Network of mutually repressive metastasis regulators can promote cell heterogeneity and metastatic transitions

Area of Science:

• Molecular Biology
• Cancer Research
• Systems Biology

Background:

• Nongenetic variability significantly influences metastatic progression, but its sources remain largely unknown.
• Raf kinase inhibitory protein (RKIP) is a known metastasis suppressor.
• The transcription factor BACH1 promotes breast cancer metastasis and is negatively regulated by RKIP.

Purpose of the Study:

• To characterize the transcriptional regulatory network of RKIP.
• To elucidate the role of BACH1 in regulating RKIP and its impact on metastatic progression.
• To investigate the mechanisms underlying nongenetic variability in cancer metastasis.

Main Methods:

• Transcriptional regulatory network analysis of RKIP and BACH1.
• Investigation of feedback loops involving BACH1 and RKIP.
• Single-cell analysis to confirm network dynamics.
• Experimental manipulation using histone deacetylase inhibitors and polycomb repressor depletion.

Main Results:

• BACH1 forms a double-negative feedback loop inhibiting RKIP transcription in breast cancer cells.
• BACH1 also negatively autoregulates its own transcription.
• An inverse relationship between BACH1 and RKIP, exhibiting monostable and bistable transitions, was identified, contributing to nongenetic variability.
• Single-cell analyses confirmed monostable and bistable-like behaviors.
• Modulation of histone deacetylase inhibitors or enhancer of zeste homolog 2 led to a prometastatic state.

Conclusions:

• The mutually repressive relationship between RKIP and BACH1 is a key driver of nongenetic variability and metastatic progression in cancer.
• Understanding these regulatory networks offers potential therapeutic targets for controlling cancer metastasis.
• Nongenetic mechanisms play a critical role in the complex process of cancer metastasis.