Leukemia (1999) 13, 653–663 1999 Stockton Press All rights reserved 0887-6924/99 $12.00 http://www.stockton-press.co.uk/leu REVIEW Dendritic cell-based vaccine: a promising approach for cancer immunotherapy K Tarte1 and B Klein1,2 1INSERM U 475, Montpellier; and 2Unit For Cellular Therapy, CHU Saint Eloi, Montpellier, France The unique ability of dendritic cells to pick up antigens and to + + and interstitial DC pick up antigens (Ag) in peripheral tissues activate naive and memory CD4 and CD8 T cells raised the and migrate to lymphoid organs through lymphatic vessels in possibility of using them to trigger a specific anti-tumor 8 immunity. If numerous studies have shown a major interest in response to inflammatory stimuli. Activated mature DC, dendritic cell-based vaccines for cancer immunotherapy in ani- which express CD1a and CD83 antigens, represent the latter mal models, only a few have been carried out in human can- stage of LC and interstitial DC maturation. According to their cers. In this review, we describe recent findings in the biology high expression of MHC class I, MHC class II and costimu- of dendritic cells that are important to generate anti-tumor cyto- latory molecules, they present, efficiently, Ag-derived peptides toxic T cells in vitro and we also detail clinical studies reporting to CD4+ and CD8+ T lymphocytes in lymph node T cell areas the obtention of specific immunity to human cancers in vivo using reinfusion of dendritic cells pulsed with tumor antigens. (Figure 1). Recently, another subset of DC was identified on Keywords: dendritic cells; cancer; immunotherapy the basis of their high expression of the interleukin-3 receptor alpha chain (IL-3R␣hi). These cells are able to migrate to lymphoid organs without any prior activation by inflamma- 9 Introduction tory stimuli. The possibility of generating DC in vitro has helped to Despite progress in chemotherapy regimens, several malig- understand their ontogeny and to further characterize their nancies remain incurable by conventional therapies. It is thus phenotype. As illustrated in Figure 2, all DC subsets originate from bone marrow CD34+ hematopoietic precursor cells fol- necessary to develop alternative strategies, in particular anti- 10–12 tumor immunotherapy. Dendritic cells (DC) play a crucial role lowing two overlapping pathways. Granulocyte–macro- in the initiation of primary immune response and are therefore phage colony-stimulating factor (GM-CSF) and tumor necrosis factor ␣ (TNF␣) are the two main cytokines necessary for DC probably the best adjuvant for anti-tumor immunity. However, 13 their very low frequency in vivo has limited research in this maturation. Stem cell factor (SCF) and Flt3 ligand (Flt3L) enhance the yield of DC generated in vitro from CD34+ field. The possibility of obtaining large numbers of DC in vitro 14 has boosted the understanding of their ontogeny and func- cells, and Flt3L-treated mice show a great increase in the number of mature DC.15 The differentiation of CD34+ cells tions. In this paper, we will briefly review the main recent ␤ features of DC characteristics that are important for cancer into LC requires, in addition, transforming growth factor 1 ␤ ␤ −/− vaccination and discuss the various strategies to vaccinate (TGF 1) since TGF 1 knockout mice are completely devoid 16 ␤ cancer patients with DC. of LC. Moreover, TGF 1 cooperate with Flt3L for the devel- opment of CD1a+ Lag+LC in vitro.17 DC can also be generated from peripheral blood CD14+ MO, at least in vitro.18–20 In the Dendritic cells: phenotype and ontogeny presence of macrophage colony-stimulating factor (M-CSF), MO are induced to differentiate into CD14+ M⌽. However, DC constitute a heterogeneous leukocyte population defined in the presence of GM-CSF and interleukin-4 (IL-4) or interleu- kin-13 (IL-13),21–23 macrophage differentiation is blocked24,25 by morphologic, phenotypic and functional criteria which dis- − + − tinguish them from monocytes (MO) and macrophages (M⌽).1 and MO differentiate into CD14 CD1a Lag immature DC. Finally, the addition of TGF␤1 leads to obtaining CD14− Although there is evidence that a lymphoid precursor can gen- + + 26 + − erate DC, T, B and NK cells,2,3 we will focus only on myeloid CD1a Lag LC. CD1a CD83 immature MO-derived DC are lineage-derived DC which are used both in vitro and in vivo induced into highly efficient Ag presenting cells (APC) (CD1a+CD83+ mature DC) in the presence of TNF␣27,28 or in to enhance specific immune response. Originally, DC were 29,30 characterized by the presence of veils, polarized lamellipodia response to CD40 ligand (CD40L) stimulation which mim- and long spiny processes that were continually being ics interaction with T lymphocytes in T cell areas of lymphoid extended and retracted thus allowing them to be highly