PARP inhibition is a modulator of anti-tumor immune response in BRCA-deficient tumors

Area of Science:

• Oncology
• Immunology
• Genetics

Background:

• PARP inhibitors are synthetically lethal with BRCA1/2 mutations, leading to DNA damage and cell death.
• DNA damage can activate anti-tumor immune responses, suggesting a potential synergy with immune checkpoint blockade (ICB).

Purpose of the Study:

• To investigate the impact of olaparib combined with ICB on anti-tumor activity and the tumor immune microenvironment.
• To explore the mechanisms by which olaparib affects immune pathways in BRCA-mutated and wild-type tumors.

Main Methods:

• Preclinical studies using BRCA-mutated (Brca1m BR5) and patient-derived xenograft (PDX) models (BRCA1m HBCx-10, BRCA WT HBCx-9).
• In vitro assays to assess olaparib's effect on dendritic cell transactivation.
• Analysis of patient samples from the MEDIOLA trial (NCT02734004) to correlate preclinical findings with human disease.

Main Results:

• Concurrent olaparib and ICB demonstrated durable and deeper anti-tumor activity compared to monotherapies in the Brca1m BR5 model.
• Olaparib and combination treatment increased CD8+ T cells and NK cells, and upregulated type I IFN and STING signaling.
• Olaparib induced dose-dependent immune pathway upregulation (JAK/STAT, STING, type I IFN) in BRCA-mutated tumor cells, but not BRCA wild-type cells.
• In vitro, olaparib induced BRCA-mutated tumor cell-specific dendritic cell transactivation.
• Patient samples showed increased type I IFN, STING, and JAK/STAT pathway expression after olaparib treatment.

Conclusions:

• Concurrent olaparib and ICB provides enhanced anti-tumor activity in BRCA-mutated settings.
• Olaparib modulates the immune microenvironment by increasing immune cell infiltration and activating key immune pathways, particularly in BRCA-mutated tumors.
• These findings support a mechanism for combining olaparib with ICB, offering a potential therapeutic strategy for BRCA-mutated cancers.