The role of immunosuppression of mesenchymal stem cells in tissue repair and tumor growth

Cell & Bioscience

Lixin Wei¹  Yufang Shi²  Yan Liu¹  Shanshan Zhang¹  Yingying Jing¹  Zhipeng Han¹ 

[1] Tumor Immunology and Gene Therapy Center, Eastern Hepatobiliary Surgery Hospital, the Second Military Medicial University, Shanghai, China;Institute of Health Sciences and Shanghai Institute of Immunology, Chinese Academy of Sciences and Shanghai Jiao Tong University School of Medicine, 225 South Chongqing Road, Shanghai, China

关键词: Tumor growth;    Immunosuppression;    Mesenchymal stem cells;   

Others  :  793598
DOI  :  10.1186/2045-3701-2-8

 received in 2011-11-29, accepted in 2012-03-05,  发布年份 2012

【 摘 要 】

Mesenchymal stem cells (MSCs) have acquired great interests for their potential use in the clinical therapy of many diseases because of their functions including multiple lineage differentiation, low immunogenicity and immunosuppression. Many studies suggest that MSCs are strongly immunosuppressive in vitro and in vivo. MSCs exert a profound inhibitory effect on the proliferation of T cells, B cells, dendritic cells and natural killer cells. In addition, several soluble factors have been reported to involved in the immunosuppressive effects by MSCs such as TGF-β, HGF, PGE2, IDO and iNOS. These results suggest that MSCs can be used in the therapy of immune disorder diseases, prevention of organ transplantation rejection and tissue injury. In recent study, we demonstrated that MSCs in tumor inflammatory microenvironment might be elicited of immunosuppressive function. Thus, the application of MSCs in cancer therapy might have negative effect by helping tumor cells escaping from the immune surveillance.

【 授权许可】

   
2012 Han et al; licensee BioMed Central Ltd.

【 图 表 】

Figure 1.

Figure 2.

