Inhibitors of class I HDACs and of FLT3 combine synergistically against leukemia cells with mutant FLT3

Acute myeloid leukemia (AML) with mutations in the FMS-like tyrosine kinase (FLT3) is a clinically unresolved problem. AML cells frequently have a dysregulated expression and activity of epigenetic modulators of the histone deacetylase (HDAC) family. Therefore, we tested whether a combined inhibition of mutant FLT3 and class I HDACs is effective against AML cells. Low nanomolar doses of the FLT3 inhibitor (FLT3i) AC220 and an inhibition of class I HDACs with nanomolar concentrations of FK228 or micromolar doses of the HDAC3 specific agent RGFP966 synergistically induce apoptosis of AML cells that carry hyperactive FLT3 with an internal tandem duplication (FLT3-ITD). This does not occur in leukemic cells with wild-type FLT3 and without FLT3, suggesting a preferential toxicity of this combination against cells with mutant FLT3. Moreover, nanomolar doses of the new FLT3i marbotinib combine favorably with FK228 against leukemic cells with FLT3-ITD. The combinatorial treatments potentiated their suppressive effects on the tyrosine phosphorylation and stability of FLT3-ITD and its downstream signaling to the kinases ERK1/ERK2 and the inducible transcription factor STAT5. The beneficial pro-apoptotic effects of FLT3i and HDACi against leukemic cells with mutant FLT3 are associated with dose- and drug-dependent alterations of cell cycle distribution and DNA damage. This is linked to a modulation of the tumor-suppressive transcription factor p53 and its target cyclin-dependent kinase inhibitor p21. While HDACi induce p21, AC220 suppresses the expression of p53 and p21. Furthermore, we show that both FLT3-ITD and class I HDAC activity promote the expression of the checkpoint kinases CHK1 and WEE1, thymidylate synthase, and the DNA repair protein RAD51 in leukemic cells. A genetic depletion of HDAC3 attenuates the expression of such proteins. Thus, class I HDACs and hyperactive FLT3 appear to be valid targets in AML cells with mutant FLT3

Removal of the Pyrrolidine Group by Dehydrogenation of a 4-Pyrrolidin-2-yl-tetrahydroisoquinoline

Dehydrogenation of 6,7-dimethoxy-1-methyl-4-(N-methyl-pyrrolidin-2-yl)-3,4-dihydroisoquinoline (9) by Pd/C in tetraline leads to dehydrogenated products, rearrangement, and elimination of the pyrrolidine group mainly as N-methylpyrrolidine (Scheme 3). Die Dehydrierung von 6,7-Dimethoxy-1-methyl-4-(N-methyl-pyrrolidin-2- yl)-3,4-dihydroisochinolin (9) mit Pd/C in Tetralin führt zu dehydrierten Produkten, zur Umlagerung und zur Abspaltung der Pyrrolidingruppe hauptsächlich als N-Methylpyrrolidin (Schema 3)

Enantioselective synthesis and biological investigation of tetrahydro‐β‐carboline‐based HDAC6 inhibitors with improved solubility

Aberrant epigenetic changes in DNA methylation and histone modification by acetylation or deacetylation regulate the pathogenesis of many diseases. Especially selective inhibitors are getting more and more attention. We recently reported on a new class of potent and selective anti-inflammatory and antirheumatic histone deacetylase 6 (HDAC6) inhibitors (e.g., Marbostat-100). The attachment of a morpholinoethoxy part to the head group dramatically enhances the solubility, in particular the solubility in aqueous solutions, of the lead compound Marbostat-100. Here, we present the enantioselective synthesis of small-molecule compounds based on the tetrahydro-beta-carboline core system with improved solubility, and the influence of the stereochemistry on the biological activity. The enantiomers were synthesized in good enantiomeric excess (ee) purity and were potent and selective HDAC6 inhibitors, whereas the S-derivative S-21 is clearly the eutomer. The potency of our selective HDAC6 inhibitors is demonstrated by K-i values in the range of 0.5-2 nM toward HDAC6, and the selectivity was proved in cellular assays by Western blot analysis taking ac-tubulin as surrogate parameter

Synthesis of arcyriarubine regioisomers by Pd(0)-catalysis or via lithiated indole derivatives - conformational analysis by semiempirical and X-ray methods

Regioisomers of arcyriarubines were synthesized by the reaction of N-protected indoles with dibromomaleimide either in the presence of a Pd(0)-catalyst or n-BuLi. Methods for N-alkylation of these bisindolylmaleimides and deprotection of the indole-N are described. The structure of the bisindolylmaleimide I (R = R1 = R2 = H) was studied by semiempiric quantum-chem. calcns., the structure of its deriv. I (R = CH2CH2Br, R1 = SO2Ph, R2 = H) was ascertained by X-ray anal

Homo-arcyriaflavin: The synthesis of ring-expanded arcyriaflavin analogs

The construction of the ring-expanded carbazole system, forming arcyriaflavin homologues, is efficiently accomplished by the reaction of 2,2'-bridged bis-indoles with 3,4-dibromo-2,5-dihydro-1H-2,5-pyrroledione derivs. under Grignard conditions. A ring size of up to nine members in the central ring is achievable. Substitutions either at the indole system or at the imide-N are also possible. The conformation of homoarcyriaflavins as a cross-link between the rigid arcyriaflavins and the flexible arcyriarubins was investigated by NMR, X-ray, and semiempiric quantum chem. calcn. methods

Preparation and GC-MS-Identification of N-Methyl-Δ³-pyrroline

The preparation of N-methyl-Δ3-pyrroline by 1) reduction of N-methylpyrrole followed by gc-separation or by 2) condensation of cis-l,4-dichloro- 2-butene with methylamine is described. The title compound is identified by GC-MS. Die Darstellung von N-Methyl-Δ3-pyrrolin 1) durch Reduktion von NMethylpyrrol mit anschließender gc-Trennung und 2) durch Kondensation von cis-l,4-Dichlor-2-buten mit Methylamin wird beschrieben. Die Titelverbindung wird durch GC-MS identifiziert