Liposomal targeting of bcl-2 antisense oligonucleotides with enhanced stability into human myeloma cell lines

Cellular pharmacology of P-ethoxy antisense oligonucleotides targeted to Bcl-2 in a follicular lymphoma cell line

A P-ethoxy oligonucleotide (oligo), 20 bases long and specific for the translation initiation site of human Bcl-2 mRNA, was incorporated into liposomes to increase its intracellular delivery. This oligo selectively inhibited Bcl-2 protein expression and induced growth inhibition in t(14;18)-positive transformed follicular lymphoma (FL) cell lines. We studied the inhibitory effects of shorter liposomal P-ethoxy oligos (7, 9, 11 or 15 mer) in order to determine the activity of different oligo chain lengths targeted to the same Bcl-2 mRNA. At 12 microM, all the oligos inhibited the growth of a FL cell line. We compared the 7-mer oligo with the 20-mer oligo. The two oligos inhibited Bcl-2 protein expression similarly: 66% and 60% for the 7- and 20-mer, respectively. The uptake and retention of both oligos were also very similar. Our results indicate that the Bcl-2 inhibitory activity is maintained with P-ethoxy antisense oligos ranging from 7 to 20 bases.

Antitumor effect of bcl-2 antisense phosphorothioate oligodeoxynucleotides on human renal-cell carcinoma cells in vitro and in mice

BACKGROUND AND PURPOSE

Programmed cell death is a genetically regulated pathway that is altered in many cancers. This process is, in part, regulated by the bcl-2 oncogene. Antisense oligodeoxynucleotides (ODNs) targeted to specific oncogenes have been used with some therapeutic success in animal models of leukemia and melanoma cells and human Hodgkin's lymphoma. We evaluated the effects of antisense ODNs targeted to the bcl-2 oncogene on the proliferation of human renal-cell carcinoma (RCC) cells in vitro and on the growth of human RCC xenografts in BALBc nude (nu/nu) mice.

MATERIALS AND METHODS

Expression bcl-2 mRNA in five RCC cell lines (ACHN, Caki-1, RCZ, RCW, and OS-RC-2) was analyzed by reverse transcriptase-polymerase chain reaction. The effects of phosphorothioated ODNs containing human bcl-2 sense and bcl-2 antisense sequences that were transfected with Lipofectin on the proliferation and viability of cultures of established human RCC cell lines were determined by MTS assay. The expression of Bcl-2 protein in ACHN tumor cells following antisense bcl-2 (AS2) ODN treatment was evaluated by Western blot analysis, and the extent of apoptosis in these cells was determined by fluorescence-activated cell sorter (FACS) analysis. The antitumor activity in ACHN xenografts in nu/nu mice was monitored by measuring differences in tumor weight in treated and control mice.

RESULTS

Expression of bcl-2 mRNA was detected in all five RCC lines. Treatment with antisense bcl-2 ODNs inhibited the growth of all tested RCC cells and decreased Bcl-2 protein expression in ACHN cells. The AS2 antisense ODN complementary to the coding region of bcl-2 mRNA showed a superior antiproliferative effect compared with AS1 ODN complementary to the translation initiation region. Inhibition by antisense bcl-2 ODNs of ACHN cells was dose dependent. The FACS analysis revealed that growth inhibition was associated with the induction of programmed cell death. In vivo, AS2 ODN antitumor activity was noted in locally injected groups.

CONCLUSIONS

Treatment of human RCC with antisense ODNs targeted to bcl-2 inhibits growth and is associated with the induction of programmed cell death. These results suggest therapeutic use of antisense bcl2 in the treatment of RCC.

Cyclodextrins in oligonucleotide delivery

The aim of this contribution is to summarize recent findings on the potential use of cyclodextrins and their derivatives as carriers for oligonucleotide agents. Their peculiar properties could be exploited in such an emerging therapeutic area by virtue of their capability of interacting with cellular membranes, thus giving rise to improved cellular uptake. In particular, some specific derivatives could be considered as promising future excipients for the delivery of "naked" antisense and/or decoy oligonucleotides which are difficult to formulate with existing pharmaceutical excipients.

