Introduction

Lung cancer is the leading cause of cancer-related deaths worldwide, and its incidence rate is ranked second in the world1. Lung adenocarcinoma (LUAD) is the most common subtype of lung cancer which accounts for about 40% of all lung cancers2,3,4. Despite the great advances in cancer treatment in the fields of surgery, chemotherapy, radiotherapy, and targeted therapy in recent years have led to improved survival rates for LUAD5. However, there are still many LUAD patients who cannot achieve the desired outcome with conventional therapies due to the heterogeneity, metastasis, and drug resistance, and the heterogeneity within the tumor also leads to different benefit levels for each LUAD6,7,8,9. Therefore, it is necessary to develop a biomarker that can effectively differentiate different subtypes of LUAD for precise clinical treatment of patients to improve the prognosis of lung adenocarcinoma.

The invasive ability and metastatic ability of tumors are closely interrelated, and they directly affect patient prognosis as major hallmarks of cancer10. Accumulating evidence shows that molecular characteristics are generally altered between tumors with different invasiveness or between the primary and metastatic sites of tumors11,23. Similarly, in a study by Santisteban et al.61, it was found that CD8 T cells can induce EMT transformation to promote cancer progression. (in which EMT, as one of the tumor markers, is closely related to the invasive ability of the tumor). In addition, it has also been reported that the remodeling of inflammatory tumor microenvironment in lung adenocarcinoma is closely associated with the altered EMT status62. Comparatively, in the C3 subtype, which has the least distribution of IRGS, the TME attributes are dominated by Th17 and Th1, and low to moderate tumor cell proliferation, where Th17 is thought to suppress tumor63. From these results, we can see that immune infiltration, including T cells, can induce changes in the invasive capacity of tumors, and that the changes in tumor invasive capacity induced by differences in the type of T-cell infiltration as well as the different degree of infiltration. Overall, multiple factors within TME can contribute to a patient’s transformation to an invasive malignant phenotype.

To further expand the potential clinical value of IRGS. We analyzed the drug sensitivity of each patient, and LUAD patients with high IRGS showed sensitivity to drugs such as Docetaxel, Erlotinib, Paclitaxel, and Gefitinib. Subsequent in vitro experiments validated the greater killing effect of paclitaxel on high IRGS cell lines. This means that this IRGS may be able to provide some extent of guidance in the selection of clinical treatment options. CMap analysis screened for drugs including purvalanol-a, angiogenesis-inhibitor, and masitinib as therapeutic candidates for invasive LUAD. These drugs may have an important role in suppressing the invasive phenotype and preventing metastasis in LUAD. Among them, the CMap database perturbation scores showed that purvalanol-a was the most perturbative drug on the expression of highly aggressive LUAD molecules. purvalanol-a acts as a CDK inhibitor, which effectively inhibits cell progression from the G2 phase to mitosis. In a previous study, Chen et al. reported that purvalanol-a could enhance the cytotoxic effect of purvalanol on non-small cell carcinoma by inhibiting tumor protein 18 (Oncoprotein 18)64. In gastric cancer, Iizuka et al. found that purvalanol-a could promote apoptosis in X-ray irradiated gastric cancer cells by activating the active fragment of caspase 365. And in colon cancer, purvalanol-a can promote apoptosis of colon cancer cells by upregulating the protein expression of Bax and Puma66. Overall, these studies consistently suggest that purvalanol-a could be a potential therapeutic agent for patients with highly invasive phenotypes, which provides further evidence for purvalanol-a-related clinical drug development.

However, there are still limitations to this study. Firstly, although our invasion-related gene score has been validated in several datasets as well as in vitro experiments in predicting the invasive ability and prognosis of patients. But further in vivo experiments are still needed for validation. Second, Further exploration of the potential link between TME and tumor invasive capacity is still needed to shed more light on the potential factors that contribute to the heterogeneity of tumor invasive capacity. Thirdly, the effects of potential drugs screened based on IRGS for invasive LUAD still need further vivo experimental validation. Furthermore, more clinical samples are still needed to corroborate the efficiency of IRGS in predicting the invasive ability of LUAD patients.

Conclusions

In summary, this study identified novel invasive molecular subtypes of LUAD based on the expression patterns of metastasis-related pathways and established the invasion-related gene score (IRGS), which is effective in predicting the prognosis and invasiveness of LUAD. It can provide some reference for the selection of clinical decisions.