LncRNA NEAT1 knockdown attenuates autophagy to elevate 5-FU sensitivity in colorectal cancer via targeting miR-34a.

Abstract

BackgroundsColorectal carcinoma (CRC) is a common malignant tumor. Increasing evidences indicated that CRC showed a resistance to 5‐fluorouracil (5‐FU) and further resulted in a poor prognosis. In this study, we aim to investigate the effect of long noncoding RNA nuclear paraspeckle assembly transcript 1 (LncRNA NEAT1) on cell viability, sensitivity to 5‐FU, and autophagy of CRC cell lines.MethodsMTT (3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyl‐2‐Htetrazolium bromide) was used to detect cell viability, immunofluorescent staining was used to detect autophagy puncta, and luciferase reporter system was used to determine binding ability between miR‐34a and NEAT1 or putative targets. Additionally, indicated mRNAs and protein expressions were determined by qRT‐PCR or western blotting, respectively.ResultsWe found that NEAT1 expression was increased in CRC tissues and cells, which showed a negative correlation with miR‐34a expression. In addition, NEAT1 knockdown noticeably inhibited the proliferation of CRC cells and enhanced 5‐FU sensitivity. It revealed that NEAT1 knockdown suppressed the LC3 puncta and the expressions of Beclin‐1, ULK1, and ratio of LC3II/I. Overexpression of miR‐34a showed similar trends with NEAT1 knockdown. miR‐34a was validated to target the putative binding sites in 3′‐UTR of HMGB1, ATG9A, and ATG4B, which are involved in the activation of autophagy. Inhibition of miR‐34a or overexpression of HMGB1 could effectively reverse elevated 5‐FU sensitivity upon NEAT1 knockdown. In addition, 3‐MA reversed NEAT1 overexpression‐induced resistance in HT29 cells.ConclusionThese findings indicate that LncRNA NEAT1 could target miR‐34a and promote autophagy to facilitate 5‐FU chemoresistance in CRC.