Oligonucleotides covalently linked to intercalating agents. Influence of positively charged substituents on binding to complementary sequences

Overcoming multidrug resistance in human carcinoma cells by an antisense oligodeoxynucleotide--doxorubicin conjugate in vitro and in vivo

Multidrug resistance (MDR), a major obstacle to successful cancer chemotherapy, may be induced by amplification of the MDR1 gene and overexpression of the P-glycoprotein (P-gp), which acts as drug efflux pump decreasing intracellular drug accumulation. In this study, an antisense oligodeoxynucleotide--doxorubicin conjugate was used to overcome MDR in a human carcinoma-resistant cell line, both in vitro and in vivo, through downregulation of P-gp expression and mRNA levels. Compared with the unmodified antisense-oligodeoxynucleotide (AS-ODN), the conjugate markedly inhibited P-gp expression and mRNA levels. With in vitro treatment with the conjugate, the intracellular accumulation of doxorubicin (DOX) was increased 4.4-fold compared to treatment with DOX alone; by contrast, a 2.2-fold increase was observed when treated with AS-ODN alone. In the in vivo studies, it was approximately 3.5-fold higher compared to the control group treatment with DOX alone and 2.1-fold higher than found with AS-ODN. The weight of tumors formed was markedly decreased after conjugate treatment as compared to either treatments with AS-ODN or DOX alone. Furthermore, treatment with combinations of the agents appeared to be well tolerated. These results suggest that a strategy using the conjugate in combination with antitumor drugs may comprise a powerful treatment for MDR.

Quantification intracellular levels of oligodeoxynucleotide-doxorubicin conjugate in human carcinoma cells in situ

Bifunctional oligodeoxynucleotide-intercalator conjugates provide new tools for a selective control of gene expression and may have potential applications as novel therapeutic agents. An 'in situ' analysis method has been developed to determine intracellular levels of oligodeoxynucleotide- doxorubicin conjugate which may be used to reverse the multidrug resistance in KB-A-1 cells. A linear response over a broad concentration range (0.05-6.0 microM, r2 = 0.97) was obtained. The limit of detection and quantitation was set at 0.015 and 0.05 microM, respectively. Assay validation studies revealed that compared with HPLC, the method is rapid, high simple, high throughput and convenient for the determination of the conjugate in cells in situ. The uptake studies of the conjugate in cells using this method demonstrated that the cellular accumulation of the conjugate in KB-A-1 cells was dependent on a dynamic balance between influx and efflux processes.

An antisense oligodeoxynucleotide-doxorubicin conjugate: preparation and its reversal multidrug resistance of human carcinoma cell line in vitro

An antisense oligodeoxynucleotide-doxorubicin conjugate was synthesized by an aminocaproic acid linker. The synthetic conjugate was identified by HPLC analysis and UV-vis spectra. Properties of the conjugate in vitro conditions were investigated. The results demonstrated that the conjugate was remarkably stabilized by doxorubicin. When incubated in Dulbecco Phosphate-Buflered Saline (pH 7.4) at 37 degrees C, the conjugate was more stable than doxorubicin or the mixture of doxorubicin and antisense oligodeoxynucleotide. When incubated in 10% fetal serum at 37 degrees C, the conjugate showed a remarkable stabilization as compared to the unmodified oligodeoxynucleotide. Melting experiments demonstrated that the covalent attachment of doxorubicin strongly stabilized the binding of the oligodeoxynucleotide to its complementary sequence. In addition, in vitro reversion of multidrug resistance by the conjugate was assayed in a human carcinoma cell line (KB-A-1) resisting to doxorubicin. The result showed that the conjugate displayed very high reversal multdrug resistance activity in KB-A-1 cells in vitro. The conjugate lowered the IC50 value from 21.5 microM to 2.2 microM with a fold-reversal factor of 10. In contrast, a slight decrease of the IC50 value was observed when they combined with the "free" antisense oligodeoxynucleotide: the IC50 value was down from 21.5 microM to 16.8 microM. This study suggested that antisense oligodeoxynucleotide-doxorubicin conjugate might be helpful in multidrug resistance reversal.

Phenylalkyl backbone modified oligodeoxynucleotides, their synthesis and the influence of the alkyl chain length

Phenylalkyl modified phosphoramidites (alkyl chain length n = 1, 2, 3, 5; Fig. 1) were synthesised and incorporated into a DNA hexamer (5'-d(GCCp-GCG); p = place of modification). The obtained diastereomeres were separated by RP-HPLC. After hybridisation with the complementary DNA strand Tm-value and thermodynamic data were measured. The stability of duplexes depends on the linker length and the absolute configuration of the backbone modified oligodeoxynucleotides (Rp, Sp).

Synthesis and hybridization properties of the conjugates of oligonucleotides and stabilization agents--II

New pyranone derivatives having tri- or pentamethylenamine linker functions were synthesized. These derivatives were covalently attached through the 5'-phosphoramide linkage to heptanucleotide pd(CCAAACA). Complementary complexes of the octanucleotide pd(TGTTTGGC) and above oligonucleotide conjugates were tested for their thermodynamic response. The Tm data and thermodynamic parameters for complex formation have demonstrated the ability of chromone (gamma-pyrone) and coumarin (alpha-pyrone) derivatives to stabilize strongly 7-mer/8-mer complementary complex, most likely through the stacking interaction of the pyran aromatic system with the neighboring nucleotide bases. The effect of chromone (or coumarin) derivatives on the stability of the oligonucleotide complexes (delta delta G at 37 degrees C ranged from -1.0 to -1.7 kcal/mol) was shown to be comparable to the effect of one nucleotide base pair and similar to the effect (delta delta G at 37 degrees C ranged from -1.5 to -2.0 kcal/mol) found for acridineoligonucleotide conjugates served in this study as a reference.

Potential targets for antiviral chemotherapy

Serendipity and random screening have been successful in producing effective antiviral agents. The increase in our knowledge of the basic biochemistry of viral replication and of virus-host interrelationships has revealed not only an understanding of the targets upon which existing antiviral agents exert their inhibitory effect, but also has uncovered new potential targets. The hope is that such molecular understanding will afford the synthesis of compounds with selective antiviral activity. A review of various viral targets which are potentially susceptible to attack, and a few approaches for development of antiviral agents are presented.