We previously utilized an in vivo peptide phage display selection technique, which included
the use of detergent elution of phage from excised tumor, to obtain tumor-targeting phage with the
ability to extravasate the vasculature and bind directly to prostate tumor tissue. It is hypothesized that
this same in vivo phage selection technique can be used to functionally select for molecules that not
only bind to cancer cells but also kill them. Here we analyzed two different in vivo phage display
selected phage clones, G1 and H5, retrieved from PC-3 human prostate carcinoma xenografted tumors.
First, cell de-attachment as an endpoint criterion for apoptosis and cell cycle was examined. After 2.5
hours incubation with G1 phage, PC-3 cell attachment was reduced by 23.8% and the percent of cell population in M
phase reduced by 32.1%. In comparison, PC-3 cells incubated with H5 phage had a reduction of 25.0% cell attachment
and 33.6% of cell population in M phase. These changes in combination with elevated caspase activation within cells in M
phase, and no significant changes to G1/G0 or S phase cell populations suggest that the cytotoxic phages are targeting
actively dividing PC-3 cells. Microscopic studies were also performed to further analyze the nature of cytotoxicity of
these two phage clones. It was found that G1 phage induced and co- localized with tubulin based projections within
apoptotic cells, while H5 phage did not. These phage may form the foundation for a new class of targeted prostate cancer
Keywords: PC-3 prostate carcinoma, phage display, cytotoxic peptides, cytoskeleton, apoptosis, tumor-targeting peptides.
Rights & PermissionsPrintExport