Substance P analogues, including [D-Arg(1),D-Trp(5,7,9),Leu(11)]SP (SPA) are 
broad-spectrum G protein-coupled receptor (GPCR) antagonists that have potential 
antitumorigenic activities, although the mechanism(s) are not completely 
understood. Here, we examined the effects of SPA in ductal pancreatic cancers 
that express multiple GPCRs for mitogenic agonists and also produce 
proangiogenic chemokines. Using HPAF-II, a well-differentiated pancreatic cancer 
cell line as our model system, we showed that SPA inhibited multiple 
neuropeptide-induced Ca(2+) mobilization, DNA synthesis, and 
anchorage-independent growth in vitro. SPA also significantly attenuated the 
growth of HPAF-II tumor xenografts in nude mice beyond the treatment period. 
Interestingly, SPA markedly increased apoptosis but moderately decreased 
proliferation marker, Ki-67 in the tumor xenografts implying additional 
mechanism(s) for the significant growth inhibitory effect observed in vivo. 
HPAF-II cells express ELR(+) CXC chemokines, including IL-8/CXCL8, which bind to 
CXCR2 (a member of GPCR superfamily) and promote angiogenesis in multiple 
cancers, including pancreatic cancer. SPA inhibited CXCR2-mediated Ca(2+) 
mobilization and blocked specifically IL-8/CXCL8-induced angiogenesis in rat 
corneal micropocket assay in vivo. A salient feature of the results presented 
here is that SPA markedly reduced tumor-associated angiogenesis in the HPAF-II 
xenografts in vivo. Our results show that SPA, a broad-spectrum GPCR antagonist 
attenuates tumor growth in pancreatic cancer via a dual mechanism involving both 
the antiproliferative and antiangiogenic properties. We conclude that this novel 
dual-inhibitory property of SPA could be of significant therapeutic value in 
pancreatic cancer, when used in combination with other antiproliferative and/or 
antiangiogenic agents.