TNMD expression and genetic alteration analysis in pan-cancer
To elucidate the expression patterns of TNMD across various cancers, we analyzed TNMD mRNA levels in tumor tissues and adjacent normal samples, utilizing data from TCGA and the GTEx project. TNMD was significantly upregulated in several cancers, including GBM, low-LGG, COAD, READ, LIHC, PAAD, TGCT, UCS, LAML, ACC, and THYM. Conversely, it exhibited markedly lower expression in cancers, including BLCA, BRCA, CESC, CHOL, ESCA, HNSC, KICH, KIRC, KIRP, LUAD, LUSC, OV, PRAD, SKCM, STAD, THCA, and UCEC (Fig. 1a). Further investigations revealed that TNMD mRNA expression levels were highest in UCS, READ, COAD, SARC, and KIRC among all TCGA tumors (Fig. 1b). Utilizing resources from the HPA, we identified distinctive TNMD mRNA expression patterns across various cancer cell lines, with the highest levels detected in uterine cancer, testis cancer, and uncategorized cell lines (Fig. 1c). TNMD protein expression also varied significantly across tumor types, showing the most pronounced levels in CRC, lymphoma, thyroid cancer, liver cancer, and pancreatic cancer (Fig. 1d). Moreover, an analysis using the cBioPortal online tool revealed that the primary genetic alterations in TNMD across diverse TCGA cancer samples included missense mutations, amplifications, and deep deletions, with mutations being the most frequent DNA alteration observed (Fig. 1e).
TNMD shows high diagnostic efficacy and correlates with pathologic stages in multiple cancers
TNMD demonstrates substantial diagnostic efficacy across multiple malignancies. Specifically, in eight cancer types (CESC, BRCA, OSCC, KIRP, KICH, ESCC, THYM, and HNSC), TNMD’s area under the curve (AUC) spans from 0.867 to 0.981 (Figs. 2a-h). This study examined TNMD expression variations in 33 tumor types across T, N, and pathologic stages. The findings reveal significant correlation between TNMD expression and the pathologic T stage in BRCA, COAD, HNSC, and KICH (Figs. 2i-l), the pathologic N stage in BRCA, PRAD, STAD, and HNSC (Figs. 2m-p), and the overall pathologic stage in HNSC, KICH, OSCC, and COAD (Fig. 2q-t). Furthermore, TNMD expression correlates with the T stage in BLCA, KIRC, OSCC, and LUSC; the N stage in KICH, KIRC, OSCC, and LUSC; and the pathologic stage in BLCA, BRCA, KIRC, GBMLGG, PAAD, TGCT, LUSC, and THCA (Additional Fig. 1).
Higher TNMD expression correlates with improved survival outcomes in multiple cancers.
We employed the surv_cutpoint function from the survminer package to determine optimal cut-off values and evaluate TNMD’s prognostic significance across 33 tumor types in the TCGA database. TNMD expression was significantly associated with overall survival (OS) in BRCA (p = 0.02), GBM (p = 0.024), ACC (p = 0.021), READ (p = 0.001), COAD (p = 0.014), STAD (p = 0.005), KIRP (p = 0.019), KIRC (p = 0.001), and LGG (p = 0.003) (Fig. 3a-i). In READ, COAD, GBM, and KIRC, higher TNMD expression levels were correlated with improved prognosis compared to lower expression levels. In BRCA, elevated TNMD expression enhanced survival rates compared to those with lower expression during the initial 4000 days post-diagnosis; lower TNMD expression predicted superior long-term survival beyond this period. In the other tumors, lower TNMD expression consistently predicted superior survival.
TNMD interacts with key genes and influences critical pathways in pan-cancer
Using the STRING database, we identified 44 genes closely associated with TNMD and constructed a protein-protein interaction (PPI) network (Fig. 4a). The cytohubba plugin in Cytoscape identified ten central hub genes: COL1A1, COL1A2, CCN2, GAPDH, TGFβ1, MMP13, TGFβ3, DCN, TNMD, and RUNX2 (Fig. 4b). GO/KEGG enrichment analyses were performed on these TNMD-associated genes (Fig. 4c). Patients from the TCGA database were grouped by high and low TNMD expression levels and DEGs between these groups were used for hallmark enrichment analysis via GSEA. A bubble plot generated with the ggplot2 package in R visualized key findings, highlighting significant pathways: Xenobiotic Metabolism, UV Response Downregulation, Myogenesis, KRAS Signaling Upregulation, Interferon Gamma Response, G2M Checkpoint, Epithelial-Mesenchymal Transition, and Allograft Rejection (Fig. 4d).
