An isolated nucleic acid includes a sequence encoding a mutant human deoxycytidine kinase (hdCK) capable of converting prodrugs, such as a nucleoside analogue, into cytotoxic drugs. An isolated vector can include the nucleic acid and an isolated host cell can be genetically engineered with the isolated vector. The polypeptides can be obtained by a procedure using recombinant techniques. A pharmaceutical composition, which includes the isolated nucleic acid, the expression vector, the host cell, or an isolated mutant hdCK, can be used as a medicament, such as for the treatment of cancer or for the prevention of a viral infection. The polypeptides and nucleic acids can be used for the treatment of malignancies and viral infections, in methods of sensitizing cells to prodrugs, in methods of gene therapy, in methods of non-invasive nuclear imaging and in methods of inhibiting pathogenic agents in a subject.
