The CRL7^FBXW8 Complex Controls the Mammary Stem Cell Compartment through Regulation of NUMB Levels

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• NUMB acts as a tumor suppressor by inhibiting NOTCH signaling and promoting p53 activity.
• Loss of NUMB function (LOF) is a frequent and causal event in breast cancer (BC).
• NUMB LOF in BC is predominantly caused by protein hyper-degradation.

Purpose of the Study:

• To identify the E3 ligase complex responsible for NUMB hyper-degradation in BC.
• To investigate the therapeutic potential of targeting this E3 ligase complex in BC.

Main Methods:

• RNAi-based screening to identify the E3 ligase.
• Genetic and pharmacological inhibition of the identified E3 ligase complex.
• Assessment of NUMB protein levels and BC phenotypes in cell lines and xenografts.

Main Results:

• The CRL7^FBXW8 complex was identified as the E3 ligase mediating NUMB hyper-degradation in BC.
• Inhibition of CRL7^FBXW8 restored NUMB protein levels.
• Inhibition of CRL7^FBXW8 rescued BC cell transformation phenotypes and tumor growth in xenografts.

Conclusions:

• Enhanced CRL7^FBXW8 activity contributes to BC pathogenesis by degrading NUMB.
• Targeting CRL7^FBXW8 represents a potential therapeutic strategy for precision medicine in BC.
• Restoring NUMB protein levels via CRL7^FBXW8 inhibition shows promise for BC treatment.