Human leukocyte antigen class II-based immune risk model for recurrence evaluation in stage I-III small cell lung cancer

Abstract

Background: Immunotherapy has revolutionized therapeutic patterns of small cell lung cancer (SCLC). Human leukocyte antigen class II (HLA class II) is related to antitumor immunity. However, the implications of HLA class II in SCLC remain incompletely understood.

Materials and methods: We investigated the expression patterns of HLA class II on tumor cells and tumor-infiltrating lymphocytes (TILs) by immunohistochemistry staining and its association with clinical parameters, immune markers, and recurrence-free survival (RFS) in 102 patients with stage I-III SCLC with radical surgery. Additionally, an HLA class II-based immune risk model was established by least absolute shrinkage and selection operator regression. With bioinformatics methods, we investigated HLA class II-related enrichment pathways and immune infiltration landscape in SCLC.

Results: HLA class II on tumor cells and TILs was positively expressed in 9 (8.8%) and 45 (44.1%) patients with SCLC, respectively. HLA class II on TILs was negatively associated with lymph node metastasis and positively correlated with programmed death-ligand 1 (PD-L1) on TILs (p<0.001) and multiple immune markers (CD3, CD4, CD8, FOXP3; p<0.001). Lymph node metastasis (OR 0.314, 95% CI 0.118 to 0.838, p=0.021) and PD-L1 on TILs (OR 3.233, 95% CI 1.051 to 9.95, p=0.041) were independent predictive factors of HLA class II on TILs. HLA class II positivity on TILs prompted a longer RFS (40.2 months, 95% CI 31.7 to 48.7 vs 28.8 months, 95% CI 21.4 to 36.3, p=0.014). HLA class II on TILs, PD-L1 on TILs, CD4, and FOXP3 were enrolled in the immune risk model, which categorized patients into high-risk and low-risk groups and had better power for predicting the recurrence than tumor stage. Pathway enrichment analyses showed that patients with high HLA class II expression demonstrated signatures of transmembrane transportation, channel activity, and neuroactive ligand-receptor interaction. High-risk SCLC patients had a higher proportion of T follicular helper cells (p=0.034) and a lower proportion of activated memory CD4-positive T cells (p=0.040) and resting dendritic cells (p=0.045) versus low-risk patients.

Conclusions: HLA class II plays a crucial role in tumor immune microenvironment and recurrence prediction. This work demonstrates the prognostic and clinical values of HLA class II in patients with SCLC.

Keywords: antigen presentation; immunohistochemistry; lung neoplasms; lymphocytes; tumor microenvironment; tumor-infiltrating.

Figure 1

Survival analysis by HLA class II on tumor cells and TILs. HLA class II, human leukocyte antigen class II; RFS, recurrence-free survival; TILs, tumor infiltrating lymphocytes.

Figure 2

Establishment of immune risk model in SCLC. (A) The lambda (λ) selection process in the LASSO regression. Two immune risk models were obtained based on lambda.min (left dotted line) and lambda.1se (right dotted line). (B) LASSO coefficient profiles of each variable against the log(λ). The optimal immune risk model was achieved based on the lambda.min (left dotted line, 0.0279), and it enrolled four variables: HLA class II on TILs, PD-L1 on TILs, FOXP3, and CD4. (C) ROC curves and AUC values of immune risk model, single immune factors and tumor stage. The AUC value of immune risk score (0.709) exceeded that of tumor stage (0.655) and single immune factors (all <0.70). (D) Survival analysis of immune risk score. AUC, area under the curve; HLA class II, human leukocyte antigen class II; LASSO, least absolute shrinkage and selection operator; PD-L1, programmed death-ligand 1; ROC, receiver operating characteristic; SCLC, small cell lung cancer; TILs, tumor-infiltrating lymphocytes.

Figure 3

GO and KEGG enrichment analysis of HLA class II expression in SCLC. (A) Top 10 enriched GO terms in molecular function, cellular components, and biological processes. (B) KEGG pathway enrichment analysis. GO, gene ontology; HLA class II, human leukocyte antigen class II; KEGG, Kyoto Encyclopedia of Genes and Genomes; SCLC, small cell lung cancer.

Figure 4

Immune infiltration in SCLC patients with high-risk and low-risk. (A) The proportion of 22 immune cells in high-risk patients with SCLC. (B) The proportion of 22 immune cells in low-risk patients with SCLC. (C) Differentially infiltrated immune cells in high-risk and low-risk patients with SCLC, including activated memory CD4+ T cells, T follicular helper cells, and resting dendritic cells. SCLC, small cell lung cancer.