miR-145-5p has been reported to be downregulated and described functioning as a tumor suppressive gene in colorectal cancer (CRC), yet its detailed regulatory function and mechanism in malignant progression of the disease have not been thoroughly understood. In our study, miR-145-5p and rhomboid domain containing 1 (RHBDD1) in CRC tissues and cells were examined by qRT-PCR and western blot. MTT, colony formation, wound healing, Transwell invasion, and flow cytometry assays were performed to evaluate the malignant phenotypes of CRC cells. Xenograft tumor, qRT-PCR, and western blot assays were applied to validate the roles and mechanism of miR-145-5p in CRC in vivo. The interaction between miR-145-5p and RHBDD1 was investigated by luciferase reporter assay and western blot. The changes of the EGFR/Raf/MEK/ERK pathway were detected by western blot. We found miR-145-5p was lowly expressed and low miR-145-5p predicted poor prognosis in CRC, while RHBDD1 was greatly enhanced in CRC cells and tissues. RHBDD1 silencing resulted in inhibiting cell proliferative, invasive, and migratory potentials as well as elevating apoptotic ones in CRC cells. miR-145-5p was inversely related with RHBDD1 expression in CRC tissues. miR-145-5p was found to directly bind to RHBDD1 and restrained its expression in CRC cells. miR-145-5p overexpression repressed CRC cell proliferation, invasion, migration and induced apoptosis, and these effects were reversed by RHBDD1 upregulation. Moreover, in CRC xenograft tumor, its growth was impeded by miR-145-5p via suppressing RHBDD1. Furthermore, miR-145-5p inhibited the expression of EGFR, p-MEK1/2 and p-ERK1/2, in vitro and in vivo by targeting RHBDD1. In conclusion, our study revealed that miR-145-5p overexpression inhibited tumorigenesis in CRC by downregulating RHBDD1 via suppressing the EGFR-associated signaling pathway (EGFR/Raf/MEK/ERK cascades).

据报道，miR-145-5p被下调并被描述为在大肠癌（CRC）中具有抑癌基因的功能，但是其在疾病恶性进展中的详细调控功能和机制尚未得到充分了解。在我们的研究中，通过qRT-PCR和Western blot检测了CRC组织和细胞中的miR-145-5p和含有1的菱形结构域（RHBDD1）。进行MTT，集落形成，伤口愈合，Transwell侵袭和流式细胞术测定以评估CRC细胞的恶性表型。应用异种移植肿瘤，qRT-PCR和western blot方法验证miR-145-5p在体内CRC中的作用和机制。miR-145-5p和RHBDD1之间的相互作用通过荧光素酶报告基因分析和Western印迹进行了研究。用western blot检测EGFR / Raf / MEK / ERK途径的变化。我们发现miR-145-5p的表达低，而miR-145-5p的低则预示着CRC的不良预后，而RHBDD1在CRC细胞和组织中则大大增强。RHBDD1沉默导致抑制细胞增殖，侵袭和迁移的潜力，以及提高CRC细胞中的凋亡。miR-145-5p与CRC组织中RHBDD1的表达呈负相关。发现miR-145-5p直接结合RHBDD1并抑制其在CRC细胞中的表达。miR-145-5p的过表达抑制了CRC细胞的增殖，侵袭，迁移和诱导的细胞凋亡，而这些作用被RHBDD1上调所逆转。此外，在CRC异种移植肿瘤中，miR-145-5p通过抑制RHBDD1阻止了其生长。此外，miR-145-5p抑制EGFR，p-MEK1 / 2和p-ERK1 / 2的表达，通过靶向RHBDD1在体外和体内。总之，我们的研究表明，miR-145-5p过表达通过抑制EGFR相关信号通路（EGFR / Raf / MEK / ERK级联）下调RHBDD1来抑制CRC的肿瘤发生。