3.1 Download and analysis of data.
We searched the ICC related data set in the GEO database and found that GSE45001 contained 10 ICC samples and 10 normal tissue samples, which met our research needs, so we chose the GSE45001 data set for download analysis. In addition, the details are shown in Table 1, where the odd mantissa is a normal tissue sample, and the even mantissa is a tumor tissue sample. Finally through data correction, we obtained 7 pairs of available sample data for the next analysis.
3.2 Analysis of the content of immune cells in the sample.
The 7 normal samples and 7 ICC samples obtained by the correction were put into the CIBERSORT database to calculate the immune cell content, and the obtained results were plotted as a histogram. Then, we further draw the results into a principal component diagram, from which we can find that the tumor tissue group and the normal tissue group have significantly different immune cell content (Figure 1). Finally, we draw a heat map and visually analyze the expression of immune cells in the sample (Figure 2). The results show that the expression of some immune cells shows differences between tumor tissues and normal tissues.
3.3 Co-expression analysis between immune cells.
Co-expression analysis of the expression levels of immune cells obtained in this study showed that the correlation between T cells regulatory (Tregs) [10-13]and Neutrophils [14-17] was the strongest, with a coefficient of 0.78, and the two cells with the weakest correlation were Macrophages [18-19] and T cells follicular helper [20-21], the correlation coefficient is -0.59 (Figure 3).
3.4 Immune cells with significantly different expressions in ICC and normal tissues are screened.
By drawing a violin chart (Figure 4), We found that the expression levels of Dendritic cells activated (Figure5A), Macrophages M2 (Figure5B) and T cells regulatory (Tregs) (Figure5C) in ICC were higher than normal tissues and the expression levels of Monocytes (Figure5D), T cells follicular helper (Figure5E) and Macrophages M1 (Figure5F) in ICC were lower than normal tissues
3.5 Principal Component Analysis (PCA)
After obtaining the matrix of immune cells, we wondered whether these immune cells could distinguish between the normal group and the tumor group. Then we did principal component analysis. The dimensionality was reduced to PCA1 and PCA2 by PCA, and the X-axis was labeled as PCA1 and Y-axis as PCA2. Then an ellipse was simulated for the normal group and the tumor group, respectively. If the two ellipses did not cross, it suggested that the 22 immune cells could distinguish the normal group from the tumor group well. We used the "GGplot2" package for analysis, and the results showed that the two ellipses did not cross (Figure 6), indicating that the 22 kinds of immune cells in this study could well distinguish the tumor group from the normal group.
3.6 Immune cells related to ICC survival prognosis.
By querying in the TIMER 2.0 database, two immune cells (Monocytes, T cells regulatory) were found to be related to the survival prognosis of ICC patients, and there was statistical significance (Figure 7). And these two cells also fit the logic of this study.