Clinical Features,Tumor Immune Microenvironment And Pathogenesis Of Primary Pulmonary Lymphoepithelioid Carcinom

Background:Primary pulmonary lymphoepitheliomatoid carcinoma is a rare subtype of primary non-small cell lung cancer.PPLELC is morphologically similar to poorly differentiated squamous cell carcinoma.PPLELC is generally considered to have a favorable outcome and unique clinical features and genomic landscape compared to other lung cancer types.Purpose:The pathogenesis and optimal treatment of PPLELC are still not fully established.New therapies are urgently needed to further improve the survival rate of patients with this deadly disease.Method:1.172 patients with advanced PPLELC admitted to five first-class hospitals from August 2018 to August 2021 were retrospectively collected and divided into PPLELC group.Another 260 patients with squamous cell carcinoma of the lung admitted on the same day were divided into the LUSC group.The basic clinical status,progression-free survival,overall survival and remission rate were compared between the two groups.2.Immunohistochemistry and immunofluorescence were used to analyze the tumor immune microenvironment of the PPLELC group and LUSC group.3.10 serum samples were selected,5 in PPLELC group and 5 in LUSC group.DIA was identified and differential protein screening analysis were carried out.Finally,the differential proteins were verified by ELISA,immunohistochemistry and immunofluorescence.4.25 serum samples were selected,including 10 cases in the PPLELC group and 15 cases in the LUSC group.Untargeted metabolomic identification and differential metabolite analysis were carried out.5.Firstly,PPLELC PDX model is constructed and verified.Then,nude mice were divided into control+IgG group,ω-6+IgG group and ω-6+Tisotumab group,implanted into PDX model and were given corresponding diet and drugs respectively.The differences of tumor immune microenvironment were explored.Molecular changes were explored by qPCR and WB.Finally,nude mice were divided into corn oil+IgG group,WY-14643+IgG group and WY-14643+Tisotumab group for verification.Results:1.PPLELC patients were mainly middle-aged women and non-smokers,with lower ECOG score and a higher proportion of stage Ⅳ patients.Bone and liver metastases were more common,while brain metastases are less common.The expression status of PD-L1 in advanced PPLELC was significantly different from that in advanced LUSC,and the positive rate of PD-L1 and high expression rate of PD-L1 were higher in the PPLELC group.Advanced PPLELC had a greater survival advantage than advanced LUSC,and subgroup analysis suggested that immunotherapy had a more significant benefit in the PPLELC group.2.TMIT type Ⅰ subgroup had the best survival benefit,and TMIT type Ⅱsubgroup had the worst survival benefit.In PPLELC group,TMIT type Ⅰ accounted for the largest proportion,which was significantly higher than LUSC group.The density of CD20+ B cells,CD3+T cells,CD8+T cells and CD68+TAM cells and the expressions of B7-H3,BTLA,ICOS and VISTA of PPLELC group was significantly higher than that of LUSC group in tumor microenvironment.3.Quantitative analysis and comparison of DIA in serum of PPLELC group and LUSC group showed that 259 proteins were detected,including 16 different proteins,of which 6 were down-regulated and 10 up-regulated.KEGG pathway enrichment analysis showed that differential proteins were involved in iron death,HIF-1 signaling pathway,metabolism,leukocyte transendothelial migration and other pathways.TF protein was the most widely enriched pathway,and TF protein was upregulated 1.55 times in PPLELC,P<0.05.4.Non-targeted metabolomics analysis of serum of PPLELC group and LUSC group showed that a total of 3175 metabolites were detected,including 946 secondary identified metabolites and 35 differential metabolites,7 of which were downregulated and 28 of which were up-regulated.The enrichment was mainly concentrated in fatty acid metabolites include Linoleic acid and FFA(16:0),and amino acid metabolites include L-Histidine.5.The progression of PPLELC induced by LA can be reversed by TF inhibitor Tisotumab;M2-type TAM infiltration increased and NK cell infiltration decreased due to LA diet,which was reversed by TF inhibitor.LA affected the expression of TF through PPAR-α;PPAR-α agonists induced tumor progression could be reversed by TF inhibitors.Conclusions:1.As a rare subtype of NSCLC,PPLELC is significantly different from LUSC in clinical characteristics and tumor immune microenvironment,and can be benefit from immune checkpoint therapy.2.Linoleic acid promotes the expression of TF through PPAR-a to alter the tumor immune microenvironment of PPLELC which lead to tumor progression.