RETRACTED ARTICLE: PTBP3 splicing factor promotes hepatocellular carcinoma by destroying the splicing balance of NEAT1 and pre-miR-612

Abstract

Nuclear-enriched RNA-binding proteins (RBPs) are mainly involved in transcriptional regulation, which is a critical checkpoint to tune gene diversity and expression levels. We analyzed nuclear RBPs in human HCC tissues and matched normal control tissues. Based on the gene expression levels, PTBP3 was identified as top-ranked in the nuclei of HCC cells. HCC cell lines then were transfected with siRNAs or lentiviral vectors. PTBP3 promoted HCC cell proliferation and metastasis both in vitro and in vivo. RNA immunoprecipitation (RIP), fluorescence in situ hybridization (FISH) and qRT-PCR assays verified that PTBP3 protein recruited abundant lnc-NEAT1 splicing variants (NEAT1_1 and NEAT1_2) and pre-miR-612 (precursor of miR-612) in the nucleus. NEAT1_1, NEAT1_2 and miR-612 expression levels were determined by PTBP3. Correlational analyses revealed that PTBP3 was positively correlated with NEAT1, but it was inversely correlated with miR-612 in HCC. The P53/CCND1 and AKT2/EMT pathways were determined by NEAT1 and miR-612 respectively in HCC. The PTBP3 and NEAT1/miR-612 patients had a shorter overall survival. Therefore, nuclear-enriched RBP, PTBP3, promotes HCC cell malignant growth and metastasis by regulating the balance of splicing variants (NEAT1_1, NEAT1_2 and miR-612) in HCC.

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

“…A lncRNA, gastric adenocarcinoma predictive long intergenic noncoding RNA (GAPLINC), also induces CD44 expression by suppressing miR-221, a CD44-targeting miRNA [33]. Although the suppression of miR-221 by NEAT1 has not been reported, a number of miRNAs, including miR-101, miR-124, miR-129, miR-193a, miR-612, and miR-613, are reportedly regulated by NEAT1 in HCC [22,[38][39][40][41][42].…”

“…NEAT1 has been recognized as a p53 target gene [21][22][23][24]. NEAT1 harbors a consensus p53-binding site in its promoter region, and p53, upon its activation under stress conditions, such as DNA damage, induces NEAT1 transcription [21,24].…”

“…In this context, NEAT1 allows the cells to overcome oncogene-induced replication stress, eventually leading to tumorigenesis. Yang et al [22] demonstrated that NEAT1 increases the proliferation of HCC cells by suppressing p53 expression and activating cyclin D1 expression. In contrast, although Mellow et al [24] also found that NEAT1 is a p53 target gene, they showed that NEAT1 protects cells from oncogenic transformation.…”

“…In HuH7 and HepG2 cells, the induction rate of NEAT1 expression in spheroids were lower than the other cell lines (Figure 1). Moreover, HuH7 and HepG2 cells harbor mutant and wild-type TP53 gene, respectively, which is suggested to be related to the function of NEAT1 [21][22][23][24]. Thus, hereafter, we used these two cell lines in further experiments.…”

“…Although the function of paraspeckles remains unclear, it was reported that NEAT1 induces IL8 transcription in response to immune stimuli [20]. Moreover, NEAT1 is also involved in the development of cancer by suppressing p53 function, or by forming a transcriptional repressor complex [21][22][23]. However, it has been reported that NEAT1 has tumor-suppressive function under the transcriptional control of p53 [24].…”