Dual Targeting of Chromatin Stability By The Curaxin CBL0137 and Histone Deacetylase Inhibitor Panobinostat Shows Significant Preclinical Efficacy in Neuroblastoma

Abstract

Purpose: We investigated whether targeting chromatin stability through a combination of the curaxin CBL0137 with the histone deacetylase (HDAC) inhibitor, panobinostat, constitutes an effective multimodal treatment for high-risk neuroblastoma. Experimental Design: The effects of the drug combination on cancer growth were examined in vitro and in animal models of MYCN-amplified neuroblastoma. The molecular mechanisms of action were analyzed by multiple techniques including whole transcriptome profiling, immune deconvolution analysis, immunofluorescence, flow cytometry, pulsed-field gel electrophoresis, assays to assess cell growth and apoptosis, and a range of cell-based reporter systems to examine histone eviction, heterochromatin transcription, and chromatin compaction. Results: The combination of CBL0137 and panobinostat enhanced nucleosome destabilization, induced an IFN response, inhibited DNA damage repair, and synergistically suppressed cancer cell growth. Similar synergistic effects were observed when combining CBL0137 with other HDAC inhibitors. The CBL0137/panobinostat combination significantly delayed cancer progression in xenograft models of poor outcome high-risk neuroblastoma. Complete tumor regression was achieved in the transgenic Th-MYCN neuroblastoma model which was accompanied by induction of a type I IFN and immune response. Tumor transplantation experiments further confirmed that the presence of a competent adaptive immune system component allowed the exploitation of the full potential of the drug combination. Conclusions: The combination of CBL0137 and panobinostat is effective and well-tolerated in preclinical models of aggressive high-risk neuroblastoma, warranting further preclinical and clinical investigation in other pediatric cancers. On the basis of its potential to boost IFN and immune responses in cancer models, the drug combination holds promising potential for addition to immunotherapies.

The Combination of Curaxin CBL0137 and Histone Deacetylase Inhibitor Panobinostat Delays KMT2A-Rearranged Leukemia Progression

“…CBL0137 significantly decreased leukemia burden compared to vehicle-treated mice at any given time point ( Figures 1B–D and Supplementary Figure 1A ) and significantly extended event free survival (EFS, CBL0137 vs control: P=0.0015, Figure 1E and Table 1 ). In line with the potential of CBL0137 to induce an interferon response ( 15 , 19 , 20 ), the serum of mice treated with CBL0137 contained augmented levels of the chemokine Interferon γ-induced protein 10 (IP-10, CXCL10) ( Supplementary Figure 2A ) and splenocytes expressed higher levels of IFIT3 ( Supplementary Figure 2B ), demonstrating target engagement. Panobinostat alone, despite inducing accumulation of DNA damage in splenocytes of treated mice as demonstrated by increased levels of γH2AX ( Supplementary Figure 2B ), did not significantly change average leukemia burden or survival ( Figures 1B–E ).…”

“…The observed inhibitory effects of chromatin damaging drugs on cancer cells can result from modulation of different downstream anti-cancer mechanisms, depending on the specific wiring of the cancer type under investigation. This is showcased by our previous findings on the effectiveness of the combination of CBL0137 and panobinostat in models of other high-risk pediatric cancers including neuroblastoma and diffuse intrinsic pontine glioma (DIPG) ( 15 , 29 ). The CBL0137/panobinostat combination induced enhanced interferon signaling which increased the combination efficacy in immunocompetent neuroblastoma models, while the restoration of histone H3 acetylation and trimethylation was deemed to be critical for the boosted therapeutic effects of the combination in preclinical models of DIPG harboring mutant histone H3 ( 15 , 29 ).…”

“…CBL0137 and panobinostat were administered according to administration regimens that were previously shown to enable target engagement ( 5 , 15 ). CBL0137 induced the activation of the P53 pathway as previously described and treatment with panobinostat increased levels of acetylated histone H3 and H3K27 in leukemic blasts in mouse spleens, confirming effective inhibition of histone deacetylase activity by the drug ( Supplementary Figure 11 ).…”

CPSF3 inhibition blocks pancreatic cancer cell proliferation through disruption of core histone processing

“…In this assay, protein-free DNA is digested by MNase, producing DNA fragmentation patterns that are indicators of whether chromatin is in a condensed or relaxed state. The chromatin destabilizing agent CBL0137 was used as a positive control (44). Panc1 cells treated with JTE-607 or CBL037 displayed rapid and complete chromatin digestion, as compared with DMSO-treated cells (Fig.…”

“…Histone disruption by JTE-607 may also promote synergism with chromatin modifying drugs. For example, CBL0137 has shown synergistic effect when combined with HDAC inhibitors by exacerbating chromatin destabilization (44). These discoveries may improve the efficacy of approved chromatin remodeling agents and suggest a path forward for use of JTE-607 in the clinic.…”