The flow chart of this study is shown in Fig.1.
Identification of Cuproptosis-related Differentially Expressed LncRNAs in HNSC
Data download and organization:A total of 39 normal samples and 469 tumor samples from HNSC patients in TCGA were included in this study. Transcriptome data can be found in symbol.txt. Clinical data can be found in clinical.xls. mRNAs and LncRNAs are found in LncRNA.txt and mRNA.txt.
The expression levels of cuproptosis related genes can be found in cuproptosisExp.txt. The coexpression results of cuproptosis related LncRNAs were visualized by drawing a Sankey diagram as shown in Fig. 2A. The upper bands represent cuproptosis-related genes, and different colors represent different genes. The lower bands represent LncRNAs, which are LncRNAs that have a coexpression relationship with cuproptosis. The lines connecting the two represent the co-expression relationship between LncRNAs and the corresponding cuproptosis gene.
Construction of the Prognostic Model Using the Expression Profiles of Cuproptosis-related LncRNAs
LASSO Cox regression analysis was used to establish a prognostic model using the expression profiles of cuproptosis-related genes. Patients were stratified into high-risk groups (n = 233) or low-risk groups (n = 233) according to the median cut-off value. In the forest plot (Fig. 2B), the high-risk ones are in red, and the low-risk ones are in green. Fig. 2C and Fig. 2D are the lasso regression graph and the cross-validation graph, respectively. The number of points with the smallest cross-validation in the cross-validation graph is the LncRNAs obtained by lasso regression. Fig. 2E shows the correlation of LncRNAs and cuproptosis related genes involved in model construction.
Table 1 shows the clinical statistical analysis of model grouping. According to the analysis results, it can be seen that the P values of clinical characteristics of patients between the Train group and the Test group are all greater than 0.05, indicating that there is no difference in clinical characteristics between the two groups. That is, there is no deviation of clinical traits between the two groups of samples.
Table 1.
|
Covariates
|
Type
|
Total
|
Test
|
Train
|
Pvalue
|
Age
|
<=65
|
306(65.67%)
|
152(65.24%)
|
154(66.09%)
|
0.9223
|
|
>65
|
160(34.33%)
|
81(34.76%)
|
79(33.91%)
|
|
Gender
|
FEMALE
|
120(25.75%)
|
63(27.04%)
|
57(24.46%)
|
0.5963
|
|
MALE
|
346(74.25%)
|
170(72.96%)
|
176(75.54%)
|
|
Grade
|
G1
|
59(12.66%)
|
35(15.02%)
|
24(10.3%)
|
0.2497
|
|
G2
|
277(59.44%)
|
138(59.23%)
|
139(59.65%)
|
|
|
G3
|
109(23.39%)
|
48(20.60%)
|
61(26.18%)
|
|
|
G4
|
2(0.43%)
|
1(0.43%)
|
1(0.43%)
|
|
|
unknow
|
19(4.08%)
|
11(4.72%)
|
8(3.43%)
|
|
Stage
|
Stage I
|
23(4.94%)
|
10(4.29%)
|
13(5.58%)
|
0.756
|
|
Stage II
|
66(14.16%)
|
36(15.45%)
|
30(12.88%)
|
|
|
Stage III
|
78(16.74%)
|
37(15.88%)
|
41(17.6%)
|
|
|
Stage IV
|
236(50.64%)
|
120(51.5%)
|
116(49.79%)
|
|
|
unknow
|
63(13.52%)
|
30(12.88%)
|
33(14.16%)
|
|
T
|
T1
|
42(9.01%)
|
18(7.73%)
|
24(10.3%)
|
0.6902
|
|
T2
|
126(27.04%)
|
64(27.47%)
|
62(26.61%)
|
|
|
T3
|
91(19.53%)
|
49(21.03%)
|
42(18.03%)
|
|
|
T4
|
154(33.05%)
|
80(34.33%)
|
74(31.76%)
|
|
|
unknow
|
53(11.37%)
|
22(9.44%)
|
31(13.3%)
|
|
M
|
M0
|
168(36.05%)
|
88(37.77%)
|
80(34.33%)
|
1
|
|
M1
|
1(0.21%)
|
1(0.43%)
|
0(0%)
|
|
|
unknow
|
297(63.73%)
|
144(61.8%)
|
153(65.67%)
|
|
N
|
N0
|
155(33.26%)
|
78(33.48%)
|
77(33.05%)
|
0.8504
|
|
N1
|
65(13.95%)
|
29(12.45%)
|
36(15.45%)
|
|
|
N2
|
151(32.4%)
|
77(33.05%)
|
74(31.76%)
|
|
|
N3
|
6(1.29%)
|
3(1.29%)
|
3(1.29%)
|
|
|
unknow
|
89(19.1%)
|
46(19.74%)
|
43(18.45%)
|
|
Relationship Between Cuproptosis-related LncRNA Signature and Clinical Characteristics in HNSC
Survival curves were constructed by survival analysis: As shown in Fig. 3A, the P values of the high- and low- risk groups in the test group and the train group were both less than 0.05, indicating that there was a difference in the survival of patients between the high- and low- risk groups, and that the constructed model could distinguish patients in these groups. It can be seen that the P value in PFS analysis was less than 0.05 which indicated that there was a difference in the progression-free survival of patients between the high- and low- risk groups. The risk curve was shown in Fig. 3B. From top to bottom are the risk curves of the whole group, the test group, and the train group. The patients were divided into two groups, high and low risk, according to the median risk. The low risk group was blue, and the high risk was red. In the Survival time curve, mortality increases as patient risk increases. The risk heat map was used to observe which LncRNAs were at high risk and which ones were at low risk. In the independent prognostic analysis, the single factor and multiple factors of the constructed model were all less than 0.05, indicating that the model could be used as an independent prognostic factor independently of other clinical traits (Fig. 3C).
