c Src binds the activated intracellular domain of EGFR and therefore is temporarily activated. c Src activates EGFR by phosphorylation on residue Tyr845 which is situated in the activation loop on the catalytic domain. The phosphorylation is essential for full catalytic and biological activity. The inhibition of c Src showed an opposite impact on EGFR and its downstream molecules STAT3 KSP or STAT5. A decreased protein expression of STAT5 might be verified in Western blot evaluation. Thinking of the final results obtained from microarray studies, it becomes obvious that Src and Egfr had been not altered. This is extremely exceptional since a reduction in protein concentration commonly causes an induction in gene expression. Possibly, a feedback mechanism is interrupted. In regards to the human hepatocellular carcinoma cell line HepG2 an induction of Egfr gene expression was observed, that verifies the elevated protein expression. After therapy with Si135 also as Si162 several genes affecting cytoskeletal dynamics were altered in their expression. c Abl and c Src activity are critical for growth aspect and integrin signalling that induces reorganization from the cytoskeleton. Crucial substrates are amongst other folks the Rho household, GTPases and FAKs.
The latter dual DNA-PK inhibitor indicated also a decreased protein expression soon after treatment with Si162, activation of p53 and induction of Gadd45a and p21Cip1. Additionally, the inhibition of c Abl and c Src caused numerous effects to the cytoskeleton, leading to impaired spindle formation.
Induced by DNA harm, c Abl activates stress activated protein kinases, too as janus kinase and p38 MAPK. Furthermore, an activation of p73 by phosphorylation by way of p38 MAPK has been reported to foster an induction of apoptosis. As evidenced by Western blot, p73 was unchanged while p38 MAPK was decreased but p53 was strongly induced to suggest a powerful apoptotic signal, possibly due to its capacity to interfere with cytoskeleton dynamics. Comparison of approved and experimental dual kinase inhibitors Due to the fact the discovery in the pathogenic Bcr Abl translocation in chronic myeloid leukaemia the amount of rationally designed drugs improved continuously. Imatinib was the first selective tyrosine kinase inhibitor approved for the therapy of CML. It’s reported to inhibit the chimeric Bcr/Abl kinase with an IC50 of 527 nM, whereas the antiproliferative effect for leukaemia cells was in the submicromolar range. For comparison, imatinib,s IC50 was determined amongst 10 and 30 mM for all investigated cell lines soon after 24 h and 96 h of remedy. Following repeated remedy of tumour cell lines no decline from the IC50 was marked. Note, an IC50 of two.7 and 5.0 mM was calculated for the dual kinase inhibitors Si135 and Si162 immediately after 96 h of treatment.