Xuemei Sui,1,* Hong Zhou,2,* Lei Zhu,3 Deqiang Wang,4 Sumei Fan,5 Wei Zhao6 1Clinical Laboratory, The First Affiliated Huai’an Hospital of Nanjing Medical University, 2Huai’an No 4 People’s Hospital, Huai’an, 3Department of Digestive System, Jiangsu Province Hospital of TCM, Nanjing, 4Cancer Therapy Center, Affiliated Hospital of Jiangsu University, Zhenjiang, 5Geriatric Department, The Affiliated Huai’an Hospital of Xuzhou Medical University, Huai’an, 6Clinical Laboratory, Obstetrics and Gynecology Hospital Affiliated to Nanjing Medical University, Nanjing, Jiangsu, People’s Republic of China *These authors contributed equally to this work Abstract: Increasing evidence suggests that CUL4A, a ubiquitin ligase, is involved in the promotion of cancer malignancy and correlated with worse clinical prognosis in several kinds of human cancers. Although its effect and mechanism on the progression of colorectal cancer (CRC) remain unknown. Our clinical data show that CUL4A protein is overexpressed, positively associated with lymph nodes status, differentiation degree, tumor size, and poor prognosis in 80 CRC patients. CUL4A overexpression promotes cell proliferation and colony formation of CRC cells. Knockdown of CUL4A inhibits cell proliferation and migration. CUL4A can significantly promote the in vitro migration of CRC cells via induction of the epithelial–mesenchymal transition process. And the modulation of CUL4A expression altered the level of H3K4 trimethylation at the E-cadherin, N-cadherin, and vimentin gene promoters, which in turn transcriptionally regulated their expression. Moreover, knockdown of CUL4A also decreased the tumor volume and tumor weight in vivo. Together, our results reveal that CUL4A plays as an oncogene in CRC and may become a potential therapeutic target in the treatment of colorectal cancer. Keywords: colorectal cancer, CUL4A, EMT, migration, H3K4 trimethylation