Osteopontin expression in the invasive front stroma of colorectal adenocarcinoma is associated with tumor budding and prognosis.

Background: Tumor budding (TB) is an important prognostic factor in colorectal carcinoma (CRC). Osteopontin (OPN) functions in various processes such as immune response, migration and invasion, angiogenesis, epithelial-mesenchymal transition (EMT) and metastasis. However, the involvement of OPN and CD44v6, which is a receptor for OPN, in TB has not been clarified. Therefore, we examined the relationship of OPN with TB in CRC and compared the clinicopathological features.

Methods: We investigated the expression of OPN and CD44v6 in 83 cases of CRC by immunostaining and analyzed the clinicopathological features.

Results: OPN expression was observed mostly in the cytoplasm of stromal cells such as macrophages and fibroblasts, and rarely in cancer cells. There was a significant correlation between OPN positivity and the degree of differentiation at the invasive front and TB grade. CD44v6 was positive in cancer cells in 72 cases (86.7 %) and negative in 11 cases (13.3 %). A statistically significant effect on overall survival (OS) was identified between the OPN-positive group [median OS: 1586 (range, 30-2749) days] and the OPN-negative group [median OS: 1901 (range, 8-2665) days] (log-rank test, p = 0.011).

Conclusions: OPN analysis in CRC stromal cells may have prognostic implications.