Immunohistochemical Analysis of PDAC Samples

With approval from the Ethics Committee, PDAC samples were obtained from 85 patients (aged 31 years to 73 years) undergoing surgical resection with histologic diagnosis of PDAC at the Tianjin Medical University Cancer Institute and Hospital. Another cohort was 76 PDAC patients undergoing surgical resection and Gem treatment at the Tianjin Medical University Cancer Institute and Hospital. Immunohistochemistry for IL-37, HIF-1α and p-STAT3 (705) of PDAC patient tissues was performed using a DAB substrate kit (ZSGB-BIO, Beijing, China). Immunoreactivity was semi-quantitatively scored according to the estimated percentage of positive tumor cells as previously described 21 (link). Staining intensity was scored 0 (negative), 1 (low), 2 (medium), and 3 (high). Staining extent was scored 0 (0% stained), 1 (1%-25% stained), 2 (26%-50% stained), and 3 (51%-100% stained). The final score was determined by multiplying the intensity scores with staining extent and ranged from 0 to 9. Final scores (intensity score × percentage score) less than 2 were considered as negative staining (-), 2-3 were low staining (+), 4-6 were medium staining (++) and > 6 were high staining (+++).