The extracellular matrix component periostin is a secreted protein that 
functions as both a cell attachment protein and an autocrine or paracrine factor 
that signals through the cell adhesion molecule integrins αvβ3 and αvβ5. 
Periostin participates in normal physiological activities such as cardiac 
development, but is also involved in pathophysiological processes in vascular 
diseases, wound repair, bone formation, and tumor development. It is of 
increasing interest in tumor biology because it is frequently overexpressed in a 
variety of epithelial carcinomas and is functionally involved in multiple steps 
of metastasis progression. These include the maintenance of stemness, niche 
formation, EMT, the survival of tumor cells, and angiogenesis, all of which are 
indispensable for gastric cancer metastasis. Periostin has been reported to 
activate the PI-3K/AKT, Wnt, and FAK-mediated signaling pathways to promote 
metastasis. Therefore, periostin represents a potentially promising candidate 
for the inhibition of metastasis. In this review article, we summarize recent 
advances in knowledge concerning periostin, its antagonist PNDA-3, and their 
influence on such key processes in cancer metastasis as maintenance of stemness, 
niche formation, epithelial-to-mesenchymal transition, tumor cell survival, and 
angiogenesis. In particular, we focus our attention on the role of periostin in 
gastric cancer metastasis, speculate as to the usefulness of periostin as a 
therapeutic and diagnostic target for gastric cancer metastasis, and consider 
potential avenues for future research.