A cell-penetrating MARCKS mimetic selectively triggers cytolytic death in glioblastoma

Area of Science:

• Oncology
• Molecular Biology
• Drug Discovery

Background:

• Glioblastoma (GBM) is an aggressive brain cancer with poor outcomes.
• Standard therapies (surgery, radiation, temozolomide) are often ineffective due to GBM's resistance mechanisms.
• Dysregulated phosphoinositide signaling is a common feature in GBM, contributing to therapy resistance.

Purpose of the Study:

• To investigate the therapeutic potential of peptide mimetics derived from the Myristoylated alanine-rich C-kinase substrate (MARCKS) effector domain (ED) against GBM.
• To determine if these peptides can overcome GBM resistance to apoptosis and target all molecular subtypes of GBM.
• To elucidate the mechanism of cell death induced by MARCKS ED peptides.

Main Methods:

• Utilized molecularly classified patient-derived xenograft (PDX) GBM lines cultured in stem-cell conditions.
• Tested cell-permeable MARCKS ED peptides for efficacy and selectivity against GBM cells and normal human astrocytes.
• Performed mechanistic studies to identify the mode of cell death, including caspase inhibition assays and analysis of plasma membrane targeting and intracellular calcium levels.
• Administered peptides via tail-vein injection in GBM PDX models to assess tumor targeting.

Main Results:

• MARCKS ED peptides demonstrated potent targeting across all molecular classes of GBM while sparing normal astrocytes.
• The peptides induced rapid cytotoxicity in GBM, effectively overcoming caspase inhibition.
• A GBM-selective cytolytic cell death mechanism was identified, involving plasma membrane disruption and intracellular calcium accumulation.
• Tail-vein injection showed effective tumor targeting in intracranial GBM PDX models.

Conclusions:

• MARCKS ED peptides represent a promising novel therapeutic strategy for glioblastoma.
• These peptides can overcome traditional GBM resistance mechanisms, including resistance to apoptosis.
• Further development of MARCKS ED peptide therapeutics is warranted for glioblastoma treatment.