Open AccessDEAD box protein DDX 1 promotes colorectal tumorigenesis through transcriptional activation of the LGR5 gene
Author(s) -
Tanaka Kiyoko,
Ikeda Narumi,
Miyashita Kazuya,
Nuriya Hideko,
Hara Takahiko
Publication year - 2018
Publication title -
cancer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.035
H-Index - 141
eISSN - 1349-7006
pISSN - 1347-9032
DOI - 10.1111/cas.13661
Subject(s) - lgr5 , cancer research , biology , carcinogenesis , colorectal cancer , cancer stem cell , cancer cell , transfection , stem cell , microbiology and biotechnology , cell culture , cancer , genetics
DDX 1, a member of the DEAD box RNA helicase family, plays a critical role in testicular tumors. However, it remains to be clarified whether DDX 1 is involved in other types of malignant tumors such as colorectal cancer. We disrupted the DDX1 gene in a human colorectal cancer cell line LoVo using the CRISPR /Cas9‐mediated gene‐targeting system. DDX 1‐ KO LoVo cells exhibited a much slower growth rate, produced fewer colonies in soft agar medium, and generated smaller solid tumors in nude mice than parental LoVo cells. Such phenotypes of the DDX 1‐ KO cells were mostly reversed by exogenous expression of DDX 1. These results indicate that DDX 1 is required for tumorigenicity of colorectal cancer cells. In the DDX 1‐ KO cells, the cancer stem cell marker genes LGR5 , CD133 , ALDH1 and SOX2 were markedly suppressed. Among them, expression of LGR 5, which is essential for tumorigenicity of colorectal cancer cells, was restored in the DDX 1‐transfected DDX 1‐ KO cells. Consistently, the DDX 1‐ KO cells lost sphere‐forming capacity in a DDX 1‐dependent fashion. Reporter and chromatin immunoprecipitation assays revealed that DDX 1 directly bound to the −1837 to −1662 region of the enhancer/promoter region of the human LGR5 gene and enhanced its transcription in LoVo cells. Repression of LGR5 by DDX 1 knockdown was observed in 2 other human colorectal cancer cell lines, Colo320 and SW 837. These results suggest that LGR 5 is a critical effector of DDX 1 in colorectal cancer cells. The DDX 1‐ LGR 5 axis could be a new drug target for this type of malignant cancer.