Pan-cancer analysis of FCER1G expression.
Pan-cancer analysis showed a significant expression difference of FCER1G levels between a variety of tumors and adjacent tissues (or GTEx) (Figure 1A and Supplementary Figure 1A). Expression of FCER1G was higher in BRCA, ESCA, GBM, HNSC, KIRC, KIRP, LAML, LGG, LIHC, OV, PAAD, SKCM, STAD, TGCT, THCA, UCEC, and UCS (p< 0.05) than normal tissues, while FCER1G was lower in tumor of ACC, DLBC, LUAD, LUSC, PRAD, and THYM (p< 0.05).
Patients in 33 types of tumor cohorts were then divided into high and low expressed group according to the median value of FCER1G gene expression. Subsequent survival analysis obtained significant differences across several cancer types. Specifically speaking, patients with high expression level of FCER1G showed a shorter overall survival (OS), progression-free interval (PFI) and disease-specific survival (DSS) than low expression patients both in LGG and GBM cohort (Figure 1B).
The expression level of FCER1G increased with the progression of glioma
In the subsequent study, we focused on exploring the clinical value of FCER1G in gliomas. To explore the expression levels of FCER1G mRNA in different stages of gliomas, we used six datasets to analyze FCER1G expression levels. We observed that the expression level of FCER1G increased in glioma with high malignancy. In CGGA dataset, a significant increase of FCER1G expression was noted in WHO grade III (n = 334), and grade IV (n = 388) than grade II (n = 291) (IV versus III: P<0.001; IV versus II: P<0.001; III versus III: P=0.037, Figure 2A). In the TCGA-GBMLGG dataset, a remarkable upward trend in FCER1G expression with tumor progression was further confirmed in grade II (n = 226), III (n = 244) and IV (n = 150 glioma patients (IV versus III: P<0.001; IV versus II: P<0.001; III versus III: P=0.0012, Figure 2B). Furthermore, the same trend was also found in the Rembrandt dataset with 98 grade II, 85 grade III, and 130 grade IV patients (IV versus III: P<0.001; IV versus II: P<0.001; III versus III: P=0.31, Figure 2C). Moreover, according to analysis of GEO dataset, we also found that the GSE16011 cohort with grade II (n = 24), grade III (n = 85), and grade IV (n = 159) glioma patients (IV versus III: P<0.001; IV versus II: P<0.001; III versus III: P=0.48, Figure 2D), GSE43289 dataset with 3 grade II, 6 grade III, and 28 grade IV patients (IV versus III: P=0.3; IV versus II: P=0.0071; III versus III: P=0.38, Figure 2E), and the GSE4412 dataset (26 grade III and 59 grade IV patients, P<0.0001, Figure 2F) all exerted higher expression of FCER1G in high grade glioma.
To further validate these results, IHC for FCER1G and qRT-PCR was performed to assess FCER1G expression in patient-derived glioma tissue samples. As expected, in comparison with low grade glioma (LGG) tissues, a significant increase of FCER1G was revealed in high grade glioma (HGG) tissues (Figure. 2G and H). according to the above data, the expression of FCER1G increased with the development of glioma, suggesting that FCER1G may be involved in the malignant progression of glioma.
Increased FCER1G expression predicts poor prognosis in gliomas
After we illustrated the correlation between FCER1G expression level and tumor progression of glioma, we next investigated the prognostic value of FCER1G.
According to the median value of FCER1G expression, patients were divide into high and low expression group. The Kaplan–Meier curve and log-rank test analysis revealed that patients with higher expression of FCER1G from CGGA (HR:0.69, 95% CI: 0.49-0.98), TCGA dataset (HR:0.31, 95% CI: 0.23-0.41), Rembrandt (HR:0.49, 95% CI: 0.39-0.61), and GSE16011 (HR:0.49, 95% CI: 0.38-0.64), showed significantly poorer overall survival (OS) than those with low expression (Figure 3A, C, E and F), while patients from GSE43289 and GSE4412 dataset showed similar trend with no statistic significance (Figure 3E and F). The sample sizes of the six cohorts were very different, three over 500 samples and two less than 200 samples. To improve the stability of the results, a fixed effects model was employed to pool the HRs of the six cohorts, and the result also validated that patients with high level of FCER1G expression exerted shorter OS times than patients with low expression level (RR= 1.30, 95% CI = 1.24-1.38, Figure 3G).
