We addressed whether AKT is acti vated in acute leukemia and evaluated phospho

We additionally created several more Ba F3 cell lines transfected with tyrosine kinases harboring known leukemia driving gain of function mutations and tested for NVP BGT226 and NVP BEZ235 sensitivities. While NVP BGT226 again displayed a beneficial pro apoptotic profile for all tested transfectants, NVP BEZ235 surpri singly retained meaningful proapoptotic activitiy in some cell selleck chemicals阻害剤 strains. Two sensitive transfectants were immunoblotted and showed higher elevated threonine 308 phospho rylation levels compared to FLT3 ITD or BCR ABL1 transfected cells. This observation may have far reaching consequences: It is tempting to speculate that activation of the PI3K AKT pathway is at least in part dependent on the specific type of TK gain of function mutation and that different gain of function mutations may display a very distinct pattern of activated PI3K AKT signaling cas cades.<br><br> This again might influence the susceptibility of cells towards PI3K AKT targeted inhibitors. In this context, it is well described for TKI therapy of CML and GIST and has recently been shown for TKI therapy in acute leukemia as buy Lenalidomide well, that resistance towards TK inhib itors is often caused by secondary mutations within the tyrosine kinase domain of the respective tyrosine kinase. Such muta tions may activate AKT signaling, as previously demon strated for imatinib resistant GIST tumors, and sensitize cells towards targeted therapies.<br><br> We tested this theory using two cell models compar ing primary TK sensitive mutations with secondary TK insensitive mutations: The first model consists of a mast cell leukemia cell line, which harbors an imatinib sensitive KIT V560G mutation and a deriva tive sister cell line, which is characterized by a secondary LY2228820 ic50 activation loop KIT D816V mutation, rendering the cells insensitive towards imatinib. Additionally we tested the GIST solid tumor cell line GIST882 with a second cell line, which was established from a patient with relapsing GIST under imatinib therapy. 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 as well as NVP BGT226 potently induced apoptosis irrespective of the sensitivity profile towards TKI with NVP BGT226 again being the more potent inhibitor.<br><br> Together, dual PI3K MTOR inhibitors such as NVP BGT226 or NVP BEZ235 may be of special clin ical value in the desperate case of tumor progress due to TKI resistance, which is an ever increasing problem in the treatment of relapsed acute leukemia. The underlying molecular mechanisms determining the susceptibility of cells towards induction of apoptosis as well as sensitivity towards NVP BGT226 or NVP BEZ235 targets is elusive and will need to be answered in future studies. Most importantly however, we did show that dual inhi bition of pan class I PI3Kinases plus MTOR1 2 com plexes does translate into a genuine antiproliferative but also proapoptotic effect in native leukemia cells treated ex vivo with NVP BGT226 being the more potent drug with regard to induction of apoptosis. Augmented phosphorylation of AKT rather than mere expression of AKT protein levels seemed to be a prerequisite for treat ment response.