TNMD expression associates with MSI and TMB in CRC
Our research explores TNMD’s correlation with MSI and TMB in COAD, where TNMD showed the strongest association with TMB and MSI in COAD compared to other cancers (Fig. 5a, b). An MSI score above 0.4 indicates MSI-H, while below 0.4 indicates MSS [13]. Most patients with COAD in TCGA are MSS (Fig. 5c). A correlation heatmap identified 30 genes closely linked to TNMD in MSI-H COAD (Fig. 5d), involved in UV response, TNF-alpha signaling via NF-kB, and KRAS signaling pathways, impacting the tumor immune environment (Fig. 5e). Another heatmap for patients with MSS highlighted 30 TNMD-associated genes (Fig. 5f), enriched in metabolic and hormonal pathways critical for immune cell function (Fig. 5g) [14–18]. Survival analysis revealed high TNMD expression correlated with better prognosis in MSI-H COAD, while lower expression was linked to improved outcomes in MSS (Fig. 5h, i). P-values slightly exceeded 0.05 due to small sample sizes in the MSI-H and MSS groups in TCGA. These findings underscore TNMD’s complex role in COAD, suggesting it influences tumor behavior and patient survival based on MSI status.
TNMD modulates immune cell infiltration and regulatory factors in CRC
Given the significant negative correlation between TNMD expression and MSI and TMB in COAD, we focused on this cancer type to examine TNMD’s role in modulating the immune landscape, which may impact the efficacy of emerging immunotherapies. Immune stroma scores were significantly higher in the MSI-H group than in the MSS group (Additional Fig. 2a). Immune infiltration assessment revealed substantially higher scores in the MSI-H group (Additional Fig. 2b ). Scatter plots correlated TNMD expression with increased levels of monocytes, resting NK cells, and CD4 + T cells in the MSI-High group (Fig.s 6a,b,c). In the MSS group, TNMD’s expression positively correlated with regulatory T cells (Tregs) (Fig. 6d), suggesting a poorer prognosis for patients with elevated TNMD expression (Fig. 5f). Validation using the GSE81986 dataset supported these findings, showing higher Treg levels in the TNMD-High group (p = 0.096) (Fig. 6e). This slightly higher p-value might relate to the smaller dataset size compared to TCGA. Immunofluorescence double staining on pathological sections from three patients with MSI-H CRC, targeting TNMD and the NK cell marker NCAM1. The top panel of Fig. 6f displays immunofluorescence images depicting both TNMD expression and NK cell abundance, while the lower panel reveals TNMD expression alongside reduced NK cell counts. These findings corroborate a positive correlation between TNMD expression and NK cell numbers, consistent with our initial bioinformatics predictions (Fig. 6g). The heatmap illustrates TNMD’s role in COAD immune regulation, showing significant negative correlations with key immune checkpoints (SIGLEC15, LAG3, PDCD1, CD274) and most chemokines, contrasted by positive associations with CCL20 and CXCL14 and an inverse relationship with CXCL16, along with varied interactions with other immune modulators (Fig. 6g).
Increased TNMD expression enhances chemoradiotherapy and immunotherapy outcomes in CRC.
