Establishment of Clinical and Lab Algorithms for the Identification of Carriers of Mutations in CYP21A2 - A Study of 365 Children and Adolescents

BACKGROUND

Mutations of CYP21A2 encoding 21-hydroxylase are the most frequent cause of congenital adrenal hyperplasia (CAH) and are associated either with elevated basal or ACTH-stimulated levels of 17-hydroxyprogesterone (17OHP) in blood.

OBJECTIVE

The study objective was to identify the most suitable of 12 different test algorithms and appropriate cut-off levels for that test to recognize patients with non-classical congenital adrenal hyperplasia (NCCAH) and carriers of clinically relevant mutations in CYP21A2.

METHOD AND PATIENTS

Between July 2006 and July 2015 ACTH-tests were conducted in 365 children and adolescents (Age 1-20 y) suspected to have NCCAH. As a reference, results from subsequent gene sequencing of CYP21A2 was used. Inclusion criteria that were used were premature pubarche with accelerated bone age, hyperandrogenism, hirsutism, or menstrual irregularities. Receiver operating characteristics (ROC) were plotted. Evaluated test algorithms were composed around 17OHP measurements by radioimmunoassays. The most suitable test was identified by the greatest area under the curve (AUC).

RESULTS

Among the 12 tested algorithms, the sum of 30 min and 60 min stimulated 17OHP values (sum17OHPstim) showed the highest AUC of 0.774 for identifying heterozygous and bi-allelic mutations. A cut-off of 10.1 μg/l was advisable. Bi-allelic mutations only were best identified calculating the difference between 30 min and basal 17OHP values (Δ17OHP30). A cut-off of 9.4 μg/l was most effective.

CONCLUSION

Alternatively to the above mentioned cut-offs the difference of 60 min after stimulation to basal 17OHP (Δ17OHP60) can be used for the benefit of a combined test to identify both heterozygotes and bi-allelic patients. There are minimal decreases in sensitivity and specificity compared to an approach that applies two tests. However, it denotes a simpler approach in the clinical routine.

Epigenetic activation of O-linked β-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 β-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).

Variegate porphyria in a 46-year-old patient taking sibutramine for weight loss

The acute hepatic porphyrias can cause life-threatening attacks of neurovisceral symptoms that mimic other acute medical conditions. Variegate porphyria caused by mutations in the protoporphyrinogen oxidase (PPOX) gene is a latent disorder characterized by exacerbations induced by fasting, alcohol consumption or certain drugs. We describe the case of a 46-year-old female patient presenting with a first episode of symptomatic porphyria after 10 d of sibutramine treatment for weight loss. Genetic analysis showed a heterozygous R168H hot spot mutation in the PPOX gene. A putative effect of sibutramine on the hepatic haem biosynthetic pathway and reduced food intake have likely caused this exacerbation of a porphyria attack. Although this may be the first case report of this kind, the risk of acute porphyria should be considered in patients using pharmacotherapy for obesity.

A cDNA clone from Arabidopsis thaliana encoding plastidic ferredoxin:sulfite reductase

A cDNA with an open reading frame of 1929 bp (termed sir) was isolated from a lambda ZapII library of Arabidopsis thaliana leaf tissue. The polypeptide sequence deduced from the cDNA is homologous to the ferredoxin-dependent sulfite reductase (EC 1.8.7.1) from Synechococcus PCC7942 and distantly related to the hemoprotein subunit of Escherichia coli NADPH-dependent sulfite reductase (EC 1.8.1.2). A molecular mass of 71.98 kDa can be predicted for a ferredoxin sulfite reductase from A. thaliana. The polypeptide consists of 642 amino acids including a transit peptide of 66 residues (6.72 kDa) that is assumed to direct the protein into the plastid. For expression and enzymatic characterization of a putative A. thaliana ferredoxin sulfite reductase, the DNA of the transit peptide was deleted by a PCR method. The truncated cDNA clone was expressed as his-tag fusion protein. The modified gene product was enzymatically inactive but specific cross-reaction with polyclonal antibodies against ferredoxin sulfite reductase from Synechococcus is seen as confirmation of its identity as higher plant ferredoxin sulfite reductase.

Reaction mechanism of thioredoxin: 3'-phospho-adenylylsulfate reductase investigated by site-directed mutagenesis

Properties of purified recombinant adenosine 3'-phosphate 5'-phosphosulfate (PAdoPS) reductase from Escherichia coli were investigated. The Michaelis constants for reduced thioredoxin and PAdoPS are 23 microM and 10 microM, respectively; the enzyme has a Vmax of 94-99 mumol min-1 mg-1 and a molecular activity/catalytically active dimer of 95 s-1. Adenosine 3',5'-bisphosphate (PAdoP) inhibits competitively (Ki 4 microM) with respect to PAdoPS; adenosine 2',5'-bisphosphate and sulfite are not inhibitory. Alkylation by SH-group inhibitors irreversibly inactivates the enzyme. The structural gene (cysH) encodes for a small polypeptide with a single Cys residue located in a conserved cluster (KXECGI/LH) of amino acids. Involvement of the only Cys and of Tyr209 in the reduction of PAdoPS to sulfite was investigated by site-specific mutagenesis: cysH was mutated by single-strand-overlay extension PCR; the mutated genes were cloned in pBTac1 and expressed in E. coli RL 22 (delta cysHIJ). Homogenous Cys239Ser and Tyr209Phe mutant PAdoPS reductases were investigated for altered catalytic properties. Mutation of the single Cys reduced Vmax by a factor of 4.5 x 10(3) (Vmax = 0.02-0.013 mumol min-1 mg-1) with marginal effects on Km for PAdoPS (19 microM) and reduced thioredoxin (14 microM). Mutation of Tyr209 drastically affected saturation with thioredoxin (Km 1.5 microM) and decreased Vmax (0.22-0.25 mumol min-1 mg-1) in addition to a small increase in Km for PAdoPS (31 microM). Chromophores as prosthetic groups were absent from recombinant PAdoPS reductase. Difference absorption spectra between reduced and oxidized forms of wild-type and mutated proteins indicated that, in addition to Cys239 and Tyr209, an unidentified Trp (delta lambda max 292 nm) appears to be involved in the reduction. The data suggest a special ping-pong mechanism with PAdoPS reacting with the reduced enzyme isomer in a Theorell-Chance type mechanism.