【 参考文献 】

• [1]Deans RJ, Moseley AB: Mesenchymal stem cells: biology and potential clinical uses. Exp Hematol 2000, 28(8):875-884.
• [2]Bianco P, Gehron Robey P: Marrow stromal stem cells. J Clin Invest 2000, 105(12):1663-1668.
• [3]Friedenstein AJ, Gorskaja JF, Kulagina NN: Fibroblast precursors in normal and irradiated mouse hematopoietic organs. Exp Hematol 1976, 4(5):267-274.
• [4]Bianco P, Robey PG, Simmons PJ: Mesenchymal stem cells: revisiting history, concepts, and assays. Cell Stem Cell 2008, 2(4):313-319.
• [5]Pittenger MF, Mackay AM, Beck SC, Jaiswal RK, Douglas R, Mosca JD, Moorman MA, Simonetti DW, Craig S, Marshak DR: Multilineage potential of adult human mesenchymal stem cells. Science 1999, 284(5411):143-147.
• [6]Anjos-Afonso F, Bonnet D: Nonhematopoietic/endothelial SSEA-1+ cells define the most primitive progenitors in the adult murine bone marrow mesenchymal compartment. Blood 2007, 109(3):1298-1306.
• [7]In 't Anker PS, Scherjon SA, Kleijburg-van der Keur C, de Groot-Swings GM, Claas FH, Fibbe WE, Kanhai HH: Isolation of mesenchymal stem cells of fetal or maternal origin from human placenta. Stem Cells 2004, 22(7):1338-1345.
• [8]Zuk PA, Zhu M, Mizuno H, Huang J, Futrell JW, Katz AJ, Benhaim P, Lorenz HP, Hedrick MH: Multilineage cells from human adipose tissue: implications for cell-based therapies. Tissue Eng 2001, 7(2):211-228.
• [9]Barry FP, Murphy JM: Mesenchymal stem cells: clinical applications and biological characterization. Int J Biochem Cell Biol 2004, 36(4):568-584.
• [10]Noel D, Djouad F, Jorgense C: Regenerative medicine through mesenchymal stem cells for bone and cartilage repair. Curr Opin Investig Drugs 2002, 3(7):1000-1004.
• [11]Tang SJ, Ho MY, Cho HC, Lin YC, Sun GH, Chi KH, Wang YS, Jhou RS, Yang W, Sun KH: Phosphoglycerate kinase 1-overexpressing lung cancer cells reduce cyclooxygenase 2 expression and promote anti-tumor immunity in vivo. Int J Cancer 2008, 123(12):2840-2848.
• [12]Moreno M, Molling JW, von Mensdorff-Pouilly S, Verheijen RH, Hooijberg E, Kramer D, Reurs AW, van den Eertwegh AJ, von Blomberg BM, Scheper RJ, Bontkes HJ: IFN-gamma-producing human invariant NKT cells promote tumor-associated antigen-specific cytotoxic T cell responses. J Immunol 2008, 181(4):2446-2454.
• [13]Muller-Hermelink N, Braumuller H, Pichler B, Wieder T, Mailhammer R, Schaak K, Ghoreschi K, Yazdi A, Haubner R, Sander CA, Mocikat R, Schwaiger M, Forster I, Huss R, Weber WA, Kneilling M, Rocken M: TNFR1 signaling and IFN-gamma signaling determine whether T cells induce tumor dormancy or promote multistage carcinogenesis. Cancer Cell 2008, 13(6):507-518.
• [14]Eriksson F, Culp WD, Massey R, Egevad L, Garland D, Persson MA, Pisa P: Tumor specific phage particles promote tumor regression in a mouse melanoma model. Cancer Immunol Immunother 2007, 56(5):677-687.
• [15]Caplan AI: Mesenchymal stem cells and gene therapy. Clin Orthop Relat Res 2000, (379 Suppl):S67-70.
• [16]Horwitz EM, Prockop DJ, Fitzpatrick LA, Koo WW, Gordon PL, Neel M, Sussman M, Orchard P, Marx JC, Pyeritz RE, Brenner MK: Transplantability and therapeutic effects of bone marrow-derived mesenchymal cells in children with osteogenesis imperfecta. Nat Med 1999, 5(3):309-313.
• [17]Reya T, Morrison SJ, Clarke MF, Weissman IL: Stem cells, cancer, and cancer stem cells. Nature 2001, 414(6859):105-111.
• [18]Sell S: Stem cell origin of cancer and differentiation therapy. Crit Rev Oncol Hematol 2004, 51(1):1-28.
• [19]Hamada H, Kobune M, Nakamura K, Kawano Y, Kato K, Honmou O, Houkin K, Matsunaga T, Niitsu Y: Mesenchymal stem cells (MSC) as therapeutic cytoreagents for gene therapy. Cancer Sci 2005, 96(3):149-156.
