An NFATc1/SMAD3/cJUN Complex Restricted to SMAD4-Deficient Pancreatic Cancer Guides Rational Therapies.

Area of Science:

• Oncology
• Molecular Biology
• Cancer Genomics

Background:

• Pancreatic ductal adenocarcinoma (PDAC) is highly heterogeneous, challenging uniform treatment strategies.
• A specific subgroup, SMAD4-deficient with high nuclear factor of activated T cells (NFATc1) expression (SMAD4-/-/NFATc1High), exhibits aggressive tumor biology.

Purpose of the Study:

• To investigate the tumor biology and therapeutic vulnerabilities of the SMAD4-/-/NFATc1High PDAC subgroup.
• To identify a novel therapeutic strategy for this clinically relevant PDAC subtype.

Main Methods:

• Transcriptomic and clinical data analysis for prognostic relevance.
• In vitro and in vivo studies of transcription factor complex formation (immunoprecipitation, proximity ligation assays).
• Deciphering SMAD4's impact on KRAS signaling, validated by gene expression and genetic perturbations.
• Testing a novel therapeutic option in patient-derived organoids and PDAC models.

Main Results:

• Characterized the aggressive and chemotherapy-resistant SMAD4-/-/NFATc1High PDAC subgroup.
• Identified SMAD4 deficiency as essential for an oncogenic NFATc1/SMAD3/cJUN complex driving RRM1/2 expression.
• RRM1/2 replenishes nucleosides, competing with gemcitabine for DNA incorporation.
• Mitogen-activated protein kinase (MAPK) signaling inhibition disassembled the complex, normalizing RRM1/2 and synergizing with gemcitabine.

Conclusions:

• PDAC with SMAD4 deficiency and the NFATc1/SMAD3/cJUN complex is sensitive to combined MAPK signaling inhibition and gemcitabine therapy.
• This combination therapy offers a potential targeted treatment approach for this aggressive PDAC subgroup.