To test whether activin A plays a role in fibroblast-promoted tumorigenesis in vivo, we injected anti-activin A antibody or follistatin (an activin antagonist) every three days for a total of four injections into NOD/SCID/IL2Rγnull (NSG) mice xenografted with BxPC-3 tumor cells and human PSCs. This evidence concerns the gene FST and neoplasm.