Periostin from Tumor Stromal Cells Might Be Associated with Malignant Progression of Colorectal Cancer via Smad2/3

<b>Background/Objectives:</b> Cancer-associated fibroblasts (CAFs) in the tumor microenvironment have been reported to be closely associated with tumor progression in various types of cancer, including colorectal cancer (CRC). Periostin, a matricellular protein, was reported to be expressed on both cancer cells and surrounding tumor stromal cells, such as CAFs, and is regulated by Smad2/3 signaling. In this study, we aimed to clarify the clinicopathologic significance of periostin and Smad2/3 expression in CRC, with a particular focus on the tumor microenvironment. <b>Methods:</b> A total of 351 CRC patients were enrolled according to the inclusion and exclusion criteria. The expressions of periostin and Smad2/3 in the tumor specimens were examined by immunohistochemistry. <b>Results:</b> Periostin expression of CAFs and cancer cells in the 351 CRC cases was observed at 36.8% and 0.6%, respectively. Smad2/3 expression of CAFs and cancer cells was observed in 41.0% and 90.0%, respectively. In CAFs, high periostin expression was significantly correlated with high Smad2/3 expression, increased invasion depth, lymph node metastasis, venous invasion, advanced disease stage, and a higher rate of relapse. The prognoses of patients with periostin-positive CAFs were significantly poorer than those with periostin-negative CAFs (<i>p</i> < 0.001). The survival outcomes of stage 3 CRC patients with co-expression of periostin and Smad2/3 were significantly worse compared to those with stage 2 CRC. In the stage 3 group, multivariate analysis revealed that periostin was an independent prognostic factor, while univariate analysis showed that both periostin and Smad2/3 were significantly correlated with poor survival. <b>Conclusions:</b> These findings suggest that periostin is expressed mainly in CAFs in CRC and is correlated with Smad2/3 expression in CAFs. Periostin from CAFs might be associated with the malignant progression of CRC via Smad2/3 signaling.