Chemosensitization and delayed androgen-independent recurrence of prostate cancer with the use of antisense Bcl-2 oligodeoxynucleotides

BACKGROUND

Increased expression of the bcl-2 gene has been observed in prostate cancer cells after androgen withdrawal and has been associated with the development of androgen independence and chemoresistance. The objective of this study was to determine whether antisense Bcl-2 oligodeoxynucleotides could enhance paclitaxel cytotoxicity and delay androgen-independent progression.

METHODS

Northern and western blot analyses were used to measure changes in Bcl-2 expression in mouse Shionogi tumor cells after treatment with antisense Bcl-2 oligodeoxynucleotides and/or paclitaxel. Growth inhibition and induction of apoptotic cell death were assessed with the use of standard methods. All P values are two-sided.

RESULTS

Treatment of Shionogi tumor cells with 500 nM antisense Bcl-2 oligodeoxynucleotides decreased expression of Bcl-2 messenger RNA (mRNA) by approximately 85%. Paclitaxel treatment induced Bcl-2 protein phosphorylation but did not alter Bcl-2 mRNA expression. Antisense Bcl-2 oligodeoxynucleotide treatment substantially enhanced paclitaxel chemosensitivity in a dose-dependent manner. Characteristic apoptotic DNA laddering and cleavage of poly(adenosine diphosphate-ribose) polymerase were demonstrated only after combined treatment. Adjuvant in vivo administration of antisense Bcl-2 oligodeoxynucleotides and micellar paclitaxel following castration resulted in a statistically significant delay of androgen-independent, recurrent tumors compared with administration of either agent alone (P<.001, Mantel-Cox log-rank test). Combination therapy also statistically significantly inhibited the growth of established hormone-refractory tumors compared with treatment with either agent alone (P<.001, Student's t test). CONCLUSIONS. Combined treatment with antisense Bcl-2 oligodeoxynucleotides and paclitaxel could be a novel and attractive strategy to inhibit progression to androgen-independent disease as well as growth of hormone-refractory prostate cancer through deprivation of Bcl-2 function.

Targeting bcl-2 gene to delay androgen-independent progression and enhance chemosensitivity in prostate cancer using antisense bcl-2 oligodeoxynucleotides

Bcl-2 expression is upregulated in prostate cancer cells after androgen withdrawal and is associated with the development of androgen independence and chemoresistance. Induction of apoptotic cell death after androgen ablation, or chemotherapy, may be enhanced through functional inhibition of bcl-2. In this report, we tested the effects of antisense bcl-2 oligodeoxynucleotides (ODN) with androgen ablation and taxane therapy on time to androgen-independent (Al) progression in the androgen-dependent Shionogi tumor model. Treatment of Shionogi tumor cells in vitro with 500 nmol/L antisense bcl-2 ODN decreased bcl-2 mRNA by 85%, compared with treatment with 500 nmol/L mismatch control ODN. Although bcl-2 expression levels in Shionogi cells were not changed by docetaxel treatment, docetaxel treatment induced bcl-2 phosphorylation. Consequently, the formation of bcl-2/Bax heterodimer formation was inhibited in a dose-dependent manner. Treatment of Shionogi tumors in vitro with either 500 nmol/L antisense bcl-2 ODN or 10 nmol/L docetaxel alone did not induce apoptosis or reduce growth rates. However, combined treatment reduced the concentration that reduces cell viability by 50% (IC50) of docetaxel from 100 nmol/L to 10 nmol/L and induced characteristic apoptotic DNA laddering and cleavage of the poly(ADP-ribose)polymerase (PARP) protein. Adjuvant in vivo administration of antisense bcl-2 ODN and polymeric micellar paclitaxel after castration resulted in a significant delay in time to Al recurrence when compared with administration of either agent alone. Furthermore, combined treatment of mice bearing Al recurrent Shionogi tumors with antisense bcl-2 ODN and micellar paclitaxel synergistically induced tumor regression and growth inhibition when compared with treatment with either agent alone. These findings suggest that down-regulation of bcl-2 by antisense ODN chemosensitizes Al Shionogi tumors to taxanes, over and above the effects of taxane-induced phosphorylation of bcl-2. Antisense bcl-2 ODN combined with taxanes may be a novel approach to the treatment of both established and emerging Al disease.