Abstract： Objective:To explore the effects of kallikrein 12 (KLK12) on the proliferation, invasion and migration ability of pancreatic cancer cells.Methods:Pancreatic cancer tissues and para-cancer tissues were collected from 95 patients who underwent radical surgical resection, and pathologically diagnosed as pancreatic cancer at the Department of Biliary and Pancreatic Surgery of the First Affiliated Hospital of USTC between February 2014 and October 2018. Expression of KLK12 in pancreatic cancer tissues was investigated using immunohistochemistry, and the correlation between KLK12 expression and clinicopathological characteristics of pancreatic cancer was analyzed. Western blot and qPCR methods were used to detect the expression of KLK12 protein and mRNA in pancreatic cancer cell line SW1990, PANC1 and normal pancreatic gland cells HPDE6-C7. Pancreatic cancer cell lines with up-regulated and down-regulated KLK12 expression were constructed by plasmid transfection. Non-transfected pancreatic cancer cells and transfected pancreatic cancer cells carrying negative control plasmids were used as blank control group and negative control group. CCK8 and Transwell chamber experiments were used to study the changes in cell proliferation, invasion and migration.Results:The positive rate of KLK12 in pancreatic cancer tissues was significantly higher than that in para-cancer tissues (70.5% vs 29.5%, P<0.001), and was significantly related to low tumor differentiation, late TNM stage and lymph node metastasis (all P value <0.05). The expression of KLK12 protein and mRNA in SW1990 and PANC1 cell lines was higher than that in HPDE6-C7 (0.34±0.01, 0.28±0.01 vs 0.21±0.01; 3.31±0.10, 2.91±0.09 vs 1.41±0.20; all P value <0.01). In cells with down-regulated KLK12 expression and then cultured for 72 h, the A450 value of SW1990 cell proliferation (0.94±0.02 vs 1.16±0.05), the number of invading membrane penetrating cells (373.7±14.8 vs 726.0±11.8 per high magnification field) and the number of migrating penetrating cells (696.0±13.1 vs 841.3±15.4 per high magnification field) were significantly decreased. The A450 value of PANC1 cell proliferation (0.96±0.03 vs 1.21±0.03), the number of invading membrane penetrating cells (556.3±13.6 vs 646.0±15.1 per high magnification field) and the number of migrating penetrating cells (449.0±16.5 vs 595.7±8.6 per high magnification field) were also significantly decreased. When the expression of KLKL12 was up-regulated in cells and cultured for 72 h, the A450 value of SW1990 cell proliferation (1.32±0.03 vs 1.11±0.03), the number of invading membrane penetrating cells (556.3±22.2 vs 402.7±10.5 per high magnification field) and the number of migrating penetrating cells (639.3±16.5 vs 433.0±11.8 per high magnification field) were significantly increased. The A450 value of PANC1 cell proliferation (1.26±0.04 vs 1.08±0.03), the number of invading membrane penetrating cells (571.0±17.4 vs 426.7±23.3 per high magnification field) and the number of migrating penetrating cells (740.3±13.0 vs 442.7±10.3 per high magnification field) were also significantly increased (all P value <0.05). Conclusions:KLK12 is highly expressed in pancreatic cancer, and up-regulated KLK12 expression can promote the proliferation, invasion and migration ability of pancreatic cancer cells.