The present invention provides nucleic acids containing transcriptional units that encode CYP1B1 polypeptides or portions thereof, wherein the transcriptional units lack sequences found in the untranslated region (UTR) of naturally occurring forms of the CYP1B1 transcript. The nucleic acids of the invention lack translational repressor elements and thus provide for a system of enhanced translation of the CYP1B1 polypeptide or portions thereof. Also disclosed are methods of administering nucleic acids to a mammal and use in the treatment of proliferative disorders or cancer.