To better understand the role of expression of FCER1G in patients with glioma, we analyzed the CGGA dataset with clinical data of 1013 glioma patients. We divided the patients into high expression group (n = 506) and low expression group (n = 507) based on FCER1G levels. Through univariate analysis of clinical characteristics, we found that FCER1G was more likely to be associated with older age (P = 0.002), high malignancy (P <0.001) , GBM type (P <0.001), post-operative relapse (P <0.001), poorer survival (P <0.001), IDH wild type (P <0.001), and different therapeutic options (Radiotherapy, P=0.047; chemotherapy, P=0.009), however, there is no significant differences in gender (Table 1).
Table 1. Clinical characteristics of 1013 glioma patients in the CGGA dataset according to FCER1G expression levels.
FCER1G expression
|
|
High
|
low
|
P value
|
n
|
|
506
|
507
|
|
FCER1G_mRNA (median [IQR])
|
|
6.74 [6.22, 7.42]
|
4.69 [3.81, 5.22]
|
<0.001
|
Age (median [IQR])
|
|
44.00 [36.00, 54.00]
|
41.00 [34.00, 49.00]
|
0.002
|
Gender (%)
|
|
|
|
0.371
|
|
Female
|
199 (39.3)
|
214 (42.2)
|
|
|
Male
|
307 (60.7)
|
293 (57.8)
|
|
Grade (%)
|
|
|
|
<0.001
|
|
II
|
101 (20.0)
|
187 (36.9)
|
|
|
III
|
140 (27.7)
|
193 (38.1)
|
|
|
IV
|
261 (51.6)
|
126 (24.9)
|
|
|
|
4 ( 0.8)
|
1 ( 0.2)
|
|
Histology (%)
|
|
|
|
|
|
Anaplastic Astrocytoma
|
118 (23.3)
|
95 (18.7)
|
|
|
Anaplastic Oligoastrocytoma
|
2 ( 0.4)
|
19 ( 3.7)
|
|
|
Anaplastic Oligodendroglioma
|
19 ( 3.8)
|
75 (14.8)
|
|
|
Astrocytoma
|
81 (16.0)
|
92 (18.1)
|
|
|
GBM
|
261 (51.6)
|
126 (24.9)
|
|
|
Oligoastrocytoma
|
2 ( 0.4)
|
7 ( 1.4)
|
|
|
Oligodendroglioma
|
19 ( 3.8)
|
92 (18.1)
|
|
|
|
4 ( 0.8)
|
1 ( 0.2)
|
|
Recurrence (%)
|
|
|
|
0.001
|
|
Primary
|
296 (58.5)
|
350 (69.0)
|
|
|
Recurrent
|
186 (36.8)
|
147 (29.0)
|
|
|
Secondary
|
20 ( 4.0)
|
10 ( 2.0)
|
|
|
|
4 ( 0.8)
|
0 ( 0.0)
|
|
Subtype (%)
|
|
|
|
<0.001
|
|
Classical
|
110 (21.7)
|
52 (10.3)
|
|
|
Mesenchymal
|
95 (18.8)
|
19 ( 3.7)
|
|
|
Proneural
|
82 (16.2)
|
74 (14.6)
|
|
|
|
219 (43.3)
|
362 (71.4)
|
|
survival (median [IQR])
|
|
17.50 [8.80, 40.60]
|
37.00 [15.35, 75.85]
|
<0.001
|
status (%)
|
Alive
|
125 (25.3)
|
260 (53.1)
|
<0.001
|
|
Dead
|
369 (74.7)
|
230 (46.9)
|
|
IDH status (%)
|
|
|
|
<0.001
|
|
Mutant
|
213 (42.1)
|
316 (62.3)
|
|
|
Wildtype
|
287 (56.7)
|
145 (28.6)
|
|
|
|
6 ( 1.2)
|
46 ( 9.1)
|
|
1p19q (%)
|
|
|
|
<0.001
|
|
Codel
|
39 ( 7.7)
|
172 (33.9)
|
|
|
Non-codel
|
461 (91.1)
|
263 (51.9)
|
|
|
|
6 ( 1.2)
|
72 (14.2)
|
|
Radio status (%)
|
No
|
68 (14.9)
|
94 (20.0)
|
0.047
|
|
Yes
|
388 (85.1)
|
376 (80.0)
|
|
Chemo status (%)
|
No
|
117 (26.1)
|
156 (34.2)
|
0.009
|
|
Yes
|
332 (73.9)
|
300 (65.8)
|
|
By using the Cox regression model, we computed multivariate hazard ratios for different variables of 1013 glioma patients. In multivariate analysis, the hazard ratio of FCER1G expression (Low versus High) was 0.66 and 95% CI is 0.54 to 0.79 (P <0.001), whereas age (HR=1.26, 95% CI=1.04-1.52), grade (HR=2.75, 95% CI=2.06-3.68) , tumor recurrence (HR=2.17, 95% CI=1.81-2.62), and chemotherapeutic status (HR=1.4, 95% CI=1.20-1.80) are also included (Table 2). The expression level of FCER1G was significantly related to the OS in glioma patients. FCER1G expression value was a stable factor affecting the survival level of glioma patients.
