Prevalence of prkdc mutations and association with response to immune checkpoint inhibitors in solid tumors.

Abstract

e15250 Background: Predictive biomarkers of response to immune checkpoint inhibitors (ICIs) help to identify cancer patients who will benefit from immunotherapy. PRKDC is an important gene relates to DNA double-strand break (DSB) repair and central T-cell tolerance. We aim to investigate the association between PRKDC mutations and tumor mutation burden (TMB), tumor microenvironments (TME), and response to ICIs. Methods: The whole exome sequencing data of 4022 solid tumor samples from the Cancer Genome Atlas (TCGA) and the panel-based sequencing data of 4652 solid tumor samples from GenePlus-Beijing, China were used to analyze TMB. The mRNA expression data of 3541 solid tumor samples from TCGA was used to explore the effect of PRKDC mutation on TME. Four ICIs-treated cohorts were analyzed for verifying the correlation between PRKDC mutation and the response to ICIs. Results: In TCGA datasets and GenePlus datasets, we both found that the TMB in PRKDC mutation samples were significantly higher than PRKDC wild-type samples(P < 0.05, P<0.0001 respectively). When compare to other pivotal DNA damage response (DDR) genes, it showed an identical effect of the degree in TMB by PRKDC mutation with MMR ( PMS2/ MLH1/ MSH2/ MSH6) genes, POLE/D1 and BRCA1/2 mutation (P > 0.05). Further, in TCGA datasets, it showed that PRKDC mutation samples were associated with significant expression increase of CD8+ T cells, NK cells, immune-checkpoint, chemokines etc compared to PRKDC wild-type samples (P < 0.05). In ICIs-treated cohorts, we also found the PRKDC mutation was associated with superior survival(median PFS, not reached (NR) vs. 6.8 months HR, 0.2893 95% CI, 0.1255-0.6672 P = 0.0650, Hellmann cohort; median OS, 1184 days vs. 250 days HR, 0.5126 95% CI, 0.2715-0.9679 P = 0.1020, Allen cohort), and the superiority was significantly in multivariate Cox regression analyses (HR, 0.361 95% CI,0.155-0.841; P = 0.018, Allen cohort; HR, 0.240 95% CI,0.058-0.998; P = 0.050, Hellmann cohort). Conclusions: PRKDC mutations are associated with an increased TMB, an inflamed TME and a better response to ICIs, it may be a potential predictive biomarker for ICIs-immunotherapy.