ABSTRACT: Lung cancer remains a substantial health challenge, with distinct genetic factors influencing disease susceptibility and progression. This study aimed to decipher the landscape of DNA repair gene mutations in Pakistani lung cancer patients using Whole Exome Sequencing (WES) and to investigate their potential functional implications through downstream analyses. WES analysis of genomic DNA from 15 lung cancer patients identified clinically important pathogenic mutations in 6 DNA repair genes, including, BReast CAncer gene 1 (BRCA1), BReast CAncer gene 2 (BRCA2), Excision Repair Cross Complementing rodent repair deficiency, complementation group 6 (ERCC6), Checkpoint Kinase 1 (CHEK1), mutY DNA glycosylase (MUTYH), and RAD51D (RAD51 Paralog D). Kaplan-Meier (KM) analysis showed that pathogenic mutations in BRCA1, BRCA2, ERCC6, CHEK1, MUTYH, and RAD51D genes were the prognostic biomarkers of worse OS in lung cancer patients. To explore the functional impact of these mutations, we performed Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Immunohistochemistry (IHC) analyses. Our results revealed a down-regulation in the expression of the mutated genes, indicating a potential link between the identified mutations and reduced gene activity. This down-regulation could contribute to compromised DNA repair efficiency, thereby fostering genomic instability in lung cancer cells. Furthermore, targeted bisulfite sequencing analysis was employed to assess the DNA methylation status of the mutated genes. Strikingly, hypermethylation in the promoters of BRCA1, BRCA2, ERCC6, CHEK1, MUTYH, and RAD51D was observed across lung cancer samples harboring pathogenic mutations, suggesting the involvement of epigenetic mechanism underlying the altered gene expression. In conclusion, this study provides insights into the genetic landscape of DNA repair gene mutations in Pakistani lung cancer patients. The observed pathogenic mutations in BRCA1, BRCA2, ERCC6, CHEK1, MUTYH, and RAD51D, coupled with their down-regulation and hypermethylation, suggest a potential convergence of genetic and epigenetic factors driving genomic instability in lung cancer cells. These findings contribute to our understanding of lung cancer susceptibility and highlight potential avenues for targeted therapeutic interventions in Pakistani lung cancer patients.
