Introduction

Lung cancer is the leading cause of cancer deaths globally[1]. Though the most common cause of lung cancer is tobacco smoking, studies estimate that approximately 25% of lung cancers worldwide occur in individuals who have never smoked[2]. Recently, lung cancer in never smokers (LCINS) were molecular profiled and new genomic features were revealed[3–9]. For now, further stratification of LCINS based on different risk factors would be helpful to reveal the oncogenic mechanisms and develop more targeted therapies. Air pollutants, which can directly affect the pulmonary airway, play crucial roles in promoting lung adenocarcinoma[10–12]. More than 20 environmental and occupational agents are lung carcinogens[13, 14] and amount of studies have been made to investigate molecular mechanisms in tumor progression of air pollution chemicals or components using cell lines or mouse/rat models[15–17]. However, a comprehensive molecular characterization of clinical lung cancer samples associated with air pollution is still lacking.

The Xuanwei area has the highest rate of lung cancer in China, and extensive research has established a strong link between lung cancer and exposure to domestic coal smoke[18–23]. Specifically, etiologic link between smoky coal burning and cancer was epidemiologically established[18, 19] and association between household stove improvement and lower risk of lung cancer was observed[23]. Moreover, genomic evidence of lung carcinogenesis associated with coal smoke in Xuanwei area, China was provided in our previous study[22]. Thus, lung cancer in Xuanwei areas exemplifies the ideal disease to study characteristics of lung cancers associated with air pollution. In recent years, the molecular features of Xuanwei lung cancer have been gradually revealed[24–26] [22]. A large sample size with multi-comic molecular profiling is urgent needed to explicit the air pollution chemicals and furthermore propose more targeted therapies.

To better understand the molecular mechanisms and heterogeneity of XWLC and to advance precision medicine, we expanded the sample size of our next-generation sequencing dataset to 169 sample size and performed proteomic and phosphoproteomic profiling to 112 samples. Furthermore, we integrated 107 radiomic features derived from X-ray computed tomography (CT) scans to 115 samples to non-invasively distinguish molecular subtypes. This allowed us to identify potential major risk factor, distinguish the genomic features and establish clinically relevant molecular subtypes. Our study provides an exceptional resource for future biological, diagnostic, and drug discovery efforts in the study of lung cancer related to air pollution.

Results

To investigate unique biological features of LUAD associated with air pollution, three previous LUAD datasets related to different carcinogens were used for comparison (Fig. 1a). CNLC is the subset of lung adenocarcinoma from non-smoking patients in Chinese Human Proteome Project (CNHPP project) [8] (n=77). TSLC is the subset of lung adenocarcinoma from smoking female in TCGA-LUAD project [27] (n=168). TNLC is the subset of lung adenocarcinoma from non-smoking female in TCGA-LUAD project[27] (n=102). The clinicopathological characteristics of patients from CNLC, TSLC and TNLC cohorts were supplied in Supplementary Table 1a and 1b.

Fig 1.

Proteogenomic landscape in Xuanwei lung cancer (XWLC)

The present study prospectively collected primary samples of lung adenocarcinoma (LUAD) from 169 never-smoking women from the Xuanwei area in China (Supplementary Table 1c). The XWLC cohort had a median age of 56 years (Fig. 1b), and the majority of tissue samples were in the early stages of the disease (145 were stage I/II, and 24 were stage III/IV, Fig. 1c). A total of 135, 136, 102 and 102 tumor samples were profiled with whole-exome sequencing (WES), RNA-seq, label-free protein quantification, and label-free phosphorylation quantification, respectively (Fig.1d-e and Extended Fig.1a and 1b). Analysis of the WES data from the paired tumor and normal tissue samples revealed 37,149 somatic mutations, including 1,797 InDels, 32,972 missense mutations, 2,345 nonsense mutations, and 35 nonstop mutations (Supplementary Table 2). Copy number analysis showed 140,396 gene-level amplifications and 67,605 deletions across 40 cytobands (Supplementary Table 3). The mRNA-seq data characterized the transcription profiles of 19,182 genes (Supplementary Table 4). The label-free global proteomics identified 9,152 proteins (encoded by 6,864 genes) with an average of 6,457 proteins per sample (Supplementary Table 5). The label-free phosphoproteomics identified 24,990 highly reliable phosphosites from 5,832 genes with an average of 10,478 phosphosites per sample (Supplementary Table 6). The quality and reproducibility of the mass spectrometry data were maintained throughout the study (Extended Data Fig. 1c-e).

