Gene modification of eukaryotic cells by electroporation is a widely used method to express selected genes in a defined cell population for various purposes, like gene correction or production of therapeutics. Here, we describe the generation of a cell-based tumor vaccine via fourfold transient gene modification of a human renal cell carcinoma (RCC) cell line for high expression of CD80, CD154, GM-CSF, and IL-7 by use of MIDGE(®) vectors. The two co-stimulatory molecules CD80 and CD154 are expressed at the cell surface, whereas the two cytokines GM-CSF and IL-7 are secreted yielding cells with enhanced immunological properties. These fourfold gene-modified cells have been used as a cell-based tumor vaccine for the treatment of RCC.