The expression and mutation Profiling of TIMP2 in different cancer types
Cancer is a disease of the genome and develops as one end-product of accumulating somatic mutation [13, 14]. Remarkable advances in next-generation sequencer (NGS) and computational technology dealing with massive data make it available to synthetically analyze cancer genome profiles at clinical and research levels [14]. Thus, our aim was to explore genomic mutation profiling of TIMP2 in pan-cancer, regarding analysis of TIMP2 was exhibited by cBioPortal database. The genetic alteration characterization of TIMP2 showed that its amplification was one of the most important single factors for alteration in liver cancer, BRCA, mesothelioma, sarcoma, lung adenocarcinoma, LGG, CRC, uveal melanoma, PCPG, esophagus cancer, pancreas cancer, thyroid cancer, GBM and ccRCC. Besides, TIMP2 mutation frequencies are the highest in liver cancer, BRCA and mesothelioma (Figure. 1A). The Oncomine database showed that TIMP2 mRNA levels were significantly upregulated in nine cancer datasets, especially lymphoma (15 reported). Meanwhile, leukemia was the most down-expression cancer type (9 reported). Additionally, we visualized the expression of TIMP2 genes in various cancer tissues and adjacent tissues in Figure 1C, the higher TPM levels of TIMP2 in multiple cancers were observed (P < 0.05). Data extracted from TCGA database revealed that TIMP2 expression was notably higher in 10 tumor types compared to matched TCGA normal tissues and GTEx data, including CHOL, GBM, HNSC, KIRP, LAML, LGG, LIHC, PAAD, SKCM, STAD (Figure 1C).
The prognostic significance of TIMP2 expression in different cancer types
Kaplan Meier curves displayed elevated expression of TIMP2 was an unfavorable prognostic factor for cancer patients, including overall survival (OS, Figure 2A) and disease-free survival prognosis (DFS, Figure 2B). As shown in Figure 2C, high mRNA expression of TIMP2 predicted worse survival for UCEC (HR = 1.3, 95%CI: 1.08-1.55, P = 0.0046), BLCA (HR = 1.15, 95%CI: 1.05-1.25, P = 0.0019), MESO (HR = 1.59, 95%CI: 1.13-2.24, P = 0.0082), STAD (HR = 1.25, 95%CI: 1.07-1.45, P = 0.0037) LGG (HR = 1.39, 95%CI: 1.05-1.85, P = 0.022), and KICH (HR = 2.16, 95%CI: 1.12-4.17, P = 0.022) respectively.
The correlation between TIMP2 expression and immune infiltrates
When analyzing the association between TIMP2 expression and immune sub-types, it was found that the expression of TIMP2 was most positively associated with central memory CD4+ T cell, central memory CD8+ T cell, effector memory CD4+ T cell, effector memory CD8+ T cell, gamma delta T cell, immature dendritic cell, mast cell, MDSC, memory B cell, natural killer cell, natural killer T cell, plasmacytoid dendritic cell, regulatory T cell, T follicular helper cell and type 1 T helper cell. Furthermore, TIMP2 was most positively associated with major immune cells in OV, LUAD, LUSC, PARD, BLCA, ESCA, PAAD, LIHC, BRCA, COAD, STAD, THCA, READ and LGG (Figure. 3A). With regards to gene markers of immune cells, the expression of TIMP2 was found to positively correlate with CD276. PRAD, COAD, THCA and KICH were top four tumors which had the most gene markers of immune cells positively associated with TIMP2 expression (Figure. 3B). Analysis of the relationship between TIMP2 expression and six common immune cells revealed that the expression of TIMP2 positively correlated with COAD, LIHC, PRAD, LUAD, OV, ACC, LGG, READ and THCA (Figure. 3C). In addition, our study found that TIMP2 expression were positively correlated with ImmuneScore, StromalScore, and ESTIMATEScore in THCA, HNSC, LAML, READ, LGG, DLBC, KICH, OV, LUAD, LUSC, PRAD, BLCA, ESCA, TGCT and PAAD (Figure. 3D). These results suggested that TIMP2 expression might be involved in regulating the aforementioned immune molecules and play a vital role in immune microenvironment.
Relationship between TIMP2 expression and TMB, MSI, and neoantigen
TMB is defined as the number of somatic mutations detected on next generation sequencing (NGS) per megabase (mb) [15, 16]. As measured by immunohistochemistry, high TMB is an emerging biomarker of predicting the response to immune checkpoint inhibitors [17]. Across tumor diagnoses, patients with high TMB might be an optimal subgroup for ICI therapy and have a higher likelihood of immunotherapy [16, 18]. More broadly, neoantigens arise from tumor-specific mutations that differ from wild-type antigens, which is a major factor in the activity of clinical immunotherapies and may guide application of immunotherapies [19] [20]. These observations indicated that TMB, MSI, and neoantigen might form biomarkers in the immune response to cancer patients and provide the progress of novel therapeutic approaches with an incentive. In addition, TIMP2 was positively correlated with TMB in OV, LGG and SKCM, and negatively correlated with TMB in STAD and KIRP (Figure. 4A). TIMP2 was positively correlated with MSI in UVM and TGCT, and negatively correlated with MSI in HNSC, STAD and UCEC (Figure. 4B). TIMP2 was negatively correlated with neoantigen in with MSI in STAD (Figure. 4C).
Functional Annotation of Co-expression Gene Network of TIMP2
The TIMP family (TIMP-1, 2, 3, 4), a class of transcription factors, has four members, are roughly 40% identical in amino acid sequence, and TIMP2 and TIMP4 share most similarities [21]. As shown in Figure 5A, 20 genes showed the greatest association with TIMPs in the gene interaction network, including RECK, MMP1, MMP14, MMP3, MMP2, AGTR2, PCSK5, ESR1, ADAM17, MMP9, MXRA8, EFEMP1, MMP8, ETV4, JUND, EGR1, ADAMTS4, ADAM15, STAT3 and JUNB. Further functional analysis revealed that the top six pathways related to these genes were M3468: NABA ECM REGULATORS (logP=-22.8947, z-score=30.68476), M167: PID AP1 PATHWAY (logP= -19.2461, z-score= 37.29148), R-HSA-6785807: Interleukin-4 and Interleukin-13 signaling (logP=-19.1111, z-score= 31.49618), GO:0051045: negative regulation of membrane protein ectodomain proteolysis (logP=-17.967, z-score=47.44123), GO:1901652: response to peptide (logP=-15.867, z-score=16.87997), and GO:0001568: blood vessel development . (Figure. 5C) Moreover, it was also related to the metabolism of insulin, glucose, and fat, and cell surface receptor signaling pathways which regulate immune response. The top 3 most relevant MCODE modules were NABA ECM regulators, degradation of the extracellular matrix and extracellular matrix disassembly (Figure. 5D).