Study characteristics.
The National Center for Biotechnology Information (NCBI) stores a vast amount of raw microarray data from different studies in their embedded repository database called Gene Expression Omnibus (GEO)(7). The raw data of this meta-analysis was downloaded from the GEO database. This project includes microarray profiling data of cancer patients’ samples from four different studies with GEO Series accession number (GSE #) (GSE99070(8), GSE93157(9), GSE79691(10), and GSE67501(11)) as shown in Table 1. These four studies include transcriptomic data of cancer tissue samples for seven types of cancers (malignant pleural mesothelioma, head and neck, lung non-squamous, squamous lung, melanoma, melanoma skin metastasis, and renal cell carcinoma). The microarray chip technology used in three of these studies were Illumina High-Density Silica Bead-Based Microarray Technology, while one study used GPL19965 nCounter PanCancer Immune Profiling Panel, (Table 1) shows the specific chips used from each study set with the Geo Sample Accession Number (GSM #) identifier provided. These GSM chips were from patients’ samples that had either complete/partial response (CR/PR) or no- response/progressed disease (PD) to anti-PD1 immunotherapy. All other microarray chips that had stable disease status or any other status were excluded from this study. The included GSM samples that responded to the anti-PD1 immunotherapy in all seven types of cancer equaled 34 samples, while the GSM samples from patients that did not respond to the anti-PD1 immunotherapy equaled 44 samples.
Common DEGs identified across different types of cancer.
Common DEGs between any two or more types of cancer were identified and shown in Table 2. All DEGs were significantly dis-regulated (p-value<0.05). The full list of significantly dis-regulated genes for each type of cancer is provided in supplementary excel sheet (Data1e). Malignant pleural mesothelioma shared common genes with five types of cancer included in this study (Figure 1A), yet, the number of common DEGs between the malignant pleural mesothelioma and other types of cancer varied. For example, malignant pleural mesothelioma shared one common gene with lung non-squamous cancer, and also shared the highest common DEGs with renal cell carcinoma 79 genes (Figure 1A). Six DEGs were shared in common among malignant pleural mesothelioma and two other types of cancers (melanoma skin metastasis and renal cell carcinoma) (Table 2 and Figure 1A).
Lung non-squamous cancer shared common DEGs with 4 types of cancer, [squamous lung cancer (2 genes), melanoma (2 genes), melanoma skin metastasis (1 gene), and renal cell carcinoma (5 genes)] (Table 2).
The highest number of cancers to share common genes was four [squamous lung cancer, melanoma, melanoma skin metastasis, and renal cell carcinoma]. These four types of cancer shared one gene in common (Table 2).
The highest number of common DEGs shared was between melanoma skin metastasis and renal cell carcinoma (105 genes) (Table 2).
Pattern of expression and potential signatures of the DEGs in this study.
To further detail and identify potential gene expression signatures associated with response or no-response to the anti-PD1 immunotherapy, we looked at the pattern of expression of common DEGs among different types of cancer included in this study. The Venn diagram in Figure 1A shows common DEGs shared between malignant pleural mesothelioma and five types of cancer that were previously detailed in part in Table 2.
The graph in Figure 1B shows the pattern of expression of the MX1 gene which was found to be common between malignant pleural mesothelioma and lung non-Squamous cancer. The MX1 gene shows dissimilar (anti-parallel) pattern of expression, the negative logarithmic fold change value of any gene [MX1 as an example here (logFC= -1.3)] indicates that the gene expression is up-regulated in the samples of patients that had complete response (CR) or partial response (PR) to the anti-PD1 immunotherapy compared to the patients’ samples that had no-response (indicated as progressed disease “PD”). “Figure 1C left bar graph for the malignant pleural mesothelioma”. This pattern of expression was opposite in patients of lung non-squamous cancers, where MX1 gene had a positive logarithmic fold change value (logFC=1.19011) which indicates that MX1 is down-regulated in samples of patients that had complete response (CR) compared to the sample of patients that had progressed disease (PD) (Figure 1C ‘right bar graph’ for the lung non-squamous cancer).
The Venn diagram in Figure 1A also shows common genes between malignant pleural mesothelioma and squamous lung cancer [two genes (IFNL2 and CLEC4C) (Figure 1A and Figure 2A)]. The IFNL2 has similar (parallel) gene expression pattern (logFC= -0.158 and -0.965708 in both malignant pleural mesothelioma and squamous lung cancer respectively (Figure 2A, 2C)), the negative logFCs of the IFNL2 indicates its up-regulation in samples from patients who responded to the anti-PD1 immunotherapy in both malignant pleural mesothelioma and squamous lung cancer. The gene (CLEC4C) on the other hand shows dissimilar (anti-parallel) pattern (the positive, logFC= 0.134 indicates up-regulation in malignant pleural mesothelioma samples of patients who did not respond to the immunotherapy), while it has an up-regulation pattern (logFC= -1.342245 in the squamous lung cancer samples’ of patients who responded to the immunotherapy) (Figure 2A).
Malignant pleural mesothelioma shares two common DEGs (LILRB2 and IL10) with melanoma (Figure 1A, 2B, 2C). In both, malignant pleural mesothelioma and melanoma, up-regulation of LILRB2 were found to be associated with response to the anti-PD1 immunotherapy. The IL10 gene, on the other hand, was found to have anti-parallel pattern of expression, malignant pleural mesothelioma IL10 was up-regulated in the no-response patients, while IL10 in melanoma was up-regulated in patients that responded to the anti-PD1 immunotherapy (Figure 2B, 2C).
