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Peixuan Zhu,1,* Jiahao Liu,2,* Meijuan Lu,1 Gongfa Wu,3 Xutao Lin,1 Longmei Cai,4 Xiaona Zhang1 1The Sixth Affiliated Hospital of Sun Yat-sen University, Guangzhou, People’s Republic of China; 2Cancer Center, Traditional Chinese Medicine-Integrated Hospital, Southern Medical University, Guangzhou, People’s Republic of China; 3Department of Pathology, Zengcheng District People’s Hospital of Guangzhou City, Guangzhou, People’s Republic of China; 4Department of Radiation Oncology, Nanfang Hospital, Southern Medical University, Guangzhou, People’s Republic of China*These authors contributed equally to this workCorrespondence: Longmei CaiDepartment of Radiation Oncology, Nanfang Hospital, Southern Medical University, No. 1838 North Guangzhou Avenue, Guangzhou 510515, People’s Republic of ChinaTel +86 206 278 7747Email cailongmeibestlove@163.comXiaona ZhangGraceland Medical Center The Sixth Affiliated Hospital of Sun Yat-Sen University, No. 26 Yuancun Er Heng Road, Guangzhou 510655, People’s Republic of ChinaTel +86 203 877 7688Email zhangxn33@mail.sysu.edu.cnObjective: This study aimed to identify the changes of miRNAs in colorectal cancer (CRC) complicated with diabetes mellitus (DM) (CRC+DM) tissues and their potential effects.Methods: The changes of miRNAs in CRC+DM tissues were determined by miRNA microarray. The expression levels of miR-99a in 40 clinical specimens and 6 CRC cell lines were determined by qRT-PCR. The capacity for miR-99a to induce cell proliferation and invasion was examined with miR-99a-overexpressing HCT-116 cells. The relative mTOR mRNA and protein levels were determined by qRT-PCR and Western blotting, respectively, in HCT-116 cells transfected with miR-99a. The dual luciferase assay was performed to confirm the direct regulation of miR-99a on mTOR 3′-UTR. The HCT-116 cells were treated with 100mg/L advanced glycation end products (AGEs); then, the mTOR expression levels were determined by qRT-PCR, Western blotting, and immunohistochemistry.Results: Seventeen miRNAs were found to be differentially expressed among normal tissue, CRC tissue, and CRC with DM tissue, including 15 upregulated and 2 downregulated with fold changs of more than 2 times. qRT-PCR confirmed that miR-99a was downregulated in CRC and CRC+DM tissues. In addition, miR-99a overexpression remarkably impaired CRC cell proliferation and metastasis, and negatively regulated mTOR signaling through direct binding to the 3′-UTR of mTOR. AGEs could suppress miR-99a and stimulate mTOR signaling in CRC cells. Increased mTOR was also identified in CRC with DM tissues.Conclusion: Our findings indicate that miR-99a is a potential marker and therapeutic target of CRC complicated with DM, and that AGEs impair miR-99a-overactivated mTOR signaling in CRC with DM patients, which promotes CRC development.Keywords: miR-99a, colorectal cancer, diabetes mellitus, mTOR