Given that the early BCR signaling activities are inhibited on SFK inhibition, we next examined whether the additional downstream pathways are impacted as nicely. In B cells, ERK is a major downstream target that is phosphorylated in response to BCR signaling. In BKS 2, CH12.

Lx, OCI Ly3, OCI Ly10 lymphoma cells, we observed constitutive ERK activation, fluorescent peptides constant with constitutively energetic BCR signaling. Treatment method with 10 M PP2 for 1 hr completely blocked the ERK phosphorylation in these lymphoma cells except OCI Ly3, which demands increased dose of PP2 for full blocking of SFK activity. At 1 M PP1, which is not sufficient for blocking all the SFK activity, phosphorylation of ERK is not inhibited. Constant with this, the proliferation of BKS 2 cells is not inhibited at this dose. Considering that ERK MAPK pathway is controlled by Src kinases, subsequent we asked regardless of whether JNK MAPK is also controlled by Src kinases. PP2 does not influence the phosphorylation of JNK in CH12, Ly3, BKS 2, and Ly10 and two other B lymphoma cell lines tested, suggesting that JNK pathway is not controlled by Src kinases.

Dasatinib as well did not reduce JNK phosphorylation in BKS 2 cells. PI 3 kinase/AKT pathway is an crucial survival pathway activated in several cancer cells. In B cells, Lyn phosphorylates CD19 to activate PI 3 kinase/AKT pathway in response to antigen BYL719 stimulation. Typical splenic B cells had quite minimal levels of basal AKT phosphorylation which was enhanced by anti IgM stimulation. In contrast, B lymphoma cells have higher levels of AKT phosphorylation and remedy with ten M PP2 totally blocked its phosphorylation. At a reduce dose of PP2, the AKT phosphorylation is only slightly inhibited due to insufficient blocking of SFK activity. Dasatinib was discovered to inhibit both BCR Abl and Src kinases for Philadelphia chromosome positive leukemia cells.

Because B lymphoma cells do not express BCR Abl kinase, dasatinib is most likely to inhibit the B lymphoma development by blocking Src kinases. Treatment of BKS 2 cells with a hundred nM dasatinib for 1 hr totally blocked the phosphorylation fluorescent peptides of SFK. As with PP1 or PP2, the phosphorylation of AKT and ERK was also entirely blocked by dasatinib. In addition, the transcription aspect Egr 1, which was shown by us to be critical for B lymphoma development was reduced 60% on dasatinib treatment method, most likely due to the blocking of ERK activity. Considering that Lyn is an early component of BCR signaling pathway, we next asked whether or not the effect of blocking SFK can be rescued by immediately activating downstream pathways. Dasatinib potently inhibited the BKS 2 lymphoma growth by more than 80%. The development inhibition brought on by dasatinib was partially rescued by PMA, an activator of PKC or CpG ODN, an activator of MAPK and NF B.

Though Lyn is important for B lymphoma BYL719 growth, distinct B lymphoma cell lines exhibited different sensitivity to PP2 or dasatinib induced apoptosis.