• [20]Khakoo AY, Pati S, Anderson SA, Reid W, Elshal MF, Nguyen AT, Malide D, Combs CA, Hall G, Zhang J, Raffeld M, Rogers TB, Stetler-Stevenson W, Frank JA, Reitz M, Finkel T: Human mesenchymal stem cells exert potent antitumorigenic effects in a model of Kaposi's sarcoma. J Exp Med 2006, 203(5):1235-1247.
• [21]Singer NG, Caplan AI: Mesenchymal stem cells: mechanisms of inflammation. Annu Rev Pathol 6:457-478.
• [22]Di Nicola M, Carlo-Stella C, Magni M, Milanesi M, Longoni PD, Matteucci P, Grisanti S, Gianni AM: Human bone marrow stromal cells suppress T-lymphocyte proliferation induced by cellular or nonspecific mitogenic stimuli. Blood 2002, 99(10):3838-3843.
• [23]Zappia E, Casazza S, Pedemonte E, Benvenuto F, Bonanni I, Gerdoni E, Giunti D, Ceravolo A, Cazzanti F, Frassoni F, Mancardi G, Uccelli A: Mesenchymal stem cells ameliorate experimental autoimmune encephalomyelitis inducing T-cell anergy. Blood 2005, 106(5):1755-1761.
• [24]Krampera M, Glennie S, Dyson J, Scott D, Laylor R, Simpson E, Dazzi F: Bone marrow mesenchymal stem cells inhibit the response of naive and memory antigen-specific T cells to their cognate peptide. Blood 2003, 101(9):3722-3729.
• [25]Tse WT, Pendleton JD, Beyer WM, Egalka MC, Guinan EC: Suppression of allogeneic T-cell proliferation by human marrow stromal cells: implications in transplantation. Transplantation 2003, 75(3):389-397.
• [26]Potian JA, Aviv H, Ponzio NM, Harrison JS, Rameshwar P: Veto-like activity of mesenchymal stem cells: functional discrimination between cellular responses to alloantigens and recall antigens. J Immunol 2003, 171(7):3426-3434.
• [27]Fouillard L, Bensidhoum M, Bories D, Bonte H, Lopez M, Moseley AM, Smith A, Lesage S, Beaujean F, Thierry D, Gourmelon P, Najman A, Gorin NC: Engraftment of allogeneic mesenchymal stem cells in the bone marrow of a patient with severe idiopathic aplastic anemia improves stroma. Leukemia 2003, 17(2):474-476.
• [28]Aggarwal S, Pittenger MF: Human mesenchymal stem cells modulate allogeneic immune cell responses. Blood 2005, 105(4):1815-1822.
• [29]Maccario R, Podesta M, Moretta A, Cometa A, Comoli P, Montagna D, Daudt L, Ibatici A, Piaggio G, Pozzi S, Frassoni F, Locatelli F: Interaction of human mesenchymal stem cells with cells involved in alloantigen-specific immune response favors the differentiation of CD4+ T-cell subsets expressing a regulatory/suppressive phenotype. Haematologica 2005, 90(4):516-525.
• [30]Rasmusson I, Ringden O, Sundberg B, Le Blanc K: Mesenchymal stem cells inhibit the formation of cytotoxic T lymphocytes, but not activated cytotoxic T lymphocytes or natural killer cells. Transplantation 2003, 76(8):1208-1213.
• [31]Augello A, Tasso R, Negrini SM, Amateis A, Indiveri F, Cancedda R, Pennesi G: Bone marrow mesenchymal progenitor cells inhibit lymphocyte proliferation by activation of the programmed death 1 pathway. Eur J Immunol 2005, 35(5):1482-1490.
• [32]Djouad F, Plence P, Bony C, Tropel P, Apparailly F, Sany J, Noel D, Jorgensen C: Immunosuppressive effect of mesenchymal stem cells favors tumor growth in allogeneic animals. Blood 2003, 102(10):3837-3844.
• [33]Chabannes D, Hill M, Merieau E, Rossignol J, Brion R, Soulillou JP, Anegon I, Cuturi MC: A role for heme oxygenase-1 in the immunosuppressive effect of adult rat and human mesenchymal stem cells. Blood 2007, 110(10):3691-3694.
• [34]Jones BJ, Brooke G, Atkinson K, McTaggart SJ: Immunosuppression by placental indoleamine 2, 3-dioxygenase: a role for mesenchymal stem cells. Placenta 2007, 28(11-12):1174-1181.
• [35]Selmani Z, Naji A, Zidi I, Favier B, Gaiffe E, Obert L, Borg C, Saas P, Tiberghien P, Rouas-Freiss N, Carosella ED, Deschaseaux F: Human leukocyte antigen-G5 secretion by human mesenchymal stem cells is required to suppress T lymphocyte and natural killer function and to induce CD4+CD25highFOXP3+ regulatory T cells. Stem Cells 2008, 26(1):212-222.
