Therapeutic strategies for diffuse midline glioma from high-throughput combination drug screening

Abstract

Diffuse midline gliomas (DMGs) are universally lethal malignancies occurring chiefly during childhood and involving midline structures of the central nervous system, including thalamus, pons, and spinal cord. These molecularly related cancers are characterized by high prevalence of the histone H3K27M mutation. In search of effective therapeutic options, we examined multiple DMG cultures in sequential quantitative high-throughput screens (HTS) of 2706 approved and investigational drugs. This effort generated 19,936 single-agent dose responses that inspired a series of HTS-enabled drug combination assessments encompassing 9195 drug-drug examinations. Top combinations were validated across patient-derived cell cultures representing the major DMG genotypes. In vivo testing in patient-derived xenograft models validated the combination of the multi–histone deacetylase (HDAC) inhibitor panobinostat and the proteasome inhibitor marizomib as a promising therapeutic approach. Transcriptional and metabolomic surveys revealed substantial alterations to key metabolic processes and the cellular unfolded protein response after treatment with panobinostat and marizomib. Mitigation of drug-induced cytotoxicity and basal mitochondrial respiration with exogenous application of nicotinamide mononucleotide (NMN) or exacerbation of these phenotypes when blocking nicotinamide adenine dinucleotide (NAD+) production via nicotinamide phosphoribosyltransferase (NAMPT) inhibition demonstrated that metabolic catastrophe drives the combination-induced cytotoxicity. This study provides a comprehensive single-agent and combinatorial drug screen for DMG and identifies concomitant HDAC and proteasome inhibition as a promising therapeutic strategy that underscores underrecognized metabolic vulnerabilities in DMG.

Super elongation complex as a targetable dependency in diffuse midline glioma

“…Insights stemming from the identification of the oncohistone H3K27M as the unifying driver of these tumors, however, have introduced the potential for therapies targeting the dysregulated epigenetic milieu imparted by these recurrent mutations. Recognition of the aberrancies introduced across the epigenetic regulatory landscape by the H3K27M mutation has led several groups to explore and define epigenetic therapies such as histone demethylase inhibition (50) or histone deacetylase inhibition (20,47,51,52) as promising therapeutic strategies for DMG. Several of these agents are now moving forward in phase I clinical trials (NCT02717455, NCT03632317, NCT03566199) but have yet to demonstrate clinical efficacy.…”

Neuronal signatures in cancer

“…The distinct origin and associated molecular biology of DMGs provides the basis for more targeted therapeutic approaches, such as Chimeric Antigen Receptor T-cell 73 or histone deacetylase inhibitor therapy. 16,[74][75][76] In adults, the majority of diffuse (WHO II ) and anaplastic (WHO III ) gliomas but less than 10% of GBs (WHO IV ) harbor a mutation in the isocitrate dehydrogenase (IDH) genes. 7 The incidence of IDH mutant glioma increases abruptly in the third decade of life, and decreases in the fourth and fifth decade.…”

Differential kinase activity of ACVR1 G328V and R206H mutations with implications to possible TβRI cross-talk in diffuse intrinsic pontine glioma

“…That work demonstrated a modest benefit of the combination therapy with a ~20% increase in overall survival time of xenograft mice models 42 . Interestingly, the same study also showed varied combination effects between panobinostat and different CDK inhibitors 42 , i.e., they were synergistic, antagonistic or essentially absent depending on the individual CDK inhibitor. CDK2/4 kinases are known to regulate the subcellular localization, stability and function of Smad proteins downstream of TβRI via direct phosphorylation 31 .…”

“…This underscores the limited understanding of the molecular mechanisms that link epigenetics to gene transcription and phenotypical response in DIPG. During the revision of our manuscript, a new study on high-throughput combination drug screening against DIPG showed synergy between panobinostat and the proteasome inhibitor marizomib on inhibiting patient derived DIPG cells 42 . That work demonstrated a modest benefit of the combination therapy with a ~20% increase in overall survival time of xenograft mice models 42 .…”

“…During the revision of our manuscript, a new study on high-throughput combination drug screening against DIPG showed synergy between panobinostat and the proteasome inhibitor marizomib on inhibiting patient derived DIPG cells 42 . That work demonstrated a modest benefit of the combination therapy with a ~20% increase in overall survival time of xenograft mice models 42 . Interestingly, the same study also showed varied combination effects between panobinostat and different CDK inhibitors 42 , i.e., they were synergistic, antagonistic or essentially absent depending on the individual CDK inhibitor.…”