Antisense oligonucleotides (oligos) have demonstrated their efficacy in inhibiting the growth of prostate and
breast tumor cells. Previous studies employed first generation, phosphorothioated,
cDNA oligos synthesized complimentary to
mRNA encoding
transforming growth factor-alpha (
TGF-alpha),
epidermal growth factor receptor (EGFR), the anti-apoptosis
protein bcl-2, and the
androgen receptor (AR). In an effort to construct oligos with greater than one
mRNA binding site, bi-specifics have been developed which target combinations of the above
proteins, and these have been shown at least as effective as the mono-specific oligos from which their sequences were derived. While all bi-specifics have inhibitory effects, which can be enhanced by the combined administration of an additional chemotherapeutic agent, those bi-specifics which target bcl-2 and EGFR were reported to be the most effective. The experiments presented here are an effort to evaluate a new group of bi-specifics whose targets include the chaperone
protein clusterin, whose expression is up regulated in many
tumors and activity is known to inhibit apoptosis. Of particular interest were those bi-specifics constructed to target both
clusterin and bcl-2 (also an apoptosis inhibitory
protein). Cell lines targeted included both prostate LNCaP and PC-3, as well as the breast derived MCF-7. In order to identify agents which enhance oligo activity, but contribute less toxicity, oligos were tested both alone and in combination with either the immune inhibitor
Rapamycin, or the chemotherapeutic (and more toxic)
Taxol. Results indicate that bi-specifics targeting
clusterin are statistically effective, and are similarly enhanced by
Rapamycin, or
Taxol. When bi-specifics including
clusterin as a target, were tested against LNCaP and MCF-7 cells, the level of activity was intermediate between that of the mono-specific compounds tested separately. In experiments which compared both, bi-specifics which included a target for
clusterin had inhibitory activity similar to the previously described bi-specifics directed towards bcl-2 and EGFR.