• [36]Sato K, Ozaki K, Oh I, Meguro A, Hatanaka K, Nagai T, Muroi K, Ozawa K: Nitric oxide plays a critical role in suppression of T-cell proliferation by mesenchymal stem cells. Blood 2007, 109(1):228-234.
• [37]Tomchuck SL, Zwezdaryk KJ, Coffelt SB, Waterman RS, Danka ES, Scandurro AB: Toll-like receptors on human mesenchymal stem cells drive their migration and immunomodulating responses. Stem Cells 2008, 26(1):99-107.
• [38]Pevsner-Fischer M, Morad V, Cohen-Sfady M, Rousso-Noori L, Zanin-Zhorov A, Cohen S, Cohen IR, Zipori D: Toll-like receptors and their ligands control mesenchymal stem cell functions. Blood 2007, 109(4):1422-1432.
• [39]Nemeth K, Leelahavanichkul A, Yuen PS, Mayer B, Parmelee A, Doi K, Robey PG, Leelahavanichkul K, Koller BH, Brown JM, Hu X, Jelinek I, Star RA, Mezey E: Bone marrow stromal cells attenuate sepsis via prostaglandin E(2)-dependent reprogramming of host macrophages to increase their interleukin-10 production. Nat Med 2009, 15(1):42-49.
• [40]Deng W, Han Q, Liao L, You S, Deng H, Zhao RC: Effects of allogeneic bone marrow-derived mesenchymal stem cells on T and B lymphocytes from BXSB mice. DNA Cell Biol 2005, 24(7):458-463.
• [41]Corcione A, Benvenuto F, Ferretti E, Giunti D, Cappiello V, Cazzanti F, Risso M, Gualandi F, Mancardi GL, Pistoia V, Uccelli A: Human mesenchymal stem cells modulate B-cell functions. Blood 2006, 107(1):367-372.
• [42]Banchereau J, Steinman RM: Dendritic cells and the control of immunity. Nature 1998, 392(6673):245-252.
• [43]Mellman I, Steinman RM: Dendritic cells: specialized and regulated antigen processing machines. Cell 2001, 106(3):255-258.
• [44]Jiang XX, Zhang Y, Liu B, Zhang SX, Wu Y, Yu XD, Mao N: Human mesenchymal stem cells inhibit differentiation and function of monocyte-derived dendritic cells. Blood 2005, 105(10):4120-4126.
• [45]Zhang W, Ge W, Li C, You S, Liao L, Han Q, Deng W, Zhao RC: Effects of mesenchymal stem cells on differentiation, maturation, and function of human monocyte-derived dendritic cells. Stem Cells Dev 2004, 13(3):263-271.
• [46]Beyth S, Borovsky Z, Mevorach D, Liebergall M, Gazit Z, Aslan H, Galun E, Rachmilewitz J: Human mesenchymal stem cells alter antigen-presenting cell maturation and induce T-cell unresponsiveness. Blood 2005, 105(5):2214-2219.
• [47]Steinbrink K, Wolfl M, Jonuleit H, Knop J, Enk AH: Induction of tolerance by IL-10-treated dendritic cells. J Immunol 1997, 159(10):4772-4780.
• [48]Buelens C, Verhasselt V, De Groote D, Thielemans K, Goldman M, Willems F: Interleukin-10 prevents the generation of dendritic cells from human peripheral blood mononuclear cells cultured with interleukin-4 and granulocyte/macrophage-colony-stimulating factor. Eur J Immunol 1997, 27(3):756-762.
• [49]Ding L, Shevach EM: IL-10 inhibits mitogen-induced T cell proliferation by selectively inhibiting macrophage costimulatory function. J Immunol 1992, 148(10):3133-3139.
• [50]Chen L, Zhang W, Yue H, Han Q, Chen B, Shi M, Li J, Li B, You S, Shi Y, Zhao RC: Effects of human mesenchymal stem cells on the differentiation of dendritic cells from CD34+ cells. Stem Cells Dev 2007, 16(5):719-731.
• [51]Djouad F, Charbonnier LM, Bouffi C, Louis-Plence P, Bony C, Apparailly F, Cantos C, Jorgensen C, Noel D: Mesenchymal stem cells inhibit the differentiation of dendritic cells through an interleukin-6-dependent mechanism. Stem Cells 2007, 25(8):2025-2032.
• [52]Biron CA: Activation and function of natural killer cell responses during viral infections. Curr Opin Immunol 1997, 9(1):24-34.
• [53]Smyth MJ, Hayakawa Y, Takeda K, Yagita H: New aspects of natural-killer-cell surveillance and therapy of cancer. Nat Rev Cancer 2002, 2(11):850-861.