The air pollutant Benzo[a]pyrene (BaP) primarily contributes to the mutation landscape of XWLC

To infer the primary risk factor responsible for the progression of XWLC, we used SomaticSignatures[28] to identify mutational signatures from single nucleotide variants. Mutational signatures were identified in each cohort and a cosine similarity analysis was performed against mutational signatures in COSMIC mutational signatures[29, 30] and environmental agents mutational sigantures[31] allowing for inference of the underlying causes (Fig. 1f-i and Extended Fig. 2). Generally, exposure tobacco smoking carcinogens (COSMIC signature) and chemicals such as BaP (environmental agent signature) were identified as the most significant contributing factors in both the XWLC and TSLC cohorts (Fig. 1f and 1g). In contrast, defective DNA mismatch repair and endogenous mutational processes initiated by spontaneous deamination of 5-methycytosine were inferred as the major causes in the TNLC and CNLC cohorts (Fig. 1h and 1i). Therefore, the XWLC and TSLC cohorts are more explicitly influenced by environmental carcinogens, while the TNLC and CNLC cohorts may be more affected by age or endogenous risk factors. BaP, a representative compound of polycyclic aromatic hydrocarbons (PAHs), is found in both cigarette smoke and coal smoke and is recognized as a major environmental risk factor for lung cancer[32–34]. Upon metabolism, BaP forms the carcinogenic metabolite 7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE), which creates DNA adducts leading to mutations and malignant transformations. This process involves two key regulators: CYP1A1 and AhR. CYP1A1 plays a crucial role in BaP epoxidation at the 7,8 positions, which is the most critical step in BPDE formation[35]. AhR is a ligand-activated transcription factor that responds to various chemicals, including chemical carcinogens, and is activated by BaP[36]. Accordingly, our results demonstrated significantly higher expression of CYP1A1 and AhR in tumor samples compared to normal samples (Fig. 1j and 1k). To validate the association between BaP and the elevated incidence of lung cancer in the Xuanwei area, we assessed the serum BPDE levels in individuals residing in this region (Methods). Our findings revealed that the serum BPDE content in individuals from the Xuanwei area averaged around 0.85 nm/ml, and there was no difference between younger and older cases (Fig. 1l and Supplementary Table 7). Furthermore, we treated hiPSC (human induced pluripotent stem cell (hiPSC) with BaP in vitro and found that sites such as Y1173 and Y1068 of EGFR were more phosphorylated in BaP treated cells whereas the total abundance of EGFR showed no significant differences (Fig. 1m). All these results provided further evidence for the involvement of BaP and its metabolite in the development of lung cancer.

Fig 2.

Though coal-smoke related lung cancer (XWLC cohort) and cigarette-smoke related lung cancer (TSLC cohort) showed similar environmental carcinogens, we found that downstream pathway activation and therapeutic targeted potential showed distinctive features. Firstly, the correlation of genomic mutations between XWLC and TSLC was found to be low (Fig. 2a). Secondly, there was a remarkable difference in the fraction of samples affected by pathway mutations between two cohorts (Fig. 2b). Notably, the TSLC cohort exhibited a higher fraction of samples affected by oncogenic pathways comparing to XWLC cohort. Thirdly, mutation frequencies, such as EGFR, TP53, RBM10, and KRAS (Fig. 2c), as well as the distribution of amino acid changes in EGFR and TP53, showed significant differences between the XWLC and other cohorts (Fig. 2d). Specifically, the XWLC cohort exhibited a higher mutation rate in G719C/A/D/S and E746_A750del within the EGFR gene compared to the other three cohorts. For the TP53 gene, frame shift mutations including D9Gfs*3 (n=1), S15Ifs*28 (n=1), D22Efs*61 (n=1), and V34Wfs*49 (n=2) were exclusively detected in the XWLC cohort, whereas tetramer domain mutations were only found in the other three cohorts (Fig. 2d). Finally, there was a noticeable disparity in the percentage of samples with actionable targets among the cohorts. (Fig. 2e). Actionable targets in XWLC cohort were mainly focus on EGFR mutations including pG719S, pG719C, pG719A, pL858R, p.E746_A750del whereas TSLC cohort had more actionable targets in CHEK2 p.K373E, KRAS p.G12V/D/C/A (Fig. 2e).

