Mutant CEBPA promotes tolerance to inflammatory stress through deficient AP-1 activation

Area of Science:

• Molecular Biology
• Cancer Biology
• Immunology

Background:

• CCAAT enhancer-binding protein alpha (CEBPA) is a transcription factor frequently mutated in acute myeloid leukemia (AML).
• CEBPA mutations often lead to biallelic loss and production of a truncated p30 isoform, distinct from the canonical p42 isoform.
• The functional consequences of CEBPA mutations, particularly the p30 isoform's role in AML pathogenesis, remain incompletely understood.

Purpose of the Study:

• To elucidate the distinct transcriptional programs regulated by the canonical p42 and AML-associated p30 CEBPA isoforms.
• To investigate how these isoforms influence cellular responses to inflammatory stimuli and stress.
• To identify potential therapeutic vulnerabilities associated with mutant CEBPA in AML.

Main Methods:

• Comparative analysis of gene expression profiles between cells expressing p42 and p30 isoforms.
• Assessment of transcriptional induction dynamics in response to lipopolysaccharide (LPS) stimulation.
• Evaluation of cytokine secretion profiles.
• Investigation of AP-1 family protein regulation and ATF4 function under ER stress conditions.

Main Results:

• Cells expressing the p30 isoform exhibit reduced baseline inflammatory gene expression.
• p30-expressing cells show altered transcriptional responses to LPS, leading to modified cytokine secretion.
• These cells display increased resistance to prolonged inflammatory signals.
• Differential regulation of AP-1 family proteins, including ATF4, underlies these functional changes.
• Impaired ATF4 function in p30-expressing cells affects the response to endoplasmic reticulum (ER) stress.

Conclusions:

• Mutant CEBPA (p30 isoform) significantly alters inflammatory gene expression and cytokine secretion in AML cells.
• The p30 isoform confers a survival advantage by increasing resistance to inflammatory stress.
• Dysregulation of AP-1 proteins and altered ER stress response are key mechanisms.
• These findings highlight a critical link between mutant CEBPA, inflammation, and stress response pathways in AML, suggesting novel therapeutic targets.