circHIPK3 promotes oxaliplatin-resistance in colorectal cancer through autophagy by sponging miR-637.

Resistance to oxaliplatin-based chemotherapy is a major cause of recurrence in colorectal cancer (CRC) patients. There is increasing evidence indicating that circHIPK3 is involved in the development and progression of tumours. However, little is known about the potential role of circHIPK3 in CRC chemotherapy and its molecular mechanisms in chemoresistance also remain unclear. Quantitative real-time PCR was performed to detect circHIPK3 expression in tissues of 2 cohorts of CRC patients who received oxaliplatin-based chemotherapy. The chemoresistant effects of circHIPK3 were assessed by cell viability, apoptosis, and autophagy assays. The relationship between circHIPK3, miR-637, and STAT3 mRNA was confirmed by biotinylated RNA pull-down, luciferase reporter, and western blot assays. In the pilot study, increased circHIPK3 expression was observed in chemoresistant CRC patients. Functional assays showed that circHIPK3 promoted oxaliplatin resistance, which was dependent on inhibition of autophagy. Mechanistically, circHIPK3 sponged miR-637 to promote STAT3 expression, thereby activating the downstream Bcl-2/beclin1 signalling pathway. A clinical cohort study showed that circHIPK3 was upregulated in tissues from recurrent CRC patients and correlated with tumour size, regional lymph node metastasis, distant metastasis, and survival. circHIPK3 functions as a chemoresistant gene in CRC cells by targeting the miR-637/STAT3/Bcl-2/beclin1 axis and might be a prognostic predictor for CRC patients who receive oxaliplatin-based chemotherapy. National Natural Science Foundation of China (81301506), Shandong Medical and Health Technology Development Project(2018WSB20002), Shandong Key Research and Development Program (2016GSF201122), Natural Science Foundation of Shandong Province (ZR2017MH044), and Jinan Science and Technology Development Plan(201805084, 201805003).

Zhang Y ，Li C ，Liu X ，Wang Y ，Zhao R ，Yang Y ，Zheng X ，Zhang Y ，Zhang X ... -  《EBioMedicine》

CircHIPK3 promotes colorectal cancer cells proliferation and metastasis via modulating of miR-1207-5p/FMNL2 signal.

Increasing evidences demonstrate that circular RNAs (circRNAs) are extensively implicated in various cancers including colorectal cancer (CRC). In the present study, we found that circRNA HIPK3 (circPIK3) was upregulated in CRC. We identified that circHIPK3 was closely related with unfavorable clinicopathological features in patients with CRC. Functional transwell assay and proliferation assay indicated that circHIPK3 served as an oncogene and promoted CRC cells migration, invasion and proliferation. Meanwhile, we found that formin like 2 (FMNL2) was a key downstream molecule in circHIPK3-induced metastasis and proliferation in CRC cells. We further verified that circHIPK3 was mainly located at cytoplasm through an immunofluorescence assay. An online bioinformatics screening and a GEO datasets analysis showed that microRNA 1207-5p (miR-1207-5p) was downregulated in CRC. Also, we found that miR-1207-5p shared a similar miR-1207-5p response elements (MREs-1207-5p). Meanwhile, we showed that miR-1207-5p suppressed CRC cells migration, invasion and proliferation via directly targeting of FMNL2. Even further, via a constructed luciferase assay, we indicated that circHIPK3 was another target of miR-1207-5p. Functionally, we proved that circHIPK3 enhanced FMNL2 mediated promotion of migration, invasion and proliferation by sponging of miR-1207-5p in CRC cells. In summary, the outcomes of this study illustrated that circHIPK3 promoted CRC cells migration, invasion and proliferation modulating of FMNL2 by sponging of miR-1207-5p. Our findings indicated that circHIPK3/miR-1207-5p/FMNL2 axis might be a new strategy in molecular treatment of CRC.

Yan Y ，Su M ，Qin B 《-》

The HSF1/miR-135b-5p axis induces protective autophagy to promote oxaliplatin resistance through the MUL1/ULK1 pathway in colorectal cancer.