Six genes were found to be common among three types of cancer (malignant pleural mesothelioma, melanoma skin metastasis, and renal cell carcinoma) (Figure 1A). TOM1L1 gene is the only gene that shows a parallel expression pattern among these three types of cancer (Figure 2c, 2D). Up-regulation of TOM1L1 exhibited an association with no-response to anti-PD1 immunotherapy in all of the malignant pleural mesothelioma, melanoma skin metastasis and renal cell carcinoma (logFC= 0.115, 0.3382833, and 0.6702321 respectively). Five other genes exhibited a dissimilar pattern of expression as shown in Figure 2C, and 2D.
Malignant pleural mesothelioma also shares common DEGs signatures with melanoma skin metastasis (46 genes), and with renal cell carcinoma (79 genes) (Figure 1A). The genes signatures were sorted into similar or dissimilar pattern signatures. Appendix 1A contains a list of 17 genes that constitute a similar signature pattern in both malignant pleural mesothelioma and melanoma skin metastasis, this pattern exhibit up-regulation of these genes in samples of patients which responded to the anti-PD1 immunotherapy (Figure 3A).
Another set of 14 genes in Appendix 1A constitute a second similar pattern of genes signatures, yet, these genes signatures show up-regulation of expression in samples of patients which had no-response to the anti-PD1 immunotherapy (Figure 3B).
Malignant pleural mesothelioma and melanoma skin metastasis have another two DEGs expression signatures that are dissimilar in their pattern of expression. Nine genes of malignant pleural mesothelioma (Appendix 1B) show up-regulation in samples of patients which responded to the anti-PD1 immunotherapy, the same nine genes but in melanoma skin metastasis samples were up-regulated in patients that did not respond to the anti-PD1 immunotherapy (Figure 3C). The opposite scenario is seen in another DEGs signatures consist of six genes between malignant pleural mesothelioma and melanoma skin metastasis (Appendix 1B and Figure 3D).
In addition to the one common gene that lung non-squamous cancer share with malignant pleural mesothelioma (Figure 1B), this study also found that lung non squamous cancer share common genes with four other types of cancer [(squamous lung cancer, melanoma, melanoma skin metastasis, and renal cell carcinoma) two genes, two genes, one gene, and five genes respectively] (Figure 4A). The patterns of expression signatures (similar and dissimilar) of these common genes between lung non-squamous and four other types of cancer are illustrated in Figures 4B, 4C, 4D, 4E and the inset table (Figure 4F).
The head and neck cancer in this study share one common gene (CX3CL1) with renal cell carcinoma (Figure 5A, 5C, and 5D), this gene shows dissimilar regulation signature in these two types of cancer. Therefore, CX3CL1 up-regulation could be an indicator of response in head and neck cancer, while the opposite can be interpreted from CX3CL1 which was up-regulated in the no-response group of the renal cell carcinoma (Figure 5C). Head and neck cancer, melanoma skin metastasis and squamous lung cancer share one gene in common (S100A7), however, S100A7 gene was up-regulated in squamous lung cancer patients which responded to the anti-PD1 immunotherapy (Figure 5B), on the other hand, S100A7 gene in melanoma skin metastasis and head and neck was up-regulated in the no-response patients (Figure 5B).
Four types of cancers are the most to share common genes in this study as shown in Figure 6B. Melanoma, squamous lung cancer, melanoma skin metastasis, and renal cell carcinoma they share PLAUR gene in common. PLAUR gene up-regulation is associated with the response to the anti-PD1 in all types of cancer except for the melanoma skin metastasis (associated with no-response as shown in Figure 6D).
This study also highlights a noteworthy gene expression signatures that is shown between melanoma and renal cell carcinoma (six genes as shown in Figure 6A). All six genes have similar up-regulation pattern of gene expression and associated with the response to anti-PD1 immunotherapy (Figure 6E, 6F). On the other hand, melanoma and melanoma skin metastasis shared seven common DEGs. All seven genes had dissimilar patterns of gene expression (Figure 6C, 6F). The seven genes in melanoma were up-regulated in the response patients, while same seven genes in melanoma skin metastasis were up-regulated in the no-response patients.
Melanoma skin metastasis and renal cell carcinoma share the most common DEGs in this study (105 genes) (Figure 6A). Among the 105 genes, 28 up-regulated DEGs were associated with response to anti-PD1 in both melanoma skin metastasis and renal cell carcinoma (Figure 7A, and appendix 2A). Another gene expression signatures of 26 up-regulated DEGs were associated with no-response in both melanoma skin metastasis and renal cell carcinoma (Figure 7B, and Appendix 2B). In addition to the two similar DEGs signatures, two dissimilar gene expression signatures were also identified between melanoma skin metastasis and renal cell carcinoma. 24 genes were significantly up-regulated and associated to the response to anti-PD1 in melanoma skin metastasis sample, while same 24 genes were up-regulated in the renal cell carcinoma but were associated to the no-response (Figure 7C, and Appendix 2C). The opposite gene expression signature pattern which comprised 27 genes was identified between melanoma skin metastasis and renal cell carcinoma. (Figure 7D, and Appendix 2D).