Investigation of LGALS2 expression in the TCGA database reveals its clinical relevance in breast cancer immunotherapy and drug resistance

Abstract

Breast cancer (BRCA) is known as the leading cause of death in women worldwide and has a poor prognosis. Traditional therapeutic strategies such as surgical resection, radiotherapy and chemotherapy can cause adverse reactions such as drug resistance. Immunotherapy, a new treatment approach with fewer side effects and stronger universality, can prolong the survival of BRCA patients and even achieve clinical cure. However, due to population heterogeneity and other reasons, there are still certain factors that limit the efficacy of immunotherapy. Therefore, the importance of finding new tumor immune biomarker cannot be emphasized enough. Studies have reported that LGALS2 was closely related to immunotherapy efficacy, however, it is unclear whether it can act as an immune checkpoint for BRCA immunotherapy. In the current study, changes in LGALS2 expression were analyzed in public datasets such as TCGA-BRCA. We found that LGALS2 expression was associated with immune infiltration, drug resistance and other characteristics of BRCA. Moreover, high LGALS2 expression was closely related to immunotherapy response, and was associated with methylation modifications and clinical resistance for the first time. These findings may help to elucidate the role of LGALS2 in BRCA for the development and clinical application of future immunotherapy strategies against BRCA.

Figure 1

Transcriptional alterations and diagnostic/prognostic value of LGALS2 in BRCA patients. (A) Expression of LGALS2 in paracancers and tumors in TCGA database. The significance of the difference was tested with an unpaired student’s t test. (B) LGALS2 expression in BRCA patients based on the TCGA database. The significance of the difference was tested with an unpaired student’s t test. (C) KM analysis of the diagnostic value of LGALS2 in TCGA database. (D) ROC analysis of the prognostic value of LGALS2 in TCGA database. (E–G) KM analysis of overall survival of LGALS2 in patients with different subtypes of BRCA. (H–J) ROC analysis of prognostic of LGALS2 in patients with different subtypes of BRCA. ns, P ≥ 0.05, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.

Figure 2

Analysis of various clinical factors associated with LGALS2 expression. (A) The landscape of LGALS2-related clinicopathological features of BRCA in TCGA database. (B–I) LGALS2 and various clinicopathological features of BRCA in TCGA databases. (B–D) LGALS2 was not significantly different in Pathologic-, T-, N-stage in TCGA database. The significance of the difference was tested by one‐way ANOVA. (E–I) LGALS2 was not significantly different in M-stage, radiation therapy, pharmaceutical therapy and gender in TCGA database. The significance of the difference was tested with an unpaired student’s t test. (H) there was a significant difference between LGALS2 expression and patient age in TCGA databases. The significance of the difference was tested with an unpaired student’s t test.

Figure 3

Diagnostic analysis of LGALS2 expression with TNBC. (A–C) Expression of LGALS2 in ER, HER2, PR. LGALS2 was enriched in the negative subtype of BRCA in the Metabric database. The significance of the difference was tested with an unpaired t test. (D) LGALS2 was highly expressed in claudin-low subtype of BRCA in the Metabric database. The significance of the difference was tested by one‐way ANOVA. (E) The ROC curve showed the high‐expression specificity of LGALS2 in TNBC in the Metabric database.

Figure 4

GO and KEGG analysis of LGALS2. (A) Volcano plot of differentially expressed genes. Red dots indicate upregulated genes, blue dots indicate downregulated genes, grey dots indicate not significant. (B) Heat map showing the differentially expressed genes, and the different colors represent the trend of gene expression. The top 50 up-regulated genes and top 50 down-regulated genes were shown in this figure (C,E) KEGG enrichment analysis. (D,F) GO enrichment analysis. Colors represent the significance of differential enrichment, the size of the circles represents the number of genes, the larger the circle, the greater the number of genes. (|LogFC|> 1, Adjusted P < 0.05).

Figure 5

Correlation analysis between LGALS2 and immune function. (A) Heatmap showing LGALS2 expression and the enrichment scores of immune functions of each patient in TCGA, and the column and line graph on the right shows the R and P values for correlation analysis. (B) Analysis of the correlation between LGALS2 and immune cells. The size of the circle represents the correlation, with the larger the circle the higher the correlation. (C) Scatter plot of LGALS2 and T cell enrichment. LGALS2 expression levels were positively correlated with T cell enrichment. The significance of the difference was tested by Spearman correlation analysis.

Figure 6

Analysis of the correlation between LGALS2 and T cell immunity and inflammation. (A) Pearson correlation between LGALS2 and inhibitory immune checkpoints. The color of the band represented the P‐value. The correlation was tested by Pearson correlation analysis. (B) Correlation matrix of LGALS2 and inflammatory‐related metagenes. The bottom left showed the correlation coefficient. which are shown as a scale of the pie charts. The correlation was tested by Pearson correlation analysis.

Figure 7

Single-cell sequencing analysis of LGALS2. (A) Single-cell sequencing analysis showing the cellular subtypes of BRCA, based on the GEO database (GSE161529). (B) LGALS2 is highly expressed in cluster 4 and 5. (C,D) Expression of T cell markers in different subtypes. Verification of cluster 4 and cluster 5 as T cells.

Figure 8

Methylation-related analysis of LGALS2. (A) Promoter methylation level of LGALS2 in BRCA. The significance of the difference was tested with an unpaired student’s t test. (B) LGALS2 promoter methylation expression based on BRCA subclasses. The significance of the difference was tested with an unpaired student’s t test. (C) LGALS2 promoter methylation expression based on age of BRCA patients. The significance of the difference was tested with an unpaired student’s t test. (D–F) Relationship between DNA methyltransferases (DNMT1, DNMT3A and DNMT3B) and LGALS2 expression in BRCA patients. The significance of the difference was tested with an unpaired student’s t test. (G–I) Methylation probe linked to LGALS2 in BRCA patients. The significance of the difference was tested by Spearman correlation analysis. ns, P ≥ 0.05, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.

Figure 9

Evaluation of LGALS2 and IC50 for clinical drugs. (A–C) LGALS2 reduces IC50 of clinical drugs and reduces drug resistance. The significance of the difference was tested with an unpaired student’s t test. ns, P ≥ 0.05, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.