Mitochondrial complex I activity and NAD+/NADH balance regulate breast cancer progression
Antonio F. Santidrian, Akemi Matsuno-Yagi, Melissa Ritland, Byoung B. Seo, Sarah E. LeBoeuf, Laurie J. Gay, Takao Yagi, Brunhilde Felding-Habermann
Antonio F. Santidrian, Akemi Matsuno-Yagi, Melissa Ritland, Byoung B. Seo, Sarah E. LeBoeuf, Laurie J. Gay, Takao Yagi, Brunhilde Felding-Habermann
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Research Article Oncology

Mitochondrial complex I activity and NAD+/NADH balance regulate breast cancer progression

Abstract

Despite advances in clinical therapy, metastasis remains the leading cause of death in breast cancer patients. Mutations in mitochondrial DNA, including those affecting complex I and oxidative phosphorylation, are found in breast tumors and could facilitate metastasis. This study identifies mitochondrial complex I as critical for defining an aggressive phenotype in breast cancer cells. Specific enhancement of mitochondrial complex I activity inhibited tumor growth and metastasis through regulation of the tumor cell NAD+/NADH redox balance, mTORC1 activity, and autophagy. Conversely, nonlethal reduction of NAD+ levels by interfering with nicotinamide phosphoribosyltransferase expression rendered tumor cells more aggressive and increased metastasis. The results translate into a new therapeutic strategy: enhancement of the NAD+/NADH balance through treatment with NAD+ precursors inhibited metastasis in xenograft models, increased animal survival, and strongly interfered with oncogene-driven breast cancer progression in the MMTV-PyMT mouse model. Thus, aberration in mitochondrial complex I NADH dehydrogenase activity can profoundly enhance the aggressiveness of human breast cancer cells, while therapeutic normalization of the NAD+/NADH balance can inhibit metastasis and prevent disease progression.

Authors

Antonio F. Santidrian, Akemi Matsuno-Yagi, Melissa Ritland, Byoung B. Seo, Sarah E. LeBoeuf, Laurie J. Gay, Takao Yagi, Brunhilde Felding-Habermann

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Figure 5

NAD+ level modulation by complex I and NAD+ synthesis and recycling pathways regulate AKT/mTORC1 activity, autophagy, and metastasis.

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NAD+ level modulation by complex I and NAD+ synthesis and recycling path...
(A) Ndi1 expression enhanced NAD+/NADH balance. NAD+/NADH ratios in whole-cell or mitochondrial extracts of MDA-MB-435 or MDA-MB-231 control versus Ndi1-expressing cells. Ndi1 stabilized NAD+/NADH ratios, especially under metabolic stress induced by glucose deprivation and hypoxia. NAD+/NADH ratios under stress were measured in whole-cell extracts after 48 hours of culture. (B) Interference with NAD+ synthesis and recycling pathways reduced NAD+/NADH ratios. Knockdown of NAMPT (shNAMPT) in MDA-MB-435 and MDA-MB-231 cells decreased NAD+/NADH ratios (whole-cell extracts after 48 hours growth in 5 mM glucose and normoxia). (C) NAMPT knockdown increased lung colonization activity in MDA-MB-435 and MDA-MB-231 cells (n = 6 per group). (D) NAMPT knockdown affected mTORC1 activity and p62 elimination. Western blot analysis for p62, phospho-AKT substrates, phospho-S6Ser240/244, and phospho-4EBPThr37/46 in MDA-MB-435 and MDA-MB-231 NAMPT-knockdown versus control cells. β-Tubulin served as protein loading control. Signal quantification, measured by infrared imaging (total of detectable bands) and expressed relative to control, is shown below. Lanes were run on the same gel but were noncontiguous (white lines). Results are representative of 3 independent experiments. (A–C) Data are mean ± SEM. *P < 0.05, **P < 0.01, unpaired 2-tailed Student’s t test (A and B) or nonparametric Mann-Whitney test (C).