Lung adenocarcinoma is the primary cause of cancer-related death worldwide, with an estimated 1.8 million fatalities each year (1). Researchers are still considering possible links involving lung cancer risk. Although smoking is still the leading cause of lung cancer, accounting for 80 to 90 percent of all cases, genetic susceptibility may play a role in lung cancer in some situations (2). Previous studies have demonstrated that genetic susceptibility was thought to be closely related to the development of familial lung cancer (3, 4). However, the risk factors for hereditary lung cancer are unknown at this time. Several research has looked into the function of germline mutations, primarily selected somatic mutations, in lung cancer susceptibility (5–7).

Ataxia Telangiectasia and Rad3 related (ATR) kinase plays a crucial role in the repair of replication-associated DNA damage (8). The study of cell cycle checkpoint signaling through ATR, as well as the related pathways implicated in oncogenesis and cancer progression, has resulted in the discovery and development of effective and selective ATR inhibitors (ATRi) (9). According to recent research of inherited germline mutations in a Chinese population with lung cancer assessed using an NGS, the majority of the discovered germline mutations (85.5 percent) were implicated in DNA damage repair (DDR) pathways (10). There have previously been reports of rare events in lung cancer patients, which may be related to the genetic susceptibility to lung cancer (11). As a high-throughput method, next-generation sequencing (NGS) has become routine in clinical practice and has altered the clinical management of lung cancer (12, 13). This method enables for massively parallel characterization of thousands of cells at the transcriptome level. In this study, we identified an interesting ATR mutation by whole-exome sequencing in three sisters of this family with lung cancers.

Carcinogenesis is a multi-factor and multi-stage process and gene mutation is an important cause of cancer occurrence and development (28). Germline mutations including somatic mutation and germline mutations. Germline mutations which occur in the reproductive cells, it can be passed on to the next generation, affecting every cell in the next generation. However, most studies on tumor mutations have focused on somatic mutations. The mining and identification of tumor germline mutations are very limited, with only a few cases reported in lung adenocarcinoma. As a result, the identification of novel germline mutations is critical for both fundamental research and clinical cancer treatment (29).

In previous studies, most of the genes with germline mutations in lung adenocarcinoma were typical oncogenes and proto-oncogenes, which included BRCA2, CHECK2, CDKN2, BAP1, EGFR (30–32). The genomic alternations of these genes were thought to be important in familial lung cancer. Then, with the development of high-throughput sequencing data, germline altered variants in other genes (MAST1, CENPE, LCT) (33–35) were identified to exhibit an essential role in the development of lung adenocarcinoma, and they were suspected to be related to the development of lung cancer through whole-exome or genome sequencing of samples from many lung cancer patients.

In this study, we continue to focus on the germline mutation of genes in lung adenocarcinoma and we have identified seven different variants (SMG5, RAB3GAF2, EI24, XDH, PTPRA, ATR, GSTZ1) in three sibling patients suffering from lung cancer. The most significant is a rare somatic mutation in the ATR gene named c.7667C>G (p.T2556S), and this ATR gene variation has never been observed in genome and exome research within combined populations. Then, we analyzed the expression and prognosis of ATR in lung adenocarcinoma. Compared with normal patients, the expression of ATR was down-regulated in LUAD, and the down-regulated expression of ATR was associated with poor prognosis. Furthermore, we employed single-cell sequencing data to investigate the expression of ATR in lung adenocarcinoma cell types. Compared with normal patients, we found that the expression level of ATR in the stromal cells (fibroblasts, epithelial cells, and endothelial cells) of tumor patients was low. In addition to T/NK cells, the expression level of ATR in immune cells (myeloid cells, B lymphocytes, MAST cells) of tumor patients is higher. In view of this, we have reason to believe that germline ATR c.7667C>G (p.T2556S) mutation may lead to familial clusters of lung adenocarcinoma and differentially expressed ATR may play an essential role in the occurrence and development of lung adenocarcinoma. Moreover, based on somatic mutation data, we found common driver gene mutations such as EGFR, BRCA1, ROS1, etc. We predicted 136 new driver gene mutations such as PNCK, IP6K2, CLEC18C, etc. through OncodriveCLUST software (36). These gene mutations may be secondary somatic mutations based on germline ATR c.7667C>G (p.T2556S) mutations, which eventually lead to the occurrence and progression of lung adenocarcinoma.

ATR, as a necessary gene in the DNA damage repair pathway, is involved in the coordination of cell-cycle transitions, DNA replication, DNA repair, and apoptosis (37). Previous studies have shown that germline gene mutations that occur in the DNA damage repair pathway often irreversibly lead to tumors (38, 39). Furthermore, germline abnormalities in DNA repair genes lead to advanced solid tumor (such as prostate, ovarian, pancreatic, and breast cancer) susceptibility to poly ADP ribose polymerase (PARP) inhibitors (40–42). To our knowledge, this is the first such case report confirming the presence of c.7667C>G (p.T2556S), a germline ATR mutation, in a family with three occurrences of lung adenocarcinoma The resulting amino acid mutation, p.Thr2556Ser, was detected in the ATR’s conserved Phosphoinositide 3- and 4-kinase domain, which is involved in biological processes such as cell growth, proliferation, differentiation, motility, survival, and intracellular trafficking (43).

The population frequency in the entire population is 0.0399361 percent, suggesting that this ATR germline mutation may be a genetic susceptibility factor for lung adenocarcinoma. Our findings contribute to the understanding of the genesis and mechanism of lung cancer and may give clues for oncology treatment strategies and cancer prevention.

The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found below: NCBI [accession: PRJNA800743].

The studies involving human participants were reviewed and approved by ethics committees of the First Hospital of China Medical University. The patients/participants provided their written informed consent to participate in this study. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.

GB conceived and designed the study, and drafted the manuscript. XG, YX, and YY collected, analyzed and interpreted the experimental data. JL, TL, and XZ revised the manuscript for important intellectual content. All authors contributed to the article and approved the submitted version.

This work was supported by Wu Jieping Medical Foundation (320.6750.2020-17-7).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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