Characterization of LGR5 expression in poorly differentiated colorectal carcinoma with mismatch repair protein deficiency

BACKGROUND: Leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5) is a promising intestinal stem cell and carcinoma stem cell marker. We examined the relationship between mismatch repair (MMR) protein deficiency and LGR5 expression in poorly differentiated (PD) colorectal carcinoma (CRC). METHODS: In 29 cases of PD-CRC, deficiencies in MMR proteins (MLH1, PMS2, MSH2, MSH6) and β-catenin expression were identified by immunohistochemistry (IHC). LGR5 expression was examined by the RNAscope assay in tissue microarrays. RESULTS: LGR5 H-scores in MMR-deficient (MMR-D) cases were significantly lower than those in MMR-proficient (MMR-P) cases (P = 0.0033). Nuclear β-catenin IHC scores in MMR-D cases were significantly lower than those in MMR-P cases (P = 0.0024). In all cases, there was a positive correlation between LGR5 H-score and nuclear β-catenin IHC score (r = 0.6796, P < 0.001). Even in MMR-D and MMR-P cases, there was a positive correlation between LGR5 H-score and nuclear β-catenin IHC score (r = 0.7180, P < 0.0085 and r = 0.6574, P < 0.003, respectively). MMR-D CRC cases showed low expression of LGR5, which may be due to low activation of the Wnt/β-catenin signaling pathway. CONCLUSIONS: Our results reveal the relationship between LGR5 expression and MMR protein profiles in PD-CRC. A further study is warranted to confirm these findings.