The latest advance of phase 3 trials ADAURA study (NCT02511106) confirmed Adjuvant osimertinib could get a significant 85% 5-year OS benefit among patients with completely resected, EGFR-mutated, stage IB to IIIA NSCLC, showing the powerful therapy efficiency of targeted therapy (Tsuboi, Herbst, John et al. 2023). Recent clinical trial research on perioperative immunotherapy in early-stage non-small cell lung cancer (NSCLC), including phase 3 trials such as CheckMate 816 and KEYNOTE-671, has yielded remarkable advancements. These findings signify a paradigm shift in research focus from exploring survival benefits solely in advanced metastatic NSCLC to encompassing the early and mid-stage NSCLC patients and establishing a new perioperative treatment pattern (Forde, Spicer, Lu et al. 2022; Wakelee, Liberman, Kato et al. 2023). Despite significant advancements in clinical trials for targeted therapy and immunotherapy, leading to improved outcomes in LUAD patients, a subset of patients cannot undergo surgery or lack targetable biomarkers. Therefore, it is imperative to explore effective biomarkers to stratify patients and identify additional targetable biomarkers (Sun, Bleiberg, Hwang et al. 2023). Consequently, our objective is to identify tumor-specific informative genes based on mutation characteristics, facilitating risk stratification for patients, particularly with limited treatment options.
In this study, we retrospectively collected a moderate-size LUAD cohort and profiled the somatic altered features based on the genomic data of multiple gene sequencing panel. The alteration of the RTK-RAS pathway and smoking are identified as the main carcinogenic factors. We first explore the association between somatic tumor mutations and clinical risk factors. A total of 45 CCRGs are significantly closely related to the high-risk clinicopathological characteristics, including smoking, advanced pathology stage (Stage II − IV), lower historical differential grade, solid historical subtype, age ≥ 50 years old, tumor size ≥ 2cm, ki67 expression proportion ≥ 10%, family history of cancers, BMI index ≥ 24, lymph node metastasis, as well as the presence of STAS and vascular invasion. The TP53 mutation is significantly associated with tobacco consumption (Le Calvez, Mukeria, Hunt et al. 2005). In addition, TP53 mutations are substantially higher in patients with other high-risk clinical factors, including STAS+, high ki67 expression, larger tumor size, and lymph node metastasis. The TP53 mutation in tumors could result in the loss of tumor-suppressing function, promoting tumor proliferation and metastasis (Alvarado-Ortiz, de la Cruz-López, Becerril-Rico et al. 2020). Regarding STAS, Ye et al. conducted a study to investigate the molecular characteristics distinguishing NSCLC patients with STAS + and STAS-. Their findings revealed significant TP53 mutation and ALK fusion occurrences in STAS + NSCLC patients (Ye, Yu, Zhao et al. 2023). In our study, we also observed a correlation between STAS + and several oncogene mutations, namely MTOR and CTNNB1, as well as tumor suppressor genes, including BARD1, DDX3X, and SUFU. However, recurrent mutations of EGFR and KRAS were not found to be associated with STAS+, which is consistent with previous studies (Zeng, Wang, Li et al. 2020; Zhang, Liu, Feng et al. 2020). KEAP1 is a tumor suppressor gene in NSCLC, which is associated with a higher BMI index of LUAD patients in our study. There is no reported relationship between KEAP1 and BMI index. Still, we found KEAP1 mutation and BMI index are proven to be related to survival benefits from immunotherapy in NSCLC, which provides new insight for further study (Di Federico, De Giglio, Parisi et al. 2021; Kichenadasse, Miners, Mangoni et al. 2020). Significant associations were observed between vascular invasion and mutations in oncogenes ERBB2 and PDGFRA, as well as tumor suppressor genes POLD1 and PTPRT. PDGFRA is an angiogenesis-related gene, and the mRNA expression of PDGFRA and vascular invasion are positively related to HIF-1alpha in hepatocellular carcinoma (HCC), which could promote tumor inflammation (Dai, Gao, Qiu et al. 2009). Furthermore, mutations in tumor suppressor genes LRP1B, SETD2, and TP53 are strongly associated with larger tumor size, elevated ki67 expression, lymph node metastasis, and advanced pathological stage in patients with LUAD, implying a significant association with proliferation and metastasis of LUAD. Kadara et al. found that the SETD2 mutations were related to the progression and poor survival of patients with LUAD (Kadara, Choi, Zhang et al. 2017). LRP1B mutations significantly affect the Cell Cycle and Antigen Processing and Presentation pathways, which are crucial in tumorigenesis. Notably, NSCLC patients with LRP1B mutations exhibit high TMB values and derive incredible survival benefits from immunotherapy (Chen, Chong, Wu et al. 2019). These CCRG genes provide new insight into the molecular mechanisms underlying the occurrence of high-risk clinical factors, thus providing valuable avenues for further investigation in this area of research.
In addition to identifying gene mutations significantly associated with these clinical features, we also identified novel driver genes, including SPAT1, ANKRD11, ERCC3, RAD50, WRN, BLM, WISP3, CDK8, PAK3, and WEE1, which have not been reported in the Cancer Gene Census (CGC) database. Further experimental validation is required to elucidate their biological mechanisms in LUAD.
