Analysis of mutation detection of POLD1/pole in pan-cancer.

Abstract

3142 Background: Previous studies proved that mutation of POLD1 and POLE elevates base-substitution mutations and lead to the elevation of tumor mutation burden (TMB). Other signature needs to explore to identify driver mutations in these two genes. Methods: Using gene-panel target-capture next generation sequencing, we analyzed the TMB and POLD1/POLE mutation in 17383 tumor tissue or plasma ctDNA samples from different patients. Results: Tumor mutation burdens were calculated of all the 17383 samples. According to the present research and our panel, we use 10 and 100 Mut/Mb to define hypermutation and ultra-hypermutation. Samples with hypermutation possessed 18.8% (n = 3268) and ultra-hypermutation possessed 0.3% (n = 58). In unselected, hypermutation and ultra-hypermutation group, POLD1 or/and POLE mutations were identified in 3.5% (n = 625), 56.1% (n = 32) and 87.9%(n = 372) samples. There were 0.5% (n = 81), 17.0% (n = 73) and 87.7%(n = 51) identified more than one mutation. These results showed that POLD1 or/and POLE mutations were enriched in samples with high TMB. We screened every known POLE and POLD1 driver mutations. There were 22 ultra-hypermutation samples identified these mutations, including A456P(3), P286R(10), V411L(6), M444K(1), S459F(1) in POLE and R1016H(1) in POLD1. Interestingly, all of them were identified in microsatellite stable (MSS) samples, which suggest that driver mutation may enriched in MSS samples. These already known driver mutation was not detect in 24 high-level microsatellite instability (MSI-H) and ultra-hypermutation samples. We further analyzed 10 POLD1/POLE mutations in other 5 MSS and ultra-hypermutation samples. POLE L424V was a pathogenic germline mutation but not defined as a driver mutation clearly before. POLE P286C had not been biochemically characterized but had different residue with P286R in the same position. Others had not been biochemically characterized (R232H, A234T, V945M, S1064I, Y467H in POLD1, D462N and R749Q, E1956D in POLE). These mutations were potential driver mutations and further research need to be support. Conclusions: We found that not only POLD1 or/and POLE mutations were enriched in samples with high TMB, but also driver mutations were enriched in microsatellite stable tumors. Further researches need to continue to identify more driver mutations of POLD1 and POLE.