PARENT SESSION

Experimental and Clinical Therapeutics

(PP178) A Phase I Hyperthermia- induced Interleukin- 12 gene- therapy trial in spontaneously arising feline soft tissue sarcomas.

Siddiqui, Farzan^*,1, Avery, Paul², LaRue, Susan¹, Hauck, Marlene ³, Dewhirst, Mark⁴, Li, Chuan- Yuan⁴, Ullrich, Robert¹, ¹ Department of Environmental and Radiological Health Sciences, Fort Collins, CO, USA² Department of Microbiology, Immunology and Pathology, CO, Fort Collins, CO, USA³ Department of Clinical Sciences, Raleigh, NC⁴ Department of Radiation Oncology, Durham, NC, USA

ABSTRACT- PURPOSE AND OBJECTIVES Cytokine genes are the most widely and extensively studied immunostimulatory agents in cancer gene therapy. In several studies, interleukin-12 (IL-12) was the most effective cytokine in inducing the eradication of experimental tumors, preventing development of metastases, and eliciting long-term antitumor immunity. However, IL-12 protein therapy has been limited by dose-dependent toxicity. Local and efficient expression of IL-12 and other cytokine genes in tumors represents an alternative immunotherapeutic approach that may avoid systemic toxicity of recombinant cytokines. To achieve this goal of localizing gene expression, a heat-inducible adenoviral gene therapy vector with feline IL-12 being placed under the control of a heat inducible promoter was developed (Ad hsp fIL-12). The rationale for using this heat shock promoter (hsp70B) is that hyperthermia is most likely to be used as an adjuvant therapy with radiation and chemotherapy in the treatment of cancers. Heating the tumor leads to activation of the hsp promoter and subsequent local IL12 production. MATERIALS AND METHODS Thirteen cats with spontaneously arising soft tissue sarcomas presenting for treatment were recruited for a Phase I dose escalation gene therapy trial. The cats underwent radiation therapy to a total dose of 48 Gy in 16 fractions. Four- five days later the gene construct was injected intratumorally. 24 hours post- injection the tumor was heated to a target temperature of 41oC for 60 minutes using a microwave applicator. Cats were treated at increasing dose levels of viral construct. Tumor expression of cytokines interleukin 12 and interferon- was quantitatively determined using real time PCR. The cats were monitored for hematologic and hepatic toxicity. RESULTS High intratumoral levels of interleukin 12 were achieved with interferon- present at high dose levels only. Hematologic and hepatic toxicity were dose dependent. CONCLUSIONS It is possible to limit the toxicity of interleukin- 12 using the hyperthermia induced gene- therapy approach. Cats with spontaneously arising soft tissue sarcomas serve as an excellent model for the study of this approach that can be similarly applied to human cancer treatment.

Key words: gene therapy, hyperthermia- induced, interleukin-12, soft tissue sarcomas