Expression of cyclin D1 isoforms by native MCL cells. MCL (A) and the control CLL/SLL (B) patient samples were examined for the expression of cyclin D1a (top rows; open arrowheads), cyclin D1b (middle rows; solid arrowheads), and actin (bottom rows) proteins with Jeko-1 MCL line serving as a positive control. (C) Expression by MCL cells of mRNA coding for cyclin D1a, cyclin D1b, and control actin. Results are representative of at least 3 independent experiments.