Published online Apr 21, 2021. doi: 10.3748/wjg.v27.i15.1578
Peer-review started: December 1, 2020
First decision: December 21, 2020
Revised: January 22, 2021
Accepted: February 24, 2021
Article in press: February 24, 2021
Published online: April 21, 2021
The intestinal crypt-villus structure harbors two distinct pools of putative stem cells, the active [leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5)+ cells] and the quiescent stem cell populations (B lymphoma Moloney murine leukemia virus insertion region 1 homolog+ or telomerase reverse transcriptase+ cells). Current evidence indicates that CRC is indeed a disease of colon stem cells that are resistant to current therapeutics and can rapidly proliferate to re-establish the tumor. Furthermore, it was reported that colon cancer carcinoma specimens contain a subset of LGR5-expressing stem cells. Human colon cancer cell lines, such as Caco-2 and LoVo, are extensively used in drug screening and colon cancer research and express high levels of LGR5.
To establish criteria for the selection of suitable cell lines for drug discovery and reveal potential variability between colon cell lines, we here identify the cancer stem cell (CSC) population(s) within colon cancer cell lines, quantify differences in gene expression signatures in these cells, and assess their proliferative and tumorgenicity capacities.
The present study aimed to isolate cells expressing LGR5 in Caco-2 and LoVo colon cancer cell lines and investigate whether these cells constitute the CSC compartments in these cell lines. This was achieved through the creation of a transgenic proliferating stem cell-specific reporter construct based on the proximal promoter of LGR5 gene.
Using a portable fluorescent reporter construct based on a conserved fragment of the LGR5 promoter, subpopulations of cells from the colon cancer cell lines (Caco-2 and LoVo) were sorted into three cell compartments expressing different levels of LGR5 (high-, low-, and no-expression of LGR5). Next these cell compartments were characterized based on their gene expression signatures, proliferation, and tumorgenicity properties.
Cells expressing high levels of LGR5 with Caco-2 colon cancer cell line appear to represent a CSC-like population. In contrast, in the LoVo cell line, the LGR5 negative fraction possessed some features of the intestinal stem cells, e.g., a specific gene expression signature, suggesting that this cell line was likely derived from a CSC population other than LGR5+ cells.
LGR5 marks the stem cell compartments of the Caco-2, but not LoVo, cell lines. Thus, it would appear that different colon cancer lines possess properties of different stem cell compartments. The portable LGR5 reporter outlined in this study constitutes a valuable tool for the identification and purification of LGR5-expressing cells from mixed cell populations.
The portable LGR5 reporter described in this study constitutes a valuable tool for the identification and purification of LGR5-expressing cells from mixed cell populations.