In April 2023, Cancers published a study titled "High Dosage NMN Promotes Ferroptosis to Suppress Lung Adenocarcinoma Growth through the NAM-Mediated SIRT1-AMPK-ACC Pathway " investigating the role of high dose NMN in lung adenocarcinoma.

The results showed that excess niacinamide (NAM) was produced by the metabolism of high doses of NMN, and overexpression of niacinamide phosphoribosyl transferase (NAMPT) could significantly reduce the intracellular NAM content, thereby promoting cell proliferation in vitro and in vivo.

Mechanistically, high doses of NMN promote iron death through NAM-mediated SIRT1-AMPK-ACC signaling.

First, the researchers established a series of cell and mouse models, and subsequently evaluated the antitumor effects of high doses of NMN. Transmission electron microscopy and Mito FerroGreen labeled immunofluorescence assay (Fe2+) were used to demonstrate iron death.

01

High doses of NMN inhibit cancer growth through non-apoptotic, non-autophagy, and non-necrotic procedures

To determine the effect of NMN on cancer cell growth under different dosing regiments, the researchers performed cell proliferation and inhibition experiments using different concentrations of NMN in A549 and SPCA1 cells, and were determined using CCK8.

The results showed that NMN increased cell proliferation at low doses (10 and 20mM) and prolonged exposure (48 h), but inhibited cell proliferation at high doses (100 mm), and the results of tumor colony formation assays confirmed this finding.

In addition, high doses of NMN can promote cell death. That is, high doses of NMN inhibit cancer cell growth by regulating non-apoptotic forms of cell death.

High dose of NMN induced non-apoptotic regulatory death of lung adenocarcinoma cells

Subsequent experiments further verified the inhibitory effect of high doses of NMN on cancer growth. High doses of NMN can inhibit tumor growth, and this effect is independent of apoptosis procedures. HE and ki67 staining of tumor samples showed that high doses of NMN significantly increased intratumoral necrosis and inhibited tumor proliferation independently of apoptotic procedures.

02

High doses of NMN inhibit cancer growth by inducing iron death programs

How does high dose NMN promote cell death? Results of cell colony formation assays confirmed that high doses of NMN failed to inhibit cell growth after blocking the iron death program with Fer-1.

In addition, even when treated with iron death inducers erastin and RSL3, NMN accelerated the death of A549 and SPCA1 cells. These results suggest that high doses of NMN induce iron death in lung adenocarcinoma cells, thereby inhibiting cell growth.

03

High doses of NMN inhibit cancer growth through its metabolite NAM

Exogenous NMN is rapidly decomposed into NR and NAM in vivo, and after entering cells, NR and NAM are catalyzed into NMN by NRK or NAMPT, and finally NAD+ is synthesized.

To clarify whether NMN or its metabolites NAM or NR play a key role in inhibiting tumor growth, the researchers measured the amounts of NAM, NR and NMN in A549 and SPCA1 cells treated with high doses of NMN.

The results showed that the metabolite NAM content increased significantly, and the NAD+/NADH content decreased significantly after high dose of NMN. In addition, in vivo validation results also showed that the NMN metabolite NAM has an inhibitory effect on cancer growth.

The results of this study suggest that local application of high doses of NMN strongly inhibits tumor growth in lung adenocarcinoma cells and induces tumor iron death. In the context of high doses of NMN, NAM produced by excessive metabolism inhibits AMPK phosphorylation by targeting SIRT1, triggers iron death through ACC activation pathway, and inhibits lung adenocarcinoma growth.

In summary, this study highlights the effect of high doses of NMN on tumors in the manipulation of cancer cell metabolism, providing a new perspective for the clinical treatment of lung adenocarcinoma patients.