LGR5 is required for the maintenance of spheroid-derived colon cancer stem cells

Abstract

Colon cancer stem cells (CCSCs) are involved in colon cancer and promote tumor progression and recurrence. LGR5, a marker for intestinal stem cells (ISCs), is also considered to serve as a marker for CCSCs. However, the precise function of LGR5 in CCSCs is unclear. In this study, we demonstrated that LGR5 was highly expressed in CCSCs-enriched HT29 spheroid cells. Downregulation of LGR5 with small interfering RNA (siRNA) decreased the expression of stem the cell markers CD133 and CD44 in HT29 spheroid cells. In addition, silencing of LGR5 inhibited cell proliferation, secondary tumor sphere formation and induced cell apoptosis, and G0/G1 phase arrest in vitro by modulating Bcl-2, Bcl-xL and Bax. Knockdown of LGR5 enhanced chemosensitivity and reduced the invasive ability of HT29 spheroid cells. Moreover, LGR5-siRNA suppressed tumorigenicity of HT29 spheroid cells in vivo. The findings suggested that LGR5 plays a vital role in the maintenance of CCSCs and is a potential therapeutic target for colon cancer.

Colorectal cancer-derived tumor spheroids retain the characteristics of original tumors

“…In addition, recent studies have shown that expression level of LGR5 in the colon tissues is closely associated with increased lymph node invasion, distant metastasis, and poor chemotherapy response [28,29] and that LGR5 plays a critical role in maintaining colorectal CSCs [30]. Results of FACS analysis and RT-PCR performed in the present study showed differential levels of these potential colorectal CSC markers in the three CTOS lines.…”

SW480 colorectal cancer cells that naturally express Lgr5 are more sensitive to the most common chemotherapeutic agents than Lgr5-negative SW480 cells

“…Unfortunately, the authors of the paper have not considered important CRC stem cell properties such as enhanced resistance to chemotherapy. The available data in the literature show that the participation of Lgr5 in the chemotherapy resistance problem is controversial; some researchers assert that Lgr5 expression coincides with drug resistance [4][5][6], whereas others claim that it contributes to drug sensitivity [9,10].…”

“…As the presence of Lgr5 directs CRC cells to increase proliferation (Lgr5 silencing has a small inhibitory effect on proliferation of these cells; this implies that Lgr5 increases proliferation), motility, and the production of clones [4,11], we hypothesized that cells that naturally express Lgr5 should be more sensitive to classical chemotherapeutic treatments designed to block frequently dividing and metabolically active cells compared with similar cells without Lgr5. Our data from separated cells that naturally differ in Lgr5 expression support our hypothesis; floating cells, which are Lgr5 positive [11], are more sensitive to anticancer drugs used most often (Fig.…”

“…Many publications suggest that as Lgr5-expressing cells are stem cells, they should be protected from chemotherapy. There are some data that support this hypothesis by showing that blocking Lgr5 expression using inhibitory RNA increases the chemosensitivity of colon cancer cells and that overexpression of Lgr5 is correlated with chemoresistance, presumably through the control of promoters for multidrug resistance-determining transporters like ABCB1 [4][5][6]. As Wnt/β-catenin signaling is required to support stemness, inhibition of Wnt signaling is expected to increase the sensitivity of CRC cells to cytotoxic therapy; indeed, supporting data were obtained by some researchers [7,8].…”

Kynurenine promotes the goblet cell differentiation of HT-29 colon carcinoma cells by modulating Wnt, Notch and AhR signals

“…Lgr5, a marker for intestinal stem cells, is also required for the maintenance and proliferation of colorectal cancer cells via the Wnt3/β-catenin signaling pathway (25,26). HT-29 cells grown in RPMI expressed Lgr5 (Fig.…”