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ATM is preferentially activated by DSBs and phosphorylates Chk2 on threonine 68, ATR is preferentially activated by stalled replication forks and phosphorylates serine 345 of Chk1.

DNA PK is an additional PIKK household member that contributes to damage induced signaling and each ATM and DNA PK can phosphorylate histone H2AX on Serine139 following IR. To investigate prospective effects of CP466722 on DNA PK, phosphorylation of histone H2AX was assessed in wild type along with a T cells due to the fact DNA PK phosphorylates this (-)-MK 801 Maleate site in the absence of ATM kinase activity. While H2AX phosphorylation following IR was inhibited by CP466722 or KU55933 in wild type cells, these ATM inhibitors failed to inhibit IR induced H2AX phosphorylation in A T cells, demonstrating a lack of detectable effects on DNA PK. In response to growth factor stimulation, AKT is activated by phosphorylation of threonine 308 by the PI3K pathway and serine 473 by other PIKK family members.

To address whether CP466722 inhibits cellular Abl and Src kinases, we utilized a mouse pre B cell model. In this system, the BCR Abl fusion protein is constitutively active, driving autophosphorylation of residue tyrosine 245 and phosphorylation of a downstream target CrkL on tyrosine 207. Src kinase undergoes intermolecular autophosphorylation NSCLC of residue tyrosine 416 on its activation loop to become fully activated. In cells expressing BCR Abl, SRC kinases are activated and increased levels of Src phosphorylation have been reported suggesting that Src is active and undergoing autophosphorylation. As a control, CP466722 and KU55933 were shown to inhibit ATM kinase activity in the mouse pre B cells as demonstrated by disruption of p53 phosphorylation and p53 stabilization in response to IR.

This data indicates that at doses capable of inhibiting ATM, CP466722 and KU55933 do not inhibit Abl kinase activity in cells, however, both compounds have inhibitory effects on Src kinase activity in (-)-MK 801 Maleate this system.