Combination gene therapy for salivary gland cancer.

An established combination gene therapy strategy involving adenovirus vector delivery of the herpes thymidine kinase (tk) and murine interleukin-2 genes was adapted to treat salivary gland cancer in a murine model. Salivary tumors were generated by transcutaneous injection of 5 x 10(5) murine squamous carcinoma cells into the submandibular gland of syngeneic C3H/HeJ mice. After one week, established submandibular gland tumors were injected with a recombinant adenovirus containing therapeutic and control genes. Animals were subsequently administered ganciclovir twice daily (25 mg/kg) for six days. All animals receiving tk and ganciclovir demonstrated tumor regression, however a significantly greater response was seen in mice that were treated with both tk + mIL-2. Residual tumors from all treatment and control groups were harvested for microscopic evaluation and immunohistochemistry staining. Specific immunostaining revealed a predominance of CD8+ lymphocytes in the tumor beds of the animals treated with IL-2, suggesting a preferential immune response resulting from the local IL-2 expression. Although still in its infancy, the concept or using adenoviral gene therapy strategies to provide less invasive means of treating salivary tumors is promising.