Angiogenesis, the development of new blood vessels by the sprouting of the existing vasculature or by endothelium-dependent intussusceptive microvascular growth, occurs in a limited range of healthy adult tissues such as the ovary and endometrium during the menstrual cycle and in wound healing but also occurs in various diseases, including cancer. During tumor growth its cells undergo the transformation to an angiogenic phenotype and malignant cells are capable of inducing proliferation and migration in endothelial cells. Because rapid tumor growth requires its own blood supply, when new vasculature is not adequate tumor become necrotic or apoptotic.

Angiogenesis is a complex process that involves extracellular matrix remodeling, endothelial cells migration and proliferation. Cell surface integrins, which are the major receptors for extracellular matrix, participate in all of these processes. They are heterodimeric transmembrane glycoproteins, composed of noncovalently-associated α and β subunits. Until now 24 of integrin receptors are known. They are composed from various combinations of 18 α and 8 β chains. The most abundant subfamily of integrins is that consist of β1 chain.

Based on given above reasons DNAzymes to β1 mRNA were synthesized – active and inactive ones. The DNAzyme is single-stranded anti-sense oligodeoxynucleotide with enzymatic activity. The model of DNAzyme has a catalytic domain of 15 highly conserved deoxyribonucleotides, flanked by 2 substrate-recognition domains. To increase the stability of DNAzyme in cells and to protect it from nucleases, modified oligonucleotides with 2’-O-methyl-substituted residues were introduced at two final nucleotides both on the 5’ and 3’ sides.

Presented work is showing that gene-inactivating agents - metylated derivative of DNAzymes, can be used to downregulate neovascularization process in mouse models. Angiogenesis was examined using a bFGF supplemented Matrigel plugs in BALB/c mice. The DNAzymes were locally administrated every second day causing reduction in revascularization in Matrigel plugs, which was detected by measurement of haemoglobin level.

In Human Tumor Xenograft Models, where BALB/cA nude (nu-/-) - B6.Cg - Foxn1^nu athymic mice were used, to subcutaneously created human colorectal and prostatic carcinomas DNAzymes were injected. We provide evidence that the active form of mouse DNAzyme to β1 integrin subunit decreased tumors volume and kinetic of their growth, intensity of neovascularisation process evaluated by measurement of haemoglobin concentration as well as PECAM-1 (Platelet Endothelial Cell Adhesion Molecul-1, CD31) immunohistochemical staining. In conclusion, these DNAzymes might ultimately provide a therapeutic means to inhibit pathological angiogenesis in tumors.

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