PDXK and colorectal carcinoma: In line with our previous studies showing that PKH-retaining tumor cells were endowed with higher tumorigenic capacity and chemotherapy resistance [14, 16], we undertook an in-depth molecular characterization of PKH26+ cells isolated from CRC xenografts through gene expression analysis and reverse-phase proteomic arrays, providing for the first time a combined picture of both transcriptional circuits and activated protein pathways.