MicroRNA‑936 inhibits the malignant phenotype of retinoblastoma by directly targeting HDAC9 and deactivating the PI3K/AKT pathway

Abstract

MicroRNA-936 (miR-936) has been reported to play important roles in the progression of non-small cell lung cancer and glioma. However, the expression and functions of miR-936 in retinoblastoma (RB) remain elusive and need to be further elucidated. Herein, the aims were to measure miR-936 expression in RB, identify the functional importance of miR-936 in the oncogenicity of RB, and investigate the underlying molecular mechanisms. Reverse-transcription quantitative PCR was carried out to determine miR-936 expression in RB tissues and cell lines. Cell proliferation, colony formation, apoptosis, migration, and invasion in vitro and tumor growth in vivo were examined respectively by Cell Counting Kit-8, colony formation, flow cytometric, and Transwell migration and invasion assays and a subcutaneous heterotopic xenograft experiment. The potential target of miR-936 was predicted by bioinformatic analysis and was subsequently validated by luciferase reporter assay, reverse-transcription quantitative PCR, and western blotting. miR-936 expression was weak in both RB tissues and cell lines and was correlated with differentiation, lymph node metastasis and TNM staging in RB. RB cell proliferation, colony formation, migration, and invasion in vitro and tumor growth in vivo were attenuated by exogenous miR-936, whereas apoptosis was enhanced by miR-936 overexpression. Further molecular investigation identified histone deacetylase 9 (HDAC9) as a direct target gene of miR-936 in RB cells. HDAC9 depletion had effects similar to those of miR-936 overexpression in RB cells. Recovery of HDAC9 expression counteracted the tumor-suppressive action of miR-936 on the oncogenicity of RB cells. Ectopic miR-936 expression deactivated the PI3K/AKT pathway in RB cells in vitro and in vivo by decreasing HDAC9 expression. Downregulated miR-936 is related to poor prognosis in RB, and its upregulation inhibits RB aggressiveness via direct targeting of HDAC9 mRNA and thereby inactivation of the PI3K/AKT pathway.

Histone deacetylase (HDAC) 9: versatile biological functions and emerging roles in human cancer

“…Several recent studies have found that microRNAs (miRs) are involved in post-transcriptional downregulation of HDAC9. Specifically, HDAC9 has been found to be downregulated by miR-188 in bone marrow stromal cells [27], by miR-361-5p in cells associated with cardiac hypertrophy [28], by miR-936 or miR-101-3p in retinoblastoma cells [29,30], by miR-383-5p in gastric carcinoma cells [31], by miR-211-5p in bladder cancer cells [32], by miR-30d-5p in esophageal squamous cell carcinoma cells [33], by miR-509 3p in nonsmall cell lung cancer cells [34] and by miR-377 in oral squamous cell carcinoma cells [35].…”

HDAC9 Is Preferentially Expressed in Dedifferentiated Hepatocellular Carcinoma Cells and Is Involved in an Anchorage-Independent Growth

“…HDAC genes showed differential regulation in that only the HDAC9 gene was up-regulated, and class I HDACs were down-regulated during the EMT process. A number of studies have shown an involvement of HDAC9 in the ability of migration and invasion [ 20 , 21 , 22 , 23 ]. However, in the case of TGF-β-induced EMT, HDAC9 suppression barely inhibited the phenotypic change of HuH1 cells, suggesting that HDAC9 does not locate in the upstream of EMT induction mediated by TGF-β-SMAD or non-SMAD pathway [ 19 ].…”

“…In endothelial cells, HDAC9 is induced via signal transducer and activator of transcription 3 (STAT3) signaling to proliferate by PDAC-secreted proangiogenic factors [ 24 ]. HDAC9 is reported to be regulated post-transcriptionally by several micro RNAs in retinal, oral, breast, and gastric cancer, and as being associated with poor prognosis [ 21 , 23 , 25 , 26 ]. Analysis of other signaling pathways that induce dedifferentiation and malignant phenotype via HDAC9 may help us to understand the essential role of HDAC9 in tumor dedifferentiation.…”

Exosomes derived from retinoblastoma cells enhance tumour deterioration by infiltrating the microenvironment

“…Current treatments for retinoblastoma include chemotherapy, plaque radiotherapy, external beam radiotherapy, cryotherapy and surgery ( 2 ). However, despite the clinical response to such comprehensive strategies, tumour metastasis and extraocular invasion in the advanced stage still cause death in children ( 3 , 4 ). Therefore, investigation of the underlying mechanism of retinoblastoma tumourigenesis and development is necessary to improve therapeutic efficacy.…”