organs. Interestingly, the phenotype of these differentiated ⌽ motile.4 As illustrated in Figure 1, three major DC populations cells can be reverted since even fully mature M can be induced into CD1a+CD83− immature DC in the presence of have been identified in vivo: Langerhans cells (LC), interstitial + − DC and activated mature DC. LC are present in skin epidermis IL-4, and vice versa, immature CD1a CD83 DC, unlike + + ⌽ and mucosae and express CD1a, the cutaneous associated mature CD1a CD83 DC, can acquire a M phenotype when 31 antigen (CLA), E-cadherin and the Lag antigen associated with GM-CSF and IL-4 are replaced by M-CSF. the presence of Birbeck granules.5–7 CD1a+ interstitial DC are The phenotype of these various DC populations is now bet- found in various organs especially liver, kidney and heart. LC ter known (Table 1). DC are defined as lineage-negative cells, ie they do not express classical T cell, B cell, NK cell and monocyte (especially CD14) markers.1,32,33 The usual DC Correspondence: B Klein, INSERM U475, 99, rue Puech Villa, 34197 markers are: CD1a which is expressed by LC, MO-derived DC Montpellier, Cedex 5, France; Fax: 33 04 67 04 18–63 and lymph node DC but not by blood DC and which is Received 8 September 1998; accepted 27 January 1999 involved in the presentation of lipid and glycolipid Ag to T Review K Tarte and B Klein 654 Figure 1 Immature DC are localized in peripheral tissues and migrate to lymphoid organs where they activate T lymphocytes. Figure 2 DC ontogeny and lineage. 33–36 44 ␣ ␤ ⌽ cells; CD83 which is present on some rare circulating ecules (Figure 3). In particular, v 5 is absent on MO/M blood DC34 and which is induced during DC maturation and this could explain why these cells are unable to present (cultured blood DC, mature MO-derived DC, lymph node Ag derived from apoptotic cells, even if they internalize apop- DC);37 CMRF-44 which is less specific than CD83 and is also totic cells very efficiently. Ag capture is optimal for immature expressed by a subset of blood DC and LC. CD83 and CMRF- dendritic cells generated from peripheral blood MO after 5– 44 have unknown functions but they are interesting for DC 7 days of culturing with GM-CSF and IL-4. When DC are positive selection.38 induced to mature in vitro, in particular in the presence of TNF␣ or CD40L stimulation, they lose their ability to internal- ize soluble Ag and apoptotic cells39,44 (Figure 3). Together Dendritic cell functions in vitro and in vivo with Ag uptake, Ag processing is also modulated during DC maturation. Ag are concentrated in MHC II compartments in Again, due to the possibility of producing DC in vitro, their immature cells and, after treatment with TNF␣, these intra- maturation and function have been extensively characterized. cellular vesicules disappear and surface MHC II expression is Immature DC are able to capture and process Ag extensively upregulated.39,45 It is now well documented that immature DC in the periphery. They can internalize soluble Ag by macropi- can process exogenous soluble proteins captured by macropi- nocytosis,39 ie uptake of large vesicules (0.5–3 ␮m), as well nocytosis for MHC class I presentation.46–48 This could explain as by endocytosis of small vesicules40 by at least two types of the cross-priming phenomenon: in vivo, MHC I-restricted receptors for Ag uptake: Fc receptor and mannose receptor. tumor Ag are presented mainly, if not exclusively, by pro- CD32 (Fc␥RII), CD64 (Fc␥RI) and mannose receptor are fessional APC (mainly DC) that have taken up Ag released by downregulated during DC maturation in vitro39,41,42 (Figure 3). dying tumor cells, rather than by the tumor cells themselves.49 LC and interstitial DC are phagocytic but to a lesser extent This is of major importance for vaccination strategies for can- than M⌽ and this capacity is lost during DC maturation.42,43 cer patients. The method of Ag capture influences its presen- Immature DC are also able to internalize apoptotic cells by tation. Endocytosis via mannose receptor seems more efficient ␣ ␤ ␣ ␤ binding them through v 5, v 3 and CD36 adhesion mol- for MHC class I presentation than endocytosis via Fc recep- Review K Tarte and B Klein 655 Table 1 Surface molecules express on DC kines, namely macrophage inflammatory protein (MIP)-1␣, MIP-1␤ and RANTES. Induction of DC maturation by CD40 Functions ligand (CD40L), TNF␣ or LPS results in a rapid downregul- ation of these receptors, allowing DC to leave inflamed Dendritic-specific markers tissues. It also results in the slower induction of CCR7, which CD1 MHC-like molecules is the receptor for MIP-3␤/EBI1 ligand chemokine (ELC) and Presentation of non-peptide Ag to T cells secondary lymphoid tissue chemokine (SLC), two chemokines CD83 Unknown function constitutively produced in lymphoid organs.