes, polymers, micelles and antibodies. In the vast majority of cases, however, and especially in patients, nanomedicine formulations are only able to attenuate the toxicity of the conjugated or entrapped chemotherapeutic drug, and they generally fail to improve the efficacy of the intervention. To overcome this shortcoming, and to broaden the clinical applicability of tumor-targeted nanomedicines, in the past 5 years we have developed several concepts for using N-(2-hydroxypropyl)methacrylamide (HPMA)-based polymer therapeutics to enhance the efficacy of combined modality anticancer therapy. Regarding surgery, HPMA copolymers were shown to be able to improve the retention of intratumorally administered chemotherapeutic agents at the pathological site, and to thereby increase their therapeutic index. Regarding radiotherapy, a synergistic interaction was observed, with radiotherapy improving the tumor accumulation of the copolymers, and with copolymers improving both the efficacy and the tolerability of radiochemotherapy. Futhermore, regarding chemotherapy combinations, we have for the first time provided in vivo evidence showing that passively tumor-targeted polymeric drug carriers can be used to deliver two different drugs to tumors simultaneously. Based on these findings, and on the fact that the concepts developed are considered to be broadly applicable, we conclude that nanomedicine formulations are highly suitable systems for improving the efficacy of combined modality anticancer therapy.
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Affiliation(s)
- Twan Lammers
- Department of Experimental Molecular Imaging, RWTH-Aachen University, Pauwelsstrasse 30, 52074 Aachen, Germany.
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53
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Dinosaurs and ancient civilizations: reflections on the treatment of cancer. Neoplasia 2011; 12:957-68. [PMID: 21170260 DOI: 10.1593/neo.101588] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 11/15/2010] [Accepted: 11/15/2010] [Indexed: 12/14/2022] Open
Abstract
Research efforts in the area of palaeopathology have been seen as an avenue to improve our understanding of the pathogenesis of cancer. Answers to questions of whether dinosaurs had cancer, or if cancer plagued ancient civilizations, have captured the imagination as well as the popular media. Evidence for dinosaurian cancer may indicate that cancer may have been with us from the dawn of time. Ancient recorded history suggests that past civilizations attempted to fight cancer with a variety of interventions. When contemplating the issue why a generalized cure for cancer has not been found, it might prove useful to reflect on the relatively limited time that this issue has been an agenda item of governmental attention as well as continued introduction of an every evolving myriad of manmade carcinogens relative to the total time cancer has been present on planet Earth. This article reflects on the history of cancer and the progress made following the initiation of the "era of cancer chemotherapy."
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54
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Chemotherapy with hybrid liposomes for acute lymphatic leukemia leading to apoptosis in vivo. Int J Pharm 2011; 406:173-8. [DOI: 10.1016/j.ijpharm.2010.12.041] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Revised: 12/15/2010] [Accepted: 12/31/2010] [Indexed: 11/18/2022]
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55
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Hiscox S, Barrett-Lee P, Nicholson RI. Therapeutic targeting of tumor-stroma interactions. Expert Opin Ther Targets 2011; 15:609-21. [PMID: 21388336 DOI: 10.1517/14728222.2011.561201] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
INTRODUCTION Cancers exist within a complex microenvironment populated by diverse cell types within a protein-rich extracellular matrix. It is becoming increasingly apparent that molecular interactions between epithelial cells and cells in the surrounding stroma promote growth, invasion and spread of the tumor itself and thus represents a crucial underlying driving force in tumorigenesis. AREAS COVERED This article reviews how key interactions between tumor epithelial cells and surrounding mesenchymal and immune cells can promote tumor progression and highlights molecular elements that might represent novel therapeutic targets. EXPERT OPINION The tumor microenvironment is increasingly being viewed as a potential therapeutic target with a number of strategies being developed to disrupt tumor-stroma interactions, in order to delay or circumvent tumor progression. Targeting elements of the tumor microenvironment, or signaling pathways in tumor cells activated as a consequence of stromal interactions, may prove a useful therapeutic strategy to prevent tumor development and progression. However, given the tumor cells' ability to circumvent various therapeutic agents when given as monotherapy, the success of these agents is likely to be seen when used in combination with existing treatments.
