Germline DNA damage repair gene alterations in Chinese prostate patients: More than HRR and MMR.

Abstract

e13041 Background: Prostate cancer is a worldwide most occurred malignancy in male population. Genetic aberrations of homologous recombination repair (HRR) pathway were proved to be associated with aggressive disease and poorer outcome but may also lead cancer cells more vulnerable to PARP inhibitors. Other than HRR, germline variants in mismatch repair (MMR), nucleotide excision repair (NER) were also identified. Thus, it is important to clarify the distribution of germline alterations of DDR pathways in Chinese prostate cancer patients. Methods: Sixty-five prostate cancer patients unselected for family history, stage of disease, or age at diagnosis were collected. DNA from peripheral blood was extracted. Whole-exon was captured and sequenced subsequently using MGI-SEQ 2000 platform. A total of 229 DDR genes were selected for further analysis. Germline variants were determined to be deleterious according to the ACMG 2015 guidelines. Results: Ten of 65 patients (15.38%) had 7 pathogenic/likely pathogenic germline variants involving 5 different genes: FANCD2 (n = 5), BRCA2 (n = 3), CHEK2 (n = 1), ATM (n = 1) and RECQL (n = 1). Nine patients (13.84%) carried variants predicated to be deleterious via in silico predicators. Taken together, deleterious/potential deleterious germline variants were categorized into 5 DDR pathways which were Fanconi Anemia (9.2%), HRR (9.2%), MMR (4.6%), BER (4.6%) and NER (1.5%). Patients with pathogenic/likely pathogenic germline variants had tendency to be early-onset (mean age [range] at diagnosis, 52[43-67] versus 64[37-80] years, P = 0.001). PSA level at initial diagnosis and self-reported family history did not have significant difference between deleterious mutation carriers and non-carriers (P = 0.396 for PSA level, P = 0.753 for family history). Moreover, metastasis and Gleason score were not associated with deleterious germline variants. Conclusions: Our data showed approximately 52% DDR mutation occurred in other DNA repair pathways besides HRR and MMR, which was a unique spectrum of germline variants in Chinese prostate cancer patients. This indicated distinct genetic etiology and potential therapeutic targets of prostate cancer in Chinese population. Moreover, early-onset in patients with deleterious germline variants is an important clinical character. Whole DDR pathway genes’ testing and counseling should be considered for application for young individuals.