ACT of cblb-deficient hyperreactive immune cells

To date, therapeutic efficacy of adoptive T cell therapy for cancer in the clinic is limited, mainly due to insufficient in vivo activation, expansion and survival of adoptively transferred effector T cells. As transferred tumor-specific T cells encounter suppressive milieu signals exerted by both the tumor and regulatory T cells, strategies rendering adoptively transferred immune cells resistant to inhibitory environmental cues are considered attractive for improvement of current cancer immunotherapy regimens. Gene ablation of casitas b-lineage lymphoma proto- oncogene b (cblb), a member of the mammalian family of RING E3 ubiquitin ligases and dominant "tolerogenic" T cell threshold regulator, in the CD8 + cytotoxic T lymphocyte (CTL) compartment has been shown to be sufficient to induce potent anti-tumor immunity in immuno-deficient mice, since cblb-deficient CD8 + T cells are hyperproliferative, independent of CD28 costimulation and resistant to suppressive effects of TGF-beta. Unexpectedly, however, the adoptive cell transfer (ACT) of T cells isolated from non- T cell receptor (TCR)- transgenic cblb-/- animals by itself is unable to eradicate tumors in immuno-competent recipient mice. Consequently, we searched for an experimental setting that may allow an in vivo selection and increased activation of tumor-antigen specific T cells upon ACT of cblb-deficient polyclonal CTLs. As a first approach, combination of adoptive transfer of cblb-deficient CTLs with active dendritic cell (DC)-based immunization markedly delays tumor outgrowth, leading to a substantial improvement of survival rates in pre-clinical tumor models. Since Cbl-b regulates the activation thresholds of several immune cells during tumor cell clearance, I propose in my HF fellowship application a composite analysis of Cbl-b cell type-selective functions in a variety of effector cells of both the innate and the adaptive immune system, particularly and based on our current knowledge and preliminary data, CD8 + and CD4 + T cells, B cells, natural killer (NK) cells as well as DCs. Employing cblb knockout immune cells, the potentially induced augmentation of immune effector functions ex vivo as well as enhanced anti-tumor efficacy after adoptive transfers in in vivo model systems will be systematically studied, employing both, our established induced and additionally spontaneous tumor model systems. For these ACT studies tumor volume will be measured using non-invasive quantification of tumor burden via MRI. Complementary, detailed analysis of the migratory potential of adoptively transferred cblb-deficient immune cells in the cancer setting will be performed, since we know that entry of e.g. T cells into secondary lymphoid organs for stimulation by APC as well as to the tumor site is a prerequisite for a sufficient in vivo anti-tumoral activity. As an additional step the combination of ACT of cblb knockout immune cells in combination with chemotherapy-mediated induction of immunogenic tumor cell death will be investigated. Finally, potential caveats of these ACT, e.g. that cblb-deficient immune cells may cause unwanted autoimmunity, will be investigated in detail.