In this context, Vemurafenib it's very well described for TKI therapy of CML and GIST and has just lately been proven for TKI therapy in acute leukemia also, that resistance in the direction of TK inhib itors is often triggered by secondary mutations within the tyrosine kinase domain on the respective tyrosine kinase. This kind of muta tions could activate AKT signaling, as previously demon strated for imatinib resistant GIST tumors, and sensitize cells in direction of targeted therapies. We tested this concept utilizing two cell versions compar ing major TK sensitive mutations with secondary TK insensitive mutations The very first model consists of a mast cell leukemia cell line, which harbors an imatinib sensitive KIT V560G mutation plus a deriva tive sister cell line, and that is characterized by a secondary activation loop KIT D816V mutation, rendering the cells insensitive towards imatinib.
Furthermore we tested the GIST sound tumor cell line GIST882 which has a 2nd cell line, which was established from a patient with relapsing GIST below imatinib treatment. This cell line harbors a primary homo zygous juxtamembrane KIT mutation plus a sec ondary heterozygous imatinib insensitive activation loop mutation. Indeed, in our experiments, NVP BEZ235 at the same time as NVP BGT226 potently induced apoptosis irrespective with the sensitivity profile in the direction of TKI with NVP BGT226 again being the more potent inhibitor. Together, dual PI3K MTOR inhibitors such as NVP BGT226 or NVP BEZ235 may very well be of special clin ical value inside the desperate situation of tumor progress as a consequence of TKI resistance, that is an ever increasing problem during the therapy of relapsed acute leukemia.
The underlying molecular mechanisms determining the susceptibility of cells in the direction of induction of apoptosis too as sensitivity towards NVP BGT226 or NVP BEZ235 targets is elusive and can have to be answered in future studies. Most importantly nonetheless, we did show that dual inhi bition of pan class I PI3Kinases plus MTOR1 2 com plexes does translate right into a real antiproliferative but additionally proapoptotic impact in native leukemia cells taken care of ex vivo with NVP BGT226 getting the additional potent drug with regard to induction of apoptosis. Augmented phosphorylation of AKT as opposed to mere expression of AKT protein amounts seemed to become a prerequisite for treat ment response. However, this observation will need prospective validation.
Moreover, efficacy was not re stricted to leukemia samples with recognized genomic mechanisms of AKT activation, suggesting substitute mechanisms of acti vation nevertheless for being recognized. Of note, between the native leukemia samples treated successfully ex vivo with both agent have been scenarios from patients with bad prognostic characteristics lacking productive therapeutic alternatives. By way of example, the two agents were helpful in AML with mutant FLT3, which includes a patient with TKI resistant FLT3 ITD optimistic AML who had relapsed right after allogeneic stem cell transplantation.