Epigenetic activation of O-linked ß-N-acetylglucosamine transferase overrides the differentiation blockage in acute leukemia.

BACKGROUND: Overriding the differentiation blockage in acute myeloid leukemia (AML) is the most successful mode-of-action in leukemia therapy - now curing the vast majority of patients with acute promyelocytic leukemia (APL) using all-trans retinoic acid (ATRA)-based regimens. Similar approaches in other leukemia subtypes, such as IDH1/2-mutated AML, are under active investigation. We herein present successful release of the differentiation blockage upon treatment with the natural (-)-Δ9-Tetrahydrocannabinol isomer dronabinol in vitro and in vivo. METHODS: Cellular maturation and differentiation were followed in two patients employing whole genome methylation profiling, proteome analyses, NGS deep sequencing and multispectral imaging flow cytometry. For functional studies lentiviral OGT knock-down in vitro and ex vivo cell models were created to evaluate proliferative, apoptotic and differentiating effects of OGT in acute leukemia. FINDINGS: In here, we provide molecular evidence that dronbinol is capable to override the differentiation blockage of acute leukemia blasts at the state of the leukemia-initiating clone. We further identify the O-linked ß-N-acetyl glucosamine (O-GlcNAc) transferase (OGT) to be crucial in this process. OGT is a master regulator enzyme adding O-GlcNAc to serine or threonine residues in a multitude of target proteins. Aberrant O-GlcNAc modification is implicated in pathologies of metabolic, neurodegenerative and autoimme diseases as well as cancers. We provide evidence that dronabinol induces transcription of OGT via epigenetic hypomethylation of the transcription start site (TSS). A lentiviral OGT-knock out approach proves the central role of OGT exerting antileukemic efficacy via a dual-mechanism of action: High concentrations of dronabinol result in induction of apoptosis, whereas lower concentrations drive cellular maturation. Most intriguingly, overriding of the differentiation blockage of acute leukemia blasts is validated in vivo following two patients treated with dronabinol. INTERPRETATION: In conclusion, we provide evidence for overcoming the differentiation blockage in acute leukemia in subentities beyond promyelocytic and IDH1/2-mutated leukemia and thereby identify O-GlcNAcylation as a novel (drugable) field for future leukemia research. FUNDING: Unrestricted grant support by the IZKF Program of the Medical Faculty Tübingen (MMS) and Brigitte Schlieben-Lange Program as well as the Margarete von Wrangell Program of the Ministry of Science, Research and the Arts, Baden-Württemberg, Germany (KKS) and Athene Program of the excellence initiative University of Tübingen (KKS).

A phase I pharmacokinetic study of matuzumab in combination with paclitaxel in patients with EGFR-expressing advanced non-small cell lung cancer.

Matuzumab is a humanized IgG1 EGFR monoclonal antibody. This phase I study investigated the tolerability, safety and pharmacokinetics (PK) of matuzumab in combination with paclitaxel in patients with EGFR-expressing advanced non-small cell lung cancer (NSCLC). Six dose levels/schedules of matuzumab were explored in combination with paclitaxel. Dose was escalated from 100 mg to 1,600 mg on a modified Fibonacci scheme according to the incidence of dose-limiting toxicity (DLT) over the first two cycles. DLT was assessed in patients who completed the first two treatment cycles or who stopped treatment because of a DLT during those cycles. Patients with non-progressive disease could then continue to receive study treatment for up to 6 months. The safety population comprised 44 patients, with DLT evaluable in 33. The maximum tolerated dose was not reached, with only one DLT reported at the 1,600 mg 3-weekly dose level. The most frequent grade 3/4 adverse events across all cycles were dyspnea (23 %) and neutropenia (11 %). Matuzumab exhibited non-linear PK, with accumulation after escalation and repeated dosing. Tumor growth control was seen in 15/44 (34 %) patients, including 5/9 (56 %) at the 800 mg weekly dose level. Matuzumab combined with paclitaxel was generally well tolerated in patients with advanced NSCLC. There was some evidence of anticancer activity in relation to the matuzumab 800 mg weekly dose.

FLT3 K663Q is a novel AML-associated oncogenic kinase: Determination of biochemical properties and sensitivity to Sunitinib (SU11248).

Somatic mutations of FLT3 resulting in constitutive kinase activation are the most common acquired genomic abnormality found in acute myeloid leukemia (AML). The majority of these mutations are internal tandem duplications (ITD) of the juxtamembrane region (JM). In addition, a minority of cases of AML are associated with mutation of the FLT3 activation loop (AL), typically involving codons D835 and/or I836. We hypothesized that other novel mutations of FLT3 could also contribute to leukemogenesis. We genotyped 109 cases of AML and identified two novel gain-of-function mutations. The first mutation, N841 H, is similar to previously described mutations involving amino-acid substitutions of codon 841. The other novel mutation, FLT3 K663Q, is the first AML-associated gain-of-function mutation located outside the JM and AL domains. Of note, this mutation was potently inhibited by Sunitinib (SU11248), a previously described FLT3 kinase inhibitor. Sunitinib reduced the proliferation and induced apoptosis of transformed Ba/F3 cells expressing FLT3 K663Q. The potency of Sunitinib against FLT3 K663Q was similar to its potency against FLT3 ITD mutations. We conclude that FLT3 mutations in AML can involve novel regions of the TK1. Future studies are needed to define the incidence and prognostic significance of FLT3 mutations outside the well-established JM and AL regions.