Prognostic impact of the expression of putative cancer stem cell markers CD133, CD166, CD44s, EpCAM, and ALDH1 in colorectal cancer

Abstract

Background: The aim of this study was to elucidate the prognostic impact of putative cancer stem cell markers CD133, CD166, CD44s, EpCAM, and aldehyde dehydrogenase-1 (ALDH1) in colorectal cancer.

Methods: A tissue microarray of 1420 primary colorectal cancers and 57 normal mucosa samples was immunostained for CD133, CD166, CD44s, EpCAM, and ALDH1 in addition to 101 corresponding whole tissue sections. Invasive potential of three colorectal cancer cell lines was tested.

Results: Differences between normal tissue and cancer were observed for all markers (P<0.001). Loss of membranous CD166 and CD44s were linked to higher pT (P=0.002, P=0.014), pN (P=0.004, P=0.002), an infiltrating growth pattern (P<0.001, P=0.002), and worse survival (P=0.015, P=0.019) in univariate analysis only. Loss of membranous EpCAM expression was also linked to higher pN (P=0.023) and infiltrating growth pattern (P=0.005). The CD44s, CD166, and EpCAM expression were lost towards the invasive front. The CD44-/CD166- cells from three colorectal cancer cell lines exhibited significantly higher invasive potential in vitro than their positive counterparts.

Conclusions: Loss, rather than overexpression, of membranous CD44s, CD166, and EpCAM is linked to tumour progression. This supports the notion that the membranous evaluation of these proteins assessed by immunohistochemistry may be representative of their cell adhesion rather than their intra-cellular functions.

Figure 1

Colorectal cancer samples with membranous positivity and corresponding negative staining for CD133 (A and B), CD166 (C and D), CD44s (E and F), EpCAM (G and H) and cytoplasmic positivity and negativity for ALDH1 (I and J).

Figure 2

Kaplan–Meier survival curves illustrating survival time differences in patients with (A) loss vs overexpression of membranous CD166, (B) loss vs overexpression of CD44s, and (C) loss of both CD166 and CD44s vs all other combinations (loss of either CD166 or CD44s or none) on tissue microarray.

Figure 3

Kaplan–Meier survival curves illustrating survival time differences in patients with loss of both CD166 and CD44s vs all other combinations (loss of either CD166 or CD44s or none) on whole tissue sections.

Figure 4

The CD44−/CD166− tumour cells display higher invasive potential than CD44+/CD166+ cells. The CD44−/CD166− and CD44+/CD166+ cell subsets were sorted by flow cytometry, according to the gates depicted, from LS180, SW480, and Colo205 cell lines. Sorted subsets were tested in invasion assays. Percentages of cell invasion (mean values±s.d.) are shown. Data are representative of six independent experiments.