SYK is required for various processes of B-cell development, including transition from pro-B to pre-B cells, proliferation and survival of pre-B cells, as well as the survival of mature B-cells. When other transforming factors are present, loss of SYK in pro-B cells may contribute to development of pro-B cell ALL, possibly by blocking further differentiation. Deregulated or constitutive activation of SYK is able to transform pre-B cells to pre-B cell ALL. In addition, pre-BCR-induced SYK activation is required for transformation of pre-B cells to pre-B cell ALL by other transforming factors (e. g. c-MYC). BCR-mediated tonic activation of SYK, as well as other SYK-dependent but BCR-independent signals are required for survival of mature B-cell lymphomas and B-lineage CLLs.