Taken together, we found that the XWLC and TSLC cohorts, which are smoke-related lung adenoma groups, demonstrated distinct etiology compared to the TNLC and CNLC cohorts which may be influenced by endogenous risk factors to a greater extent. The blood serum assay provided support for BaP as a promising risk factor specifically in the XWLC cohort. Additionally, significant disparities were observed between XWLC and TSLC in terms of downstream pathway activations and specific oncogene loci. Consequently, we conclude that air pollution-associated lung cancer represents a distinct subtype within LUAD.

The EGFR-G719X mutation, which is a hotspot associated with BaP exposure, possesses distinctive biological features

Notably, the XWLC cohort displayed a distinguishable mutation pattern in specific EGFR mutation sites compared to the other cohorts (Fig.3a and Fig.2d). In particular, the G719C/A/D/S (G719X) mutation was the most prevalent EGFR mutation in the XWLC cohort (20%), while it was rarely found in the other three cohorts (CNLC: 1.9%; TSLC: 1.9%; TNLC: 0) (Fig. 3b). Notably, we found it was a hot spot associated with BaP exposure (Fig. 3c and 3d). Specifically, GGC is the 719 codon, the first G can be converted to T (pG719C, n=13) or A (pG719S, n=5), the second G can be converted to A (pG719D, n=1) or C (pG719C, n=8). Thus, pG719C was the most detected mutation type (Fig. 3c). G>T/C>A transversion can be induced by several compounds such as BaP or dibenz(a,h)anthracene (DBA), unlike other compounds, the tallest peak induced by BaP occurs at GpGpG, reflecting how their DNA adducts are formed principally at N²-guanine[31]. Our result showed that the most frequently detected pG719C AAchange was correspond to GGGC>GTGG transversion (Fig. 3d). Thus, pG719C is a hot spot associated with BaP exposure.

Fig 3.

We conducted further investigations into the biological characteristics of samples carrying the G719X mutations. Notably, we observed a moderate to high expression of MAPK signaling components, MAP2K2 (MEK), and MAPK3 (ERK1), in tumors harboring the EGFR-G719X mutation compared to other EGFR statuses (Fig. 3e-3h). Utilizing hallmark capability analysis and RNA-seq-based estimation of immune cell infiltration, we found that tumors with G719X mutations exhibited similarities to those with L858R mutations (Extended Data Fig. 3a-b). However, patients with G719X mutations were notably younger than those with L858R mutations, indicating a higher occurrence rate of G719X in younger female patients (Fig. 3i). Analysis of overall survival and progression-free interval (PFI) revealed that patients with the G719X mutation had worse outcomes compared to other EGFR mutation subtypes (Fig. 3j and 3k). Furthermore, there were no significant differences in mutation burden or the number of neoantigens between tumors with G719X mutations and tumors with other EGFR mutation statuses (Extended Data Fig. 3c).

To explore the heterogeneity of signaling pathways activated by different EGFR mutation statuses, we conducted Kinase-Substrate Enrichment Analysis (KSEA) [37, 38] based on the XWLC phosphoproteomics dataset. Our analysis of the phosphoproteome across various EGFR mutation types revealed distinct activation patterns of kinases. Specifically, the G719X mutation was associated with the activation of PRKCZ, CDK2, AURKB, CSNK1A1, CDK4, and HIPK2. The L858R mutation showed activation of PRKCZ, MAPK7, MAPK12, HIPK2, and CSNK2A1. The Exon19del mutation exhibited activation of CHUK, TTK, PRKCZ, PLK1, NEK2, MAP2K2, CDK2, PRKDC, and MAP2K6. Other EGFR mutations were associated with the activation of AURKB, NEK2, TTK, PLK1, PRKACB, and PRKACG. EGFR-WT mutations showed activation of CSNK1E, PRKCZ, AURKB, CDK2, AURKC, CDK1, CSNK1A1, PRKDC, and CSNK2A1 (Fig. 3l). In Extended Data Fig. 3d, we provide a list of FDA-approved drugs that target the activated kinases in tumors harboring the G719X mutation. Currently, afatinib is widely regarded as a first-line therapy for patients with the G719X mutation[39–42]. However, reports indicate that 80% of patients with this mutation may develop resistance to afatinib, even in the absence of T790M[43], underscoring the need for a deeper understanding of the downstream pathways associated with the G719X mutation. Therefore, a promising approach to overcome resistance in tumors with this mutation could involve combining afatinib, which targets activated EGFR, with FDA-approved drugs that specifically target the activated kinases associated with G719X.

