Chimeric antigen receptors (CARs) are synthetic antigen receptors enabling T cells to specifically eliminate cancer cells. CD19-specific CAR-T cells were capable of inducing complete remissions in several patients with relapsed/refractory lymphoma. Nevertheless, currently available CAR-T cell products are not effective in the majority of metastatic tumors (e.g. pancreas carcinoma, colon cancer). Major reasons for the low efficacy of CAR T cells in solid tumors include an insufficient in-vivo expansion and a lack of suitable target structures on the tumor cells. In the present project, the combination of CAR-T cells with immunostimulatory substances will be analyzed. The aim of this endeavor is to improve the in-vivo expansion of CAR T cells and to attack cancer cells with these immunostimulatory substances, independently of the CAR.