SWI/SNF regulates a transcriptional program that induces senescence to prevent liver cancer

Area of Science:

• Molecular Biology
• Cancer Research
• Epigenetics

Background:

• Oncogene-induced senescence (OIS) is a critical tumor suppressor mechanism.
• Identifying regulators of OIS is crucial for understanding cancer progression and developing therapies.
• Hepatocellular carcinoma (HCC) often involves deletions in genes like ARID1B, suggesting its role in tumor suppression.

Purpose of the Study:

• To identify novel regulators of senescence, particularly those involved in hepatocellular carcinoma (HCC).
• To investigate the role of the SWI/SNF component ARID1B in OIS and liver tumor development.
• To explore the mechanisms by which SWI/SNF components regulate senescence beyond transcriptional control.

Main Methods:

• Screening of an shRNA library targeting genes deleted in HCC to identify senescence regulators.
• Investigating the effects of ARID1B knockdown on OIS, tumor formation, and associated molecular pathways (DNA damage, oxidative stress, p53).
• Conducting a focused shRNA screen to identify SWI/SNF targets regulating senescence, including ENTPD7.

Main Results:

• ARID1B knockdown abrogates OIS and cooperates with RAS to drive liver tumorigenesis.
• ARID1B regulates key senescence markers (p16INK4a, p21CIP1a) and cellular stress responses.
• ENTPD7 was identified as a novel senescence regulator affecting oxidative stress and DNA damage.
• Re-expression of ENTPD7 or nucleotide synthesis inhibition restores senescence in ARID1B-depleted cells.

Conclusions:

• Epigenetic regulators like ARID1B play multifaceted roles in tumor suppression by controlling senescence.
• SWI/SNF complexes utilize diverse mechanisms, including regulation of cellular stress, to maintain OIS.
• ENTPD7 represents a novel target for modulating senescence and potentially treating SWI/SNF-mutated cancers.
• Prosenescence therapies targeting nucleotide synthesis could be effective against SWI/SNF-mutated cancers.