Cutting edge: Constitutive B cell receptor signaling is critical for basal growth of B lymphoma

B lympbomas account for the majority of the lymphoma cases. BCR expression appears to be important for B lymphoma because most oncogenes are translocated to nonrearranged Ig loci and because all of the variants that arise in anti-idiotypic Ab-treated lymphoma patients remain BCRpositive. Based on this and the fact that BCR is required for mature B cell survival, we tested the requirement for continued expression of BCR for the growth and survival of B lymphoma cell. Using Ig alpha or Ig beta-specific small interfering RNA (siRNA) to inhibit BCR expression, we demonstratefor the first time that constitutive signaling by BCR is critical for survival andproliferation of both murine and human B lymphoma cells. The BCR signals in lymphoma appear to be mediated by Syk, as it is constitutively active in a variety of B lymphoma cells. Blocking Syk activity by selective inhibitors suppresses growth of several murine and human B lympbomas.