| Cancer biotherapy, started in 1980s after surgery, radiation therapy, chemotherapy for the treatment of cancer, is another technique promoted by the development of modern molecular biology and bioengineering. Inerleukin-12 (IL-12) is a heterodimeric cytokine with diverse biologic activities that plays an important role in the process of tumor immunity, infection immunity and autoimmune disease as a key immunological regulation factor. However, systemic administration of IL-12 causes dose-dependent toxicity in animals and in human trials. To reduce systemic toxicity, local expression of IL-12 gene in tumors has been explored. Tumor cells are genetically engineered to produce IL-12 to a high level, resulting in the inducing, activation and enhancing of antitumor immune responses to suppress tumor growth or eradicate the primary tumors and metastatic lesions. Recombinant adenovirus vector has been used to integrate the transgenes into many kinds of host cells efficiently and to infect both proliferating and nonreplicating tumor cells. It also can express a transgene to high levels without intergrating into the cellular genome, and can be grown to high viral titers to 1011PFU/ml after ultracentrifugating in vitro. These provide thorough insights regarding recombinant adenovirus vector as one of the most effective transgene vectors and the promising biology carrier in cancer gene therapy. However, AdCMVIL-12 has an inefficiency therapeutic effect on larger tumors (>10mm in diameter ) concerning its severer side effect after increasing dosage and the limited anti-tumor immunoreaction time period together with reject reaction after the first injection...
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