Table 2. Univariate and multivariate analysis for overall survival of glioma patients.
Variable
|
Univariate analysis
|
Multivariate analysis
|
Age
|
|
HR
|
95% CI
|
p‑value
|
HR
|
95% CI
|
p‑value
|
|
(≥40 vs <40)
|
1.6
|
(1.4-2.0)
|
<0.001
|
1.26
|
(1.04−1.52)
|
0.017
|
Gender
|
|
|
|
|
|
|
|
|
Female vs male
|
0.98
|
(0.83-1.2)
|
0.79
|
|
|
|
Grade
|
|
|
|
|
|
|
|
|
II vs III vs IV
|
3.6
|
(2.2-6.2)
|
<0.001
|
2.75
|
(2.06−3.68)
|
<0.001
|
Recurrence
|
|
|
|
|
|
|
|
|
Primary vs Recurrent vs Secondary
|
2.5
|
(1.8-3.2)
|
<0.001
|
2.17
|
(1.81−2.62)
|
<0.001
|
IDH status
|
|
|
|
|
|
|
|
|
Wildtype vs Mutant
|
3.1
|
(2.6-3.6)
|
<0.001
|
2.46
|
(1.97-3.01)
|
<0.001
|
Radio status
|
|
|
|
|
|
|
|
|
yes vs no
|
1
|
(0.83-1.3)
|
0.73
|
|
|
|
Chemo status
|
|
|
|
|
|
|
|
|
yes vs no
|
1.5
|
(1.3-1.9)
|
<0.001
|
1.4
|
(1.2-1.8)
|
<0.001
|
FCER1G
|
|
|
|
|
|
|
|
|
Low vs High
|
0.43
|
(0.36-0.51)
|
<0.001
|
0.66
|
(0.54−0.79)
|
<0.001
|
FCER1G is associated with immune infiltration and immune activation in gliomas.
Patients diagnosed with the same histological cancer types may have different immune infiltration levels, which could lead to diverse clinical outcomes. The immune profile of gliomas relating to the prognosis and immunotherapy has been widely reported in several cancers, including gliomas. FCER1G is served as an important regulatory player, involving in initiating the transfer from T-cells to the effector T-helper 2 type and mediating the allergic inflammatory signaling of mast cells and interleukin 4 production from basophils (28,29). Therefore, the correlation of FCER1G and immune infiltration levels was evaluated to reveal the possible mechanism by which FCER1G affects the prognosis of gliomas. The relative quantity of the 28 immune cells from the CGGA dataset was systematically estimated using the ssGSEA algorithm (Figure 4A). The correlations of FCER1G expression with infiltrating levels of immune cells was evaluated by spearman method, which revealed close relationship between FCER1G with T cells, macrophages, and B cells (Figure 4B). These results suggested that FCER1G expression was involved in immune infiltration remodeling of gliomas.
Next, we try to further elucidate the relationship between FCER1G expression and immune infiltration and to explore the molecular mechanisms of FCER1G with STRING database. The result showed that FCER1G had a closely interactions with FCGR3A, ITGB2, LYN, SYK, in which FCER1G acts as a core gene (Figure 4C). Moreover, we analyzed the differential expression values between high and low FCER1G group. A total of 372 genes were up-regulated and 22 genes were down-regulated (adj.pvalue< 0.05, FC>1.5 or <-1.5, Figure 4D).
Then we analyzed the enriched GO terms and KEGG pathways with the DEGs. Among the biological process terms of GO, most of DEGs were enriched in neutrophil activation, leukocyte migration, collagen-containing extracellular matrix, and cell adhesion molecule binding (Figure 4E). According to the KEGG analysis results, staphylococcus aureus infection, phagosome, and cell adhesion molecules (CAMs) were remarkably enriched (Supplementary Figure 2).
