Circ_0007031 enhances tumor progression and promotes 5-fluorouracil resistance in colorectal cancer through regulating miR-133b/ABCC5 axis

Colorectal cancer (CRC) remains one of the most commonly diagnosed malignancies worldwide. Circular RNAs (circRNAs) are being found to play crucial roles in human cancer, including CRC. The purpose of this study was to explore the function and mechanism of circ_0007031 on CRC progression and 5-fluorouracil (5-FU) resistance. The levels of circ_0007031, ATP-binding cassette subfamily C member 5 (ABCC5) and miR-133b were assessed by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot. Cell survival and proliferation were detected by the 3-(4,5-dimethylthiazol-2yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay. Cell colony formation was evaluated using a standard colony formation assay. Transwell assays were performed to determine cell migration and invasion. Targeted correlations among circ_0007031, miR-133b and ABCC5 were verified by dual-luciferase reporter, RNA immunoprecipitation (RIP) and RNA pulldown assays. Animal experiments were performed to observe the role of circ_0007031 in vivo. Our data indicated that circ_0007031 up-regulation was associated with CRC resistance to 5-FU. Circ_0007031 knockdown repressed CRC cell proliferation, migration and invasion and enhanced 5-FU sensitivity. Circ_0007031 directly interacted with miR-133b. Moreover, circ_0007031 knockdown regulated CRC cell progression and 5-FU sensitivity by miR-133b. ABCC5 was a direct target of miR-133b, and circ_0007031 mediated ABCC5 expression via acting as a miR-133b sponge. Furthermore, miR-133b overexpression regulated CRC cell progression and sensitivity to 5-FU by down-regulating ABCC5. Additionally, circ_0007031 knockdown suppressed tumor growth in vivo. Our current work had led to the identification of circ_0007031 knockdown that repressed CRC cell malignant progression and enhanced 5-FU sensitivity via regulating ABCC5 expression by sponging miR-133b.

Circ_0007031 Serves as a Sponge of miR-760 to Regulate the Growth and Chemoradiotherapy Resistance of Colorectal Cancer via Regulating DCP1A

Background

Colorectal cancer (CRC) is a kind of malignant tumor, and the development of chemoradiotherapy resistance (CRR) increases the difficulty of its treatment. The role of circular RNAs (circRNAs) in cancer progression has been well documented. Nevertheless, the function of circ_0007031 in the growth and CRR of CRC has not been well elucidated.

Methods

CRR cell lines were constructed using 5-Fu and radiation. Cell counting kit 8 (CCK8) assay was employed to measure the 5-Fu resistance and proliferation of cells. Clonogenic assay was used to evaluate the radiation resistance of cells. Also, the expression of circ_0007031 and microRNA-760 (miR-760) was determined using quantitative real-time polymerase chain reaction (qRT-PCR). The cell cycle distribution and apoptosis of cells were assessed by flow cytometry. Besides, the levels of apoptosis-related protein and mRNA-decapping enzyme 1a (DCP1A) protein were measured by Western blot (WB) analysis. Further, dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were used to confirm the interaction between miR-760 and circ_0007031 or DCP1A. In addition, animal experiments were performed to evaluate the function of silenced circ_0007031 on the 5-Fu and radiation resistance of CRC tumors.

Results

Circ_0007031 expression was markedly increased in CRC tissues and cells, especially in CRC resistant cells. Circ_0007031 knockdown hindered proliferation, induced cell cycle arrest in the G0/G1 phase, enhanced apoptosis, and lowered the CRR of CRC resistant cells. Further, miR-760 could be targeted by circ_0007031, and its inhibitor could reverse the inhibition effect of circ_0007031 knockdown on the growth and CRR of CRC resistant cells. Moreover, DCP1A was a target of miR-760, and its overexpression could invert the suppression effect of miR-760 overexpression on the growth and CRR of CRC resistant cells. Circ_0007031 silencing could enhance the sensitivity of CRC tumors to 5-Fu and radiation to markedly reduce CRC tumor growth in vivo.

Conclusion

Circ_0007031 might play a positive role in the CRR of CRC through regulating the miR-760/DCP1A axis, which might provide a new approach for treating the CRR of CRC.