# The Personalized Inherited Signature Predisposing to Non-Small-Cell Lung Cancer in Non-Smokers

## TL;DR

This study identifies unique inherited genetic mutations in non-smokers with lung cancer, suggesting personalized treatment strategies.

## Contribution

The study introduces a novel approach to uncovering a personalized, inherited genetic signature in non-smoker lung cancer patients.

## Key findings

- Each patient has a unique combination of six private mutations in tumor-predisposing genes.
- RNA sequencing confirmed the pathogenic role of identified variants through gene expression changes.
- The findings suggest a 'private genetic epidemiology' model for non-small-cell lung cancer in non-smokers.

## Abstract

Building on the idea of a germline oligogenic origin of lung cancer, we performed WES of DNA from patients’ peripheral blood and their unaffected sibs. Filtering for rare variants and potentially damaging effects, we identified 40 deleterious variants mapping in genes previously associated with cancer exclusively identified in patients. Transcriptome profiling on both tumor and normal lung tissues revealed that, among the selected mutated genes, 16 variants mapping in 16 genes were either down- or upregulated in cancer specimens. Among the downregulated genes, 9 variants in 9 genes carried the mutated allele suggesting a loss of heterozygosity. Notably, the group of mutated genes was unique for each patient, pinpointing to a “private” oligogenic germline signature. In the era of precision medicine, this report emphasizes the importance of an “omic” approach to uncover an oligogenic germline signature underlying cancer development and identify suitable therapeutic targets.

Lung cancer (LC) continues to be an important public health problem, being the most common form of cancer and a major cause of cancer deaths worldwide. Despite the great bulk of research to identify genetic susceptibility genes by genome-wide association studies, only few loci associated to nicotine dependence have been consistently replicated. Our previously published study in few phenotypically discordant sib-pairs identified a combination of germline truncating mutations in known cancer susceptibility genes in never-smoker early-onset LC patients, which does not present in their healthy sib. These results firstly demonstrated the presence of an oligogenic combination of disrupted cancer-predisposing genes in non-smokers patients, giving experimental support to a model of a “private genetic epidemiology”. Here, we used a combination of whole-exome and RNA sequencing coupled with a discordant sib’s model in a novel cohort of pairs of never-smokers early-onset LC patients and in their healthy sibs used as controls. We selected rare germline variants predicted as deleterious by CADD and SVM bioinformatics tools and absent in the healthy sib. Overall, we identified an average of 200 variants per patient, about 10 of which in cancer-predisposing genes. In most of them, RNA sequencing data reinforced the pathogenic role of the identified variants showing: (i) downregulation in LC tissue (indicating a “second hit” in tumor suppressor genes); (ii) upregulation in cancer tissue (likely oncogene); and (iii) downregulation in both normal and cancer tissue (indicating transcript instability). The combination of the two techniques demonstrates that each patient has an average of six (with a range from four to eight) private mutations with a functional effect in tumor-predisposing genes. The presence of a unique combination of disrupting events in the affected subjects may explain the absence of the familial clustering of non-small-cell lung cancer. In conclusion, these findings indicate that each patient has his/her own “predisposing signature” to cancer development and suggest the use of personalized therapeutic strategies in lung cancer.