Circ_0005615 Regulates the Progression of Colorectal Cancer Through the miR-873-5p/FOSL2 Signaling Pathway

Circ_0005615 enhances multiple myeloma progression through interaction with EIF4A3 to regulate MAP3K4 m6A modification mediated by ALKBH5

BACKGROUND

Circular RNAs (circRNAs) are associated with development and progression of multiple myeloma (MM). However, the role and mechanism of circ_0005615 in MM have not been elucidated.

METHODS

Circ_0005615 was determined by GEO database. quantitative RT-PCR was performed to confirm the expression of circ_0005615 in peripheral blood of MM patients and MM cells. The roles of circ_0005615 in MM were analyzed using CCK8, transwell invasion, cell apoptosis and tumor xenograft experiments. Bioinformatics tools, RIP and RNA pull down assays were conducted to explore the downstream of circ_0005615. Furthermore, the mechanism was investigated by quantitative RT-PCR, western blot, dot blot and meRIP-PCR assays.

RESULTS

Circ_0005615 was upregulated in MM. Overexpression of circ_0005615 promoted cell viability and invasion, and suppressed apoptosis in vitro, which were opposite when circ_0005615 was knockdowned. Mechanistically, EIF4A3, a RNA-binding protein (RBP), could directly bind to circ_0005615 and ALKBH5, where ALKBH5 could directly combine with MAP3K4, forming a circ_0005615- EIF4A3-ALKBH5-MAP3K4 module. Furthermore, circ_0005615 overexpression increased m6A methylation of MAP3K4 by inhibiting ALKBH5, leading to decreased MAP3K4. Further functional experiments indicated that ALKBH5 overexpression weakened the promoting roles of circ_0005615 overexpression in MAP3K4 m6A methylation and tumor progression in MM. The above functions and mechanism were also verified in vivo.

CONCLUSIONS

Elevated circ_0005615 decreased MAP3K4 mediated by ALKBH5 through interacting with EIF4A3, thereby accelerating MM progression. Circ_0005615 might be a promising biomarker and target of MM.

Roles of circRNAs in the progression of colorectal cancer: novel strategies for detection and therapy

Endogenous noncoding RNAs with a covalently closed loop are known as circular RNAs (circRNAs). Recently, published works have revealed that circRNAs, which act as microRNA sponges, are critical for the biological behavior of several kinds of malignancies, including tumor cell proliferation, apoptosis, invasion, and metastasis. Additionally, there is a significant correlation between circRNAs and tumor resistance, stage, prognosis, and size. At present, colorectal cancer (CRC) is one of the most serious malignant tumors for human health. CircRNAs could represent potential targets to use in the prevention, diagnosis, and therapy of CRC, according to many studies. To fully comprehend the role of circRNAs in the incidence and progression of CRC, this review outlines the regulatory role and mechanisms of circRNAs in CRC and assesses their potential relevance as diagnostic and treatment possibilities for CRC. Our goal is to offer meaningful biological information for clinical evaluation and decision-making process for CRC treatment.

Tumorigenic and tumoricidal properties of exosomes in cancers; a forward look

In recent decades, emerging data have highlighted the critical role of extracellular vesicles (EVs), especially (exosomes) Exos, in the progression and development of several cancer types. These nano-sized vesicles are released by different cell lineages within the cancer niche and maintain a suitable platform for the interchange of various signaling molecules in a paracrine manner. Based on several studies, Exos can transfer oncogenic factors to other cells, and alter the activity of immune cells, and tumor microenvironment, leading to the expansion of tumor cells and metastasis to the remote sites. It has been indicated that the cell-to-cell crosstalk is so complicated and a wide array of factors are involved in this process. How and by which mechanisms Exos can regulate the behavior of tumor cells and non-cancer cells is at the center of debate. Here, we scrutinize the molecular mechanisms involved in the oncogenic behavior of Exos released by different cell lineages of tumor parenchyma. Besides, tumoricidal properties of Exos from various stem cell (SC) types are discussed in detail.

Role of Fra-2 in cancer

Fos-related antigen-2 (Fra-2) is the most recently discovered member of the Fos family and, by dimerizing with Jun proteins, forms the activator protein 1 (AP-1) transcription factor. By inducing or repressing the transcription of several target genes, Fra-2 is critically involved in the modulation of cell response to a variety of extracellular stimuli, stressors and intracellular changes. In physiological conditions, Fra-2 has been found to be ubiquitously expressed in human cells, regulating differentiation and homeostasis of bone, muscle, nervous, lymphoid and other tissues. While other AP-1 members, like Jun and Fos, are well characterized, studies of Fra-2 functions in cancer are still at an early stage. Due to the lack of a trans-activating domain, which is present in other Fos proteins, it has been suggested that Fra-2 might inhibit cell transformation, eventually exerting an anti-tumor effect. In human malignancies, however, Fra-2 activity is enhanced (or induced) by dysregulation of microRNAs, oncogenes and extracellular signaling, suggesting a multifaceted role. Therefore, Fra-2 can promote or prevent transformation, proliferation, migration, epithelial-mesenchymal transition, drug resistance and metastasis formation in a tumor- and context-dependent manner. Intriguingly, recent data reports that Fra-2 is also expressed in cancer associated cells, contributing to the intricate crosstalk between neoplastic and non-neoplastic cells, that leads to the evolution and remodeling of the tumor microenvironment. In this review we summarize three decades of research on Fra-2, focusing on its oncogenic and anti-oncogenic effects in tumor progression and dissemination.

Recent advances of exosomal circRNAs in cancer and their potential clinical applications

Circular RNA (circRNA) is a type of non-coding RNA that forms a covalently closed, uninterrupted loop. The expression of circRNA differs among cell types and tissues, and various circRNAs are aberrantly expressed in a variety of diseases, including cancer. Aberrantly expressed circRNAs contribute to disease progression by acting as microRNA sponges, functional protein sponges, or novel templates for protein translation. Recent studies have shown that circRNAs are enriched in exosomes. Exosomes are spherical bilayer vesicles released by cells into extracellular spaces that mediate intercellular communication by delivering cargoes. These cargoes include metabolites, proteins, lipids, and RNA molecules. Exosome-mediated cell-cell or cell-microenvironment communications influence the progression of carcinogenesis by regulating cell proliferation, angiogenesis, metastasis as well as immune escape. In this review, we summarize the current knowledge about exosomal circRNAs in cancers and discuss their specific functions in tumorigenesis. Additionally, we discuss the potential value of exosomal circRNAs as diagnostic biomarkers and the potential applications of exosomal circRNA-based cancer therapy.