A requirement of STAT3 DNA binding precludes Th-1 immunostimulatory gene expression by NF-κB in tumors

Area of Science:

• Molecular Biology
• Cancer Biology
• Immunology

Background:

• Signal transducer and activator of transcription 3 (STAT3) and nuclear factor kappa B (NF-κB) are key transcription factors persistently activated in various cancers.
• These factors regulate genes involved in tumor proliferation, survival, angiogenesis, and metastasis.
• STAT3 paradoxically suppresses NF-κB-driven antitumor immune genes despite elevated NF-κB levels in tumors.

Purpose of the Study:

• To investigate the regulatory role of STAT3 DNA binding in the expression of NF-κB target genes in cancer.
• To elucidate how STAT3 influences the binding of NF-κB to oncogenic and immunostimulatory genes.

Main Methods:

• Analysis of STAT3 DNA binding in relation to NF-κB target gene expression in tumor cells and immune cells.
• Site-specific mutagenesis to introduce STAT3-binding sequences into gene promoters.
• Investigating the interaction between STAT3 and NF-κB on gene promoters.

Main Results:

• Expression of many NF-κB downstream genes in tumors is dependent on STAT3 DNA binding.
• Elevated STAT3 in tumors leads to NF-κB interacting with STAT3 and preferentially binding to genes with STAT3-binding sites.
• Genes associated with antitumor immunity lack STAT3-binding sites and are activated by NF-κB only upon STAT3 inhibition.
• STAT3 facilitates NF-κB binding to tumor growth genes while inhibiting binding to Th-1 immunostimulatory genes.

Conclusions:

• STAT3 plays a critical role in directing NF-κB binding to specific gene sets, thereby regulating both oncogenic and immune responses in the tumor microenvironment.
• Understanding this STAT3-NF-κB interplay provides insights into differential gene regulation in cancer, impacting oncogenesis and antitumor immunity.