In the ex vivo gene therapy or "cancer vaccine"
approach,cancer cells are isolated from patients, transduced with various
gene vectors and expanded in vitro. After irradiation, the cells
are transplanted autologously to enhance the patient's immune response against the tumor. This strategy is not only laborious,
but the treatment is also individualized as cancer cells need to
be cultured and expanded from each patient for therapeutic
purposes. A more attractive strategy is to deliver the cytokine
genes in vivo. The retroviral vector is commonly used for the
ex vivo approach, but its low titer limits its application by in vivo
delivery. The recombinant adenoviral vector is characterized
by high titers and is capable of efficient gene transfer into a
variety of cell types in vivo. The use of recombinant adenoviral
vectors in immunotherapy of metastatic colon carcinoma is
reported.