The FLT3 inhibitor PKC412 exerts differential cell cycle effects on leukemic cells depending on the presence of FLT3 mutations

Abstract

PKC412 is a staurosporine derivative that inhibits several protein kinases including FLT3, and is highly anticipated as a novel therapeutic agent for acute myeloblastic leukemia (AML) carrying FLT3 mutations. In this study, we show that PKC412 exerts differential cell cycle effects on AML cells depending on the presence of FLT3 mutations. PKC412 elicits massive apoptosis without markedly affecting cell cycle patterns in AML cell lines with FLT3 mutations (MV4-11 and MOLM13), whereas it induces G 2 arrest but not apoptosis in AML cell lines without FLT3 mutations (THP-1 and U937). In MV4-11 and MOLM13 cells, PKC412 inactivates Myt-1 and activates CDC25c, leading to the activation of CDC2. Activated CDC2 phosphorylates Bad at serine-128 and facilitates its translocation to the mitochondria, where Bad triggers apoptosis. In contrast, PKC412 inactivates CDC2 by inducing serine-216 phosphorylation and subsequent cytoplasmic sequestration of CDC25c in THP-1 and U937 cells. As a result, cells are arrested in the G 2 phase of the cell cycle, but do not undergo apoptosis because Bad is not activated. The FLT3 mutationdependent differential cell cycle effect of PKC412 is considered an important factor when PKC412 is combined with cell cycle-specific anticancer drugs in the treatment of cancer and leukemia.

Targeting CDK1 promotes FLT3-activated acute myeloid leukemia differentiation through C/EBPα

“…Further, our observations do not rule out a potential interplay between ERK1/2 and CDK1 activity on C/EBPα function in certain FLT3ITD AML cases. The FLT3ITD and CDK1 connection was previously reported by Odgerel et al (41). While they reported that CDK1 is partially inactivated in FLT3ITD AML cell lines, our work concludes that CDK1 can be activated by FLT3ITD mutations.…”

“…We also found that activation of the CDK1 pathway by FLT3ITD involves upregulation of cyclin B1 rather than upregulation of CDK1 itself (49). While these data suggest that cyclin B1 is involved in the activation of CDK1, we cannot rule out that other CDK1 regulators, such as Myt1 and cdc25c, could also be involved (41). NU6102 demonstrated the best differentiation-promoting activity, perhaps because of the higher specificity against CDK1 versus other CDKs.…”

“…While they reported that CDK1 is partially inactivated in FLT3ITD AML cell lines, our work concludes that CDK1 can be activated by FLT3ITD mutations. This apparent contradiction could be explained by the use of different FLT3 inhibitors (PKC412 and MLN518, respectively) and the concentrations used, resulting in either effects in apoptosis (41) or differentiation (this study).…”

FLT3 inhibition and mechanisms of drug resistance in mutant FLT3-positive AML

“…In preclinical studies, PKC412 caused cell cycle arrest and induced apoptosis in mutant FLT3-positive cells by directly inhibiting the activity of the FLT3 kinase, with an IC 50 of approximately 0.01 μM in Ba/F3-FLT3-ITD cells, and inhibits FLT3-ITD phosphorylation with an IC50 of 30 nM (Weisberg et al, 2002). PKC412 induces apoptosis in mutant FLT3-expressing cells with no significant effect on cell cycle progression, however causes G2 arrest without apoptosis in wild-type FLT3-expressing cells (Odgerel et al, 2008). …”

Bortezomib overcomes cell adhesion-mediated drug resistance through downregulation of VLA-4 expression in multiple myeloma

“…Immunoblotting was carried out according to the standard method using the following antibodies: anti-CD49d (Novus Biologicals, Littleton, CO, USA), anti-CD54 (Santa Cruz Biotechnology, Santa Cruz, CA, USA), anti-caspase-8, anticaspase-9 (Becton Dickinson) and anti-GAPDH (Santa Cruz Biotechnology) (Odgerel et al, 2008).…”