The ROC curves of 1, 3 and 5 years are all greater than 0.05, indicating that the constructed model has high accuracy in predicting patient survival (Fig. 4A). The graph on the right is a combination of the constructed model and other clinical traits. It can be seen that the area under the ROC curve of the constructed model is the largest, indicating that the constructed model is better than other clinical traits in predicting survival. As shown in Fig. 4B, the model validation diagram for clinical grouping is shown. We divided patients into early (Stage I−II) and advanced (Stage III−IV) patients. It can be observed that the constructed model has a P value of less than 0.05 in both the early (left) and late (right) curves, indicating that the model is suitable for both early and late stage patients. The C-index value of the constructed model is the largest, indicating that the accuracy of predicting the survival period through the constructed model is the highest (Fig. 4C). The nomogram was used to predict the patient's survival. The score for each clinical trait can be obtained according to the individual scoring scale, and the summation value is the comprehensive score of the patient. According to the comprehensive scoring scale, the survival time of patients can be predicted according to the corresponding values at the bottom of the graph (Fig. 4D and E). Through principal component analysis, it can be observed that the difference between high- and low- risk in the Risk LncRNAs graph was the most obvious, indicating that the LncRNAs constructed by the model can distinguish patients in the high-risk group (Fig. 4F).
Analysis and Confirmation of LIPT1 Expression in Different Clinical Grading of HNSC
As mentioned above, we analyzed the expression of cuproptosis-related genes in HNSCs, but in clinical terms, it is the clinical grading that really determines the prognosis of patients. Therefore, we further analyzed the expression of all these 19 genes in different clinical stages. Among these differentially expressed genes, 9 genes (LIAS, LIPT1, LIPT2, PDHA1, PDHB, DBT, GCSH, DLST) were positively correlated with clinical grading (Fig. 5A).
We then chose LIPT1 to further explore its role in the development of HNSC. It can be seen that the expression value of LIPT1 increases as the clinical grading increases (G1-G3) by Kruskal-Wallis one-way ANOVA (Fig. 5B). G4 was not included because the sample size was too small (n=2).
Immunohistochemistry analysis showed that LIPT1 was highly expressed in HNSC. Compared with the highly and moderately differentiated samples, the expression was particularly obvious in the poorly differentiated samples (Fig. 5C).
qRT-PCR showed the same results as immunohistochemistry. The mRNA level of LIPT1 was highly expressed in the poorly differentiated samples compared to the highly and moderately differentiated samples (Fig. 5D).
The Prognostic Value of LIPT1 in HNSC Patients
The potential prognostic value of LIPT1 was assessed using Cox proportional hazards model and Kaplan-Meier analysis. The HNSC patients expressed lower LIPT1 showed longer overall survival than those expressed higher LIPT1 (Fig. 6A).
GSEA Single Gene of LIPT1 in HNSC
GSEA was used to identify relevant pathways in HNSCs affected by LIPT1 expression. The results showed that LIPT1 was positively related with cell cycle, RNA degradation, DNA replication, regulation of autophagy and P53 signaling pathway (Fig. 6B), which suggested that LIPT1 may play a role in the tumorigenesis of HNSC.
Spearman Correlation Analysis Between Single Gene and Pathway Score
Spearman Correlation Analysis was further applied to verify the relationship of LIPT1 expression on HNSC related genes and pathways. The results showed that DNA replication, tumor proliferation, G2M checkpoint, MYC targets and DNA repair were positively correlated with the expression of LIPT1 (Fig. 6C), suggesting the role of LIPT1 in the tumorigenesis of HNSC. At the same time, we observed that inflammatory response and tumor inflammation signature were negatively correlated with the expression of LIPT1 (Fig. 6C), suggesting that LIPT1 may be related to the immunity of HNSC patients.
Immune-Related Analysis of LIPT1 in HNSC
Subsequently, we evaluated the correlation between LIPT1 expression and immunity in HNSC patients. Differential infiltration of some immune cells was found between LIPT1 high expression and LIPT1 low expression groups (Fig. 6D). Compared to the LIPT1 low expression group, the infiltration of T cell CD4+ Th2 cells, common lymphoid progenitor, Class-switched memory B cell, B cell native, B cell memory and B cells were higher, while the infiltration of T cell regulatory (Tregs), T cell NK, T cell CD4+ effector memory, T cell CD4+ central memory, plasmacytoid dendritic cell, neutrophil, myeloid dendritic cell activated, myeloid dendritic cell, monocyte, mast cell and endothelial cell were lower in LIPT1-high group.
The results of immune checkpoints demonstrated the high expression group of LIPT1 was positively associated with several immune recognition molecules, such as CTLA4, SIGLEC15, HAVCR2, LAG3, PDCD1 and TIGIT (Fig. 6E). The expression of immune checkpoint molecules on immune cells will inhibit the function of immune cells, so that tumors form immune escape.