The Things Aurora B inhibitor BI-1356 Gurus Would Teach You

the BCR Abl fusion protein is constitutively energetic, driving autophosphorylation of residue tyrosine 245 and phosphorylation of a downstream target CrkL oThough the ATM related kinase, ATR, was not inhibited by CP466722 in vitro, inhibitory actions against abl and src kinases had been noted within this in vitro screen.

Disruption of ATM dependent phosphorylation events too as inhibition of ATM dependent p53 induction had been also observed in MCF 7 human breast cancer cells and primary and immortalized diploid human fibroblasts. Overall, the response to IR in cells treated with CP466722 was similar to that noticed in cells lacking ATM. Since 1 future aim would be to characterize the capacity Aurora B inhibitor of CP466722 to sensitize tumors to radiation or chemotherapeutic agents in murine models in vivo, it was important to know if CP466722 was effective at inhibiting Atm kinase in mouse cells. The ATM signaling pathway is conserved from human to mouse and ATM kinase activity can be monitored by analyzing similar downstream events. An exception is phosphorylation of Chk2 on threonine 68 which is difficult to detect in mouse cells.

While 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. Though CP466722 BI-1356 did not affect ATR kinase activity in vitro, we examined the ability of the compound to affect ATR kinase activity in cells. hTERT immortalized human fibroblasts were treated for 1h with the replication inhibitor aphidicolin in the presence or absence of CP466722. ATR dependent phosphorylation of Chk1 was not inhibited by CP466722, even though ATM dependent phosphorylation of Chk2 was blocked in these cells. Failure to inhibit aphidicolin induced Chk1 phosphorylation in cells lacking ATM provided even more definitive evidence that CP466722 does not inhibit ATR kinase in cells.

To demonstrate that CP466722 was not inhibiting PI3K or PIKK family members, human fibroblasts were serum starved for 24h before being stimulated with IGF I either in the presence or absence of CP466722, KU55933 or Wortmannin.