The levels of TMEM88 mRNA in HCC and other cancers
The analysis of TCGA RNA-seq data using the TIMER database showed that TMEM88 mRNA expression was significantly lower in BLCA (bladder urothelial carcinoma), BRCA (breast invasive carcinoma), CESC (Cervical squamous cell carcinoma and endocervical adenocarccinoma), KICH (kidney chromophobe), KIRP (kidney renal papillary carcinoma), LUAD (lung adenocarcinoma), LUSC (lung squamous cell carcinoma), READ (rectum adenocarcinoma), THYM (Thymoma), and UCEC (uterine corpus endometrial carcinoma) tissues compared with the corresponding normal tissues (Figure 1). TMEM88 mRNA expression was higher in HCC (Liver hepatocellular carcinoma) and CHOL (Cholangiocarcinoma) compared with the corresponding normal tissues. These data showed that TMEM88 expression was deregulated in most of the cancer tissues but in the liver cancer tissue.
Prognostic significance of TMEM88 expression in human cancers
Next, we analyzed the prognostic value of TMEM88 expression in human cancers using the Kaplan-Meier plotter database. Low TMEM88 expression was associated with poorer prognosis in HCC (OS: HR=0.58, 95% CI=0.41 to 0.82, P=0.0018; PFS: HR=0.59, 95% CI=0.44 to 0.8, P =0.00047; RFS: HR=0.69, 95% CI=0.49 to 0.96, P=0.026; DSS: HR=0.49, 95% CI=0.31 to 0.78, P=0.0018; Figure 2A–2D), Breast Cancer (RFS: HR =0.67, 95% CI=0.58 to 0.78, P=2.4e-07; Figure 2G) and Pancreatic Ductal Adenocarcinoma (OS: HR=0.68, 95%CI=0.45 to 1.03, P=0.066; RFS: HR=0.5, 95% CI=0.21 to 1.19, P=0.11; Figure 2L, 2M). Low TMEM88 expression was associated with better prognosis in Breast Cancer (PPS: HR=1.37, 95%CL=0.96 to 1.94, P=0.083; Figure 2F), Gastric Cancer (OS: HR=1.74, 95% CI=1.4 to 2.17, P=4.2e-07; PPS: HR=2.35, 95% CI=1.77 to 3.13, P=1.3e- 09; FP: HR=1.57, 95%CI=1.23 to 1.99, P=0.00023; Figure 2I–2K), Lung Cancer (PPS: HR=1.59, 95%CI=1.03 to 2.46, P=0.034; Figure 2O). However, TMEM88 expression was not associated with OS and DMFS in breast cancer (Figure 2E, 2H), OS and FP in Lung Cancer (Figure 2N, 2P), and OS, PFS, and PPS in Ovarian cancer (Figure 2Q–2S). These results demonstrate the prognostic significance of TMEM88 expression in liver, breast, gastric, pancreatic ductal, and lung cancers.
However TMEM88 mRNA expression was higher in HCC (Liver hepatocellular carcinoma) and CHOL (Cholangiocarcinoma) compared with the corresponding normal tissues but high TMEM88 expression was associated with better prognosis in both HCC and CHOL.(Figure 1 and Figure 2A-2D)
Correlation between TMEM88 expression and infiltration levels of immune cells of HCC patients
We used 371 HCC patients data in TIMER database to investigate the correlation of TMEM88 expression and infiltration levels of immune cells in HCC tissues (Figure 3). TMEM88 expression in HCC tissues positively correlates with infiltration levels of CD8+ T cells (partial.cor=0.004), but negatively correlates with tumor purity (cor=-0.178) and infiltration levels of B cells (partial.cor=-0.207), CD4+ T cells (partial.cor=-0.065), macrophages (partial.cor=-0.2), neutrophils (partial.cor=-0.145) and dendritic cells (partial.cor=-0.05).
