CDK4/6-MEK Inhibition in MPNSTs Causes Plasma Cell Infiltration, Sensitization to PD-L1 Blockade, and Tumor...

Area of Science:

• Oncology
• Cancer Biology
• Immunotherapy

Background:

• Malignant peripheral nerve sheath tumors (MPNST) are aggressive, lethal sarcomas lacking effective therapeutic options.
• Current treatments for MPNST are limited, necessitating the exploration of novel therapeutic strategies.

Purpose of the Study:

• To investigate the therapeutic potential of targeting cyclin-dependent kinases 4 and 6 (CDK4/6), MEK, and programmed death-ligand 1 (PD-L1) in preclinical MPNST models.
• To evaluate the synergistic effects of combined CDK4/6 and MEK inhibition on MPNST growth and immune response.

Main Methods:

• Analysis of patient-matched MPNSTs and precursor lesions using FISH, RNA sequencing, and IHC.
• Assessment of CDK4/6 and MEK inhibitors' antitumor activity in MPNST cell lines, patient-derived xenografts (PDX), and de novo mouse models.
• Evaluation of anti-PD-L1 response in de novo MPNST mouse models.

Main Results:

• Combined CDK4/6 and MEK inhibition reactivated the RB1 tumor suppressor, induced cell death, and reduced MPNST cell survival.
• Dual CDK4/6-MEK inhibition slowed tumor growth in MPNST PDXs and caused tumor regression with improved survival in immunocompetent mice.
• CDK4/6-MEK inhibition sensitized MPNSTs to anti-PD-L1 immune checkpoint blockade (ICB), leading to complete tumor regression in some cases.

Conclusions:

• CDK4/6-MEK inhibition stimulates a novel plasma cell-associated immune response, enhancing antitumor activity in MPNST.
• The combination of CDK4/6-MEK inhibition and anti-PD-L1 therapy demonstrates significant preclinical efficacy.
• These findings support the clinical translation of CDK4/6-MEK-ICB targeted therapies for improved MPNST patient outcomes.