While our RNA-Seq data reveal that several Claudin family members are expressed in CRC liver metastases with replacement-type features, we suggest that Claudin-2 represents a superior biomarker for RHGP CRCLMs due to the fact that it was the only claudin family member that was upregulated in breast cancer liver metastases and functionally shown to promote both breast and CRC metastasis to the liver24,26,27,32,35. This evidence concerns the gene CLDN2 and breast cancer.