Correlation analysis of TMEM88 and other marker genes of immune cells expression with patients survival in HCC and CHOL tissues
In this investigation we found out that the expression of TMEM88 (p=0.004) in HCC tissues was the only factor that statistically significant correlation with patients survival outcome, the higher TMEM88 expression in HCC patients the better prognosis (Figure 4). The expression of B cells (p=0.489), CD8+ cells (p=0.551), CD4+ cells (p=0.454), macrophages (p=0.153), neutrophils (p=0.2) and dendritic cells (p=0.288) was not have statistically significant correlation with patients survival outcome. On the other hand, the only marker genes have statistically significant correlation with patients survival outcome in CHOL tissues was in neutrophils (p=0.044), but not in TMEM88 (p=0.534), B cells (p=0.619), CD8+ cells (p=0.208), CD4+ cells (p=0.244), macrophages (p=0.124), and dendritic cells (p=0.131).
Table 1. Correlation of TMEM88 mRNA expression and prognosis in hepatocellular carcinoma with different clinicopathological factors by Kaplan-Meier plotter.
Clinicopathological factors
|
Overall survival
|
|
Progression-free survival
|
N
|
Hazard ratio
|
P-value
|
N
|
Hazard ratio
|
P-value
|
SEX
|
|
|
|
|
|
|
Female
|
118
|
0.44(0.24-0.79)
|
0.005
|
120
|
0.63(0.38-1.05)
|
0.0715
|
Male
|
246
|
0.58(0.37-0.91)
|
0.016
|
246
|
0.65(0.45-0.93)
|
0.0173
|
Stage
|
|
|
|
|
|
|
1
|
170
|
0.77(0.42-1.41)
|
0.3954
|
170
|
0.58(0.35-0.96)
|
0.0313
|
2
|
83
|
0.59(0.27-1.31)
|
0.1886
|
84
|
0.65(0.36-1.18)
|
0.1561
|
1+2
|
253
|
0.72(0.45-1.16)
|
0.1788
|
254
|
0.57(0.39-0.84)
|
0.0036
|
3
|
83
|
0.44(0.24-0.81)
|
0.0064
|
83
|
0.9(0.53-1.55)
|
0.7122
|
2+3
|
166
|
0.49(0.3-0.8)
|
0.0032
|
167
|
0.72(0.48-1.07)
|
0.1024
|
4
|
4
|
-
|
-
|
5
|
-
|
-
|
3+4
|
87
|
0.5(0.28-0.89)
|
0.0158
|
88
|
0.81(0.48-1.37)
|
0.4313
|
Grade
|
|
|
|
|
|
|
1
|
55
|
0.59(0.23-1.52)
|
0.2734
|
55
|
0.72(0.33-1.57)
|
0.4078
|
2
|
174
|
0.53(0.32-0.89)
|
0.015
|
175
|
0.61(0.39-0.94)
|
0.0234
|
3
|
118
|
0.39(0.21-0.75)
|
0.003
|
119
|
0.55(0.33-0.91)
|
0.0172
|
4
|
12
|
-
|
-
|
12
|
-
|
-
|
AJCC_T
|
|
|
|
|
|
|
1
|
180
|
0.79(0.44-1.41)
|
0.4186
|
180
|
0.62(0.38-1.02)
|
0.0557
|
2
|
90
|
0.47(0.22-1)
|
0.0466
|
92
|
0.62(0.36-1.08)
|
0.0887
|
3
|
78
|
0.47(0.25-0.86)
|
0.0123
|
78
|
0.75(0.43-1.33)
|
0.3288
|
4
|
13
|
-
|
-
|
13
|
-
|
-
|
Vascular invasion
|
|
|
|
|
|
|
Micro
|
90
|
0.46(0.21-1)
|
0.0452
|
91
|
0.68(0.39-1.2)
|
0.1818
|
None
|
203
|
0.71(0.43-1.19)
|
0.194
|
204
|
0.68(0.44-1.06)
|
0.0888
|
Race
|
|
|
|
|
|
|
White
|
181
|
0.68(0.43-1.07)
|
0.0967
|
183
|
0.65(0.44-0.97)
|
0.0325
|
Asian
|
155
|
0.43(0.23-0.8)
|
0.0059
|
155
|
0.6(0.38-0.97)
|
0.0346
|
Alcohol consumption
|
|
|
|
|
|
|
yes
|
115
|
0.64(0.34-1.22)
|
0.1684
|
115
|
0.6(0.35-1)
|
0.0088
|
none
|
202
|
0.5(0.31-0.81)
|
0.0037
|
204
|
0.66(0.44-0.99)
|
0.0456
|
Virus hepatitis
|
|
|
|
|
|
|
Yes
|
150
|
1.12(0.58-2.16)
|
0.7337
|
152
|
0.63(0.39-1)
|
0.0459
|
None
|
167
|
0.39(0.24-0.63)
|
7.5e-05
|
167
|
0.63(0.41-0.98)
|
0.0369
|
Bold values indicate P < 0.05.
