Priming with Dendritic Cells Can Generate Strong Cytotoxic T Cell Responses to Chronic Myelogenous Leukemia Cells In Vitro

Chronic myeloid leukemia lysate-loaded dendritic cells induce T-cell responses towards leukemia progenitor cells

Treatment of chronic myeloid leukemia with tyrosine kinase inhibitors, such as imatinib mesylate, dasatinib and nilotinib, results in high rates of cytogenetic and molecular responses. However, in many patients, minimal residual disease is detected by molecular techniques. Since chronic myeloid leukemia cells are particularly good targets for immune surveillance mechanisms, we explored active specific immunotherapy using leukemia lysate-loaded dendritic cells in vitro. Our data show the potency of dendritic cell-based vaccination strategies for the induction of T cell-mediated responses to eradicate minimal residual disease.

Dendritic cell-based immunotherapy

Dendritic cells (DCs) play a crucial role in the induction of antigen-specific T-cell responses, and therefore their use for the active immunotherapy of malignancies has been studied with considerable interest. More than a decade has passed since the publication of the first clinical data of DC-based vaccines, and through this and subsequent studies, a number of important developmental insights have been gleaned. These include the ideal source and type of DCs, the discovery of novel antigens and methods of loading DCs, the role of DC maturation, and the most efficient route of immunization. The generation of immune responses against tumor antigens after DC immunization has been demonstrated, and favorable clinical responses have been reported in some patients; however, it is difficult to pool the results as a whole, and thus the body of data remains inconclusive, in part because of varying DC preparation and vaccination protocols, the use of different forms of antigens, and, most importantly, a lack of rigorous criteria for defining clinical responses. As such, the standardization of clinical and immunologic criteria utilized, as well as DC preparations employed, will allow for the comparison of results across multiple clinical studies and is required in order for future trials to measure the true value and role of this treatment modality. In addition, issues regarding the optimal dose and clinical setting for the application of DC vaccines remain to be resolved, and recent clinical studies have been designed to begin to address these questions.