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Affiliation(s)
- Stephen Hiscox
- Cardiff University, Welsh School of Pharmacy, Cardiff, UK.
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56
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Abstract
Abdominal aortic aneurysms (AAA) affect 5% of the population in developed countries and are characterized by progressive aortic dilatation with an unpredictable time course. This condition is more common in men than in women, and in smokers than in nonsmokers. If left untreated, AAA can result in aortic rupture and death. Pathologically, aortic extracellular matrix degradation, inflammation, and neovascularization are hallmarks of AAA. Diagnosis of AAA and subsequent surveillance utilize established aortic imaging methods, such as ultrasound, CT, and MRI. More-speculative diagnostic approaches include molecular and cellular imaging methods that interrogate the underlying pathological processes at work within the aneurysm. In this Review, we explore the current diagnostic and therapeutic strategies for the management of AAA. We also describe the diagnostic potential of new imaging techniques and therapeutic potential of new treatments for the management of small AAA.
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57
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Weigert A, Sekar D, Brüne B. Tumor-associated macrophages as targets for tumor immunotherapy. Immunotherapy 2011; 1:83-95. [PMID: 20635976 DOI: 10.2217/1750743x.1.1.83] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Restoration of one of the major physiological functions of the body's immune response, the rejection of malignant cells, is a promising yet challenging task for cancer therapy. Prinicipally, immunotherapeutic approaches make use of cells of the adaptive immune system, since antigen-based tumor rejection might be the most specific approach. However, other immune cell populations, such as tumor-associated macrophages (TAMs), contribute significantly to protumor mechanisms elicited by a distorted immune response. In this review, we summarize the current knowledge about the pathology of TAMs and discuss potential therapeutic approaches to overcome TAM-mediated tumor promotion. Hereby, we focus on TAM phenotypes that were observed in the clinically relevant stages of cancer progression. The function of macrophages and other inflammatory cells in the onset of cancer has been discussed elsewhere.
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Affiliation(s)
- Andreas Weigert
- Goethe-University Frankfurt, Institute of Biochemistry I - Pathobiochemistry, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany
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58
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Kluza E, Heisen M, Schmid S, van der Schaft DWJ, Schiffelers RM, Storm G, ter Haar Romeny BM, Strijkers GJ, Nicolay K. Multi-parametric assessment of the anti-angiogenic effects of liposomal glucocorticoids. Angiogenesis 2011; 14:143-53. [PMID: 21225337 PMCID: PMC3102848 DOI: 10.1007/s10456-010-9198-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Accepted: 12/27/2010] [Indexed: 12/29/2022]
Abstract
Inflammation plays a prominent role in tumor growth. Anti-inflammatory drugs have therefore been proposed as anti-cancer therapeutics. In this study, we determined the anti-angiogenic activity of a single dose of liposomal prednisolone phosphate (PLP-L), by monitoring tumor vascular function and viability over a period of one week. C57BL/6 mice were inoculated subcutaneously with B16F10 melanoma cells. Six animals were PLP-L-treated and six served as control. Tumor tissue and vascular function were probed using MRI before and at three timepoints after treatment. DCE-MRI was used to determine K(trans), v(e), time-to-peak, initial slope and the fraction of non-enhancing pixels, complemented with immunohistochemistry. The apparent diffusion coefficient (ADC), T(2) and tumor size were assessed with MRI as well. PLP-L treatment resulted in smaller tumors and caused a significant drop in K(trans) 48 h post-treatment, which was maintained until one week after drug administration. However, this effect was not sufficient to significantly distinguish treated from non-treated animals. The therapy did not affect tumor tissue viability but did prevent the ADC decrease observed in the control group. No evidence for PLP-L-induced tumor vessel normalization was found on histology. Treatment with PLP-L altered tumor vascular function. This effect did not fully explain the tumor growth inhibition, suggesting a broader spectrum of PLP-L activities.
