Gremlin1 expression associates with serrated pathway and favourable prognosis in colorectal cancer

Gremlin1 is a bone morphogenetic protein (BMP) antagonist with a suggested role in colorectal cancer (CRC) progression. We have analysed Gremlin1 protein expression in CRC and assessed its correlation with clinicopathological characteristics, including developmental pathway and prognosis.

Material included a non-selected series of 148 surgically treated CRC cases. The tumour-node-metastasis (TNM) stage, histological grade and inflammatory infiltrate at the invasive margin were assessed, and tumours were classified to serrated or non-serrated types. Immunohistochemistry was conducted to evaluate Gremlin1 expression. Prognosis (60-month follow-up) was analysed by Kaplan-Meier methods and Cox regression analysis. Gremlin1 expression was detected in epithelial cells both in normal mucosa and in carcinomas. Abundant expression in carcinomas associated with low TNM stage (P = 0.044), low histological grade (P = 0.044), serrated histology (P = 0.033 or P = 0.053 depending on the classification cut-off) and intensive inflammatory infiltrate at the invasive margin (P = 0.044), and was a stage independent indicator of extended survival (P = 0.029).

Gremlin1 protein expression in CRC associates with low tumour stage and extended survival independently of tumour stage, suggesting that it represents a relevant prognostic indicator in CRC. High expression in carcinomas with serrated histology suggests a potential role for Gremlin1 in the serrated pathway of CRC.