Circular RNA- and microRNA-Mediated Post-Transcriptional Regulation of Preadipocyte Differentiation in Adipogenesis: From Expression Profiling to Signaling Pathway

The roles and molecular mechanisms of non-coding RNA in cancer metabolic reprogramming

One of the key features of cancer is energy metabolic reprogramming which is tightly related to cancer proliferation, invasion, metastasis, and chemotherapy resistance. NcRNAs are a class of RNAs having no protein-coding potential and mainly include microRNAs, lncRNAs and circRNAs. Accumulated evidence has suggested that ncRNAs play an essential role in regulating cancer metabolic reprogramming, and the altered metabolic networks mediated by ncRNAs primarily drive carcinogenesis by regulating the expression of metabolic enzymes and transporter proteins. Importantly, accumulated research has revealed that dysregulated ncRNAs mediate metabolic reprogramming contributing to the generation of therapeutic tolerance. Elucidating the molecular mechanism of ncRNAs in cancer metabolic reprogramming can provide promising metabolism-related therapeutic targets for treatment as well as overcome therapeutic tolerance. In conclusion, this review updates the latest molecular mechanisms of ncRNAs related to cancer metabolic reprogramming.

Expression Analysis of circRNAs in Human Adipogenesis

Purpose

Adipogenesis is one of the major pathways for generating obesity or overweight that can cause a range of metabolic disorders. Circular RNAs (circRNAs), a specific type of RNAs, have a significant influence on metabolic disorders. This study aims to find differentially expressed circRNAs (DECs) during human subcutaneous adipose tissue (SATs) adipogenesis.

Patients and Methods

The human adipose tissue-derived stromal cells (hADSCs) were isolated from human SATs (n = 3), and then induced into adipocytes. Total RNAs were extracted from hADSCs and adipocytes, and he DECs were detected using circRNA microarray. The GO and KEGG pathways of DECs were analyzed by bioinformatic methods, and partial DECs were further validated by quantitative polymerase chain reaction (qPCR).

Results

Our study detected a total of 1987 DECs, among which, 1134 were found upregulated and 853 were downregulated. GO analysis showed that the upregulated DECs have catalytic activity in intracellular organelle and cytoplasms, whereas downregulated DECs are enriched in organelle lumen, and are involved in positive regulation of developmental process. In addition, pathway results demonstrated that upregulated DECs are involved in platinum drug resistance and cellular senescence, and downregulated DECs are enriched in proteoglycans in cancer and focal adhesion pathway. Two circRNAs, namely has_circ_0001600 and has_circ_0001947 were validated to be significantly upregulated in adipocytes compared to hADSCs.

Conclusion

Our study explored DECs between hADSCs derived from SATs and adipocytes, and report that two circRNAs named has_circ_0001600 and has_circ_0001947 might be important factors involved in human adipogenesis, however, the molecular mechanism should be further explored.

MiR-184 targeting FOXO1 regulates host-cell oxidative stress induced by Chlamydia psittaci via the Wnt/β-catenin signaling pathway

Chlamydia psittaci is a human pathogen that causes atypical pneumonia after zoonotic transmission. We confirmed that C. psittaci infection induces oxidative stress in human bronchial epithelial (HBEs) cells and explored how this is regulated through miR-184 and the Wnt/β-catenin signaling pathway. miR-184 mimic, miR-184 inhibitor, FOXO1 siRNA, or negative control sequence was transfected into HBE cells cultured in serum-free medium using Lipofectamine 2000. Then, prior to the cells were infected with C. psittaci 6BC, and the cells were treated with or without 30 µM Wnt/β-catenin inhibitor ICG-001. Quantification of reactive oxygen species, malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione was carried out according to the manufacturer's protocol using a corresponding assay kit. The outcome of both protein and gene was measured by western blotting or real-time fluorescence quantitative PCR. In C. psittaci-infected HBE cells, miR-184 was upregulated, while one of its target genes, FOXO1, was downregulated. ROS and MDA levels increased, while SOD and GSH contents decreased after C. psittaci infection. When miR-184 expression was downregulated, the level of oxidative stress caused by C. psittaci infection was reduced, and the Wnt/β-catenin signaling pathway was inhibited. The opposite results were seen when miR-184 mimic was used. Transfecting with FOXO1 siRNA reversed the effect of miR-184 inhibitor. Moreover, when the Wnt/β-catenin-specific inhibitor ICG-001 was used, the level of oxidative stress induced by C. psittaci infection was significantly suppressed. miR-184 can target FOXO1 to promote oxidative stress in HBE cells following C. psittaci infection by activation of the Wnt/β-catenin signaling pathway.

Circular RNA ZNF800 (hsa_circ_0082096) regulates cancer stem cell properties and tumor growth in colorectal cancer

BACKGROUND

Cancer stem cells form a rare cell population in tumors that contributes to metastasis, recurrence and chemoresistance in cancer patients. Circular RNAs (circRNAs) are post-transcriptional regulators of gene expression that sponge targeted microRNA (miRNAs) to affect a multitude of downstream cellular processes. We previously showed in an expression profiling study that circZNF800 (hsa_circ_0082096) was up-regulated in cancer stem cell-enriched spheroids derived from colorectal cancer (CRC) cell lines.

METHODS

Spheroids were generated in suspension spheroidal culture. The ZNF800 mRNA, pluripotency stem cell markers and circZNF800 levels were determined by quantitative RT-PCR. CircZNF800-miRNA interactions were shown in RNA pulldown assays and the miRNA levels determined by stem-loop qRT-PCR. The effects of circZNF800 on cell proliferation were tested by EdU staining followed by flowcytometry. Expression of stem cell markers CD44/CD133, Lgr5 and SOX9 was demonstrated in immunofluorescence microscopy. To manipulate the cellular levels of circZNF800, circZNF800 over-expression was achieved via transfection of in vitro synthesized and circularized circZNF800, and knockdown attained using a CRISPR-Cas13d-circZNF800 vector system. Xenografted nude mice were used to demonstrate effects of circZNF800 over-expression and knockdown on tumor growth in vivo.

RESULTS

CircZNF800 was shown to be over-expressed in late-stage tumor tissues of CRC patients. Data showed that circZNF800 impeded expression of miR-140-3p, miR-382-5p and miR-579-3p while promoted the mRNA levels of ALK/ACVR1C, FZD3 and WNT5A targeted by the miRNAs, as supported by alignments of seed sequences between the circZNF800-miRNA, and miRNA-mRNA paired interactions. Analysis in CRC cells and biopsied tissues showed that circZNF800 positively regulated the expression of intestinal stem cell, pluripotency and cancer stem cell markers, and promoted CRC cell proliferation, spheroid and colony formation in vitro, all of which are cancer stem cell properties. In xenografted mice, circZNF800 over-expression promoted tumor growth, while circZNF800 knockdown via administration of CRISPR Cas13d-circZNF800 viral particles at the CRC tumor sites impeded tumor growth.

CONCLUSIONS

CircZNF800 is an oncogenic factor that regulate cancer stem cell properties to lead colorectal tumorigenesis, and may be used as a predictive marker for tumor progression and the CRISPR Cas13d-circZNF800 knockdown strategy for therapeutic intervention of colorectal cancer.