Combination therapy for KIT-mutant mast cells: targeting constitutive NFAT and KIT activity

Area of Science:

• Hematology
• Oncology
• Molecular Biology

Background:

• Resistant KIT mutations impede effective KIT kinase inhibitor therapy for systemic mastocytosis.
• Calcineurin phosphatase is a regulator of the nuclear factor of activated T cells (NFAT) pathway.

Purpose of the Study:

• To investigate the synergistic effects of combining KIT inhibition with calcineurin phosphatase inhibition in KIT-mutant mast cell lines.
• To elucidate the underlying mechanisms of this combination therapy, focusing on NFAT activity.

Main Methods:

• Utilized a panel of KIT-mutant mast cell lines to assess monotherapy and combination therapy effects on cell viability and apoptosis.
• Monitored NFAT-dependent transcriptional activity and employed shRNA to knockdown calcineurin expression.
• Evaluated the impact of NFAT-specific inhibitors in conjunction with KIT inhibitors.

Main Results:

• The combination of KIT inhibitors and calcineurin phosphatase inhibitors (CNPIs) demonstrated synergistic reduction in cell viability and induced apoptosis across six distinct KIT-mutant mast cell lines.
• Both KIT inhibitors and CNPIs decreased NFAT-dependent transcriptional activity, which was constitutively active in all tested KIT-mutant cell lines.
• NFAT-specific inhibitors replicated the synergistic apoptosis induction seen with CNPIs when combined with KIT inhibitors; calcineurin knockdown sensitized cells to KIT inhibition.

Conclusions:

• Constitutive NFAT activation is a novel and targetable characteristic in KIT-mutant mast cell disease.
• Combining KIT inhibition with NFAT inhibition presents a promising new therapeutic strategy for mast cell diseases.
• This approach may overcome resistance associated with KIT mutations in systemic mastocytosis.