Repression of Akt3 gene transcription by the tumor suppressor RIZ1

The antagonistic effect of FTO on METTL14 promotes AKT3 m6A demethylation and the progression of esophageal cancer

BACKGROUND

As the most abundant modification in eukaryotic messenger RNAs (mRNAs), N6-methyladenosine (m6A) plays vital roles in many biological processes.

METHODS

Methylated RNA immunoprecipitation sequencing (MeRIP-seq) and transcriptomic RNA sequencing (RNA-seq) were used to screen for m6A targets in esophageal cancer cells and patients. The role of m6A RNA methylase in esophageal cancer was also analyzed using bioinformatics. In vitro and in vivo experiments were used to analyze gene expression and function. CCK-8, colony formation, cell apoptosis and immunofluorescence staining assays were performed to evaluate the proliferation, migration and invasion of esophageal cancer cells, respectively. Western blot analysis, RNA stability, RIP and luciferase reporter assays were performed to elucidate the underlying mechanism involved.

RESULTS

We found that the m6A demethylase FTO was significantly upregulated in esophageal cancer cell lines and patient tissues. In vivo and in vitro assays demonstrated that FTO was involved in the proliferation and apoptosis of esophageal cancer cells. Moreover, we found that the m6A methyltransferase METTL14 negatively regulates FTO function in esophageal cancer progression. FTO alone is not related to the prognosis of esophageal cancer, and its function is antagonized by METTL14. By using transcriptome-wide m6A-seq and RNA-seq assays, we revealed that AKT3 is a downstream target of FTO and acts in concert to regulate the tumorigenesis and metastasis of esophageal cancer. Taken together, these findings provide insight into m6A-mediated tumorigenesis in esophageal cancer and could lead to the design of new therapeutic strategies.

The absence of PRDM2 involved the tumorigenesis of somatotroph adenomas through regulating c-Myc

Somatotroph adenoma is the main cause of acromegaly which have peripheral signs with growth of soft tissues and multiple comorbidities. Surgery and adjuvant therapy with somatostatin analogs (SSA) fail in more than 25% of patients. PRDM2, a tumor suppressor, plays an important role in cancer and obesity, including pituitary adenomas. In this study, we analyze the correlation of PRDM2 and oncogene c-Myc in 70 somatotroph adenomas according immunohistochemical staining, furthermore, we probed that whether PRDM2 participates in c-Myc signaling pathway in vitro experiment. 70 somatotroph adenomas patients were divided into low patients and high patients according to median of H-score of PRDM2 or c-Myc. Low PRDM2 patients had higher risk of invasive behavior, larger tumor volume and recurrence chance than high PRDM2 group (P = 0.015, P = 0.031, P = 0.017). High c-Myc patients had higher risk of invasive behavior, larger tumor volume and recurrence chance than low c-Myc group (P = 0.012, P = 0.002, P = 0.015). It was a negative correlation between H-score of PRDM2 and c-Myc (PRDM2 = -0.163 × c-Myc + 67.11, r = -0.407). The ability of cell proliferation was declined in a time dependent manner after overexpression of PRDM2 (PRDM2 group) compared to that in control GH3 cells (P < 0.05). Through flow cytometry assay, PRDM2 could induce the apoptosis and G2/M arrest in GH3 cell (both p < 0.05). Transwell experiment proved less trans-membrane cells in PRDM2 group than those in control group (415 ± 76 vs 145 ± 37, P < 0.01). RT-PCR and western blot both proved PRDM2 could inhibit the level c-Myc and elevate the levels of CDKN1A and CDKN1B. Combined with c-Myc inhibitor 10058-F4, PRDM2 further inhibited cell proliferation and induced more apoptosis in GH3 cell. Taken together, we found that PRDM2 negatively regulated the expression of c-Myc in somatotroph adenomas, and testified the synergism between PRDM2 gene therapy and c-Myc inhibitor in vitro experiment.

LncRNA MALAT1 promotes osteoarthritis by modulating miR-150-5p/AKT3 axis

BACKGROUND

Many studies have reported that long noncoding RNAs (lncRNAs) could act as sponges for microRNAs (miRNAs) and play important roles in the regulation of osteoarthritis (OA). Yet, the underlying mechanisms of lncRNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) in OA are still unclear. Therefore, we aimed to explore the regulation mechanisms of MALAT1 in OA procession.

METHODS

IL-1β treatment in chondrocyte was used to mimic OA in vitro. MALAT1, miR-150-5p and AKT3 expression levels were detected via qRT-PCR. The protein levels of AKT3, MMP-13, ADAMTS-5, Bax, Bcl-2, cleaved-PARP, collagen II and aggracan were measured by western blot. MTT assay was performed to detect cell proliferation ability. The apoptosis of chondrocytes was determined using flow cytometry and western blot. Luciferase assay and RNA immunoprecipitation (RIP) assays were used to confirm the relationship among MALAT1, miR-150-5p and AKT3.

RESULTS

In our study, MALAT1 and AKT3 were upregulated while miR-150-5p was downregulated in OA in vitro and vivo. The level of miR-150-5p was negatively correlated with that of MALAT1 or AKT3. More importantly, overexpression of MALAT1 promoted the expression of AKT3 by negatively regulating miR-150-5p. MALAT1 knockdown inhibited cell proliferation, promoted apoptosis, increased MMP-13, ADAMTS-5 expression and decreased collagen II, aggracan expression in IL-1β treated chondrocytes. MALAT1 upregulation or AKT3 overexpression enhanced proliferation, inhibited apoptosis and extracellular matrix (ECM) degradation, which was undermined by overexpression of miR-150-5p. By contrast, miR-150-5p depletion rescued the effect of MALAT1 downregulation or loss of AKT3 on IL-1β-stimulated chondrocytes.

CONCLUSION

MALAT1 was responsible for cell proliferation, apoptosis, and ECM degradation via miR-150-5p/AKT3 axis.

Transcriptional regulation of Bcl-2 gene by the PR/SET domain family member PRDM10

Bcl-2 (B-cell lymphoma 2) protein is localized in the outer membrane of mitochondria, where it plays an important role in promoting cellular survival and inhibiting the actions of pro-apoptotic proteins. PRDM10 is a member of the PR/SET family of epigenetic regulators and may play a role in development and cell differentiation. Here we show that human PRDM10 contributes to the transcriptional regulation of human Bcl-2 gene. We found that PRDM10-depletion in human cells reduced the expression of Bcl-2 protein and over-expression of PRDM10 promoted Bcl-2 protein expression. Furthermore, luciferase reporter activity of Bcl-2 gene P1 promoter was significantly increased in cells co-transfected with PRDM10, and PRDM10 was able to bind to the Bcl-2 P1 promoter in vivo. Using The Cancer Genome Atlas (TCGA) data set, we found weak positive correlation between PRDM10 and Bcl-2 in several cancer types including cancers of the breast, colon, and lung tissues. These data identify a novel function for PRDM10 protein and provide insights on the transcriptional control of Bcl-2 expression.