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Affiliation(s)
- Ewelina Kluza
- Department of Biomedical Engineering, Biomedical NMR, Eindhoven University of Technology, 2.03b N-laag, PO Box 513, 5600 MB, Eindhoven, The Netherlands.
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59
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Kluza E, Yeo SY, Schmid S, van der Schaft DWJ, Boekhoven RW, Schiffelers RM, Storm G, Strijkers GJ, Nicolay K. Anti-tumor activity of liposomal glucocorticoids: The relevance of liposome-mediated drug delivery, intratumoral localization and systemic activity. J Control Release 2010; 151:10-7. [PMID: 21130819 DOI: 10.1016/j.jconrel.2010.11.031] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Revised: 11/26/2010] [Accepted: 11/28/2010] [Indexed: 10/18/2022]
Abstract
Tumor-associated inflammation has been recognized as an important tumor growth propagator and, therefore, represents an attractive target for anti-cancer therapy. In the current study, inspired by recent findings on the anti-tumor activity of liposomal glucocorticoids, we introduce paramagnetic and fluorescent liposomes, encapsulating prednisolone phosphate (PLP), to evaluate the local delivery of liposomal glucocorticoids to the tumor and its importance for the therapeutic response. The new multifunctional liposomes (Gd-PLP-L) (120nm diameter, 5.8mg PLP/60μmol lipid, bioexponential blood-clearance kinetics (T(1/2α)=2.4±0.5h, T(1/2β)=42.0±12.4h), drug leakage of 15%/72h (in vitro)), containing 25mol% Gd-DTPA-lipid and 0.1mol% of rhodamine-lipid, were tested in B16F10 melanoma subcutaneously inoculated in C57BL/6 mice, and compared to the original PLP formulation (PLP-L). A single dose of Gd-PLP-L (20mgPLP/kg/week, i.v.) was found to significantly inhibit tumor growth compared to non-treated mice (P<0.05), similarly to PLP-L. The accumulation efficacy of the liposomal agent in the tumor was assessed with MRI, using the increase in the longitudinal relaxation rate (ΔR(1)) as a marker. Interestingly, large inter-tumor differences in ΔR(1) (0.009-0.063s(-1), 24h post-administration), corresponding to highly variable intratumoral Gd-PLP-L levels, did not correlate to the effectiveness of tumor growth inhibition. Uptake of liposomes by tumor-associated macrophages (TAM), determined by ex-vivo fluorescence microscopy, was limited to only 5% of the TAM population. Furthermore, the therapy did not lead to TAM depletion. Importantly, a 90% drop in white blood cell count both after Gd-PLP-L and PLP-L administration was observed. This depletion may reduce tumor infiltration of monocytes, which stimulate angiogenesis, and, thus, possibly co-contributes to the anti-tumor effects. In conclusion, MRI provides a powerful instrument to monitor the delivery of liposomal therapeutics to tumors and guided us to reveal that the activity of liposomal glucocorticoids is not limited to the tumor site only.