Oxaliplatin (oxa) is widely used in the treatment of colorectal cancer (CRC), but the development of oxaliplatin resistance is a major obstacle to the therapeutic efficacy in patients. MicroRNAs (miRNAs), endogenous noncoding RNAs measuring between 22 and 24 nucleotides, have been shown to be involved in the development of CRC drug resistance. However, the mechanism by which differentially expressed miRNAs induce chemotherapy resistance in CRC has not been fully elucidated to date. Here, we showed the differentially expressed miRNAs in oxaliplatin-sensitive and oxaliplatin-resistant CRC cells through miRNA microarray technology and found that miR-135b-5p was significantly increased in oxaliplatin-resistant cells. And miR-135b-5p was increased in the serum of colorectal cancer patients. More importantly, the miR-135b-5p level in the serum of oxaliplatin-resistant patients was further increased compared to that of oxaliplatin-sensitive patients. Recent studies have shown that protective autophagy is an important mechanism that promotes drug resistance in tumors. The potential role of miR-135b-5p in inducing protective autophagy and promoting oxaliplatin resistance was evaluated in two stable oxaliplatin-resistant CRC cell lines and their parental cells. We further identified MUL1 as a direct downstream target of miR-135b-5p and showed that MUL1 could degrade the key molecule of autophagy, ULK1, through ubiquitination. Mouse xenograft models were adopted to evaluate the correlation between miR-135b-5p and oxaliplatin-induced autophagy in vivo. Furthermore, we also investigated the regulatory factors for the upregulation of miR-135b-5p in CRC cells under oxaliplatin chemotoxicity. These results indicated that miR-135b-5p upregulation in colorectal cancer could induce protective autophagy through the MUL1/ULK1 signaling pathway and promote oxaliplatin resistance. Targeting miR-135b-5p may provide a new treatment strategy for reversing oxaliplatin resistance in CRC.

Wang H ，Wang X ，Zhang H ，Deng T ，Liu R ，Liu Y ，Li H ，Bai M ，Ning T ，Wang J ，Ge S ，Ba Y ... -  《-》

The c-Myc/miR-27b-3p/ATG10 regulatory axis regulates chemoresistance in colorectal cancer.

Oxaliplatin (OXA) resistance is the major obstacle to the anticancer effects of chemotherapy in colorectal cancer (CRC) patients. MicroRNAs (miRNAs) play an important role in the chemoresistance of various tumors. Our objective is to clarify the underlying mechanism of miRNAs in chemoresistance and provide a potential strategy to improve the response of CRC patients to chemotherapeutics. Methods: MiRNA microarray and Real-time PCR were performed to compare changes in miRNA expression between oxaliplatin-resistant and the parental cells. CCK8, apoptosis assay, immunofluorescence and xenograft studies were used to elucidate the impact of miR-27b-3p on regulating chemoresistance. Luciferase reporter assay and western blot were carried to assess the regulatory role of miR-27b-3p in ATG10 expression. The effects of miR-27b-3p and ATG10 on autophagy were investigated by GFP-LC3 fluorescence microscopy, transmission electron microscopy, and western blot. ChIP assay and luciferase assay were performed to test the c-Myc's occupancy on the miR-27B promoter. Results: We observed that miR-27b-3p expression was significantly downregulated in oxaliplatin-resistant cell lines (SW480-OxR and HCT116-OxR) compared to the corresponding parental cell lines and that miR-27b-3p expression was positively correlated with disease-free survival (DFS) time in colorectal cancer patients. MiR-27b-3p could sensitize colorectal cancer cells to oxaliplatin in vitro and in vivo. Under oxaliplatin treatment, chemoresistant cells showed a higher autophagy level than parental cells. Moreover, we also identified that miR-27b-3p inhibited the expression of ATG10 at the posttranscriptional level, thus inhibiting autophagy. Further study demonstrated that c-Myc can inhibit the expression of miR-27b-3p via binding to the promoter region of miR-27B gene. Conclusions: Our study identifies a novel c-Myc/miR-27b-3p/ATG10 signaling pathway that regulates colorectal cancer chemoresistance. These results suggest that miR-27b-3p is not only a potential indicator for evaluating efficiency of chemotherapy, but also a valuable therapeutic target for CRC, especially for patients with chemoresistance.

Sun W ，Li J ，Zhou L ，Han J ，Liu R ，Zhang H ，Ning T ，Gao Z ，Liu B ，Chen X ，Ba Y ... -  《Theranostics》

CircHIPK3 promotes colorectal cancer growth and metastasis by sponging miR-7.

Zeng K ，Chen X ，Xu M ，Liu X ，Hu X ，Xu T ，Sun H ，Pan Y ，He B ，Wang S ... -  《-》