Replication catastrophe induced by cyclic hypoxia leads to increased APOBEC3B activity

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Tumor heterogeneity causes variable oxygen levels, leading to hypoxic regions in solid tumors.
• Tumor hypoxia is associated with therapy resistance and genomic instability.
• The physiological conditions driving APOBEC-dependent mutations remain unclear.

Purpose of the Study:

• To investigate if replication stress induced by hypoxia increases APOBEC activity and mutations.
• To determine the role of fluctuating versus stable hypoxia on APOBEC3B expression and activity.
• To correlate APOBEC-mediated mutations with hypoxia signatures in patient tumors.

Main Methods:

• Exposure of cells to fluctuating and stable hypoxic conditions.
• Assessment of APOBEC3B expression and activity.
• Analysis of APOBEC-mediated mutations in patient tumor data.
• Correlation analysis between hypoxia signatures and mutation counts.

Main Results:

• Fluctuating/cyclic hypoxia leading to replication catastrophe induces APOBEC3B expression and activity.
• Stable/chronic hypoxia inducing replication stress alone does not induce APOBEC3B.
• A significant correlation exists between APOBEC-mediated mutations in patient tumors and a hypoxia signature.

Conclusions:

• Hypoxia-induced replication catastrophe drives genomic instability in tumors.
• APOBEC3B activity is specifically increased by fluctuating hypoxic conditions.
• This study elucidates a mechanism linking tumor hypoxia to increased APOBEC-mediated mutations.