• [54]Spaggiari GM, Capobianco A, Abdelrazik H, Becchetti F, Mingari MC, Moretta L: Mesenchymal stem cells inhibit natural killer-cell proliferation, cytotoxicity, and cytokine production: role of indoleamine 2, 3-dioxygenase and prostaglandin E2. Blood 2008, 111(3):1327-1333.
• [55]Spaggiari GM, Capobianco A, Becchetti S, Mingari MC, Moretta L: Mesenchymal stem cell-natural killer cell interactions: evidence that activated NK cells are capable of killing MSCs, whereas MSCs can inhibit IL-2-induced NK-cell proliferation. Blood 2006, 107(4):1484-1490.
• [56]Sotiropoulou PA, Perez SA, Gritzapis AD, Baxevanis CN, Papamichail M: Interactions between human mesenchymal stem cells and natural killer cells. Stem Cells 2006, 24(1):74-85.
• [57]Meisel R, Zibert A, Laryea M, Gobel U, Daubener W, Dilloo D: Human bone marrow stromal cells inhibit allogeneic T-cell responses by indoleamine 2, 3-dioxygenase-mediated tryptophan degradation. Blood 2004, 103(12):4619-4621.
• [58]Le Blanc K, Frassoni F, Ball L, Locatelli F, Roelofs H, Lewis I, Lanino E, Sundberg B, Bernardo ME, Remberger M, Dini G, Egeler RM, Bacigalupo A, Fibbe W, Ringden O: Mesenchymal stem cells for treatment of steroid-resistant, severe, acute graft-versus-host disease: a phase II study. Lancet 2008, 371(9624):1579-1586.
• [59]Uccelli A, Moretta L, Pistoia V: Mesenchymal stem cells in health and disease. Nat Rev Immunol 2008, 8(9):726-736.
• [60]Bartholomew A, Sturgeon C, Siatskas M, Ferrer K, McIntosh K, Patil S, Hardy W, Devine S, Ucker D, Deans R, Moseley A, Hoffman R: Mesenchymal stem cells suppress lymphocyte proliferation in vitro and prolong skin graft survival in vivo. Exp Hematol 2002, 30(1):42-48.
• [61]Devine SM, Cobbs C, Jennings M, Bartholomew A, Hoffman R: Mesenchymal stem cells distribute to a wide range of tissues following systemic infusion into nonhuman primates. Blood 2003, 101(8):2999-3001.
• [62]Inoue S, Popp FC, Koehl GE, Piso P, Schlitt HJ, Geissler EK, Dahlke MH: Immunomodulatory effects of mesenchymal stem cells in a rat organ transplant model. Transplantation 2006, 81(11):1589-1595.
• [63]Nauta AJ, Westerhuis G, Kruisselbrink AB, Lurvink EG, Willemze R, Fibbe WE: Donor-derived mesenchymal stem cells are immunogenic in an allogeneic host and stimulate donor graft rejection in a nonmyeloablative setting. Blood 2006, 108(6):2114-2120.
• [64]Devadas S, Das J, Liu C, Zhang L, Roberts AI, Pan Z, Moore PA, Das G, Shi Y: Granzyme B is critical for T cell receptor-induced cell death of type 2 helper T cells. Immunity 2006, 25(2):237-247.
• [65]Radvanyi LG, Shi Y, Mills GB, Miller RG: Cell cycle progression out of G1 sensitizes primary-cultured nontransformed T cells to TCR-mediated apoptosis. Cell Immunol 1996, 170(2):260-273.
• [66]Ren G, Zhang L, Zhao X, Xu G, Zhang Y, Roberts AI, Zhao RC, Shi Y: Mesenchymal stem cell-mediated immunosuppression occurs via concerted action of chemokines and nitric oxide. Cell Stem Cell 2008, 2(2):141-150.
• [67]Le Blanc K, Rasmusson I, Sundberg B, Gotherstrom C, Hassan M, Uzunel M, Ringden O: Treatment of severe acute graft-versus-host disease with third party haploidentical mesenchymal stem cells. Lancet 2004, 363(9419):1439-1441.
• [68]Li H, Guo Z, Jiang X, Zhu H, Li X, Mao N: Mesenchymal stem cells alter migratory property of T and dendritic cells to delay the development of murine lethal acute graft-versus-host disease. Stem Cells 2008, 26(10):2531-2541.
• [69]Garcia-Olmo D, Garcia-Arranz M, Herreros D, Pascual I, Peiro C, Rodriguez-Montes JA: A phase I clinical trial of the treatment of Crohn's fistula by adipose mesenchymal stem cell transplantation. Dis Colon Rectum 2005, 48(7):1416-1423.