Gene set enrichment analysis (GSEA) was also used to explore the mechanisms of FCER1G in gliomas. The CGGA data were analyzed with "MsigdbC2KEGG" (KEGG gene set, listed in Supplementary Materials). The enrichment results (nominal p value < 0.05 and FDR < 0.25) are shown in Supplementary Sheet 3. Results showed that various immune activation and tumor progression associated genes were enriched, especially in cytokine signaling in immune, DNA replication and PD-1 signaling (Figure 4F), reflecting relatively enhanced tumor progression and activated inflammation.
Identification of the correlation between FCER1G and immune phenotype of gliomas
To further explore the existence of malignant gliomas with a hot immune phenotype, manually curated gene sets related to both adaptive and innate immune responses were used to quantify the immune phenotype (Figure 5A). The heatmap showed that, with increasing FCER1G expression, the immune phenotype tended to be "hot". This was consistent with the conclusions drawn above that FCER1G played a key role in the glioma activated immune response. The Spearman’s test revealed a high correlation between the expression of FCER1G with PDL1 signaling (r=0.45, P<0.05), CTLA4 signaling (r=0.38, P<0.05), and T cell mediated immunity (r=0.42, P<0.05), which further confirmed the findings in GSEA results (Figure 5B-D).
Subgroups divided by FCER1G expression predict potential immunotherapy responses of gliomas
The above findings suggested that FCER1G was closely associated with T cells, which play an important role in immunosurveillance evasion in malignant gliomas (30). Strong correlations were found between PD1 (PDCD1) and PDL1 (CD274)/PDL2 (PDCD1LG2), between CTLA4 and CD80/CD86, and between CXCR4 and CXCL12 in gliomas (Supplementary Figure 3A-C). The relative abundances of 24 types of immune cells in the TME of gliomas were quantified with ImmuCellAI. Notably, the proportions of TIICs showed marked variations between the FCER1G high and low subgroups (Figure 6A). Moreover, FCER1G showed significant correlations with PD1 (r=0.42, P<0.01), PDL1 (r=0.62, P<0.01),and CTLA4 (r=0.34, P<0.01) (Figure 6B and C), same conclusions were also drawn in analysis of TCGA GBMLGG dataset (Supplementary Figure 3D and E). To verify transcriptome results from public datasets, 20 patients from Shanghai general hospital were included in our study and quantitative real-time PCR were utilized to investigated the correlation between expression levels of FCER1G and PD1, and the results showed that FCER1G was positively correlated with PD1 (r=0.62, p<0.01) (Supplementary Figure 4A). Patients with high FCER1G expression showed high levels of the therapeutic targets PD1, PDL1 and CTLA4, which indicated a hypothetic treatment as immune checkpoint.
To further validate this hypothesis, we utilized T cell inflammatory signature (TIS) scores in high and low FCER1G subgroups. Patients with high FCER1G expression get higher scores in the TIS signature (P<0.001), reporting to be correlated with response to anti PDL1 checkpoint inhibitor pembrolizumab, which supporting the hypothesis (Figure 6D). Furthermore, the possibility of immunotherapy response was predicted in patients with gliomas by ImmuCellAI and TIDE algorithm. The ImmuCellAI predicted that patients with high FCER1G levels were more likely to respond to immunotherapy (81.6%, 413/506, CGGA) than low FCER1G subgroup (52.5%, 266/507, CGGA. Figure 6E). Similar findings were obtained in the validation set, with high predictive efficacy of FCER1G for immunotherapy response in glioma patients (AUC: CGGA 72.11%(69.83-74.92%), TCGA 71.73%(68.96-73.44%). Supplementary Figure 4C-D), as well as high sensitivity and specificity (CGGA(sensitivity= 61.38%, specificity= 78.98%), TCGA(sensitivity= 60.36%, specificity= 79.11%)). Meanwhile, TIDE also suggested that high levels of FCER1G tended to more likely respond to immunotherapy (69.0%, 349/506, CGGA) than low FCER1G subgroup (41.8%, 212/507, CGGA. Figure 6E). We also utilized the submap algorithm (27) to compare the similarity of the expression profiles between the two subgroups of glioma patients and 47 previous melanoma patients with detailed immunotherapeutic information, and revealed that patients in FCER1G-high subgroup were more responsive to anti-PD1 treatment (Bonferroni corrected P value = 0.008) (Supplementary Figure 4B), which was consistent with the previous conclusions.
Taken together, FCER1G may be a good index for quantifying the tumor immune microenvironment and prediction for immunotherapy responses of gliomas.