The invention provides an isolated or purified nucleic acid comprising a nucleotide sequence encoding a nuclear factor of activated T-cells (NFAT) promoter operatively associated with a nucleotide sequence encoding IL-12. The invention also provides a nucleic acid comprising a nucleotide sequence encoding a nuclear factor of activated T-cells (NFAT) promoter operatively associated with a nucleotide sequence encoding IL-12, wherein the NFAT promoter is located 3 of the nucleotide sequence encoding IL-12. Also provided are related recombinant expression vectors, host cells, populations of cells, and pharmaceutical compositions. The invention further provides the use of the inventive nucleic acids or related materials in the treatment or prevention of cancer or an infectious disease in a mammal and in the induction of IL-12 expression in a mammal.