Please cite this article in press as: Garaude, J., et al., Impaired anti-leukemic immune response in PKC-deficient mice, Mol. Immunol. (2008), doi:10.1016/j.molimm.2008.03.016 ARTICLE IN PRESS G Model MIMM-2725; No. of Pages 7 Molecular Immunology xxx (2008) xxx–xxx Contents lists available at ScienceDirect Molecular Immunology journal homepage: www.elsevier.com/locate/molimm Impaired anti-leukemic immune response in PKC-deficient mice Johan Garaude a,1 , Sandra Kaminski a,1 , Seyma Charni a , Juan Ignacio Aguil ` o b , Chantal Jacquet a , Marc Plays a , Javier Hernandez a , Fernando Rodriguez c , Robert A. Hipskind a , Alberto Anel b , Martin Villalba a,∗ a Institut de G´ en´ etique Mol´ eculaire de Montpellier, CNRS UMR 5535, IFR 122, 1919 Route de Mende, 34293 Montpellier, France b Departamento de Bioqu´ ımica y Biolog´ ıa Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, Spain c Centre de Recerca en Sanitat Animal (CReSA), UAB Bellaterra, 08193 Barcelona, Spain article info Article history: Received 25 February 2008 Accepted 26 March 2008 Available online xxx Keywords: PKCq Moloney-murine leukemia virus (M-MuLV) T cell leukemias Immunosurveillance abstract The cancer immunosurveillance hypothesis has found strong experimental support in recent years. It is believed that cytotoxic lymphocytes are important effectors in this process. PKC plays an essential role in proliferation, activation and survival of these cells, but also proliferation and survival of leukemic T cells. In light of this, we tested the role of PKC in T cell leukemia progression by inducing this disease in wild- type (wt) and PKC-deficient mice with moloney-murine leukemia virus (M-MuLV). Leukemic PKC -/- and wild-type (wt) mice showed the same profile of leukemic cell types, similar spleen and thymus sizes and comparable hematocrits. In contrast, disease incidence was higher and disease onset more rapid in PKC -/- mice. Transfer of leukemic T cells from wt donors into PKC-deficient and wt recipients induced leukemia in 100% and 40% of the mice, respectively. Interestingly, leukemic cells from PKC -/- donors induced the disease in only 50% of the PKC-deficient and 10% of the wt recipients. Intravenous injection of low numbers of EL4 cells induced tumors earlier in PKC -/- mice. Taken together, our results show that PKC is essential for the immune response to leukemia in mice and raise questions about the chronic treatment of humans with PKC inhibitors. © 2008 Elsevier Ltd. All rights reserved. 1. Introduction PKC was isolated as a novel PKC isoform expressed in T cells (Baier et al., 1993). PKC-deficient mice display a selective phenotype in their mature T cell compartment, characterized by the greatly impaired proliferation and interleukin-2 (IL-2) pro- duction in response to TCR/CD28 costimulation (Pfeifhofer et al., 2003; Sun et al., 2000). This defect reflects the deficient activa- tion of the transcription factors NF-B, AP-1 and NF-AT (Altman et al., 2004; Pfeifhofer et al., 2003; Sun et al., 2000), consis- tent with observations that PKC, but not other T cell-expressed PKCs, activate the corresponding reporter genes in T cells (Altman et al., 2004; Baier-Bitterlich et al., 1996; Coudronniere et al., 2000; Lin et al., 2000; Villalba et al., 2000). In addition, PKC is essential for T cell survival, modulating the expression or activity of Bcl-2 family members (Barouch-Bentov et al., 2005; Bertolotto et al., 2000; Hindley and Kolch, 2007; Manicassamy et al., 2006; Villalba et al., 2001). Therefore, we predicted that ∗ Corresponding author. Tel.: +33 4 67 61 3667; fax: +33 4 67 04 0231. E-mail address: martin.villalba@igmm.cnrs.fr (M. Villalba). 1 These two authors have contributed equally to this work. leukemic T cells lacking PKC activity would proliferate less and be more sensitive to apoptosis in vivo (Villalba and Altman, 2002). However, NF-B, AP-1 and NF-AT are also essential for FasL expression (Dzialo-Hatton et al., 2001; Kasibhatla et al., 1998), which is also controlled by PKC (Villalba et al., 1999; Villunger et al., 1999). Consistent with this, PKC is required for maximal upreg- ulation of FasL in vivo (Manicassamy and Sun, 2007). Engagement of the death receptor Fas by its ligand FasL is one of two mech- anisms that cytotoxic lymphocytes (CTLs) use to eliminate target cells; the other is lytic granule exocytosis (Kagi et al., 1994). PKC activity is also required for this, but experiments using CTL clones did not reveal any preferential role for PKC in degranulation rela- tive to other PKCs (Grybko et al., 2007; Pardo et al., 2003). Moreover, CTL lines derived from PKC-deficient mice degranulate normally, probably due to the altered expression of other PKCs, which can compensate for the absence of PKC in vitro (Puente et al., 2006). PKC is also essential for the survival and effector function of acti- vated CD8 T cells, i.e. cytokine production (Barouch-Bentov et al., 2005). Supporting this notion, the ex vivo CTL response is dimin- ished in the absence of PKC in a TCR transgenic mice (Berg-Brown et al., 2004). In addition, PKC also controls the cytolytic activity of NK cells (Krzewski et al., 2006). Taken together these data suggest 0161-5890/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.molimm.2008.03.016