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Affiliation(s)
- Ewelina Kluza
- Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
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60
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Coimbra M, Banciu M, Fens MH, de Smet L, Cabaj M, Metselaar JM, Storm G, Schiffelers RM. Liposomal pravastatin inhibits tumor growth by targeting cancer-related inflammation. J Control Release 2010; 148:303-10. [DOI: 10.1016/j.jconrel.2010.09.011] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Accepted: 09/10/2010] [Indexed: 10/19/2022]
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61
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Lobatto ME, Fayad ZA, Silvera S, Vucic E, Calcagno C, Mani V, Dickson SD, Nicolay K, Banciu M, Schiffelers RM, Metselaar JM, van Bloois L, Wu HS, Fallon JT, Rudd JH, Fuster V, Fisher EA, Storm G, Mulder WJM. Multimodal clinical imaging to longitudinally assess a nanomedical anti-inflammatory treatment in experimental atherosclerosis. Mol Pharm 2010; 7:2020-9. [PMID: 21028895 DOI: 10.1021/mp100309y] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Atherosclerosis is an inflammatory disease causing great morbidity and mortality in the Western world. To increase the anti-inflammatory action and decrease adverse effects of glucocorticoids (PLP), a nanomedicinal liposomal formulation of this drug (L-PLP) was developed and intravenously applied at a dose of 15 mg/kg PLP to a rabbit model of atherosclerosis. Since atherosclerosis is a systemic disease, emerging imaging modalities for assessing atherosclerotic plaque are being developed. (18)F-Fluoro-deoxy-glucose positron emission tomography and dynamic contrast enhanced magnetic resonance imaging, methods commonly used in oncology, were applied to longitudinally assess therapeutic efficacy. Significant anti-inflammatory effects were observed as early as 2 days that lasted up to at least 7 days after administration of a single dose of L-PLP. No significant changes were found for the free PLP treated animals. These findings were corroborated by immunohistochemical analysis of macrophage density in the vessel wall. In conclusion, this study evaluates a powerful two-pronged strategy for efficient treatment of atherosclerosis that includes nanomedical therapy of atherosclerotic plaques and the application of noninvasive and clinically approved imaging techniques to monitor delivery and therapeutic responses. Importantly, we demonstrate unprecedented rapid anti-inflammatory effects in atherosclerotic lesions after the nanomedical therapy.
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Affiliation(s)
- Mark E Lobatto
- Translational and Molecular Imaging Institute and Imaging Science Laboratories, Mount Sinai School of Medicine, One Gustave L Levy Place, New York, New York 10029, United States
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62
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The War on Cancer rages on. Neoplasia 2010; 11:1252-63. [PMID: 20019833 DOI: 10.1593/neo.91866] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 11/03/2009] [Accepted: 11/03/2009] [Indexed: 02/08/2023] Open
Abstract
In 1971, the "War on Cancer" was launched by the US government to cure cancer by the 200-year anniversary of the founding of the United States of America, 1976. This article briefly looks back at the progress that has been made in cancer research and compares progress made in other areas of human affliction. While progress has indeed been made, the battle continues to rage on.
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63
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Shimoda S, Ichihara H, Matsumoto Y, Ueoka R. Chemotherapy with hybrid liposomes for human breast tumors along with apoptosis in vivo. Int J Pharm 2009; 372:162-8. [DOI: 10.1016/j.ijpharm.2009.01.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2008] [Revised: 01/09/2009] [Accepted: 01/10/2009] [Indexed: 11/25/2022]
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Neoplasia: the second decade. Neoplasia 2009; 10:1314-24. [PMID: 19048110 DOI: 10.1593/neo.81372] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Revised: 10/27/2008] [Accepted: 10/27/2008] [Indexed: 12/30/2022] Open
Abstract
This issue marks the end of the 10-year anniversary of Neoplasia where we have seen exciting growth in both number of submitted and published articles in Neoplasia. Neoplasia was first published in 1999. During the past 10 years, Neoplasia has dynamically adapted to the needs of the cancer research community as technologies have advanced. Neoplasia is currently providing access to articles through PubMed Central to continue to facilitate rapid broad-based dissemination of published findings to the scientific community through an Open Access model. This has in part helped Neoplasia to achieve an improved impact factor this past year, demonstrating that the manuscripts published by Neoplasia are of great interest to the overall cancer research community. This past year, Neoplasia received a record number of articles for review and has had a 21% increase in the number of published articles.
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65
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Shimoda S, Ichihara H, Matsumoto Y, Ueoka R. Nanoparticles of Hybrid Liposomes for the Inhibition of Breast Tumor Growth along with Apoptosis. CHEM LETT 2009. [DOI: 10.1246/cl.2009.134] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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66
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Schiffelers RM, Storm G. Liposomal nanomedicines as anticancer therapeutics: beyond targeting tumor cells. Int J Pharm 2008; 364:258-64. [PMID: 18773947 DOI: 10.1016/j.ijpharm.2008.08.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2008] [Revised: 08/06/2008] [Accepted: 08/08/2008] [Indexed: 12/16/2022]
Abstract
Tumor cells have long been the primary target cell type of liposomes for anticancer therapy. At present, it appears that tumor growth and metastasis is facilitated by interactions between tumor cells and supporting cells. These supporting cells consist of adaptive and innate immune cells, endothelial cells, pericytes, fibroblasts, stromal and mesenchymal cells. Insight into the activity of these cells and communication between these cells has provided new tactics for targeting alternative cell types in tumor treatment and offered new drug classes that could be used to modulate the activity of these supporting cells. Here, we provide an overview of liposomal systems that have been designed to target supporting cells in tumor tissue and therapeutic results of these systems.
