The present invention relates to non-integrating viral expression vectors for use in repeated administration regimens for non-interg rating gene therapy, such as, but not limitted to in the treatment of cancer, which do not induce a long-term adaptive immune response in the patient. The present invention relates to the new vectors, as such, as well as to their medical uses. The non-integrating expression vectors comprise a DNA sequence encoding an E2 protein of Bovine Papilloma Virus type 1 (BPV1 ), comprising a DNA-binding dimerization domain, as well as an oligomerized DNA sequence, forming a binding site for an said E2 protein. Optionally, further at least 50% of all immunostimulatory sequences (ISSs) from the plasmid backbone, the promoter and/or the expression cassette of said vector can be removed and/or modified in such a way that the vectors do not activate an innate immune response in a mammalian cell. The present invention further relates to said non-integrating expres-sion vector for use in expressing a protein or fragment(s) thereof binding an antigen and/or cell signaling molecule associated with cancer, tumor(s) and/or solid tumor(s).