Clinically relevant Subtyping in XWLC

To uncover the inherent subgroups within air-pollution-associated tumors, we employed unsupervised Consensus Clustering[44] on integrated RNA, protein, and phosphoprotein profiles of XWLC tumor samples. This analysis led to the identification of four distinct intrinsic clusters, denoted as MC-I, II, III, and IV (Fig. 4a, Extended Data Fig. 4a and Methods). Further survival analysis demonstrated that patients belonging to the MC-IV group exhibited the poorest overall survival compared to the other three subgroups, thus indicating the prognostic potential of multi-omic clustering (Fig. 4b). Notably, there were no significant differences in clinical features such as age and stage observed among the four subgroups (Fig. 4a). Since BaP has the potential to induce the expression of CYP1A1 and AhR, we utilized the expression levels of CYP1A1 and AhR as indicators of BaP activity. Consequently, we compared the expression levels of CYP1A1 and AhR among the four subtypes to identify the tumor type most strongly associated with air pollution. Our findings revealed that the MC-II subtype exhibited higher expression of CYP1A1 (Fig. 4c) and moderately elevated expression level of AhR compared to the other three subtypes (Fig. 4d) Moreover, the MC-II possessed more G719X mutations (MC-1:0.39, MC-II:0.42, MC-III: 0.20, MC-IV: 0.08). These results collectively suggest a stronger association between the MC-II subtype and BaP exposure. Notably, there was a significant correlation between CYP1A1 and EGFR expression (Fig. 4e), with EGFR being more highly expressed in the MC-II subtype (Fig. 4f). These results indicated that MC-II was more associated with air-pollution.

Fig 4.

Through Kinase Substrate Enrichment Analysis (KSEA) of the phosphoproteome in tumor samples compared to normal adjacent tissues (NATs), we identified specific kinase activations within the four subgroups. In MC-I samples, kinase activations included PRKDC, PRKCZ, CSNK1A1, NEK2, GSK3A, and ROCK1. MC-II samples showed activations of CDK2, CDK1, AURKA, TTK, CDK6, and CHUK. MC-III samples exhibited activations of AKT1, AKT3, RPS6KB1, CSNK2A1, and PAK2. Finally, CDK2 and ROCK1 were activated in MC-IV samples (Fig. 4g). Particularly noteworthy is the enrichment of CDK1/2/6 kinases, which regulate cell cycle checkpoints, in the MC-II subtype, indicating its high proliferation capabilities. These findings imply that distinct kinase pathways are activated within each subgroup, suggesting the presence of specific therapeutic targets for each subgroup. Consequently, we proceeded to explore therapeutic strategies for each subgroup as outlined below:

The MC-IV subtype exhibited the poorest overall survival compared to the other three subtypes (Fig. 4b). Given the crucial role of epithelial-mesenchymal transition (EMT) in malignant progression, our first evaluation focused on the EMT process across the four subtypes. We observed higher expression levels of mesenchymal markers such as VIM, FN1, TWIST2, SNAI2, ZEB1, ZEB2, and others in the MC-IV subtype (Fig. 5a). To comprehensively assess the EMT capability of the MC-IV subtype, we calculated EMT scores using the ssGSEA enrichment method based on protein levels and GSEA hallmark gene set (M5930)[45]. The results confirmed the elevated EMT capability of the MC-IV subtype at the protein level (Fig. 5b). Furthermore, Fibronectin (FN1), an EMT marker that promotes the dissociation, migration, and invasion of epithelial cells, was found to be highly expressed in the MC-IV subtype at the protein level (Fig. 5c). Additionally, β-Catenin, a key regulator in initiating EMT, was highly expressed in the MC-IV subtype at the protein level (Fig. 5d). Collectively, our findings demonstrate that the MC-IV subtype possesses an enhanced EMT capability, which may contribute to the high malignancy observed in this subtype.

Fig 5.

