Efficient activation of autologous tumor-specific T cells: a simple coculture technique of autologous dendritic cells compared to established cell fusion strategies in primary human colorectal carcinoma.

Different technologies have been employed to deliver the whole spectrum of tumor antigens (TAs) to dendritic cells (DCs) to be presented to T cells. These include whole tumor RNA-transfected DCs, preparations of DCs loaded with tumor-derived apoptotic bodies or tumor cell lysates, and DC tumor cell fusions. Early clinical trials have been conducted using such techniques. The presented study was aimed to revisit the necessity of tumor cell manipulation in DC-based immunotherapy strategies for colorectal carcinoma. We investigated a simple coculture method of autologous monocyte-derived DCs and human primary colorectal carcinoma (pCC) in comparison with 2 well-described cell fusion strategies for the efficacy of uptake, processing and presentation of TAs to autologous T cells. Before coculture or fusion, pCC had been cryopreserved without further manipulation. Fluorescence microscopy and flow cytometry analyses of fluorescent dye labeled cells were used for monitoring engulfment of pCC by DCs. The coculture procedure resulted in a double positive cell fraction of up to 22% and thus was comparable to that observed after cell fusion. More important, DCs after coculture with autologous pCC induced significant tumor-specific interferon-gamma-producing autologous T cells in the same number of patients as DC/pCC fusions. Furthermore, tumor-specific major histocompatibility complex class I restricted cytotoxic T lymphocytes were generated by stimulation with DCs cocultured with pCC. In prior studies for human carcinomas coculture techniques were described to be inferior. In contrast, our data strongly suggest that at least for human pCC and autologous DCs this simple coculture method is similarly efficient compared to established fusion techniques.