Lysine metabolism is a novel metabolic tumor suppressor pathway in breast cancer

Area of Science:

• Oncology
• Metabolic pathways
• Molecular biology

Background:

• Obesity is a primary preventable cause of breast cancer.
• Nuclear receptor peroxisome proliferator activated receptor γ (PPARγ) is implicated in obesity and reduced in breast cancer.
• The obese microenvironment's effect on nuclear receptors in breast cancer requires further investigation.

Purpose of the Study:

• To develop a model elucidating how obesity-induced microenvironmental changes affect nuclear receptor function in breast cancer.
• To investigate the role of PPARγ in obesity-related breast cancer phenotypes.
• To identify novel metabolic pathways involved in breast cancer suppression.

Main Methods:

• Created a novel mouse model to study obesity's impact on breast cancer.
• Utilized genetic deletion of PPARγ in mammary epithelium.
• Analyzed gene expression, cell proliferation, autophagy, and senescence markers.
• Investigated the role of 2-aminoadipate semialdehyde synthase (AASS) and its regulation by PPARγ.
• Examined the effects of AASS overexpression, acetoacetate, and HDAC inhibition in human breast cancer cell lines and in vivo.

Main Results:

• PPARγ deletion in lean mice unexpectedly increased tumor latency, reduced luminal progenitor cells, and enhanced autophagy and senescence.
• Loss of PPARγ in obese mice upregulated AASS, a regulator of lysine catabolism.
• AASS expression was decreased in human breast cancer; its overexpression or acetoacetate treatment inhibited proliferation and induced autophagy/senescence.
• HDAC inhibition promoted autophagy and senescence in mammary tumor cells.

Conclusions:

• Lysine metabolism represents a novel metabolic tumor suppressor pathway in breast cancer.
• PPARγ plays a critical role in regulating this pathway within the context of obesity.
• Targeting lysine metabolism or HDACs may offer therapeutic strategies for obesity-related breast cancer.