Anti-cancer and anti-viral aptamers
Abstract
Aptamers generated by two approaches, from purified protein and whole cell
surface selections, have the potential to serve as detection and therapeutic agents against
prostate cancer. In addition, aptamers generated from the purified viral protein NS1
have been shown to inhibit influenza virus replication in cell culture. Anti-prostate
specific membrane antigen aptamer A9 was used with high specificity for common
detection methods such as flow cytometry and confocal microscopy and for novel
detection methods such as proximity dependent ligation assay. Moreover, the PSMA
aptamer was shown to function as a delivery vehicle for siRNA and toxin. Cell-type
specific GAPDH and lamin A/C gene knockdown were demonstrated using streptavidin
as a bridge to connect biotin-conjugated aptamers to biotin-conjugated siRNA.
Cytotoxicity assays also revealed that aptamers were able to specifically deliver the
recombinant plant toxin rGelonin specifically to LNCaP cells when conjugated with the
toxin. Furthermore, aptamers were generated from whole cell surface selections of the
prostate cancer cell lines LNCaP and PC3. This suggested that anti-PC3 aptamers could
target cell surfaces through indirect immunostaining and images taken by confocal
microscopy. Membrane binding assays, FACS, and proximate dependent ligation assays
also revealed that the aptamers were able to distinguish with great sensitivity and
specificity the two non-prostate cancer cell lines, A549 and H526 as well as LNCaP and
PC3 cells from DU145, another common prostate cancer line. More importantly, these
experiments demonstrated that aptamers could be designed to have specificities to a
certain subtype of cancer cells or to the general population. In other studies, aptamers
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were also generated from purified NS1 protein encoded by the influenza virus. The
calculated Kd for these aptamers was in the range of 10 nM for the full length NS1
protein. Competition and binding assays suggested that the aptamers also targeted the
dsRNA binding domain of the NS1 protein. Transfecting aptamers to human lung cancer
cells, A549, infected with influenza virus revealed that the aptamers were able to inhibit
the replication of both the human and avian strains of influenza virus in cell cultures.
These findings strongly demonstrated the broad range and effectiveness of aptamers as
tools for detection, diagnostics, and therapeutics.
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