Clinicopathological and genomic characteristics of POLE-mutated colorectal cancer in a Chinese population.

Abstract

e15531 Background: DNA polymerase ε (POLE) is essential for proofreading and fidelity in DNA replication and repair. Previous studies found that mutation in POLE associated with higher tumor mutational burden (TMB), which is an approved biomarker for immunotherpy in solid tumors. However, the clinicopathological and mutational analyses of POLE-mutated colorectal cancer in a large Chinese population have not yet been reported. Methods: Hybrid capture-based next-generation sequencing (NGS) were performed in 4628 samples of colorectal tumors and matched normal pairs in a CAP/CLIA-approved laboratory (3DMed). NGS testing for gene mutations, TMB and MSI was implemented. Results: Of 4628 colorectal cancer patients, POLE mutations were observed in 67 patients (1.45%). A total of 11 different POLE mutations were identified, mostly associated with exonucleas domain. P286R(32,0.69%), V411L(13,0.28%), A456P(7,0.15%), S459F(3,0.06%) and S297F(3,0.06%) were the most frequently mutated sites of POLE. We also detected 1 V758L and 1 W1130R mutation outside the exonuclease domain in separate cases. Among the 4628 patients, 2157 patients were detectable for TMB by NGS panel, including 2128 POLE wild type and 29 POLE mutation patients. The TMB of patients with POLE mutations was significantly higher than that in wide type POLE tumors (mean TMB 252.3 vs 13.4 muts/Mb, P ＜0.0001). All the 29 POLE-mutated patients were TMB-H (≥10 muts/Mb) and 28 of them were MSS. A MSS patient with metastatic colon cancer harboring A456P POLE mutation responsed well to the immunotherpy and achieved a partial response. Conclusions: Our results realved a remarkable positive correlation between POLE mutation and TMB level in a Chinese colorectal cancer population, which suggests POLE gene will be a promising biomarker of immunotherpy for MSS colorectal tumor.[Table: see text]