Lyn is preferentially expressed, phosphorylated, and plays a critical role for B lymphoma growth. (Panel A) Lyn and Lck are the predominant SFK expressed in a panel of six B lymphoma cell lines. Cell lysates from six representative B lymphoma cell lines were analyzed by Western blotting for p-SFK and different kinds of SFKs. The blots were stripped and re-probed for β-actin for loading control. (B) Lyn is constitutively phosphorylated in CH12.Lx and OCI-Ly10 lymphomas. Lck, Lyn or Src were immunoprecipitated from equal amount of cell lysates from CH12.Lx and OCI-Ly10 and probed for p-Tyr by Western blotting. The blots were then stripped and re-probed for total SFKs. (C) The Lyn siRNA suppressed Lyn expression in SudHL-4 lymphoma cells. SudHL-4 cells were transiently transfected with control or Lyn specific siRNA as described in the Materials and Methods section for 48 hrs. Multiple aliquots of cell lysates were run on SDS-PAGE and transferred onto PVDF membranes. The membranes were cut and separately probed for Lyn, Lck, and Jnk. The blots were stripped and re-probed for the loading control, β-actin. (D) Blocking Lyn expression by siRNA inhibited B lymphoma growth. OCI-Ly10, SudHL-4 and SudHL-6 lymphoma cell lines were treated with control or Lyn specific siRNA as described. Then an equal number of cells with the indicated treatment were used to set up the proliferation assay as described.