Primary and cultured RS cells express PIM1, PIM2, and PIM3 kinases. (A) Western blot analysis of PIM1, PIM2, and PIM3 expression in peripheral B cells isolated from healthy donors (D#1, D#2) and a panel of 6 cHL-derived RS cell lines. GAPDH served as a loading control. (B) Immunohistochemical analysis of PIM expression in reactive germinal centers and cHL samples. Shown are representative germinal centers (GCs) originating from follicular hyperplasia lymph node samples and cHL cases, double positive for PIM1 and PIM3 (#7), PIM1 and PIM2 (#51), and PIM2 and PIM3 (#61). RS cells are indicated with arrows. Original magnification was ×600. (C) Summary of the immunohistochemical analysis of PIM expression performed in a panel of 67 patients with cHL. Solid blocks, positive cases; open blocks, negative cases.