[Clinical value of fluorescent PCR-capillary electrophoresis for detecting POLE mutations in endometrial carcinoma]

Objective: To investigate the clinical values of fluorescent PCR-capillary electrophoresis (PCR/CE) for detecting somatic mutations in the proofreading exonuclease domain of DNA polymerase epsilon (POLE-exo*) in endometrial carcinomas (EC), as compared with Sanger sequencing. Methods: A total of 280 EC cases diagnosed at the Department of Pathology at Peking University Third Hospital, Beijing, China from December 2022 to December 2023 were collected. Ten cases, which had previously been confirmed to harbor POLE pathogenic mutations through next-generation sequencing (NGS), were excluded. Subsequently, parallel sequencing using both PCR/CE and Sanger sequencing methods was conducted on the remaining 270 EC samples without prior POLE testing, aiming to examine 11 known pathogenic mutation-sites located within exons 9, 11, 13, and 14 of the POLE gene. NGS was then carried out on the EC cases in which the PCR/CE and/or Sanger sequencing results indicated the presence of POLE-exo*. Results: Among the 270 EC samples, POLE-exo* was detected in 4 cases (4/270, 1.5%) using Sanger sequencing. In contrast, the PCR/CE identified POLE-exo* in 12 cases (12/270, 4.4%). It was noteworthy that all cases in which POLE-exo* was detected through Sanger sequencing were also successfully identified using PCR/CE (4/4, with a detection rate of 100%). These results were further verified by NGS. The PCR/CE also uncovered an additional 8 cases (8/266, 3.0%) of POLE-exo* in the 266 samples that were negative for POLE mutations per Sanger sequencing. Of these 8 cases, 4 were validated using NGS, exhibiting variant allele frequency (VAF) below 10%, but tumor mutation burdens exceeding 10 mutations per megabase. However, due to small tumor sizes, NGS verification could not be performed on the remaining 4 PCR/CE-positive but Sanger-negative cases. Conclusion: The PCR/CE exhibits better sensitivity and detection capabilities than the Sanger sequencing in identifying POLE-exo* in EC samples, particularly in detecting low VAF.