Prostate cancer is the most common malignancy in Western countries. Chemokine 
C-X-C motif receptor 1 (CXCR1) and CXCR2 play a key role in generation and 
regulation of CXC chemokine signaling. CXCR1 is a receptor for interleukin 8 
(IL8), a pro-inflammatory chemokine, and CXCR1/2 are crucially involved in the 
prostate cancer development and progression. Thus, we generated a high-affinity 
human CXCR1/CXCR2 inhibitor, CXCL8 (3-72) K11R/G31P, named G31P, which is a 
synthetic derivative of the human cytokine, IL-8. In this study, we investigated 
the effects of G31P on regulation of prostate cancer cell growth in vitro and in 
nude mouse xenografts. Cell viability, adhesion, and wound healing assays were 
used to assess the effects of G31P on growth, adhesion, and migration of PC-3 
human prostate cancer cells in vitro, respectively. Nude mouse xenografts and 
xenograft implantation assays were performed to determine the effect of G31P on 
PC-3 cells in vivo. Immunohistochemistry was used to detect gene expression, and 
fluorescence imaging was used to detect tumor volume and microvessel density in 
tumor xenografts. The data showed that G31P treatment significantly reduced PC-3 
cell viability, adhesion and migration capacity in a dose-dependent manner (up 
to 100 ng/ml). Additionally, G31P treatment of nude mice suppressed the growth 
of orthotopically transplanted tumor xenografts. G31P also inhibited tumor 
tissue vascularization, which was associated with the decreased expression of 
vascular endothelial growth factor and nuclear transcription factor (NF)-κB in 
orthotopic xenograft tissues. This study provides evidence that G31P, a CXCR1/2 
inhibitor, may effectively control prostate cancer.