NEAT1 is Required for the Expression of the Liver Cancer Stem Cell Marker CD44

Abstract

CD44, a cancer stem cell (CSC) marker, is required for maintaining CSC properties in hepatocellular carcinoma (HCC). Nuclear enriched abundant transcript 1 (NEAT1), a long noncoding RNA (lncRNA), is an oncogenic driver in HCC. In the present study, we investigated the significance of the NEAT1 gene in association with CD44 expression in liver CSCs of human HCC cell lines. The CSC properties were evaluated by spheroid culture, CSC marker expression, and sensitivity to anti-cancer drugs. The expression of both NEAT1 variant 1 (NEAT1v1) and variant 2 (NEAT1v2) as well as CD44 was significantly increased in the spheroid culture, compared with that in monolayer culture. Overexpression of Neat1v1, but not Neat1v2, enhanced the CSC properties, while knockout of the NEAT1 gene suppressed them. CD44 expression was increased by the overexpression of Neat1v1 and abrogated by NEAT1 knockout. The overexpression of NEAT1v1 restored the CSC properties and CD44 expression in NEAT1-knockout cells. NEAT1v1 expression in HCC tissues was correlated with poor prognosis and CD44 expression. These results suggest that NEAT1v1 is required for CD44 expression. To our surprise, NEAT1v1 also restored the CSC properties even in CD44-deficient cells, suggesting that NEAT1v1 maintains the properties of CSCs in a CD44-independent manner.

Clinical and Biological Implications of Cancer Stem Cells in Hepatocellular Carcinoma

“…52,53 We recently elucidated that the knockout of the NEAT1 gene resulted in decreased CSC-like properties of HCC cell lines, which were concomitant with the abolishment of CD44 expression. 31 Rescue experiments supported the notion that CD44 expression in HCC was highly dependent on NEAT1 expression. As described above, since CD44 regulates CSCs, it was postulated that NEAT1 might maintain CSC-like properties via CD44.…”

“…However, we found that NEAT1 overexpression restored the CSClike properties even in CD44-deficient HCC cells. 31 These findings suggested that NEAT1 maintained the CSC-like properties of HCC cell lines in both CD44independent and CD44-dependent manners.…”

“…Recently, we demonstrated that nuclear paraspeckle assembly transcript 1 (NEAT1), a lncRNA, is involved in the enhancement and maintenance of CSC-like properties and is required for CD44 expression in HCC. 31 It has been demonstrated that the knockdown or knockout of these CSC markers in cancer cells result in the impairment of CSC-like properties, which suggests that these molecules and their downstream signaling pathways play crucial roles in the regulation of CSC-like properties. Accordingly, these CSC-specific molecules not only attract interest in terms of molecular cancer biology but also are expected as novel therapeutic targets for HCC treatment.…”

LncRNA NEAT1: Shedding light on mechanisms and opportunities in liver diseases

“…indicating that the ability of NEAT1_1 to maintain CSC properties is in a CD44-independent manner. 90 These studies suggest that NAET1…”

The novel interplay between CD44 standard isoform and the caspase-1/IL1B pathway to induce hepatocellular carcinoma progression

“…CD44 is encoded by a highly conserved gene, and its premessenger RNA could be alternatively spliced into mature mRNAs encoding variant isoforms (CD44v) or standard isoform (CD44s). CD44s have been reported to be tightly related to the poor prognosis of patients with HCC and contribute to tumor metastasis and chemoresistance [9][10][11][12] . Moreover, Bousoik et al 13 showed that shedding extracellular domain of CD44 reduced caspase-1/IL1B activation in macrophage, which suggesting CD44s might be an upstream regulator of caspase-1/IL1B.…”