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Intravesical Immunotherapy of Superficial Bladder Cancer with Chitosan/Interleukin-12

¹ Laboratory of Tumor Immunology and Biology and ² Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland

Requests for reprints: John W. Greiner, Laboratory of Tumor Immunology and Biology, Center for Cancer Research, National Cancer Institute, NIH, 10 Center Drive, Room 8B09, Bethesda, MD 20892. Phone: 301-496-9813; Fax: 301-496-2756; E-mail: jg117s{at}nih.gov.

Key Words: immunotherapy • bladder cancer • IL-12 • chitosan • intravesical

Intravesical BCG has been used successfully to treat superficial bladder cancer for three decades. However, 20% to 30% of patients will fail initial BCG therapy and 30% to 50% of patients will develop recurrent tumors within 5 years. Alternative or complementary strategies for the management of superficial bladder cancer are needed. Interleukin-12 (IL-12) is a potent T_H1 cytokine with robust antitumor activity and the ability to potentiate immunologic memory. Unfortunately, intravesical IL-12 did not show antitumor efficacy in a recent clinical study of patients with recurrent superficial bladder cancer. We hypothesized that coformulation of IL-12 with chitosan, a biocompatible, mucoadhesive polysaccharide, could improve intravesical IL-12 delivery and provide an effective and durable alternative for the treatment of superficial bladder cancer. In antitumor studies, 88% to 100% of mice bearing orthotopic bladder tumors were cured after four intravesical treatments with chitosan/IL-12. In contrast, only 38% to 60% of mice treated with IL-12 alone and 0% treated with BCG were cured. Antitumor responses following chitosan/IL-12 treatments were durable and provided complete protection from intravesical tumor rechallenge. Urinary cytokine analysis showed that chitosan/IL-12 induced multiple T_H1 cytokines at levels significantly higher than either IL-12 alone or BCG. Immunohistochemistry revealed moderate to intense tumor infiltration by T cells and macrophages following chitosan/IL-12 treatments. Bladder submucosa from cured mice contained residual populations of immune cells that returned to baseline levels after several months. Intravesical chitosan/IL-12 is a well-tolerated, effective immunotherapy that deserves further consideration for testing in humans for the management of superficial bladder cancer. [Cancer Res 2009;69(15):6192–9]