We found that HOXA4 and HOXA9 are up-regulated in CRC SCs. siRNA knockdown of HOXA4 and HOXA9 reduced: (i) proliferation and sphere-formation and (ii) gene expression of known SC markers (ALDH1, CD166, LGR5).
Results showed that the difference in percentage of <i>KRAS</i> exon 2 mutations between CD166 positive and CD166 negative CRC specimens was significant (<i>P</i> < 0.05, chi-square test).
Our findings suggest that CD166 expression may be correlated with CRC carcinogenesis and a decreased risk of vascular invasion, and it may become a predictive biomarker of survival for stage II CRC patients, but additional studies with large sample sizes are essential to validate the prognostic and predictive values of CD166 expression.
Our findings suggest that an increase in CSCs, specifically the CD44(+) CD166(-) phenotype in the colon could be a predisposing factor for the increased incidence of CRC among AAs.
Immunostaining showed that HOXA4 and HOXD10 are co-expressed with the SC markers CD166 and ALDH1 in cells at the normal crypt bottom, and the number of these co-expressing cells is increased in CRCs.
Importantly, analysis of patients with stage II CRC showed that disease-specific survival is significantly reduced for patients with elevated ALCAM shedding (P = 0.01; HR, 3.0), suggesting that ALCAM shedding can identify patients with early-stage disease at risk of rapid progression.
Analysis of the surface molecule repertoire of EpCAM(high)/CD44+ cells led to the identification of CD166 as an additional differentially expressed marker, useful for CSC isolation in three of three CRC tested.