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Background Aberrant expression of circular RNAs (circRNAs) contributes to the initiation and progression of human malignancies, but the underlying mechanisms remain largely elusive. Methods High-throughput sequencing was performed to screen aberrantly expressed circRNAs or miRNAs in colorectal cancer (CRC) and adjacent normal tissues. A series of gain- and loss-of-function studies were conducted to evaluate the biological behaviors of CRC cells. RNA pulldown, mass spectrometry, RIP, qRT-PCR, Western blot, luciferase reporter assays and MeRIP-seq analysis were further applied to dissect the detailed mechanisms. Results Here, a novel circRNA named circEZH2 (hsa_circ_0006357) was screened out by RNA-seq in CRC tissues, whose expression is closely related to the clinicpathological characteristics and prognosis of CRC patients. Biologically, circEZH2 facilitates the proliferation and migration of CRC cells in vitro and in vivo. Mechanistically, circEZH2 interacts with m6A reader IGF2BP2 and blocks its ubiquitination-dependent degradation. Meanwhile, circEZH2 could serve as a sponge of miR-133b, resulting in the upregulation of IGF2BP2. Particularly, circEZH2/IGF2BP2 enhances the stability of CREB1 mRNA, thus aggravating CRC progression. Conclusions Our findings not only reveal the pivotal roles of circEZH2 in modulating CRC progression, but also advocate for attenuating circEZH2/miR-133b/IGF2BP2/ CREB1 regulatory axis to combat CRC.

Background Prostate cancer (PCa) is the most frequently diagnosed malignancy in men, and its mechanism remains poorly understood. Therefore, it is urgent to discover potential novel diagnostic biomarkers and therapeutic targets that can potentially facilitate the development of efficient anticancer strategies. Methods A series of functional in vitro and in vivo experiments were conducted to evaluate the biological behaviors of PCa cells. RNA pulldown, Western blot, luciferase reporter, immunohistochemistry and chromatin immunoprecipitation assays were applied to dissect the detailed underlying mechanisms. High-throughput sequencing was performed to screen for differentially expressed circRNAs in PCa and adjacent normal tissues. Results Upregulation of protein arginine methyltransferase 5 (PRMT5) is associated with poor progression-free survival and the activation of multiple signaling pathways in PCa. PRMT5 inhibits the transcription of CAMK2N1 by depositing the repressive histone marks H4R3me2s and H3R8me2s on the proximal promoter region of CAMK2N1, and results in malignant progression of PCa both in vitro and in vivo. Moreover, the expression of circSPON2, a candidate circRNA in PCa tissues identified by RNA-seq, was found to be associated with poor clinical outcomes in PCa patients. Further results showed that circSPON2 induced PCa cell proliferation and migration, and that the circSPON2-induced effects were counteracted by miR-331-3p. Particularly, circSPON2 acted as a competitive endogenous RNA (ceRNA) of miR-331-3p to attenuate the repressive effects of miR-331-3p on its downstream target PRMT5. Conclusions Our findings showed that the epigenetic regulator PRMT5 aggravates PCa progression by inhibiting the transcription of CAMK2N1 and is modulated by the circSPON2/miR-331-3p axis, which may serve as a potential therapeutic target for patients with aggressive PCa.