The MC-II subtype demonstrated the second-worst outcome and was found to be more strongly associated with air pollution (Fig. 4). This subtype exhibited dysregulation of cell cycle processes, including cell division, glycolysis, and cell cycle biological processes (Fig. 4a). The KSEA analysis revealed that the CDK1 and CDK2 pathways, which are closely linked to cell cycle regulation, were predominantly activated in the MC-II subtype (Fig. 5e). Consistently, we observed higher expression levels of CDK1 and CDK2 at both the protein and phosphoprotein levels in the MC-II subtype, indicating specific elevation of the G2M phase in the cell cycle (Fig. 5e). The cell cycle and glycolysis processes are tightly coordinated, allowing cells to synchronize their metabolic state and energy requirements with cell cycle progression to ensure proper cell growth and division[46–48]. In line with this, we found that key enzymes involved in glycolysis regulation, such as Hexokinase 1 (HK1), Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and Glyceraldehyde-3-phosphate dehydrogenase-like protein (GPL), were highly expressed in the MC-II subtype (Fig. 5f). Additionally, the MC-II subtype was enriched with EGFR mutations (MC-II vs. others: 18/24 vs. 51/110; Fisher’s exact p = 0.013) and TP53 mutations (MC-II vs. others: 14/24 vs. 35/110; Fisher’s exact p = 0.019), consistent with the characteristic loss of control over cell proliferation. In summary, the MC-II subtype exhibited dysregulated cell cycle processes accompanied by an elevated glycolysis capability, indicating a distinct metabolic and proliferative phenotype.

The MC-I subtype exhibited enrichment in various biological processes including angiogenesis, the cAMP signaling pathway, complement and coagulation cascades, PDL1 expression, the PD-1 checkpoint pathway, leukocyte transendothelial migration, and actin cytoskeleton processes (Fig. 4a). In-depth exploration of key components involved in angiogenesis revealed that vascular endothelial growth factor A (VEGFA), a growth factor crucial for both physiological and pathological angiogenesis, was highly expressed in the MC-I subtype (Fig. 5g). Additionally, phosphorylation of vascular endothelial growth factor receptor 1 (VEGFR1), a receptor tyrosine kinase essential for angiogenesis and vasculogenesis, was also highly expressed in the MC-I subtype (Fig. 5h). The angiogenesis scores, calculated using the ssGSEA method based on protein levels and the hallmark gene set (M5944), were relatively high in the MC-I and MC-IV subtypes (Fig. 5i). Furthermore, the relationship between the Notch signaling pathway and angiogenesis is well-established[49]. Notch signaling plays a role in multiple aspects of angiogenesis, including endothelial cell sprouting, vessel branching, and vessel maturation [50, 51]. In the MC-I subtype, the expression of Notch receptors (Notch1-4) and ligands (DLL1, DLL4, JAG1, and JAG2) was highly elevated, indicating increased activation of Notch signaling (Fig. 5j). KEGG pathview analysis demonstrated that key regulators of the VEGF signaling pathway were highly expressed in the MC-I subtype (Extended Fig.5a). Therefore, manipulating Notch signaling could potentially serve as a strategy to regulate angiogenesis and control pathological angiogenesis in the MC-I subtype.

The MC-III subtype is characterized by the upregulation of various metabolic processes, including oxidative phosphorylation, peroxisome function, adipogenesis, fatty acid metabolism, and xenobiotic metabolism-related processes (Fig. 5k). Additionally, we conducted further investigations into the immune features across the subtypes. Interestingly, we observed higher expression of genes associated with PD-1 signaling (GSEA, SYSTEMATIC_NAME M18810) in the MC-III subtype (Fig. 5l). Since PD-1 is primarily expressed on the surface of certain immune cells, particularly activated T cells, we inferred the immune cell infiltration using the ssGSEA method based on immune cell-specific gene sets. We found that activated CD8+ T cells exhibited higher infiltration levels in the MC-III subtype compared to the other three subtypes (Fig. 5m and Supplementary Table 8), which may explain the elevated PD-1 signaling in the MC-III subtype. Furthermore, we examined the expression of receptor-ligand pairs involved in both anti-tumor and pro-tumor lymphocyte recruitment. Remarkably, the MC-III subtype exhibited specific high expression of anti-tumor lymphocyte receptors and ligands, while the expression of pro-tumor lymphocyte receptors and ligands was relatively lower (Fig. 5n). In general, the MC-I subtype showed the reverse expression trend in terms of anti-tumor and pro-tumor receptor-ligand pairs (Fig. 5n).

