Autophagy suppresses breast cancer metastasis by degrading NBR1

Area of Science:

• Oncology
• Cell Biology
• Molecular Biology

Background:

• Macroautophagy/autophagy has complex roles in cancer development.
• The precise mechanisms by which autophagy influences metastatic disease emergence are not fully understood.

Purpose of the Study:

• To investigate the role of autophagy in mammary cancer metastasis.
• To elucidate the molecular mechanisms underlying autophagy's paradoxical effects on tumor growth and metastasis.

Main Methods:

• Mammary cancer models with genetic autophagy inhibition.
• Analysis of primary tumor growth, spontaneous metastasis to the lung, and disseminated tumor cell (DTC) outgrowth.
• Assessment of tumor cell differentiation and protein accumulation (NBR1).

Main Results:

• Genetic autophagy inhibition attenuated primary tumor growth.
• Paradoxically, autophagy inhibition promoted spontaneous lung metastasis and DTC outgrowth.
• Autophagy inhibition led to the expansion of tumor cells with aggressive, pro-metastatic basal epithelial differentiation.
• The pro-metastatic effects were attributed to cytosolic accumulation of the autophagy cargo receptor NBR1.

Conclusions:

• Autophagy plays a context-dependent role in cancer, inhibiting primary tumor growth while promoting metastasis.
• Inhibition of autophagy can drive aggressive tumor cell phenotypes and enhance metastatic potential.
• The accumulation of NBR1 in autophagy-deficient cells is a key mechanism driving these pro-metastatic effects.