We are grateful to E. Holtorf for excellent technical assistance. This work was supported by grants from the Wissenschaftsfoerderung der Deutschen Brauwirtschaft e.V. (project B103), Pascoe pharmazeutische Praeparate GmbH, the Else Uebelmesser Foundation and by the German Childhood Cancer Foundation (DKS). SV was supported by the Innovation Grant of the University of Tuebingen.
Conflict of interest
The authors declare that there are no actual or potential conflicts of interest in relation to this article. The sponsors had no involvement in the study design, in the collection, analysis and interpretation of data, in the writing of the manuscript and in the decision to submit the manuscript for publication.