Invited Speaker

Preclinical Analysis of Dnazymes Suppressing Cancer Growth, Metastasis and the Development of other Vascular Disease
Levon M. Khachigian
Australia

Immediate-early genes (IEG) are those genes whose expression is rapidly and transiently induced upon stimulation without the need for de novo protein synthesis. Our studies over recent years have demonstrated that the pathogenesis of experimental restenosis, angiogenesis, inflammation and vascular permeability can be suppressed using novel catalytic synthetic DNA-based “anti-gene therapeutic” strategies targeting certain IEGs, which also serve as transcription factors.

DNAzymes are single-stranded catalytic DNA molecules that bind their target mRNA via Watson-Crick base pairing and cleave between an unpaired purine and a paired pyrimidine. We were the first to use DNAzymes as therapeutic agents in an animal model¹. Since then we have demonstrated that Dz13, a DNAzyme with 9+9 nt hybridization arms targeting the bZIP transcription factor c-Jun mRNA, inhibits the growth of numerous cell types, including tumor cells, and blocks restenosis, inflammation, rheumatoid arthritis, angiogenesis and tumor growth in animal models.

Melanoma and non-melanoma skin cancer (BCC, SCC) represent the most common types of cancer among Caucasians. Effective alternative treatments for skin cancers beyond existing chemotherapeutic, immunotherapeutic, photodynamic and surgical options are needed. We now demonstrate the capacity of Dz13 to cause regression in a sequence-specific manner of BCC, SCC and melanoma growth as dermal, rather than subcutaneous tumors, in a clinically-suitable liposomal formulation that is well–tolerated and safe in mice and monkeys. Dz13 inhibits tumor growth in both immunodeficient, and immunocompetant syngeneic mice. Growth suppression by Dz13 is mediated through inhibition of c-Jun and numerous c-Jun-

dependent pro-angiogenic and tumorigenic genes, such as MMP-2, MMP-9, VEGF-A and FGF-2. Dz13 stimulates apoptosis via both intrinsic and extrinsic pathways. Dz13 activates caspase-3, caspase-8, caspase-9 and p53 in the tumors. This follows our previous demonstration that Dz13 blocks the inducble expression of E-selectin, ICAM-1, VCAM-1 and VE-cadherin without influencing levels of JAM-1, PECAM-1, p-JNK-1 or c-Fos2, and inhibition of tumor angiogenesis and growth with another DNAzyme³. Our preclinical findings provide background justification for the clinical evaluation of Dz13.

1.  Santiago FS, Lowe HC, Kavurma MM, Chesterman CN, Baker A, Atkins DG, Khachigian LM. New DNA enzyme targeting Egr-1 mRNA inhibits vascular smooth muscle proliferation and regrowth factor injury. Nature Med. 1999;5:1264-1269.

2.  Fahmy R, Waldman A, Zhang G, Mitchell A, Tedla N, Cai H, Chesterman CN, Geczy CR, Perry MA, Khachigian LM. Suppression of vascular permeability and inflammation by targeting of the transcription factor c-Jun. Nature Biotech. 2006;24:856-863.

3.  Fahmy RG, Dass CR, Sun LQ, Chesterman CN, Khachigian LM. Transcription factor Egr-1 supports FGF-dependent angiogenesis during neovascularization and tumor growth. Nat Med. 2003;9:1026-1032.