Insulin-like growth factor 2 messenger RNA binding protein 3 (IGF2BP3) is a marker of unfavourable prognosis in colorectal cancer

Background
Evidence suggests that insulin-like growth factor 2 messenger RNA binding protein 3 (IGF2BP3, also known as IMP3) represents a promising cancer biomarker. However, the clinical, pathological, molecular and prognostic features of IGF2BP3-positive colorectal cancers remain uncertain.

Materials and methods
We evaluated IGF2BP3 expression by immunohistochemistry in 671 rectal and colon cancer cases that form part of a molecular pathological epidemiology database. Cox proportional hazards regression models were used to compute mortality hazard ratio (HR), adjusting for clinical, pathological and molecular features, including microsatellite instability, the CpG island methylator phenotype, LINE-1 methylation and KRAS, BRAF and PIK3CA mutations.

Results
Among 671 colorectal cancers, 234 (35%) tumours were positive for IGF2BP3. In contrast, normal colorectal epithelium was negative for IGF2BP3 in all 403 specimens of normal mucosa adjacent to carcinoma. IGF2BP3 positivity was associated with poor differentiation (p = 0.0003), stage III-IV disease (p = 0.0081), BRAF mutation (p = 0.031), and LINE-1 hypomethylation (p = 0.020). IGF2BP3 positivity was significantly associated with shorter colorectal cancer-specific [log-rank p < 0.0001; multivariate HR, 1.37; 95% confidence interval (CI), 1.02–1.84] and overall survival (log-rank p = 0.0004; multivariate HR, 1.32; 95% CI, 1.05–1.66).

Conclusions
IGF2BP3 expression in colorectal cancer is associated with adverse clinical outcome. Our findings support a role for IGF2BP3 as a diagnostic and/or prognostic biomarker in colorectal cancer.