This cytokine level was approximately sevenfold higher than that in the second free copy woodchuck, which had received a fourfold-lower dose of SFV-enhIL-12, suggesting that the IL-12 level in serum is dependent on the SFV dose administered. In order to verify that IL-12 expression from SFV-enhIL-12 induces increases in the levels of type I and II IFNs, tumor tissue from the third woodchuck was also analyzed for the expression of IFN-�� and IFN-�� mRNAs (Fig. (Fig.1F).1F). Tumor tissue from a fourth woodchuck with one untreated tumor with a size of approximately 1.0 cm in diameter was used as a control. Twenty-four hours after intratumoral administration of SFV-enhIL-12, the IFN-�� and IFN-�� mRNA expression levels in the SFV-treated tumor were 4- and 10-fold higher, respectively, than those in the control tumor, suggesting that the activation of any antitumoral or antiviral immune responses by SFV-enhIL-12 could be mediated via the induction of both cytokines.

HCC treatment with SFV-enhIL-12 results in partial tumor remission. For evaluating the antitumoral efficacy of a SFV vector expressing murine IL-12 on established, nontransplanted liver tumors, pairs of woodchucks were treated intratumorally with single doses of 3 �� 109, 6 �� 109, or 1.2 �� 1010 vp of SFV-enhIL-12. Three other woodchucks were injected intratumorally with saline and served as placebo-treated controls. Tumor size was determined by US every 2 to 4 weeks (Fig. (Fig.2A).2A). Tumor size was also measured with calipers at the day of treatment during laparotomy and again at the end of the study during necropsy (Fig.

(Fig.2B2B). FIG. 2. Tumor sizes in chronic WHV carrier woodchucks following intratumoral treatment with increasing doses of SFV-enhIL-12. Pairs of woodchucks received intratumorally single doses of 3 �� 109 vp (SFV-1 and SFV-2), 6 �� 109 vp (SFV-3 and SFV-4), … A dose-dependent, transient reduction in tumor size was observed by US in all woodchucks treated with SFV-enhIL-12. Reductions started immediately following treatment, were maximal between 2 and 4 weeks posttreatment, and lasted for another 2 to 8 weeks thereafter. Tumor remission in SFV-treated woodchucks, however, was only partial, and tumor growth was restored between 6 and 14 weeks posttreatment. One of two woodchucks (SFV-3) treated with the intermediate dose of SFV-enhIL-12 was euthanized at 3 weeks posttreatment due to seizures, but this animal also demonstrated a remarkable reduction in tumor size (Fig.

(Fig.2B).2B). On average, treatment with SFV resulted in a reduction of tumor volume of 58% at 4 weeks posttreatment (Fig. (Fig.2C),2C), with four of six animals demonstrating reductions of >70%. The difference in mean tumor volume between SFV-treated and control woodchucks was Brefeldin_A statistically significant at 4 weeks posttreatment (P < 0.05; two-tailed Student’s t test). Partial tumor remission is associated with activation of antitumoral immune responses.