In conclusion, our classification of lung adenocarcinoma associated with air pollution resulted in the identification of four subtypes, each exhibiting distinct biological pathway activation and immune features. The MC-I subtype demonstrated elevated angiogenesis processes, while the MC-II subtype showed a high capacity for cell division and glycolysis. The MC-III subtype exhibited a notable infiltration of CD8+ cells, and the MC-IV subtype was characterized by high EMT capability, which may contribute to its poor outcome. These findings have significant implications for the development of precision treatments for XWLC (Extended Fig.5b).

Tumor microbiota composition and radiomic features across subtypes

Host-bacterial immune interactions profoundly influence tumorigenesis, cancer progression, and response to therapy[52–54]. Thus, we further generated species-level resolution data allowing the identification of specific bacteria across subgroups. Firstly, we extracted and mapped high-quality reads of bacterial origin from RNA-Seq datasets across normal and four tumor subgroups of the XWLC cohort using PathSeq[55] while carefully mitigating the influences of microbial contamination (Supplementary Table 9 and Methods). We found that the subgroups showed distinct bacterial abundances (Fig. 6a). Principal coordinate analysis (PCoA)[56] of UniFrac distances of species abundances across subgroups revealed that the first PCoA axis generally captured differences between tumor and adjacent normal tissues, while the second axis mainly captured the differences between the MC-IV subgroup and the other three subgroups (Fig. 6b). Thus, the MC-IV subgroup showed distinguishable bacterial composition compared to the other three subgroups. We further identified 16 bacterial species that were enriched in the MC-IV subgroup, mainly belonging to the Pseudomonas, Stenotrophomonas, Acidovorax, Rheinheimera, Brevundimonas, Sphingomonas, and Methyloversatilis genera (Fig. 6c). Among them, Acidovorax and Brevundimonas have been identified within lung tumor sections[57]. Further investigation is warranted to determine whether and how the unique microbiota composition of MC-IV contributes to its malignancy.

Fig 6.

Furthermore, we built a noninvasive method to distinguish MC subtypes with radiomics which entails the extensive quantification of tumor phenotypes by utilizing numerous quantitative image features. In the initial step, we defined 107 quantitative image features that describe various characteristics of tumor phenotypes, including tumor image intensity, size, shape, and texture. These features were derived from X-ray computed tomography (CT) scans of 155 patients with XWLC (Methods). The baseline characteristics of this cohort can be found in Supplementary Table 10. Firstly, all features were compared among the four subtypes, and notably, eight features showed significant differences between the MC-II subtype and the other three subtypes (Fig. 6d), suggesting a denser image in the MC-II subtype. We further established a signature using a multivariate linear regression model with five image features to distinguish MC-II from the other three subgroups (Extended Fig.6). The performance of the five-feature radiomic signature was validated using the AUC value, which is a generation of the area under the ROC curve. The radiomic signature had an AUC value of 0.94 in the training set and 0.83 in the validation set (Fig. 6e). The confusion matrix revealed an overall accuracy of 0.875 for sample classification using the signature, indicating proficient performance. However, it exhibited suboptimal performance in terms of false-negative classification (Fig. 6f). Taken together, we found that MC-II showed a dense image phenotype, which can be noninvasively distinguished using radiomic features.

Identification of novel targets based on mutation-informed protein-protein interface (PPI) analysis

The integration of genomics and interactomics has enabled the discovery of functional and biological consequences of disease mutations[58, 59]. To explore novel targets with the concept, we created PPI networks with structural resolution using missense mutations from the XWLC, CNLC, TSLC, and TNLC cohorts (Fig.7a and Methods). OncoPPIs, defined as a significant enrichment of interface mutations in either of the two protein-binding partners across individuals, were identified in each cohort and were provided in Supplementary Tables 11. The OncoPPIs from the four cohorts are named XWLC_oncoPPIs, CNLC_oncoPPIs, TSLC_oncoPPIs, and TNLC_oncoPPIs, respectively (Fig. 7b and Extended Fig. 7a-c). Initially, the nodes from these four OncoPPIs were subjected to biological process enrichment analysis (Extended Fig. 7d). The analysis revealed that biological processes such as regulation of mitotic cell cycle, TGF-beta signaling pathway, and immune system were predominantly enriched in the genes related to OncoPPIs. Moreover, the processes disrupted by interface mutations showed a relatively higher similarity between the XWLC and TSLC cohorts (Extended Fig. 7d) suggesting convergent targets or pathways affected by smoke-induced mutations.

