Objective ·To examine the expression level of protein arginine methyltransferase 6 (PRMT6) in breast carcinoma tissues and to assess its impact on the proliferative and migratory behaviors of breast cancer cells. Methods ·The PRMT6 transcriptome sequencing data between 33 tumor tissues and normal tissues from The Cancer Genome Atlas (TCGA) database was analyzed through the R language. The gene expression profile interactive analysis (GEPIA2) online database was used to analyze the difference of PRMT6 expression in normal breast tissues and breast cancer tissues. By using the immunohistochemistry (IHC) data of human normal breast tissues and breast cancer tissues from Human Protein Atlas (HPA) database to analyze the protein expression of PRMT6. IHC was used to detect the expression of PRMT6 in breast cancer tissues and paired para-tumor tissues from 27 clinical samples. After PRMT6 was knocked down with small interfering RNA (siRNA) in MDA-MB-231 and MCF-7 cells, the expression of PRMT6 was detected by qRT-PCR and Western blotting. The proliferation ability of breast cancer cells was measured with cell counting kit-8 (CCK-8) assay and colony formation assay. The effect of PRMT6 on the migration ability of breast cancer cells was detected by wound healing assay and Transwell assay. By using the RNA-sequence data from GSE210948 of Gene Expression Omnibus (GEO) database, differentially expressed genes were analyzed in control and low expression groups of PRMT6. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis was performed to reveal the signaling pathways associated with PRMT6. Cell cycle analysis was detected by flow cytometry. The expressions of cyclin D1 and EMT-related proteins (E-cadherin, N-cadherin and Vimentin) were detected by Western blotting after knocking down PRMT6. Results ·Bioinformatics analysis and IHC results showed that PRMT6 was highly expressed in breast cancer tissues compared with normal tissues (P=0.000) and para-tumor tissues (P=0.001). qRT-PCR and Western blotting results verified that the siRNA significantly reduced the expression level of PRMT6 in MDA-MB-231 and MCF-7 cell lines compared with the control group (mRNA: P=0.006, P=0.004; P=0.001, P=0.043. Protein: P=0.035, P=0.001; P=0.003, P=0.002). After knocking down PRMT6, the proliferation (P=0.014, P=0.000; P=0.003, P=0.003) and migration (P=0.000, P=0.000; P=0.000, P=0.002) ability of breast cancer cells were inhibited significantly. The KEGG pathway enrichment analysis showed that the expression of PRMT6 affected the cell cycle pathway. After knocking down PRMT6, the expression of cyclin D1 decreased in protein level (P=0.021, P=0.000; P=0.034, P=0.014) and transcription level (P=0.036, P=0.001; P=0.044, P=0.000). Knock down of PRMT6 increased the number of cells in G0/G1 phase (P=0.000; P=0.003) and decreased the number of cells in G2/M phase of the cell cycle. The expression level of E-cadherin increased (P=0.002, P=0.012; P=0.043, P=0.003), while the expression levels of N-cadherin (P=0.004, P=0.041; P=0.032, P=0.034) and Vimentin (P=0.028, P=0.005; P=0.024, P=0.001) decreased in PRMT6 knockdown cells. Conclusion ·PRMT6 is highly expressed in breast cancer, which can promote the proliferation and migration of breast cancer cells.