# The Fluorinated NAD Precursors Enhance FK866 Cytotoxicity by Activating SARM1 in Glioblastoma Cells

## TL;DR

This study shows that fluorinated NAD precursors, when combined with FK866, can significantly increase the death of glioblastoma cells by activating SARM1.

## Contribution

The study introduces fluorinated NAD precursors as a novel way to enhance FK866's effectiveness in glioblastoma treatment.

## Key findings

- F-NR, a fluorinated NAD precursor, enhances FK866's cytotoxicity in glioblastoma cells.
- F-NR's metabolite F-NMN activates SARM1, contributing to increased cell death.
- NAD depletion precedes ATP depletion and massive cell death in glioblastoma cells.

## Abstract

In tackling the daunting challenge of glioblastoma, a severe form of brain tumor, researchers have been exploring ways to disrupt its abnormal energy production, focusing on a molecule called NAD. The drug FK866, known to deplete NAD, shows potential in curbing tumor growth but faces limitations when used alone. This study introduces a novel approach using fluorinated versions of NAD precursors, specifically a compound named F-NR, which when, combined with FK866, significantly boosts its effectiveness against glioblastoma cells. F-NR works by competing with the endogenous metabolism of NR, leading to reduced NAD levels and enhancing FK866’s ability to kill cancer cells. Another key finding is the role of SARM1, activated by one of F-NR’s metabolites, which contributes to the enhanced cell-killing effect. The sequence of events—NAD depletion followed by energy loss and ultimately, widespread cell death—highlights the potential of this strategy to improve FK866’s therapeutic impact. This research not only deepens our understanding of NAD metabolism in glioblastoma but also provides a potential strategy for treating the brain cancer.

Glioblastoma, a formidable brain tumor characterized by dysregulated NAD metabolism, poses a significant therapeutic challenge. The NAMPT inhibitor FK866, which induces NAD depletion, has shown promise in controlling tumor proliferation and modifying the tumor microenvironment. However, the clinical efficacy of FK866 as a single drug therapy for glioma is limited. In this study, we aim to disrupt NAD metabolism using fluorinated NAD precursors and explore their synergistic effect with FK866 in inducing cytotoxicity in glioblastoma cells. The synthesized analogue of nicotinamide riboside (NR), ara-F nicotinamide riboside (F-NR), inhibits nicotinamide ribose kinase (NRK) activity in vitro, reduces cellular NAD levels, and enhances FK866’s cytotoxicity in U251 glioblastoma cells, indicating a collaborative impact on cell death. Metabolic analyses reveal that F-NR undergoes conversion to fluorinated nicotinamide mononucleotide (F-NMN) and other metabolites, highlighting the intact NAD metabolic pathway in glioma cells. The activation of SARM1 by F-NMN, a potent NAD-consuming enzyme, is supported by the synergistic effect of CZ-48, a cell-permeable SARM1 activator. Temporal analysis underscores the sequential nature of events, establishing NAD depletion as a precursor to ATP depletion and eventual massive cell death. This study not only elucidates the molecular intricacies of glioblastoma cell death but also proposes a promising strategy to enhance FK866 efficacy through fluorinated NAD precursors, offering potential avenues for innovative therapeutic interventions in the challenging landscape of glioblastoma treatment.