Overexpression of Lgr5 correlates with resistance to 5-FU-based chemotherapy in colorectal cancer.

BACKGROUND: The leucine-rich repeat-containing G protein-coupled receptor 5 (Lgr5) is an adult intestinal stem cell marker frequently detected in human colorectal cancers (CRCs). However, the value of Lgr5 level in CRC prognosis and treatment prediction has not been well characterized. METHODS: We examined Lgr5 expression in 384 formalin-fixed paraffin-embedded CRC specimens from 296 CRC patients, including 64 patients treated with 5-fluorouracil (5-FU)-based chemotherapy. The effects of Lgr5 on cell proliferation, survival, and drug resistance were examined in cultured CRC cells. RESULTS: Elevated expression of Lgr5 was observed in CRC tissues, and Lgr5 protein levels were significantly correlated with an advanced American Joint Committee on Cancer stage (P < 0.001), T stage (P < 0.001), N stage (P < 0.001), and distant metastasis (P < 0.001). High expression levels of Lgr5 were significantly associated with shorter disease-free survival (P < 0.001) and shorter cancer-specific survival (P = 0.007) in CRC patients. Among the chemotherapy-treated subgroups, patients with low Lgr5 level showed a better response rate (65 %) than patients with high Lgr5 level (37 %) towards 5-FU-based treatment (P = 0.025). In cultured CRC cell lines, knocking down Lgr5 suppressed cell proliferation and colony formation ability, while it enhanced apoptosis and rendered cells more sensitive to chemotherapeutic agents. In contrast, overexpression of Lgr5 increased cell proliferation and enhanced chemoresistance. CONCLUSION: These results suggest that elevated Lgr5 level is associated with CRC progression and treatment response and has the potential to serve as a therapeutic target in CRC patients.

CBB1003, a lysine-specific demethylase 1 inhibitor, suppresses colorectal cancer cells growth through down-regulation of leucine-rich repeat-containing G-protein-coupled receptor 5 expression.

PURPOSE: Lysine-specific demethylase 1 (LSD1) was highly expressed in several malignancies and had been implicated in pathological processes of cancer cells. However, the role of LSD1 in colorectal cancer (CRC) carcinogenesis, prognosis and treatment remains uncharacterized. METHODS: In this study, we examined LSD1 expression in paraffin-embedded CRC specimens from 295 patients, including 65 patients with paired samples of colorectal carcinoma, adjacent adenoma and normal colorectal tissues. Using an LSD1 inhibitor, CBB1003, as a probe, we studied the association between LSD1 and leucine-rich repeat-containing G-protein-coupled receptor 5 (LGR5), a CRC stem cell marker involved in carcinogenesis. The anti-tumor effects of CBB1003 on CRC cells were also examined. RESULTS: LSD1 expression was significantly elevated in colorectal tumor tissues compared with adjacent adenoma and normal colorectal tissues (P < 0.001), and LSD1 levels were significantly correlated with an advanced AJCC T stage (P = 0.012) and distant metastasis (P = 0.004). CBB1003 inhibited CRC cell proliferation and colony formation. In cultured CRC cells, inhibiting LSD1 activity by CBB1003 caused a decrease in LGR5 levels while overexpression of LGR5 reduced CBB1003-induced cell death. We also observed the inactivation of ß-catenin/TCF signaling after CBB1003 treatment, consistent with the positive correlations among LSD1, LGR5, ß-catenin and c-Myc expression in human colon tumor and adenoma tissues. CONCLUSION: Our result suggested that LSD1 overexpression promotes CRC development and that the LSD1 inhibitor inhibits CRC cell growth by down-regulating LGR5 levels and inactivates the Wnt/ß-catenin pathway. Thus, LSD1 and its inhibitor might provide a new target or a useful strategy for therapy of CRC.

LGR5 regulates survival through mitochondria-mediated apoptosis and by targeting the Wnt/ß-catenin signaling pathway in colorectal cancer cells.

Colorectal cancer (CRC) is one of the most common causes of cancer-related death worldwide. The leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5) is a newly identified surface marker of colorectal cancer stem cells (CSCs). Expression level of LGR5 is commonly elevated in human CRCs. Our previous study demonstrated that the elevated expression of LGR5 is associated with CRC initiation and progression. However, the role of LGR5 in CRC pathogenesis has not been sufficiently established. In this study, we aimed to characterize the role of LGR5 in CRC pathogenesis using the loss-of-function approach. Depletion of LGR5 suppressed the growth of several cultured CRC cells and caused an increase in the fraction of apoptotic cells, which were analyzed using Annexin V/PI staining and DNA fragmentation assay. Furthermore, depleting LGR5 induced apoptosis through the loss of mitochondrial membrane potential. Additionally, depletion of LGR5 suppressed ß-catenin nuclear translocation and blocked the activity of Wnt/ß-catenin signaling as manifested in the reduced expression of c-myc and cyclin D, two Wnt/ß-catenin targets in CRC cells. Treatment with Wnt3a considerably alleviated the growth inhibition and apoptotic cell death induced by LGR5 depletion in CRC cells. These data suggested that LGR5 regulates cell proliferation and survival by targeting the Wnt/ß-catenin signaling pathway. Thus, the findings of this study suggest that LGR5 plays a vital role in CRC pathogenesis and has the potential to serve as a diagnostic marker and a therapeutic target for CRC patients.

Lgr5 promotes cancer stemness and confers chemoresistance through ABCB1 in colorectal cancer.

INTRODUCTION: Chemotherapy failure is a major problem in patients with advanced colorectal carcinoma (CRC). Leucine-rich repeat-containing G-protein-coupled receptor 5 (Lgr5) is a well-established target gene of the Wnt pathway and is a bona fide marker of CRC cancer stem cells (CSCs). Our previous study showed that CRC patients with higher Lgr5 level are associated with poor response to 5-fluoracil-based treatment. In this study, we investigated the mechanisms underlying Lgr5-associated chemoresistance in cancer stem cells derived from cultured CRC cells. MATERIALS AND METHODS: Cancer stem cells were isolated from CRC cell lines by spheroid culture. The effect of Lgr5 on CRC cancer stem cell was investigated using both gain- and loss-of-function approaches. Stemness property was evaluated using sphere formation assay, side population analysis, and stem cell marker expression. Lgr5 and ABCB1 expression in CRC tissues was determined using immunohistochemical staining. RESULTS: Forced expression of Lgr5 increased the CRC sphere-forming efficiency and spheroid size while depletion of Lgr5 reduced the stem cell property in cultured CRC cells. Over-expression of Lgr5 also reduced the sensitivity of cultured CRC cells, including adherent and spheroids, towards 5-fluoracil and oxalipatin. In addition, Lgr5 positively regulates the expression of ABCB1 in both adherent and spheroid CRC cells. Finally, in human CRC tissues, higher expression levels of Lgr5 were associated with higher ABCB1 expression. CONCLUSIONS: The present study demonstrated that Lgr5 plays an active role in promoting the cancer stem cell property and that Lgr5 confers chemoresistance to CRC cells via ABCB1 induction.