Kämpgen
E,* Dörrie J, Schaft
N, Thumann P, Haendle I, Strobel I, Steinkasserer A, Thurner B, Nicolette
C* and Schuler G*.
*Merix
Germany GmbH and Friedrich Alexander University, Dept. of Dermatology, Erlangen,
Germany.
Using the patients own immune system to fight
cancer is a promising approach. The best equipped cells to initiate an antigen-specific
cytotoxic T-cell response (CTL) are dendritic cells (DCs). For CTL induction
DCs must present antigens via the MHC class I pathway that usually presents
peptides derived from cytoplasmic proteins. One approach to gain access to
this pathway is RNA transfection of DCs, which can
be significantly enhanced by electroporation (EP) of DCs.
To generate a potent multivalent melanoma vaccine broadly applicable to melanoma patients we chose to transfect autologous DCs with quality controlled defined RNA encoding 3 antigens: the melanoma differentiation antigen MelanA, the cancer-testis antigen Mage-3 and the universal tumor antigen Survivin. DCs were generated according to GMP criteria in vitro by culturing patients´ monocytes for 6 days with GM-CSF and IL-4, and maturation of DCs was obtained by addition of inflammatory cytokines (IL-1, IL-6, TNFa, PGE2) for 24h. Expression of transfected antigens was demonstrated by intracellular staining in >90% electroporated DCs and comparable antigen expression kinetics were seen in DCs regardless whether transfected at the immature or mature state. Importantly, antigen expression kinetics did not differ when DC were simulaneously transfected with RNA encoding all three antigens. Generally, mature DC were more robust than immature DC and following EP displayed smaller alterations in size and granularity and a higher viability. In addition, DCs transfected after maturation were generally better stimulators of antigen specific CD8+ T cell clones, especially after freezing and thawing of the DCs. Based on these results a first phase I clinical trial in melanoma patients with progressive stage IV disease was initiated. Quality controlled vaccines meeting the release criteria could be generated in all patients and first immunomonitoring data are promising.
Autologous DCs transfected with RNA encoding defined tumor antigens allows treatment of tumor patients with any HLA background and hopefully may not only help patients with late stage disease but also prevent tumor outbreak in an adjuvant setting.