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Affiliation(s)
- Raymond M Schiffelers
- Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences, Department of Pharmaceutical Sciences, Faculty of Science, Utrecht University, Utrecht, The Netherlands.
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67
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Zhu J, Ji Z, Wang J, Sun R, Zhang X, Gao Y, Sun H, Liu Y, Wang Z, Li A, Ma J, Wang T, Jia G, Gu Y. Tumor-inhibitory effect and immunomodulatory activity of fullerol C60(OH)x. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2008; 4:1168-1175. [PMID: 18574800 DOI: 10.1002/smll.200701219] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The tumor-inhibitory effect of C60(OH)x was tested on the murine H22 hepatocarcinoma model. Doses of 0.2 and 1.0 mg kg(-1) body weight both showed significant antitumor activity with tumor inhibition rates of 31.9 and 38.4%, respectively, when mice were treated for 17 consecutive days. The damnification of liver was prominently reduced. Furthermore, histological examination indicated that an envelope of fibroblasts and lymphocytes was formed surrounding tumor tissues in the C60(OH)x-treated group, which inhibited the infiltration of tumor to the neighboring normal skeleton muscle tissues. To understand the antitumor mechanism, the immunomodulatory activity of C60(OH)x was investigated. The results indicate that C60(OH)x enhances the phagocytosis of peritoneal macrophages and elevates the activity of arginase and acid phosphatase in vivo. The tumor necrosis factor alpha production of C60(OH)x-treated macrophages also increases in vitro. These results suggest that C60(OH)x can enhance the innate immunity of tumor-bearing mice, and therefore inhibits growth of the tumor.
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Affiliation(s)
- Jiadan Zhu
- Beijing National Laboratory for Molecular Sciences, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P.R. China
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Investigation into the role of tumor-associated macrophages in the antitumor activity of Doxil. Pharm Res 2008; 25:1948-55. [PMID: 18523874 PMCID: PMC2469273 DOI: 10.1007/s11095-008-9629-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2008] [Accepted: 05/08/2008] [Indexed: 11/02/2022]
Abstract
PURPOSE Our recent studies show specific localization of long-circulating liposomes (LCL) within the endosomal/lysosomal compartment of tumor-associated macrophages (TAM). Based on this finding, the present study aims to investigate whether clinically applied LCL formulations such as Doxil (LCL-encapsulated doxorubicin), have alternative mechanisms of action additionally to direct drug-mediated cytotoxicity towards tumor cells. METHODS The antitumor activity of Doxil was evaluated in B16.F10 melanoma-bearing mice, in the presence and in the absence of TAM. To suppress TAM functions, liposomal clodronate (Lip-CLOD) was injected 24 h before the actual treatment. The effect of Doxil on the levels of angiogenic factors was determined using an angiogenic protein array. As positive control, the same experiments were conducted with LCL-encapsulated prednisolone phosphate (LCL-PLP), a tumor-targeted formulation with known strong anti-angiogenic/anti-inflammatory effects on TAM. RESULTS Our results show that the antitumor efficacy of Doxil was only partially attributed to the inhibition of TAM-mediated angiogenesis whereas LCL-PLP inhibited tumor growth through strong suppressive effects on pro-angiogenic functions of TAM. As described previously, the main mechanism of Doxil might be a cytotoxic effect on tumor cells. CONCLUSIONS Our findings suggest that the antitumor activity of Doxil does not depend mainly on the presence of functional TAM in tumors.
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