PPIA and neoplasm: The possibility that Pa ExoS can serve as a tool for assessing the metastatic potential of tumors is predicated on the ability of Pa to infect migrating (invasive) cells, and the ability of ExoS to target eukaryotic cell proteins that mediate tumor progression and metastasis, including Rho-GTPases, Ras family proteins, ERM proteins, vimentin and cyclophilin A (Struckhoff et al., 2011; Bos, 1988; Curto and McClatchey, 2004; Lee and Kim, 2010; Satelli and Li, 2011).