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Background: The tumor immune microenvironment (TIME) is an important regulator of tumor progression, growth and metastasis. In addition, tumor metastasis is one of the principal obstacles to the treatment of colorectal cancer (CRC). Circular RNAs (circRNAs) have been recognized as important regulators in the development of malignancies. However, their specific roles and mechanisms in both CRC metastasis and TIME have not been thoroughly investigated. Methods: High-throughput next-generation sequencing technology and real-time fluorescence quantitative PCR technology were performed to identify differential circRNAs in CRC. Functional assays including transwell assay, wound healing assay, and metastasis models were conducted to assess the effect of circRNF216 on CRC metastasis. In addition, luciferase reporter, western blot, RNA immunoprecipitation (RIP), and fluorescent in situ hybridization (FISH) were performed to explore the underlying mechanism of circRNF216. The level of immune infiltration was assessed by bioinformatics analysis and flow cytometry in CRC model. Furthermore, rescue and mutation experiments were used for verification. Results: circRNF216 was identified as a putative tumor suppressor that is downregulated in CRC tissues and cells. Overexpression of circRNF216 inhibits metastasis in vitro and vivo. Mechanistically, circRNF216 acts as a competitive endogenous RNA (ceRNA) for miR-576-5p, alleviating miR-576-5p repression on its target ZC3H12C, which in turn downregulated N-cadherin. Additionally, circRNF216 could enhance the infiltration level of CD8+ T cells by upregulating ZC3H12C, ultimately inhibiting the development of CRC, which suggests that circRNF216 is a potential biomarker for the treatment of CRC. Conclusions: Here, we provide novel mechanistic insight revealing how circRNF216 functioned in CRC metastasis and TIME via the circRNF216/miR-576-5p/ZC3H12C pathway. Therefore, circRNF216 holds promise as a potential therapeutic target and novel diagnostic marker for CRC. [ABSTRACT FROM AUTHOR]

Several studies have reported a significant role of high mobility group box protein 1 (HMGB1) in lung cancer. Nevertheless, there is a lack of knowledge regarding the expression of HMGB1 and its correlation with the clinicopathological features of lung cancer. In addition, the potential molecular mechanisms underlying the role of HMGB1 in lung cancer are still unknown. We therefore investigated the clinicopathological and prognostic significance as well as the potential role of HMGB1 in the development and progression of lung cancer. HMGB1 expression in the tumor tissues of the cohort correlated with clinicopathological features. Moreover, lung cell migration and invasion were significantly increased after treatment with HMGB1. The matrix metalloproteinase-2 (MMP-2) expression and activity were upregulated after treatment with HMGB1, while the upregulated expression of MMP-2 stimulated by HMGB1 in lung cancer cells was significantly reduced with the blockage of si-p65. These results indicated that HMGB1 expression was significantly associated with lung cancer progression. We also showed that HMGB1 promoted lung cancer invasion and metastasis by upregulating the expression and activity of MMP-2 in an NF-κB-dependent manner. Taken together, these data suggested that HMGB1 may be a potential prognosis and therapeutic marker for lung cancer. [ABSTRACT FROM AUTHOR]