Characteristics of POLE and POLD1 gene variations in Chinese cancer patients.

Abstract

e14031 Background: POLE and POLD1 gene variations have been suggested as potential markers for immunotherapy due to their significant association with the tumor mutation burden (TMB), an effective indicator for response prediction in immunotherapy. Methods: In this study, we systematically studied the spectrum and characteristics of POLE and POLD1 gene variations from 1,392 Chinese cancer patients, and their correlation with existing immunotherapeutic markers and cancer associated genes. Results: We found that the frequency of POLE variations was not statistically different from that in COSMIC database, while the frequency of POLD1 variations in Chinese lung cancer patients was significantly higher than that in COSMIC database. Variations frequency analysis showed that c.857C > G and c.2091dupC were potential high frequency variations in Chinese cancer patients. Patients carrying POLE damaging variations were significantly younger, and patients carrying POLD1 damaging variations exhibited significantly higher frequency of MSI than POLE/POLD1 WT patients. Further studies found that patients carrying POLE exonuclease domain damaging variations, POLD1 exonuclease and non-exonuclease domain damaging variations exhibited significantly higher TMB than POLE/POLD1 WT patients, while no such difference was found in patients carrying POLE and POLD1 neutral variations. Moreover, patients with POLE exonuclease domain damaging variations showed significantly higher frequency of MMR gene and driver gene variations than POLE/POLD1 WT patients, including genes associated with RTK/RAS/RAF pathway. Patients with damaging POLD1 variations also exhibited higher frequency of MMR gene variations than POLE/POLD1 WT patients. The high frequency variant genes in patients with POLE exonuclease domain damaging variations or POLD1 damaging variations were associated with MMR, RTK/RAS/RAF, TGFβ, WNT, PI3K-Akt and TP53 pathways. Conclusions: This study identified key characteristics and domains of POLE and POLD1 gene variations that related to TMB, MSI, MMR gene variations and key driver gene variations, and provided theoretical and practical basis for patient selection based on POLE or POLD1 gene status in immunotherapy.