Frequent and Persistent PLCG1 Mutations in Sézary Cells Directly Enhance PLCγ1 Activity and Stimulate NFκB, AP-1, and...

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Primary cutaneous T-cell lymphoma (CTCL), particularly Sézary Syndrome, frequently exhibits mutations in Phospholipase C Gamma 1 (PLCG1).
• Understanding the functional impact of these PLCG1 mutations is crucial for developing targeted therapies.

Purpose of the Study:

• To functionally characterize nine specific PLCG1 mutations identified in Sézary Syndrome.
• To investigate the downstream signaling pathways affected by these mutant PLCG1 forms.
• To explore the role of specific residues and domains in PLCG1 activity.

Main Methods:

• Functional interrogation of nine PLCG1 mutations (p.R48W, p.S312L, p.D342N, p.S345F, p.S520F, p.R1158H, p.E1163K, p.D1165H, and p.VYEEDM1161V indel) in diagnostic samples.
• Assays measuring inositol phosphate production to assess PLCγ1 activity.
• Analysis of downstream transcriptional activity, including NFκB, AP-1, and NFAT.
• Investigation of the role of p.Y783 phosphorylation and the C2 domain.

Main Results:

• Most PLCG1 mutations confer gain-of-function activity, leading to increased inositol phosphate production and activation of NFκB, AP-1, and NFAT.
• Activating mutations can stimulate downstream signaling independently of p.Y783 phosphorylation.
• The p.VYEEDM1161V indel suggests a regulatory role for the C2 domain in PLCG1 activity.

Conclusions:

• Mutant PLCG1 exhibits gain-of-function properties in CTCL, driving key oncogenic signaling pathways.
• These findings provide a strong rationale for developing therapeutic strategies targeting mutant PLCG1 in CTCL patients.