To assess the prognostic significance of LUAD-related genomic alterations, including CCRGs, driver genes, and gene mutations in oncogene pathways, we developed an MPGM risk model using a multivariable Cox regression algorithm in a publicly available Chinese LUAD cohort (EAS cohort). The risk model successfully stratified patients into two groups: MPGM-High and MPGM-Low. Patients in the MPGM-High group exhibited inferior OS compared to those in the MPGM-Low group, validated in an independent cohort (MSK-LUAD cohort). Subgroup analysis shows the robust predicting performance of the MPGM model to stratify the LUAD patients. The MPGM risk model could effectively distinguish LUAD patients of the EAS cohort into MPGM-High and MPGM-Low groups, irrespective of EGFR mutation status, treatment type (chemotherapy or targeted therapy), and disease stage (early or advanced). Remarkable survival differences were observed between the two risk groups, demonstrating the model's clinically solid applicability and stable prognostic performance.
Although statistical significance was not achieved in the DPH cohort, an analysis of 54 patients with complete PFS follow-up information revealed that those in the MPGM-Low group exhibited better PFS than those in the MPGM-High group. Additionally, several characteristics were observed in the MPGM-High group, including higher ki67 expression, smoking history, lower differentiation grade, high tumor mutational burden (TMB), and specific gene mutations in the RTK-RAS pathway. Significant differences were also observed in targetable gene mutation sites for targeted therapy. The MPGM-High group showed a higher prevalence mutation of ERBB2_20ins, KRAS_G12/13X, and BRAF_V600E mutations, while the MPGM-Low group had a higher occurrence of EGFR_L858R, EGFR_19del, EGFR_20ins, and EGFR_T790M, EGFR_S768I, EGFR_L861Q, and EGFR_G719A mutations. Interestingly, it was observed that all patients harboring detected oncogenic fusion genes, including RET, ROS1, ALK, and NRG1 (Ettinger, Wood, Aisner et al. 2023), were consistently classified into the MPGM-High group. These findings provide compelling evidence that patients classified as MPGH-High risk exhibit a higher risk hazard, both in clinical and molecular characteristics. Moreover, these results emphasize the model's substantial clinical utility and robust prognostic capacity in real-world settings. Due to the favorable clinical application of the MPGM risk model and improved prognosis assessment performance when combined with the clinicopathology feature, we establish a nomogram based on the Cox regression model, which is pretty valuable for the clinics to precisely predict the survival status using the clinical information at baseline and MPGM risk model according to the molecular biological characteristics, including three CCRGs (BRCA2, ALK, PDGFRA) and two driver genes (BRAF, EGFR). These five genes all play essential roles in LUAD.
To get the reason for the different survival outcomes between MPGM-High and MPGM-Low groups, we analyzed immune infiltration differences using the RNA-seq data. Patients in the MPGM-High group had higher tumor purity and a lower ESTIMATEScore, suggesting more infiltrated tumor cells and less enriched immune cells (Yoshihara, Shahmoradgoli, Martínez et al. 2013). Patients in the MPGM-Low group showed significant enrichment of dendritic cells (DC) and monocytic lineage cells, and a higher MicroenvironmentScore and ImmuneScore, demonstrating robust immune activation and anti-tumor capabilities. A previous study has confirmed that tumor-associated DC is related to increased survival outcomes in lung cancer due to an increased anti-tumor T-cell response (Broz, Binnewies, Boldajipour et al. 2014; Guilliams, Dutertre, Scott et al. 2016). The monocytic lineage cells could differentiate into macrophage cells, affecting tumor growth and survival outcomes (Ugel, Canè, De Sanctis et al. 2021). The monocyte lineage and macrophage cells demonstrate a significant interaction in LUAD, correlating with unfavorable survival outcomes and high-grade tumor subtypes (Sorin, Rezanejad, Karimi et al. 2023). But this disadvantage may be negated by heightened immune activity in the MPGM-Low group.
In summary, the significantly higher anti-tumor capability and better survival of the MPGM-Low group can mainly be attributed to the infiltration of immune cells and DCs. In contrast, the MPGM-High group exhibits extensive invasion and infiltration of tumor cells, resulting in a markedly suppressive tumor microenvironment and compromised survival prognosis. These findings reinforce the reliable and robust predictive performance of our model, highlighting its credibility and resilience.
We will apply the MPGH risk model to our clinical practice. For these 55 LUAD patients who keep a close follow-up in the DPH cohort, patients in the MPGM-High group will be paid extra attention to the disease progression and gene alterations during the subsequent follow-up. In contrast, patients in the MPGM-Low group will undergo the standard therapy method and avoid overtreatment.
There are still some limitations in our study. First, most LUAD patients are at an early stage, resulting in a loss of follow-up in the DPH cohort. Finally, only 55 patients keep regular follow-up visits. Second, the MPGM risk model doesn’t show a statistically significant difference between MPGM-High and MPGH-Low groups in the DPH cohort, mainly because the follow-up period was relatively short, and only a minority of patients experienced disease progression. However, we will persistently conduct follow-ups for this specific group of individuals.