Antisense oligonucleotides (oligos) have been evaluated for treating prostate cancer in both in vivo
and in vitro models. This study evaluates the growth inhibition of in vitro propagating LNCaP cells
employing mono- and bi-specific oligos directed against BCL-2 and employing RT-PCR, the
expression of five apoptosis regulatory proteins (BCL-2, bax, caspase-3, clusterin, AKT-1), a tumor
associated transcription factor (MED-12) and an immune blockade associated regulatory marker (PDL1)
were evaluated. LNCaP prostate tumor cells were incubated in the presence of oligos specifically
directed against BCL-2 (entering the cells through a form of nanodelivery) and compared to lipofectin
containing controls. Significant, but comparable, growth inhibition was produced by both mono- and
bi-specific forms. Employing RT-PCR to determine BCL-2 expression, we found that the greatest
amount of mRNA suppression approached 100% for each type of oligo: Mono-specific MR4 (directed
only against BCL-2), 100%, and bispecifics MR24 and MR42, 86% and 100% respectively. The
objective of these experiments was to determine a compensatory response by cells to (again) evade
apoptosis in the presence of BCL-2 suppression. Levels of mRNA encoding non-targeted bax,
caspase-3, clusterin and AKT-1 were initially evaluated, while additional experiments sought to
identify additional mechanisms of tumor adaptability and resistance. Suppression of the apoptosis
inhibitor (BCL-2) in LNCaP cells did not alter either bax or clusterin expression. However, nontargeted
caspase-3 (an apoptosis promoter) was suppressed and non-targeted AKT-1 (an apoptosis
inhibitor) was enhanced. This suggests that tumor variants can resist apoptosis through the altered
expression of non-targeted regulators of apoptosis. Additional experiments identified other
mechanisms of compensation involving transcription and immune regulation suggesting further
studies are needed.
Author (s) Details
Marvin Rubenstein
Independent Researcher, 1070 Cobblestone Ct., Northbrook, IL 60062, USA.
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