IQGAP1 Scaffold-MAP Kinase Interactions Enhance Multiple Myeloma Clonogenic Growth and Self-Renewal

Area of Science:

• Cancer Biology
• Molecular Oncology
• Hematology

Background:

• Multiple myeloma (MM) patients frequently relapse with drug-resistant disease.
• Aberrant RAS/MAPK signaling is implicated in relapsed/refractory MM.
• Cellular self-renewal is critical for MM relapse and disease persistence.

Purpose of the Study:

• To investigate the role of RAS/MAPK signaling in MM self-renewal.
• To examine IQ motif-containing GTPase-activating protein 1 (IQGAP1) as a mediator of RAS/MAPK signaling in MM self-renewal.

Main Methods:

• Assessed the impact of IQGAP1 loss on MAPK signaling and cell proliferation.
• Utilized a peptide inhibitor targeting IQGAP1-ERK interaction.
• Evaluated clonogenic growth in MM cell lines and primary samples in vitro.
• Determined tumor-initiating cell frequency in immunodeficient mouse models.

Main Results:

• Loss of IQGAP1 reduced MAPK signaling, cell-cycle progression, and tumor colony formation.
• An IQGAP1-mimicking peptide inhibited MM cell self-renewal and clonogenic growth.
• Targeting IQGAP1 decreased tumor-initiating cell frequency in vivo.

Conclusions:

• Aberrant RAS/MAPK signaling enhances MM self-renewal during disease progression.
• Targeting IQGAP1 represents a potential therapeutic strategy to inhibit MM self-renewal and overcome drug resistance.