Correlation between TMEM88 expression and clinical characteristics of HCC patients
Next, we investigated the relationship between TMEM88 expression and different clinical characteristics of HCC using the Kaplan-Meier Plotter database and the results are shown in Table 1. Low TMEM88 expression correlated with both poorer OS and PFS in males (OS: HR=0.58, P=0.0016; PFS: HR=0.65, P=0.0173), Grade 2 patients (OS: HR=0.53, P=0.015; PFS: HR=0.61, P=0.0234), Grade 3 patients (OS: HR=0.39, P=0.003; PFS:HR=0.55, P=0.0172), Asians (OS: HR=0.43, P=0.0059; PFS: HR=0.6, P=0.0346), and non-alcoholics (OS: HR=0.5, P=0.0037; PFS: HR=0.66, P=0.0456). Low TMEM88 mRNA expression correlates with worse OS in female (HR=0.44, P=0.005), stage 2+3 patients (HR=0.49, P=0.0032), stage 3 patients (HR=0.44, P=0.0064), stage 3+4 patients (HR=0.5, P=0.0158), AJCC_T grade 2 patients (HR=0.47, P=0.0466), AJCC_T grade 3 patients (HR=0.47, P=0.0123) and patients with micro vascular invasion (HR=0.46, P=0.0452). Low TMEM88 mRNA expression correlates with worse PFS in stage 1 patients (HR=0.58, P=0.0313), stage 1+2 patients (HR=0.57, P=0.0036), Whites (HR=0.65, P=0.0325), alcohol consumers (HR=0.6, P=0.0088), patients with hepatitis virus (HR=0.63, P=0.0459) and patients without hepatitis virus (HR=0.63, P=0.0369). However, TMEM88 expression did not correlate with OS and PFS in stage 2 patients (OS: HR=0.59, P=0.1886; PFS: HR=0.65, P=0.1561), grade 1 patients (OS: HR=0.59, P=0.2734; PFS: HR=0.72, P=0.4078) and AJCC_T grade 1 patients (OS: HR=0.79, P=0.4186; PFS: HR=0.62, P=0.0557). These results demonstrate that prognostic significance of TMEM88 expression in HCC patients based on their clinical characteristics, especially in late stage of HCC.
Table 2. Correlation analysis between TMEM88 and marker genes of immune cells in GEPIA.
|
|
HCC
|
|
|
CHOL
|
|
Description
|
Gene markers
|
Tumor
|
Normal
|
Tumor
|
Normal
|
|
|
R
|
P
|
R
|
P
|
R
|
P
|
R
|
P
|
Monocyte
|
CD86
|
−0.1
|
0.054
|
0.57
|
1.8e-05
|
0.05
|
0.77
|
0.87
|
0.0045
|
Neutrophils
|
CD11b
|
−0.23
|
9.4e-06
|
0.43
|
0.0019
|
−0.11
|
0.53
|
0.63
|
0.076
|
CCR7
|
0.15
|
0.0035
|
0.49
|
0.00027
|
0.21
|
0.21
|
0.89
|
0.0014
|
TAM
|
CD68
|
−0.1
|
0.051
|
0.48
|
0.00039
|
−0.24
|
0.15
|
0.75
|
0.025
|
|
IL-10
|
−0.032
|
0.54
|
0.2
|
0.17
|
0.018
|
0.92
|
-0.18
|
0.65
|
Th1
|
IFN-γ (IFNG)
|
−0.14
|
0.0064
|
0.33
|
0.02
|
0.26
|
0.13
|
0.51
|
0.16
|
|
STAT1
|
−0.17
|
0.0012
|
0.45
|
0.00091
|
−0.24
|
0.15
|
0.3
|
0.44
|
|
T-bet (TBX21)
|
0.17
|
0.00087
|
0.48
|
0.00046
|
0.33
|
0.048
|
0.82
|
0.011
|
|
TNF-α (TNF)
|
−0.11
|
0.031
|
0.3
|
0.034
|
0.21
|
0.21
