Immunohistochemistry

Pan02, PDX, and Panc01 samples (n = 3/group) were subject to IHC-P staining of CK19 (Thermo Fisher, MA5-12,663). Paraffin-embedded formalin-fixed tissue sections were deparaffinized following established xylene:ethonal wash protocol⁵⁶. Antigen retrieval was achieved through 1-h incubation at 95 °C on a hot plate in sodium citrate buffer with pH6 based upon the antibody manufacture’s suggestion. Once cooled, slides were washed twice in tris-buffered saline (TBS) plus 0.025% Triton X-100 with gentle agitation. Primary antibody was diluted (1:250) in TBS with 1% BSA and 10% FBS overnight at 4 °C. Slides were washed four times in tris-buffered saline (TBS) plus 0.025% Triton X-100 with gentle agitation, prior to 2 h room temperature incubation with secondary antibody (Cell Signaling, 7076P2) diluted (1:2000) in TBS with 1% BSA and 10% FBS. Slides were washed three times for 5 min in TBS, then developed with DAB substrate (Abcam, ab64238) following manufactures guidelines and counterstained with eosin and methyl blue.