Worldwide, lung cancer remains a highly lethal disease and the most common cause of cancer death [26]. NSCLC remains a major cause of cancer-related mortality in both men and women with survival rate of 19.3%[27].In American, the rate of decline in lung cancer mortality has accelerated, with men dropping from 3% a year during 2008 through 2013 to 5% during 2013 through 2018 and women from 2% to nearly 4% ,spurring the biggest one-year drop in overall cancer mortality of 2.2% from 2016 to 2017.However, lung cancer still has more death in 2017 than breast, prostate, colorectal and brain cancers combined [2]. LUSC and LUAD are the two major subtypes of lung cancer, in which LUSC progresses faster than LUAD of the same stage [28]. Tumor-related prognosis or predictive markers in the immune microenvironment significantly changed the treatment prospects of lung cancer and significantly improved the prognosis of some patients, especially those with adenocarcinoma [29–33].
The tumor microenvironment consists of a complex tissue system through which immune and stromal cells can regulate anti-tumor immunogenicity. Recently, many studies have shown prognostic markers in tumor microenvironment for tumor prognosis. Zeng et al provides potential TME-related biomarker for the therapy and prognosis of RCC[34].Zeng et al describe the comprehensive features of gastric cancer TME characteristics and provide new strategies for cancer treatment[35].A present study found that many elements of TME other than tumor epithelial cells influence the progression of HNSCC[36]. Another study highlights the favorable prognostic impact of an immune-inflamed TME in LUAD [37]. There is also studies analyzed the immune microenvironment of stage I LUAD and found that the high expression of IL-7R and the lower expression of IL-12Rβ2 were all independent factors of poor prognosis[38].Yue et al identified three TME-related DEGs signature which could be used to predict the prognosis of LUAD patients[39].Chen et al revealed the differentiated regulation of immune-response related genes between LUAD and LUSC[28]. However, genome changes in squamous cell lung cancer have not been fully characterized and no molecular targeted drugs have been specifically developed for the treatment [40]. Moreover, prognostic biomarkers related to TME in LUSC is still lacking. In this study, we explore differentially expressedTME-related genes and reveal prognostic biomarkers for predicting the diagnosis and prognosis of LUSC.
The present study extracted data from the TCGA database to explore TME-related genes that affect the overall survival and tumorigenesis of LUSC. Subsequently, we identified prognostic and therapeutic biomarkers for LUSC. This study first assessed the relationship between clinicopathological variables and immune and stromal scores in LUSC. Our results suggest that immune score and stromal score are associated with specific clinicopathological variables (age, gender, tumor stage). In addition, immune and stromal score showed great potential in prognostic prediction with LUSC patients.
After distinguishing the high and low immune/stromal scores groups, we identified 946 differentially expressed genes (DEGs). The functional enrichment analyses demonstrated that these DEGs are involved in immune response, immune cells differentiation and activation, extracellular matrix and membrane. For example, GO analysis revealed that DEGs enriched T cell activation, leukocyte migration, leukocyte proliferation, leukocyte cell-cell adhesion, plasma membrane, secretory granule membrane, collagen-containing extracellular matrix, MHC class II protein complex, cytokine binding, immunoglobulin binding, chemokine activity, chemokine receptor binding, cytokine activity, CCR chemokine receptor binding. Also, the above MFs are associated with surface receptor activity and protein binding. This study also showed that DEGs were most enriched in immune-related typical pathway: cytokine-cytokine receptor interaction, cell adhesion molecules (CAMs), intestinal immune network for IgA production, Phagosome, chemokine signaling pathway. Our results confirmed previous reports on genomic alterations and tumor microenvironment impact cancer proliferation and invasion and roles of immune cells and their interactions with cancer cells in LUSC [41–43].
In addition, we further clarified the interplay among DEGs by using the STRING tool to construct protein-protein interaction (PPI) networks. The results demonstrated that all the significant genes are involved in immune response, and the top six genes (C3AR1, CSF1R, CCL2, CCR1, TYROBP, CD14)were identified as hub genes.One research suggested that the exclusion of CD8 T cells from the tumor islets was associated with poorer clinical outcomes and lower lymphocyte activity in LUSC patients, but CSF1R blockade enhanced the migration and infiltration of CD8 T cells to the tumor islets [44]. CSF1R inhibitors represent a new immune-modulatory in tumor therapy [45]. A previous study reported that CCL2 overexpression was associated with total survival and progression-free survival in patients with LUSC [46]. Wang et al showed that CCR1 knockdown suppresses NSCLC cell invasion[47]. Although reports about C3AR1, and CD14 are lacking, the between those genes and immune-associated disease and other tumors has been reported [48,49]. These data suggest that our results based on the TCGA database have predictive value. Notably, most of the genes we identified have not been previously reported in LUSC, suggesting that these genes should de further validated.
Increasing evidence suggested a significant correlation between immune cell infiltration and patient outcomes [50,51]. The current study revealed positive correlations between hub genes expression and immune cell infiltration (C3AR1, CSF1R, CCL2, CCR1, TYROBP, CD14). Therefore, these genes may provide more information about immune cell infiltration and clinical outcomes in LUSC patients.
Many studies have explored the correlation between gene expression and tumorigenesis and prognosis of NSCLC or LUAD in tumor/immune microenvironment. Recently, there are several treatment methods for targeting TME-related genes and have got good results in clinical or clinical trial. We firstly used the ESTIMATE algorithm to explored the association between immune/stromal scores and LUSC clinicopathologic and got TME-related genes as the novel potential biomarkers for LUSC. Although our study has achieved very valuable results, this study was conducted in small cohorts and has significant limitations and clinical trials still need.