Induction of T cell precursors in advanced melanoma treated with autologous tumor lysate loaded dendritic cells

Abstract

2623 Background: Immunotherapy in melanoma patients (pts) is limited by tumor-induced effector cell inhibition. Dendritic cells (DC) are powerful initiators of tumor-specific immune responses. We proposed a pilot study that hypothesized that DC matured ex vivofrom the peripheral blood (PB) and pulsed with autologous tumor lysate (TuLy) would stimulate tumor-specific immune activation. Methods: 6 stage III/IV melanoma pts were enrolled and CD14+ precursors were obtained from PB by apheresis and elutriation prior to each treatment. DC were cultured ex vivo for 9 days with IL-4 and GM-CSF, pulsed with autologous TuLy and matured with TNFa. Pts received 3 treatments administered intravenously (IV) over 5–10 minutes at 4 week intervals. Efficiency of DC generation was determined by measuring total DC per apheresis and phenotype. NCI Common Toxicity Criteria v2.0 was used. Tumor-specific immune induction was evaluated using the Dye Dilution Proliferation Assay which measures T cell precursor frequencies (Tp) in response to stimuli; in this case pulsed or unpulsed mature DC. Results: 3 pts each have been treated with 1x106and 5x106DC respectively. Adequate yields of DC were achieved for all treatments. Toxicity was minimal with transient grade 2 ataxia. Mature DC highly expressed MHC class I and II, costimulatory markers (CD80, CD86, CD40) and the maturity marker CD83. We observed a 6-fold increase in CD8+ Tp and 1.5-fold increase in CD4+ Tp after 2 treatments (n=2) as shown in the table. Elevated Tp persisted 30 days following completion of treatment. Conclusions: Ex vivogeneration and IV administration of mature DC is feasible and safe. Preliminary data support induction of tumor-specific T cells evidenced by increased Tp. No significant financial relationships to disclose.