Immune dysregulation plays a vital role in colorectal cancer initiation and progression. Long noncoding RNAs (lncRNA) exhibit multiple functions including regulation of gene expression. Here, we identified an immune-related lncRNA, MIR17HG, whose expression was gradually upregulated in adjacent, adenoma, and colorectal cancer tissue. MIR17HG promoted tumorigenesis and metastasis in colorectal cancer cells both in vitro and in vivo. Mechanistically, MIR17HG increased the expression of NF-kB/RELA by competitively sponging the microRNA miR-375. In addition, RELA transcriptionally activated MIR17HG in a positive feedback loop by directly binding to its promoter region. Moreover, miR-17-5p, one of the transcribed miRNAs from MIR17HG, reduced the expression of the tumor suppressor B-cell linker (BLNK), resulting in increased migration and invasion of colorectal cancer cells. MIR17HG also upregulated PD-L1, indicating its potential role in immunotherapy. Overall, these findings demonstrate that MIR17HG plays an oncogenic role in colorectal cancer and may serve as a promising therapeutic target. Significance: These findings provide mechanistic insight into the role of the lncRNA MIR17HG and its miRNA members in regulating colorectal cancer carcinogenesis and progression.

BaCKgRoUND aND aIMS:Liver metastasis is a frequent occurrence in patients with colorectal cancer (CRC), with 15%-25% of CRC patients having liver metastases at the time of initial diagnosis. Specifically, some regional-stage patients with mild symptoms (stage 1 or 2) will also advance to liver metastases rapidly, even if the CRC lesion in situ is resected in time. Nevertheless, the precise mechanism of liver metastasis is still unclear.appRoaCH aND ReSUltS: Fresh tumor tissues from patients with CRC, adjacent noncancerous tissues, and colorectal adenoma tissues were subjected to microarray analysis to identify differentially expressed microRNA. Exosomes from human serum and cell culture medium were separated, quantitated, and verified by transmission electronic microscopy and Zetasizer Nano. Luciferase reporter assay, real-time quantitative PCR, western blot, immunoprecipitation, chromatin and re-chromatin immunoprecipitation, migration and invasion assay, PDX mouse model, flow cytometry, immunohistochemistry, and immunofluorescence staining were employed to explore the regulation among CRC liver metastases, immunosuppression, and cell adhesion. In this study, we demonstrated that the hypoxic microenvironment in primary CRC lesions boosted exosome release, selectively initiated favorable premetastatic niche formation in the liver but not in other organs. Mechanistically, Kupffer cells (KCs) can phagocytose exosomes containing highly expressed miR-135a-5p from the blood circulation into the liver. Exosomal miR-135a-5p initiated the large tumor suppressor kinase 2-yes-associated proteinmatrix metalloproteinase 7 axis to promote the occurrence of CRC liver metastasis, and cluster of differentiation 30-TNF receptor-associated factor 2-p65-mediated immunosuppression signaling also contributed to this process.CoNClUSIoNS: Hypoxia-induced exosomal miR-135a-5p correlates with the development, clinical severity, and prognosis of CRC liver metastases through the premetastatic niche; and our findings revealed that miR-135a-5p might be a promising target in halting CRC liver metastases. (Hepatology 2021;74:2633-2651.T he liver is one of the most frequent targets of colorectal cancer (CRC) metastases, with 15%-25% of patients with CRC having liver metastases at the time of initial diagnosis. (1) The 5-year relative survival rate for patients with CRC and liver metastases is 3.3%, which is significantly lower than that for those with regional-stage CRC (90.3%). (2,3) Interestingly, liver metastasis does not only occur in advanced-stage patients but also in patients whose lesion in situ is resected in time. (2) Thus, liver-tropic metastasis is one

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Metastasis associated with lung adenocarcinoma transcript-1 (MALAT1) is an evolutionarily highly conserved lncRNA that contributes to colorectal cancer development. However, the exact molecular mechanisms connecting MALAT1 to colorectal cancer have not been fully elucidated. Here, we performed a case-control study in 1,078 patients with colorectal cancer and 1,175 healthy controls to evaluate the association between potentially functional genetic variants of MALAT1 and survival outcomes in patients with colorectal cancer. MALAT1 rs664589 CG/GG genotypes significantly increased the associated risk and decreased overall survival of patients with colorectal cancer compared with the CC genotype. In vitro and in vivo experiments showed that the rs664589 C to G mutation facilitated carcinogenesis and metastasis of colorectal cancer. Mechanistically, the miRNA miR-194-5p targeted MALAT1 for degradation in the nucleus in an Ago2-dependent manner; the rs664589 G allele altered the binding of MALAT1 to miR-194-5p, resulting in increased expression of MALAT1. Colorectal cancer cells and human tissues with the rs664589 CG/GG genotype expressed significantly higher MALAT1 than those with the rs664589 CC genotype. Multivariate Cox regression analysis showed that MALAT1 was a poor prognostic factor of colorectal cancer. In summary, MALAT1 with the rs664589 G allele demonstrates altered binding to miR-194-5p in the nucleus, leading to increased MALAT1 expression and enhanced colorectal cancer development.Significance: These findings highlight the functional role of MALAT1 polymorphism in colorectal cancer metastasis and survival as well as the underlying mechanism.