Macrophage-Related SPP1 as a Potential Biomarker for Early Lymph Node Metastasis in Lung Adenocarcinoma

Abstract

Lymph node metastasis is a major factor that affects prognosis in patients with lung adenocarcinoma (LUAD). In some cases, lymph node metastasis has already occurred when the primary tumors are still small (i.e., early T stages), however, relevant studies on early lymph node metastasis are limited, and effective biomarkers remain lacking. This study aimed to explore new molecular biomarker for early lymph node metastasis in LUAD using transcriptome sequencing and experimental validation. Here, we performed transcriptome sequencing on tissues from 16 matched patients with Stage-T1 LUAD (eight cases of lymph node metastasis and eight cases of non-metastasis), and verified the transcriptome profiles in TCGA, GSE68465, and GSE43580 cohorts. With the bioinformatics analysis, we identified a higher abundance of M0 macrophages in the metastatic group using the CIBERSORT algorithm and immunohistochemistry (IHC) analysis and the enrichment of the epithelial–mesenchymal transition (EMT) pathway was identified in patients with higher M0 infiltration levels. Subsequently, the EMT hallmark gene SPP1, encoding secreted phosphoprotein 1 (SPP1), was identified to be significantly correlated with macrophage infiltration and M2 polarization, and was determined to be a key risk indicator for early lymph node metastasis. Notably, SPP1 in the blood, as detected by enzyme-linked immunosorbent assay (ELISA) showed a superior predictive capability for early lymph node metastasis [area under the curve (AUC) = 0.74]. Furthermore, a long non-coding RNA (lncRNA, AC037441), negatively correlated with SPP1 and macrophage infiltration, had also been identified and validated to be involved in the regulation of early lymph node metastasis. In conclusion, we revealed the potential role of macrophages in lymph node metastasis and identified the macrophage-related gene SPP1 as a potential biomarker for early lymph node metastasis in LUAD.

Digital Spatial Profiling of Individual Glomeruli From Patients With Anti-Neutrophil Cytoplasmic Autoantibody-Associated Glomerulonephritis

“…These data indicate that M1 macrophages might play a role in BC rupture, whereas M2 macrophages increase at the late stage of the disease, which might contribute to fibrosis. In addition, we found that the RNA and protein expression levels of CD163 increased significantly when the BC ruptured, together with the increased expression of SPP1, which was reported to be significantly correlated with macrophage infiltration and M2 polarization ( 15 ). It was previously reported that both the high expression of SPP1 and that of its receptor CD44 correlated with an increased macrophagic infiltration ( 27 ).…”

“…The above results highlighted the critical role of SPP1 in glomerulosclerosis and possibly in fibrous crescent formation. Moreover, SPP1 is known to mediate M2-type macrophage polarization ( 14 ), which also plays a role in fibrosis ( 15 , 16 ). Our data showed that the expression of CD163 gradually increased with worsening of the glomerular injury ( Figure 3I ), and SPP1, together with its receptor CD44, strongly correlated with CD163 (an M2-type macrophage marker; r = 0.8328, p < 0.0001; r = 0.7231, p < 0.0001, respectively) ( Figures 3J, L ), but not with CD86 expression (an M1-type macrophage marker; r = 0.1856, p = 0.2121) ( Figure 3K ).…”

“…CD44 upregulation was accompanied by a notably increased expression of collagen IV and the migration of parietal epithelial cells ( 25 ). Additionally, SPP1 is considered an epithelial–mesenchymal transition hallmark marker ( 15 ). Consistent with this, our data showed that the expression of SPP1 increased progressively with worsening of glomerular injury and was correlated with the expressions of fibronectin and collagen.…”

SPP1 as a key gene in the lymph node metastasis and a potential predictor of poor prognosis in head and neck carcinoma

“…Evidence showed that SPP1 mediates macrophage polarization through the upregulation of PD‐L1 and promotes immune escape in lung adenocarcinoma 28 . Thus, as a hallmark gene of epithelial‐mesenchymal transition, SPP1 was significantly correlated with macrophage infiltration and M2 polarization and was thought to be a key risk predictor for early LNM in cancer development 29 . Besides cancers, SPP1 might have a correlation with the infiltration of M2 macrophages in prostatic intraepithelial neoplasia lesions (a type of precancerous lesions), and high levels of SPP1 could be detected in these macrophages.…”

“…28 Thus, as a hallmark gene of epithelialmesenchymal transition, SPP1 was significantly correlated with macrophage infiltration and M2 polarization and was thought to be a key risk predictor for early LNM in cancer development. 29 Besides cancers, SPP1 might have a correlation with the infiltration of M2 macrophages in prostatic intraepithelial neoplasia lesions (a type of precancerous lesions), and high levels of SPP1 could be detected in these macrophages. Under this tumor microenvironment, SPP1 may stimulate the malignant transformation in the lesions by activating Akt and JNK signaling pathways.…”