• [70]Casiraghi F, Azzollini N, Cassis P, Imberti B, Morigi M, Cugini D, Cavinato RA, Todeschini M, Solini S, Sonzogni A, Perico N, Remuzzi G, Noris M: Pretransplant infusion of mesenchymal stem cells prolongs the survival of a semiallogeneic heart transplant through the generation of regulatory T cells. J Immunol 2008, 181(6):3933-3946.
• [71]Lee JW, Fang X, Gupta N, Serikov V, Matthay MA: Allogeneic human mesenchymal stem cells for treatment of E. coli endotoxin-induced acute lung injury in the ex vivo perfused human lung. Proc Natl Acad Sci USA 2009, 106(38):16357-16362.
• [72]Kim JM, Lee ST, Chu K, Jung KH, Song EC, Kim SJ, Sinn DI, Kim JH, Park DK, Kang KM, Hyung Hong N, Park HK, Won CH, Kim KH, Kim M, Kun Lee S, Roh JK: Systemic transplantation of human adipose stem cells attenuated cerebral inflammation and degeneration in a hemorrhagic stroke model. Brain Res 2007, 1183:43-50.
• [73]Chen L, Tredget EE, Wu PY, Wu Y: Paracrine factors of mesenchymal stem cells recruit macrophages and endothelial lineage cells and enhance wound healing. PLoS One 2008, 3(4):e1886.
• [74]Ortiz LA, Gambelli F, McBride C, Gaupp D, Baddoo M, Kaminski N, Phinney DG: Mesenchymal stem cell engraftment in lung is enhanced in response to bleomycin exposure and ameliorates its fibrotic effects. Proc Natl Acad Sci USA 2003, 100(14):8407-8411.
• [75]Gnecchi M, He H, Liang OD, Melo LG, Morello F, Mu H, Noiseux N, Zhang L, Pratt RE, Ingwall JS, Dzau VJ: Paracrine action accounts for marked protection of ischemic heart by Akt-modified mesenchymal stem cells. Nat Med 2005, 11(4):367-368.
• [76]Hardjo M, Miyazaki M, Sakaguchi M, Masaka T, Ibrahim S, Kataoka K, Huh NH: Suppression of carbon tetrachloride-induced liver fibrosis by transplantation of a clonal mesenchymal stem cell line derived from rat bone marrow. Cell Transplant 2009, 18(1):89-99.
• [77]Kuo TK, Hung SP, Chuang CH, Chen CT, Shih YR, Fang SC, Yang VW, Lee OK: Stem cell therapy for liver disease: parameters governing the success of using bone marrow mesenchymal stem cells. Gastroenterology 2008, 134(7):2111-2121. 2121 e2111-2113
• [78]van Poll D, Parekkadan B, Cho CH, Berthiaume F, Nahmias Y, Tilles AW, Yarmush ML: Mesenchymal stem cell-derived molecules directly modulate hepatocellular death and regeneration in vitro and in vivo. Hepatology 2008, 47(5):1634-1643.
• [79]Karp JM, Leng Teo GS: Mesenchymal stem cell homing: the devil is in the details. Cell Stem Cell 2009, 4(3):206-216.
• [80]Chen FH, Tuan RS: Mesenchymal stem cells in arthritic diseases. Arthritis Res Ther 2008, 10(5):223. BioMed Central Full Text
• [81]Xu W, Zhang X, Qian H, Zhu W, Sun X, Hu J, Zhou H, Chen Y: Mesenchymal stem cells from adult human bone marrow differentiate into a cardiomyocyte phenotype in vitro. Exp Biol Med (Maywood) 2004, 229(7):623-631.
• [82]Rasmusson I, Ringden O, Sundberg B, Le Blanc K: Mesenchymal stem cells inhibit lymphocyte proliferation by mitogens and alloantigens by different mechanisms. Exp Cell Res 2005, 305(1):33-41.
• [83]Nakamizo A, Marini F, Amano T, Khan A, Studeny M, Gumin J, Chen J, Hentschel S, Vecil G, Dembinski J, Andreeff M, Lang FF: Human bone marrow-derived mesenchymal stem cells in the treatment of gliomas. Cancer Res 2005, 65(8):3307-3318.
• [84]Han Z, Tian Z, Lv G, Zhang L, Jiang G, Sun K, Wang C, Bu X, Li R, Shi Y, Wu M, Wei L: Immunosuppressive effect of bone marrow-derived mesenchymal stem cells in inflammatory microenvironment favours the growth of B16 melanoma cells. J Cell Mol Med 2011, 15(11):2343-2352.
• [85]Hall BM, Fortney JE, Taylor L, Wood H, Wang L, Adams S, Davis S, Gibson LF: Stromal cells expressing elevated VCAM-1 enhance survival of B lineage tumor cells. Cancer Lett 2004, 207(2):229-239.