Non-Exonuclease Domain POLE Mutations Associated with Immunotherapy Benefit

Area of Science:

• Genomics and Cancer Biology
• Immunotherapy Research
• Molecular Diagnostics

Background:

• Inactivating mutations in the POLE gene's exonuclease domain lead to high tumor mutation burden (TMB) and predict benefit from immune checkpoint inhibitors (ICIs).
• The clinical significance of POLE mutations outside the exonuclease domain, particularly regarding ICI response, remains largely unexplored.
• POLE is crucial for DNA replication and proofreading, and its mutations can impact genomic stability.

Observation:

• A patient with hepatocellular carcinoma and a rare, deleterious POLE mutation (V1368M) outside the exonuclease domain, exhibiting low TMB and microsatellite stability, achieved an exceptional response to pembrolizumab.
• Analysis of 1278 advanced cancer patients treated with ICIs revealed that missense POLE mutations outside the exonuclease domain were associated with improved overall survival, even in cases of low or intermediate TMB.
• In contrast, POLE mutations did not correlate with overall survival in advanced cancer patients not exposed to ICIs.

Findings:

• Missense POLE mutations located outside the exonuclease domain can serve as predictive biomarkers for ICI therapy response, independent of TMB.
• These non-exonuclease domain POLE mutations may confer sensitivity to ICIs through mechanisms beyond altered DNA replication and proofreading.
• A specific subset of POLE mutations may identify patients likely to benefit from immunotherapy.

Implications:

• Non-exonuclease domain POLE mutations represent a novel class of biomarkers for predicting ICI efficacy in diverse cancer types.
• This research expands the understanding of POLE's role in cancer immunotherapy response, moving beyond its established link to TMB.
• Clinical strategies may be refined to incorporate POLE mutation status for patient stratification in ICI treatment decisions.