|
0.61
|
0.079
|
Th2
|
STAT6
|
0.059
|
0.26
|
0.48
|
0.00047
|
−0.031
|
0.86
|
0.77
|
0.021
|
Treg
|
CCR8
|
−0.12
|
0.018
|
0.13
|
0.18
|
0.28
|
0.047
|
0.33
|
0.39
|
|
STAT5B
|
0.012
|
0.81
|
0.26
|
0.18
|
0.29
|
0.41
|
0.63
|
0.076
|
|
TGF-β (TGFB1)
|
−0.062
|
0.23
|
0.7
|
1.9e-08
|
0.06
|
0.73
|
0.83
|
0.0083
|
T cell exhaustion
|
CTLA4
|
−0.2
|
9.1e-05
|
0.43
|
0.0016
|
0.25
|
0.13
|
0.57
|
0.11
|
|
PD-1 (PDCD1)
|
−0.13
|
0.016
|
0.46
|
0.00082
|
-0.046
|
0.79
|
0.96
|
4.8e-05
|
|
TIM-3 (HAVCR2)
|
−0.18
|
4e-04
|
0.57
|
1.8e-05
|
-0.12
|
0.5
|
0.82
|
0.011
|
Bold values indicate P < 0.05.
Correlation analysis between mRNA levels of TMEM88 and markers of different subsets of immune cells
Next, we investigated the correlation between TMEM88 expression and the status of tumor-infiltrating immune cells based on the levels of immune marker gene expression in HCC and CHOL tissues using the GEPIA database. The immune cells analyzed in HCC tissues included monocytes, neutrophils, tumor-associated macrophages (TAMs), T helper 1 (Th1), T helper 2 (Th2), regulatory T (Tregs) and exhausted T cells.
Analysis of the GEPIA database showed that TMEM88 expression in HCC tissues significantly correlated with the expression of marker genes from TAMs, neutrophils, T-helper, Treg and exhausted T cells, whereas the correlation was not significant in CHOL (Table 2).
Specifically, TMEM88 expression showed significant correlation with the expression of markers of specific immune cells such as monocyte markers, CD86 (CHOL: normal: R=o.87, P=0.0045) and CD11b (HCC: normal: r=0.43, P=0.0019), neutrophils marker, CCR7 (HCC: tumor: r=0.15, P=0.0035, normal: r=0.49, P=0.00027; CHOL: normal: r=0.89, P=0.0014), TAM marker, CD68 (HCC: normal: r=0.48, P=0.00039; CHOL: normal: r=0.75, P=0.025), Th1 markers, IFN-γ (HCC: tumor: r=-0.14, P=0.0064, normal: r=0.33, P=0.02), STAT1 (HCC: tumor: r=-0.17, P=0.0012, normal: r=0.45, P=0.00091), T-bet (HCC: tumor: r=0.17, P=0.00087, normal: r=0.48, P=0.00046; CHOL: tumor: r=0.33, P=0.048, normal: r=0.82, P=0.011), TNF-α (HCC: tumor: r=-0.11, P=0.031, normal: r=0.3, P=0.034), Th2 marker, STAT6 (HCC: normal: r=0.48, P=0.00047; CHOL: normal: r=0.77, P=0.021), Treg marker, CCR8 (HCC: tumor: r=-0.12, P=0.018; CHOL: tumor: r=0.28, P=0.047) and TGF-β (CHOL: normal: r=0.83, P=0.0083), and exhausted T cell, CTLA4 (HCC: normal: r=0.43, P=0.0016), PD-1 (HCC: tumor: r=-0.13, P=0.016, normal: r=0.46, P=0.00082) and TIM-3 (CHOL: normal: r=0.82, P=0.011). These findings strongly suggest that TMEM88 expression correlates with infiltration of immune cells in hepatocellular carcinoma.