Fig. 7

To refine the novel targets from XWLC_oncoPPs, we performed molecular dynamics simulations to predict the binding affinity change by the interface-located mutations (Methods). Mitotic Arrest Deficient 1 Like 1 (MAD1), a crucial component of the mitotic spindle-assembly checkpoint[60, 61], forms a tight core complex with MAD2, facilitating the binding of MAD2 to CDC20[62], which plays a critical role in sister chromatid separation during the metaphase-anaphase transition[63]. Specifically, MAD1 Arg558His has been identified as a susceptibility factor for lung cancer[64] and colorectal cancer[65]. Here, we found that MAD1 allele carrying a p.Arg558His substitution may disrupt the interaction between MAD1 and MAD2 (Fig.7b-c). To assess this, we performed molecular dynamics simulations and found that the binding affinity between Arg558His MAD1 and MAD2 was -195.091 kJ/mol and that of wild type was -442.712 kJ/mol (Fig.7c). Furthermore, on a per-residue basis, the predicted binding affinity (ΔΔG) of Arg558His (Extended Fig.7e) was projected to increase by 118.319 kJ/mol relative to the wild type (Extended Fig.7f), indicating that the substitution of Arg558His in MAD1 perturbs the binding affinity. Thus, our findings suggest that the MAD1 Arg558His attributed to lung cancer progression by disrupting of the interaction between MAD1 and MAD2, which showed potential to be explored as a target.

Notably, we identified TPRN as a novel significantly mutated gene in the XWLC cohort (Extended Fig.7g and 7h) whose status was also associated with patients’ outcomes (Fig.7e). Previous studies have reported that TPRN interacts with PPP1CA[66]. Thus, we assessed the binding affinity of the TPRN-PPP1CA complex affected by the mutant variant His550Gln. Our result showed that the binding affinities of the complex were -694.372 kJ/mol and -877.570 kJ/mol in mutant and WT cases, respectively (Fig.7d). On a per-residue basis, the predicted ΔΔG of His550Gln compared to the wild type exhibited an increase of 96.774 kJ/mol (Extended Fig. 7i-j). All these results indicated that TPRN His550Gln increase the binding affinity of the TPRN-PPP1CA complex. To investigate the effect of TPRN His550Gln mutation on tumor progression, we examined proliferation and migration capabilities in both A549 and H1299 lung adenocarcinoma cell lines. CCK-8 assay showed significantly enhanced cell growth after transfection of TPRN mutant allele in both A549 (Fig.7f) and H1299 cells (Extended Fig. 8a). Moreover, wound-healing assay showed that TPRN mutant cell had achieved enhanced migration capacity (Fig.7g-h and Extended Fig. 8b-c). Finally, more cell clones in TPRN His550Gln mutation cells were observed in both TPRN-mutant A549 and H1299 cells (Fig.7i). All these results supported that TPRN His550Gln could be explored as a target in XWLC.

Taken together, our integrated analysis of oncoPPIs and molecular dynamics simulations showed potential to explore novel therapeutic vulnerabilities.

Discussion

In this study, we conducted proteogenomic and characterized air-pollution-related lung cancers. We found that Benzo[a]pyrene (BaP) influenced the mutation landscape, particularly the EGFR-G719X hotspot found in 20% of cases. This mutation correlated with elevated MAPK pathway activation, worse clinical outcomes, and younger patients. Multi-omics clustering identified four subtypes with unique biological pathways and immune cell patterns. Moreover, our analysis of protein-protein interfaces unveiled novel therapeutic targets. These findings have significant implications for preventing and developing precise treatments for air-pollution-associated lung cancers.

