Antisense therapy: recent advances and relevance to prostate cancer

Methodology for Anti-Gene Anti-IGF-I Therapy of Malignant Tumours

The aim of this study was to establish the criteria for methodology of cellular “anti-IGF-I” therapy of malignant tumours and particularly for glioblastoma multiforme. The treatment of primary glioblastoma patients using surgery, radiotherapy, and chemotherapy was followed by subcutaneous injection of autologous cancer cells transfected by IGF-I antisense/triple helix expression vectors. The prepared cell “vaccines” should it be in the case of glioblastomas or other tumours, have shown a change of phenotype, the absence of IGF-I protein, and expression of MHC-I and B7. The peripheral blood lymphocytes, PBL cells, removed after each of two successive vaccinations, have demonstrated for all the types of tumour tested an increasing level of CD8⁺ and CD8⁺28⁺ molecules and a switch from CD8⁺11b⁺ to CD8⁺11. All cancer patients were supervised for up to 19 months, the period corresponding to minimum survival of glioblastoma patients. The obtained results have permitted to specify the common criteria for “anti-IGF-I” strategy: characteristics sine qua non of injected “vaccines” (cloned cells IGF-I(−) and MHC-I(+)) and of PBL cells (CD8⁺ increased level).

Induction of toll-like receptors and NALP/PAN/PYPAF family members by modified oligonucleotides in lung epithelial carcinoma cells

ISIS 199044 is a chimeric 2'-O-methyl-containing oligonucleotide that produces toxicity in several cultured cell lines. Upon investigation into the mechanism of cytotoxicity, we discovered that treatment of lung epithelial carcinoma cells, A549, with ISIS 199044 and several other cytotoxic oligonucleotides induces a group of genes that are not normally expressed in these cells. These genes are involved in host response to foreign materials. Among them were toll-like receptor 7 (TLR7) and TLR9, members of the toll-like receptor family, responsible for immune response to nucleic acids and cryopyrin, a member of NALP/PAN/PYPAF family, which is known to assemble with ASC and regulate NF-kappaB activation and to modulate apoptosis. Maximal induction occurred 12-24 hours posttreatment with 500 nM oligonucleotide in the presence of Lipofectin reagent. Furthermore, we have shown that this induction is chemistry dependent; it can be negated by certain modifications, such as replacement of 2'-O-methyl with 2'-O-methoxyethyl groups or substitution of phosphorothioates with phosphodiester linkages. DNA microarray analysis identified additional genes modulated by ISIS 199044, particularly genes involved in DNA damage/repair.

Antisense recognition of the HER-2 mRNA: effects of phosphorothioate substitution and polyamines on DNA.RNA, RNA.RNA, and DNA.DNA duplex stability

The HER-2 gene is overexpressed in a subset of breast, ovarian, lung, and pancreatic cancers. Antisense oligonucleotides suppress gene expression depending on the stability of the DNA.RNA hybrids formed at the target site. Polyamines, the cellular cations that interact with DNA and RNA, may influence hybrid stability in the cell. Therefore, we studied the ability of natural polyamines (putrescine, spermidine, and spermine) and a series of their structural analogues to stabilize DNA.RNA and RNA.RNA duplexes using melting temperature (T(m)) measurements and circular dichroism (CD) spectroscopy. Phosphodiester (PO) and phosphorothioate (PS) oligonucleotides (ODNs) (15 nucleotides, 5'-CTCCATGGTGCTCAC-3') targeted to the initiation codon region of the HER-2 mRNA, and complementary RNA and DNA ODNs, were used in this study. The relative order of thermal stability was as follows: RNA.RNA > PO-DNA.RNA > PO-DNA.PO-DNA > PS-DNA.RNA > PS-DNA.PO-DNA > PS-DNA.PS-DNA. The ability of polyamines to stabilize the duplexes improved with the cationicity of the polyamine, with hexamines being more effective than pentamines, which in turn were more effective than tetramines and triamines. However, chemical structural effects were clearly evident with isovalent homologues of spermidine and spermine. CD spectra showed B and A conformations, respectively, for the DNA and RNA helices. DNA.RNA hybrids adopted an intermediate structure between the B and A forms. These data help us to understand the role of endogenous polyamines in DNA.RNA hybrid stabilization, and provide information for designing novel polyamines to facilitate the use of antisense ODNs for controlling HER-2 gene expression.

Inhibition of PC-3 prostate cancer cell growth in vitro using both antisense oligonucleotides and taxol

Antisense oligonucleotides (oligos) directed against mRNA-encoding transforming growth factor-alpha (TGF-alpha) and the epidermal growth factor receptor (EGFR) have demonstrated in vitro and in vivo efficacy against prostate cancer tumor models. However, many therapeutic agents have increased effectiveness when given in combination with other more established agents. We evaluated the effectiveness of two oligos (3.32 and 6.64 microM/L) known to have significant activity against the PC-3 prostate cell line in combination therapy with the chemotherapeutic agent paclitaxel (Taxol) (2.5 and 5.0 nm). Therapy was evaluated when oligos and Taxol were administered either as (1) single agents, (2) simultaneously in a combined therapy, or (3) sequentially, a form of combination therapy with both agents being administered in a series. We found that when either of the two oligos were given simultaneously with Taxol, no synergistic activity was noted. However, when sequentially administered in a series 1 d apart, a pretreatment with the antisense directed against TGF-alpha (6.64 microM/L) followed by Taxol (5 nm) had significantly greater activity than these agents similarly administered in the reverse order or simultaneously.>