Green DR, Apoptotic pathways: paper wraps stone blunts scissors. cell population in M phase reduced by Phenethyl alcohol 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 phage 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 Phenethyl alcohol class of targeted prostate cancer therapeutic agents. strong class=”kwd-title” Keywords: PC-3 prostate carcinoma, phage display, cytotoxic peptides, Phenethyl alcohol cytoskeleton, apoptosis, tumor-targeting peptides Introduction: Prostate cancer is a worldwide problem with over 1,112,000 new Tmem26 cases being diagnosed and over 250,000 deaths in Phenethyl alcohol 2015 . It is estimated that 1 in 7 men will develop prostate cancer in their lifetime . While prostate cancer is treatable in its earliest stages, metastatic forms of the disease are often fatal. Diagnosis is hampered by the fact that early prostate cancer usually has no symptoms. Since the establishment of serum prostate specific antigen (PSA) screening of asymptomatic populations, both prostate cancer incidence rates and the number of men submitted to radical prostatectomy and radiation therapy have multiplied . High serum levels of PSA are indicative of prostate cancer, however men can have high levels of PSA without cancer and ~25% of prostate cancer patients have normal serum PSA levels. Survival rates for prostate cancer are greater than 80% before the occurrence of metastasis and less than 30% after. While the etiology of prostate cancer remains unclear, risk factors include older age, race, and family history. Prostate cancer treatment is not standardized and there are many options available and may include watchful waiting, surgery, radiation therapy, hormone therapy, chemotherapy, and biologic therapy . Taken together, improved indicators of prostate cancer and cancer progression as well as new-targeted therapeutic strategies are necessary to avoid needless treatment, predict disease course, and improve therapy. One of the most effective approaches for targeted drug discovery is the use of combinatorial chemistry and specifically bacteriophage (phage) display for selection of tumor-targeting compounds. George P. Smith introduced the field of phage display over 30 years ago . A phage-display library is an assortment of phage with random foreign peptides on their surface with the coding sequences for the peptides contained within the viral DNA. Each single phage clone displays a single peptide, but a library as a whole can embody billions of peptides in total. The genetic encoding of a library permits the resynthesis and rescreening of molecules with a preferred binding activity. The subsequent amplification of interacting molecules in successive rounds of affinity selection can produce very rare, specific binders from an vast pool of peptides. For screening, a library is incubated with an immobilized target or selected in vivo; binding clones are captured, and propagated in host bacteria. Usually the process is repeated several times to enrich for optimal binders. Combinatorial chemistry is currently being developed into a potentially customizable patient-specific anti-cancer technology, whereby antigens or biomarkers that may be specific to an individuals cancer are targeted. Numerous phage display selections reported in the literature have yielded peptides that target tumor cells in vitro, however, very few of the peptides have possessed the necessary pharmacokinetics for the molecular imaging or treatment of cancer in vivo . Selection and/or screening of peptides in an in vitro setting may aid in the discovery of high affinity binding peptides, but is unlikely to predict pharmacokinetic properties in vivo. The conformational structures of the selected, fused peptides are impacted by the phage virion surface microenvironment. Thus, synthetic peptides, derived from phage display selected sequences, may have binding characteristics quite distinct from those of the peptides displayed on the exterior of the phage. Added drawbacks to the use of the synthesized selected peptides for the imaging or treatment of cancer is the covalent addition of radiochelators and /or fluorescent tags to the peptide can reduce the peptides binding affinity for its target [5C6]. Further, the radioactive molecule attached to the peptide may cause serious side-effects in vivo . Of interest to our laboratory is the use of in vivo combinatorial phage display in the context of an animal for the.