Vemu, R. | Search bioRxiv

bioRxiv2025

High-dose DFMO alters protein translation in neuroblastoma

DFMO has been studied as a cancer therapeutic at doses ranging from 500-9,000 mg/m2/day. Lower doses are favored for cancer prevention studies while higher doses, often with chemotherapy, are studied in refractory cancers. DFMO inhibits the rate-limiting enzyme in polyamine synthesis, ornithine decarboxylase (ODC), an oncogene transcriptionally regulated by MYC. MYC genes are the principal oncogenic drivers of neuroblastoma, and ODC1 is co-amplified in a subset with dismal outcome, so DFMO is a rational therapeutic candidate. Low-dose DFMO has now been FDA-approved for high-risk patients though the mechanisms for its anti-tumor activity, and the exposures required to elicit them, remain obscure. We sought to define biomarkers of activity across exposures achieved in the clinic with low through high-dose DFMO. Polyamines support protein translation by providing spermidine, which is essential to hypusinate (and activate) the elongation factor, eIF5A. Selective binding of polyamines with tRNA and rRNA provide eIF5A-independent mechanisms of translation support. We show that low-dose DFMO does not extend survival in mouse models in vivo nor alter translation biomarkers in vitro. High-dose DFMO consistently extends survival in neuroblastoma models, and, in a subset of neuroblastoma cell lines, inhibits eIF5A hypusination and global translation at achievable concentrations. However, the concentration required to engage these changes across many cell lines exceeded that achievable even with high-dose DFMO. No correlation was seen among MYCN and/or ODC1 copy number and sensitivity to DFMO. Combining high-dose DFMO with additional agents to further deplete tumor polyamines may be necessary to fully engage polyamine-depletion effects on tumors, and more granular measures of translation, including codon-resolution ribosome profiling, may be required to define these effects. STATEMENT OF TRANSLATIONAL RELEVANCELow-dose DFMO is approved by the FDA for the treatment of neuroblastoma. The depletion of tumor polyamines has been shown to have activity against tumors with activated MYC signaling, like neuroblastoma, yet the degree of polyamine depletion required, the mechanisms by which this impedes tumor progression, and the DFMO exposures required to enable these are poorly understood. Here we evaluate alterations in protein translation as putative mechanisms for DFMO activity. Translation biomarkers and colony formation can be inhibited by DFMO in vitro at exposures achievable in vivo with high-dose DFMO. Similarly, high-dose DFMO, but not low-dose DFMO, extends neuroblastoma-prone mouse survival. These findings support studying DFMO at higher doses and in therapeutic combinations that further augment polyamine depletion within tumors.

cancer biology↗

bioRxiv2021

Anti-GD2 antibody therapy alters the neuroblastoma tumor microenvironment and extends survival in TH-MYCN mice

BackgroundNeuroblastoma is a commonly lethal solid tumor of childhood and intensive chemoradiotherapy treatment cures ~50% of children with high-risk disease. The addition of immunotherapy using dinutuximab, a monoclonal antibody directed against the GD2 disialoganglioside expressed on neuroblasts, improves survival when incorporated into front-line therapy and shows robust activity in regressing relapsed disease when combined with chemotherapy. Still, many children succumb to neuroblastoma despite receiving dinutuximab-based immunotherapy, and efforts to counteract the immune suppressive signals responsible are warranted. Animal models of human cancers provide useful platforms to study immunotherapies. TH-MYCN transgenic mice are immunocompetent and develop neuroblastomas at autochthonous sites due to enforced MYCN expression in developing neural crest tissues. However, GD2-directed immunotherapy in this model has been underutilized due to the prevailing notion that TH-MYCN neuroblasts express insufficient GD2 to be targeted. MethodsTH-MYCN mice were treated with 14G2a (anti-GD2 antibody), isotype antibody, or phosphate buffered saline from day 14 of life until day 100 or signs of morbidity. Survival was recorded, and tumors were isolated in terminal surgeries for analysis of GD2 expression and immune cell frequencies. Tumors from untreated mice were explanted for generation into cell lines, and GD2 expression was recorded with serial passage in tissue culture. Immunocytology and immunoblotting were performed to evaluate for adrenergic and mesenchymal markers of neuroblasts. Survival curves compared using Kaplan-Meier method with a log-rank test for significance. Unpaired two-tailed Students t-tests used for comparison of groups in flow cytometry analysis. Results14G2a markedly extends survival in such TH-MYCN mice. Additionally, neuroblasts in 14G2a-treated mice have reduced GD2 expression and fewer macrophage and myeloid-derived suppressor cells in their tumor microenvironments. Neuroblasts in TH-MYCN-driven tumors express GD2 at levels comparable to human neuroblastomas but rapidly lose GD2 expression when explanted ex vivo to establish tumor cell lines. The loss of GD2 expression ex vivo is associated with a transition from an adrenergic to mesenchymal state that is maintained when reimplanted in vivo. ConclusionsOur findings support the utility of the TH-MYCN model to inform GD2-directed immunotherapy approaches for neuroblastoma as well as opportunities to investigate drivers of adrenergic to mesenchymal fate decisions.

cancer biology↗