Abstract: Objective To investigate the expression of silent information regulator 2 homolog protein 7(SIRT7) and its correlation with immune infiltration level in pancreatic cancer. 
Methods The mRNA expression of SIRT7 in pancreatic cancer tissues was collected from Oncomine and GEPIA databases. A total of 27 clinical tissue specimens were collected by immunohistochemical staining, and SIRT7 protein expression was detected. The relationship between SIRT7 expression and immune infiltration level in pancreatic cancer was analyzed. SIRT7 gene mutation landscape was analyzed by cBioPortal based on the RNA sequencing data of pancreatic cancer samples. Proteins interacting with SIRT7 were predicted using the STRING database and gene set enrichment analysis was performed. 
Results Analyzing data from Oncomine and GEPIA database and the immunohistochemical results from clinical tissue specimens revealed that transcription and protein levels of SIRT7 were both highly expressed in pancreatic cancer tissues compared with adjacent tissues. SIRT7 expression was negatively correlated with the expression of effector memory CD8+ T cells， B cells， nature killer cells， nature killer T cells in pancreatic cancer,but positively correlated with the level of T helper cells 17. SIRT7 gene mutation occurred in 13 of 749 pancreatic cancer samples from cBioPortal, with a total mutation rate of 1.73%. Histone deacetylase 1/2/4/6/8/11(HDAC 1/2/4/6/8/11), tumor protein P53(TP53), forkhead box O3(FOXO3) had obvious interactions with SIRT 7. These proteins participated in numbers of biological process such as histone deacetylation and DNA transcription regulation, and were involved in many cancer-related pathways such as cell cycle and Notch. 
Conclusion SIRT7 is overexpressed in pancreatic cancer tissue, which is closely related to tumor immune infiltration. The proteins interacted with it are involved in numbers of pancreatic cancer-related pathways. SIRT7 may be a potential target for pancreatic cancer diagnosis, treatment and evaluation of immune therapy effect.

Key words: pancreatic neoplasms, silent information regulator 2 homolog protein 7, immune infiltration