Published online April 2, 2007
doi:10.1084/jem.20061699
The Journal of Experimental Medicine, Vol. 204, No. 4, 879-891
The Rockefeller University Press, 0022-1007 $30.00
© 2007 Loeser et al.
Spontaneous tumor rejection by cbl-b–deficient CD8+ T cells
Stefanie Loeser1,
Karin Loser2,
Martijn S. Bijker3,
Manu Rangachari1,
Sjoerd H. van der Burg4,
Teiji Wada1,
Stefan Beissert2,
Cornelis J.M. Melief3, and
Josef M. Penninger1
1 Institute of Molecular Biotechnology of the Austrian Academy of Science, 1030 Vienna, Austria
2 Department of Dermatology and Interdisciplinary Center of Clinical Research, University of Münster, D-48149 Münster, Germany
3 Department of Immunohematology and Blood Transfusion and 4 Department of Clinical Oncology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands
CORRESPONDENCE Josef M. Penninger: Josef.penninger{at}imba.oeaw.ac.at
The concept of tumor surveillance implies that specific and nonspecific components of the immune system eliminate tumors in the early phase of malignancy. Understanding the biochemical mechanisms of tumor immunosurveillance is of paramount significance because it might allow one to specifically modulate spontaneous antitumor activity. We report that inactivation of the E3 ligase Casitas B cell lymphoma-b (Cbl-b) confers spontaneous in vivo rejection of tumor cells that express human papilloma virus antigens. Moreover, cbl-b–/– mice develop significantly fewer ultraviolet B (UVB)–induced skin malignancies and reject UVB-induced skin tumors. CD8+ T cells were identified as key players in the spontaneous tumor rejection response. Loss of Cbl-b not only enhances antitumor reactivity of CD8+ T cells but also occurs in the absence of CD4+ T cells. Mechanistically, cbl-b–/– CD8+ T cells are resistant to T regulatory cell–mediated suppression and exhibit enhanced activation and rapid tumor infiltration. Importantly, therapeutic transfer of naive cbl-b–/– CD8+ T cells is sufficient to mediate rejection of established tumors. Even up to 1 yr after the first encounter with the tumor cells, cbl-b–/– mice carry an "anticancer memory." These data identify Cbl-b as a key signaling molecule that controls spontaneous antitumor activity of cytotoxic T cells in different cancer models. Inhibition of Cbl-b is a novel approach to stimulate long-lasting immunity against cancer.
Abbreviations used: Cbl-b, Casitas B cell lymphoma-b protein; HPV, human papilloma virus.
K. Loser and M.S. Bijker contributed equally to this work.

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