Targeting H3.3 mutated pediatric high grade gliomas – A high throughput screening approach to identify novel therapeutic agents

Pediatric high grade gliomas (pHGG) are among the most common malignant brain tumors in childhood and account for the majority of cancer related mortality in this age group. The recent discovery of two recurrent mutations in the tail of histone variant H3.3, resulting either in a substitution of Glycine at position 34 (G34R/V) or Lysine at position 27 (K27 M), has deepened our understanding of this tumor entity and led to a new molecular classification system. However, the functional consequences of these mutations on the tumor biology remain largely unknown. Consequently, no potential drug targets could be delineated among the genes that are differentially regulated in K27 M and G34R/V mutated tumors.

We thus aim at identifying drugs that specifically act on either K27 or G34 mutated tumors. Therefore, we are currently conducting a high throughput (HT) compound screening using 80,000 substances on both a K27 and a G34 mutated pHGG cell line. In parallel, we are performing a combinatorial smaller scale substance screening (15 targeted drugs and classical cytostatics) to identify the optimal combination of current drugs to target pHGG. Additionally, xenografts of K27 and G34 mutated pHGG are currently being established, allowing us to adequately model hemispheric (G34 mutated) and midline (K27 mutated) pHGG in vivo.

Upon completion of the HT screening, the most promising substances will be subjected to a counterscreening including also non-neoplastic control cell lines. An extensive pharmacological profile of candidate compounds will be generated and the resulting substances will subsequently be transferred to in vivo testing on xenografted mice.

As a long term goal, we thus seek to open the avenue for the development of new treatment strategies, targeting the molecular roots of pHGG.