Previously considered uncommon, the EGFR-G719X mutation was detected in only 1-2% of CNLC or TCGA-LUAD cohort samples. Limited knowledge exists from G719X, mostly based on isolated case reports or small series studies[67–71]. In vitro experiments using G719X mutant cell lines and patient-derived xenografts (PDX) demonstrated that osimertinib effectively inhibits signaling pathways and cellular growth, leading to sustained tumor growth inhibition[72]. However, in silico protein structure analysis suggests that G719 alterations may confer osimertinib resistance due to reduced EGFR binding[73]. Presently, afatinib is proposed as the first-line therapy for G719X mutation patients[39–42]. Unfortunately, 80% of G719X patients develop acquired resistance to afatinib without detecting the T790M mutation40. Hence, further mechanistic studies are warranted for G719X. Our study reveals that the G719X mutation is prevalent in the XWLC cohort, significantly impacting treatment selection. Additionally, the large number of G719X samples allowed us to uncover variations in biology and pathway activation, which may facilitate the development of more precise targeted therapies for these patients.

There is substantial evidence linking lung cancer in the Xuanwei area to coal smoke[18, 19, 21, 22, 74, 75]. In addition, we conducted a rat model study that demonstrated the induction of lung cancer by local coal smoke exposure[22]. However, the specific chemical compound in coal smoke responsible for causing lung cancer remains largely unknown. Previous research has mainly focused on studying indoor concentrations of airborne particles and BaP[18, 19, 21, 23, 76]. For instance, studies have shown an association between the concentration of BaP and lung cancer rates across counties[18]. Moreover, improvements in household stoves have led to reduced exposure to benzopyrene and particulate matter, benefiting people’s health[23, 76]. However, these studies primarily relied on epidemiological data, which may be influenced by confounding factors. In our study, we used clinical samples and linked the mutational signatures of XWLC to the chemical compound BaP, which advanced the etiology and mechanism of air-pollution-induced lung cancer.

In summary, our proteogenomic analysis of clinical tumor samples provides insights into air-pollution-associated lung cancers, especially those induced by coal smoke and offers an opportunity to expedite the translation of basic research to more precise diagnosis and treatment in the clinic.

Declarations

Ethical Approval

The study protocol was reviewed and approved by the ethical committees of Yunnan Cancer Hospital & The Third Affiliated Hospital of Kunming Medical University (KYCS2022067) and conformed to the ethical standards for medical research involving human subjects, as laid out in the 1964 Declaration of Helsinki and its later amendments.

Consent to participate

Participants provided written informed consent prior to taking part in the study.

Consent for publication

Written informed consent was obtained from the patient and the ethical committees of Yunnan Cancer Hospital & The Third Affiliated Hospital of Kunming Medical University for publication of this study.

Competing interests

The authors declare no competing interests.

Authors’ contributions

Honglei Zhang, Gaofeng Li, Xiaosan Su and Yong Zhang conceived the study. Honglei Zhang, Chao Liu, Qing Wang and Shuting Wang performed data analysis. Honglei Zhang wrote the manuscript. Xu Feng, Heng Li, Zhiyong Deng, Huawei Jiang, Yunyan He, Chao Luo, Rou Qian, Minjun Zhou, Zhi Li, Li Xiao, Yong Zhang interpreted the data analysis and drafted the manuscript and critically revised the manuscript. All authors critically revised and gave final approval of the manuscript.

Funding

This work was supported by National Natural Science Foundation (Nos. 82273501, 81960322, 82160343, 82060519, 81860171); Yunnan young and middle-aged academic and technical leaders Reserve Talents Project (No. 202005AC160048); Yunnan basic research program (Nos.202101AZ070001-002, 202001AY070001-277, 2019FE001(-236)); Medical Reserve Personnel Training Program of Yunnan Provincial Health Commission(No. H-2018097); “Famous Doctor” Special Project of Ten Thousand People Plan of Yunnan Province(Nos.CZ0096, YNWR-MY-2020-095); Medical Leading Talents Training Program of Yunnan Provincial Health Commission (No.L-2019028).

Data Availability

Raw sequencing data have been deposited in the Genome Sequence Archive for Human (GSA-Human, https://ngdc.cncb.ac.cn/gsa-human/) under accession codes HRA000124, HRA001481 and HRA001482. Proteomics and phosphoproteomics data have been deposited in the Open Archive for Miscellaneous Data (OMIX, https://ngdc.cncb.ac.cn/omix/) under accession codes OMIX001292. The raw lung CT images used in this paper are available from OMIX under accession codes OMIX002491.

Acknowledgements

We thank Novogene Co., Ltd. and Beijing Qinglian Biotech Co., Ltd. for the analysis of mass spectrometric data.