We analyzed the relationship between TNMD expression and outcomes of chemoradiotherapy and immunotherapy in patients with COAD using the Genomics of Drug Sensitivity in Cancer database. Scatter plots revealed correlations between TNMD levels and IC50 values for various drugs: Vorinostat and VE-822 were more effective at higher TNMD levels, while Lapatinib and Bortezomib showed resistance (Fig. 7a). Further analysis detailed TNMD’s impact on drug responses. A significant positive correlation (R = 0.82, p < 0.001) was found between TNMD levels and the IC50 of Lapatinib in RECOAD cell lines, affecting the RTK pathway (Fig. 7b). Conversely, a negative correlation (R=-0.35, p = 0.02) was observed with VE-822, a DNA damage response pathway inhibitor (Fig. 7c). Radiotherapy sensitivity associated with TNMD expression was confirmed in the GSE35452 database, revealing improved outcomes at higher expression levels (p < 0.05) (Fig. 7d). Additionally, TNMD expression was examined before and after chemotherapy and immunotherapy in patients with MSS-type CRC using the GSE179351 database. Among five patients with paired data, only one with increased TNMD expression during treatment showed a partial response; the others experienced disease progression (Fig. 7e). Further analysis using TCGA data and TIDE revealed that higher TNMD expression correlated with better immunotherapy responses (Fig. 7f). In patients with MSS-type CRC, those with elevated TNMD expression had higher Merck18 scores, indicating effective immunotherapy responses (Fig. 7g). Validation through TIDE analysis in the GSE81986 database supported that patients with higher TNMD levels are more likely to benefit from immunotherapy (Additional Fig. 2c, d). These findings suggest that increased TNMD expression in patients with MSS-type CRC potentially enhances outcomes in both chemoradiotherapy and immunotherapy.
TNMD influences immune cell interactions in the CRC microenvironment
To explore the impact of TNMD on the cellular landscape of the CRC immune microenvironment, we performed single-cell RNA sequencing (scRNA-seq) on 23 tissue samples from patients with CRC. Batch effects across individual patients were corrected using the Harmony algorithm (Fig.s 8a, b). Post-correction, we identified 24 cell clusters (Additional Fig. 3a.) and annotated eight cell types SingleR package: epithelial cells, monocytes, B cells, CD4 + T cells, macrophages, CD8 + T cells, fibroblasts, and endothelial cells (Fig. 8c). Marker gene expression patterns validated these classifications (Fig. 8d). The robustness of these annotations was verified by analyzing upregulated genes and unique biological features specific to each type (Fig. 8d), revealing that TNMD expression is predominantly in epithelial cells (Fig. 8e). GO analysis linked TNMD’s roles in tumor cell invasion, metastasis, and inflammatory responses, particularly in immune response and inflammation regulation (Fig. 8f). KEGG analysis highlighted pathways affected by Human T-cell leukemia virus type 1 infection, emphasizing its impact on T-cell functionality and tumor immune evasion, particularly in steroid, lipid, and pyruvate metabolism (Fig. 8g). Comparing TNMD-positive and TNMD-negative tumor subpopulations showed stronger interactions between TNMD-positive tumor cells with fibroblasts and macrophages, mediated by distinct ligand-receptor pairs (Fig. 8h, i; Additional Fig. 3a). These findings underscore TNMD’s role in shaping the CRC immune microenvironment, highlighting its potential as a therapeutic target for modulating tumor immunity.
TNMD promotes LOVO cell migration and invasion in vitro and clinical validation
To validate the bioinformatics findings on TNMD expression, we conducted Western blot analyses on tumor and adjacent normal tissues from seven patients with CRC. Our findings revealed significantly higher TNMD levels in the tumor tissues (Fig. 9a). Further analyses of normal colon mucosal cells (NCM460) and three colon cancer cell lines (LOVO, HCT116, HT29) showed elevated TNMD levels, particularly in LOVO cells (Fig. 9b). Immunohistochemical staining of pathological slides from 23 patients with CRC confirmed higher TNMD expression in tumor tissues (Figs. 9c, d). To explore TNMD’s potential role in promoting tumor metastasis, as indicated by bioinformatic analysis, we conducted wound healing and Transwell invasion assays using LOVO cells. The expression of epithelial-mesenchymal transition (EMT)-related markers in LOVO cells was evaluated using Western blot analysis after Si-TNMD treatment. The wound healing assay demonstrated that TNMD knockdown significantly impaired LOVO cell migration (Figs. 9e, f), while the Transwell invasion assay confirmed a reduced invasion capacity following TNMD depletion (Figs. 9g, h). We validated TNMD knockout efficiency at both the mRNA and protein levels (Fig. 9i, j). Subsequent Western blot analyses post-knockdown revealed increased E-cadherin and decreased N-cadherin and Vimentin, consistent with EMT reversal (Fig. 9j). These results suggest that TNMD knockdown effectively inhibits migration and invasion in LOVO colon cancer cells.