Expression of MICA/b, a ligand for natural killer (NK) cell recognition, on human pancreatic adenocarcinoma and potential for NK intervention.
129 Background: Pancreatic cancer remains a leading cause of cancer-related mortality because of lack of means for early detection and notable refractoriness to standard chemotherapy in advanced stages of disease. Mobilization of the immune system is therefore an important option to explore. Natural Killer (NK) cells are potent effector cells in immune surveillance against cancer and offer a unique advantage because of expression of a C-type, lectin-like, type II transmembrane glycoprotein, NKG2D, on the cell surface. NKG2D is a receptor that specifically recognizes common stress-induced proteins such as MICA/B on tumor cells, targeting them for perforin/granzyme B-mediated destruction. The goal of this study is to examine if MICA/B is expressed on human pancreatic cancer cells, allowing the potential to direct immunotherapy against pancreatic cancer via NK cell therapy. Methods: This study was conducted under an IRB approved protocol. Pancreatic samples were taken from 121 patients with pancreatic ductal adenocarcinoma (PDA) and 103 cases of normal adjacent pancreatic tissues (NP) were included for comparison in a tissue microarray developed in the Tissue Core. All cases were stained for MICA/B AB using the Ventana automated immunostainer Discovery XT (Ventana,Tucson, AZ). Human pancreatic cell lines were also immunostained for MICA/B expression and tested for sensitivity to NK cell lysis in vitro. Results: A significant increase in MICA/B expression was observed during the progression from NP to PDA (p value < 0.0001) in pancreatic tumor tissues. Additionally, all pancreatic cell lines, including MiaPaca, Panc-1, and PCSC, express MICA/B and were readily lysed by NK cells. Conclusions: We report an increase in MICA/B expression during the progression of pancreatic ductal adenocarcinoma and MICA/B may represent a new immunotherapeutic target in pancreatic gastric carcinogenesis.