This research found that the mRNA levels of cytoskeleton-related genes in bladder cancer versus normal tissues and identified 546 differentially expressed genes. There were notable OS and PFS variations between the two clusters that were produced as a result of the DEGs-based NMF study. In order to better evaluate the predictive power of these cytoskeleton-associated genes, We built a prediction model based on 11 cytoskeleton-associated genes by Cox univariate analysis and regression analysis using LASSO and Cox to predict the accurate survival of BLCA patients based on these results. Columnar line plots were constructed to predict survival by combining significant clinical data and risk scores and then verified that the feature performed well in the external dataset. Enrichment analysis performed using the Generalized Method of Squares (GSEA) revealed that DEGs between the HRGs and LRGs were associated with cell adhesion pathways. Immune cell infiltration analysis and differential analysis was performed between HRGs and LRGs, then revealed generally elevated levels of infiltrating immune cells in HRGs compared to the LRGs.
More than 90% of cancer-related fatalities are caused by the metastasis, or spread, of tumor cells to other parts of the body(8). In recent years, numerous studies have documented that the dynamic remodeling of the actin cytoskeleton has a predominant impact on cancer development and metastasis(9–11). The research carried out by Corry J. and colleagues showed that several members of the Rho family play a role in the invasion of cancer cells and metastasis via the regulation of the actin cytoskeleton(12). Izdebska M et al. discovered that actin and ABPs (actin-binding proteins) are engaged in cancer cells throughout carcinogenesis(13). The spectraplakin family includes microtubule actin cross-linking factor 1 (MACF1), has a role in metastatic invasion and other processes where cytoskeleton structure plays a crucial role in tumor growth in different types of human malignancies(14). In addition, several research on the regulation of the cytoskeleton to influence the advancement of bladder carcinogenesis have come to light in recent years. For example, transcription factor ATF3 reduces bladder cancer cells' ability to move and spread through the mechanism of cytoskeleton regulation by actin-binding protein GSN(15). Actin cytoskeleton and PI3K/Akt pathway downregulation prevent the growth and progression of bladder cancer(16). Potentially useful for both diagnosis and prognosis, transgelin is a new biomarker for BLCA, as it is implicated in the actin cytoskeleton control of BLCA(17). Research like this suggests that a better knowledge of the actin cytoskeleton's movements will aid in the creation of tailored medicines that halt the growth and spread of cancer cells. However, a risk profile that is based on the expression patterns of genes associated with the cytoskeleton has not yet been created for bladder cancer. Thus, we combined cytoskeleton-related gene expression profiles to identify eleven gene signatures, which we used to construct a predictive model with prognostic significance based on the transcriptome data of 411 tumors and 19 nearby normal samples from the TCGA database.
Notably in this study, most of these 11 cytoskeleton-related DEGs have been documented to be strongly associated with disease progression and metastasis. Tumors such as cervical, breast, and lung adenocarcinoma all benefit from Rho GTPase-activating protein's (6ARHGAP6) tumor-suppressing abilities, as it induces cell cycle arrest and death in these malignancies(18). The epithelial membrane protein 1 (EMP1) gene is critical in controlling cell proliferation and metastasis in many different types of cancer and is overexpressed in many malignancies(19, 20). Homologous frame C8 (HOXC8) is a transcription factor reported to be overexpressed in various tumors and boosts the development of tumor cells and the spread of metastases both in vitro and in vivo(21, 22). High expression of MLLT11 increases bladder cancer cell proliferation and tumor growth(23). Overexpression of P4HB may promote the progression of malignant tumors, including gastric cancer, renal clear cell carcinoma, and bladder cancer, and the expression of P4HB mRNA possesses a notably high level in advanced pathological T-stage(24). PDGFD messenger RNA expression levels correlate with disease severity (i.e., high T-stage, positive lymph node status, and reduced survival)(25). Rac3 is a GTPase that belongs to the Rho family and is regulated by C3 botulinum toxin. Many cellular processes, such as cell migration, adhesion, mitosis, and kinase activity, are regulated by Rho and Rac GTPases, which drive cancer growth(26). In summary, six genes in the prognostic model (EMP1, HOXC8, MLLT11, P4HB, PDGFD, and Rac3) were shown to be promoters of multiple cancers and may perform the same tumor cell migration-promoting and invasive effects in patients with bladder cancer.
In GSEA analysis, “extracellular matrix (ECM)-receptor interactions”, “cytokine-cytokine interaction receptors”, “adherent spots”, “cancer pathways”, and “SLE” were identified as the top 5 enriched pathways. ECM, a key component involved in cancer cell invasion, regulates many cellular functions during cancer progression, including proliferation, migration, invasion, and protein synthesis(27). Recent research by Zhu et al. demonstrated that ECM-receptor interaction signaling pathway activation of collagen genes can drive NMIBC to MIBC progression(28). Our study found that the HRGs was significantly enriched in the ECM-receptor interaction signaling pathway according to the constructed prognostic model, suggesting that cytoskeleton-related genes are affected by the ECM-receptor interaction signaling pathway.
In addition, we investigated the invasion of immune cells and the immune cells themselves to investigate the tumor immune microenvironment. According to the findings of this research, the prognostic index has a significant and favorable correlation with CD8 T cells, monocyte lineage, endothelial cells, and fibroblasts. This result suggests that higher levels of infiltration of these four immune cells may be observed in high-risk patients. However, among these four immune cells, fibroblasts showed the highest correlation with the prognostic index. The tumor microenvironment (TME) includes fibroblasts, which can facilitate tumor cell migration by acting as a scaffold and can also increase the tumor's resistance to adverse conditions. Normal fibroblasts transform into cancer-associated fibroblasts (CAFs) in response to either exogenous or endogenous stimuli (29). CAFs have multiple functions, including stromal deposition and remodeling, extensive mutual signaling interactions with cancer cells, and crosstalk with infiltrating leukocytes(30). Recent research has confirmed the cancer-promoting role of CAFs in bladder cancer by showing that CALD1, a critical gene linked with cancer-associated fibroblasts, can enhance bladder cancer growth through modifying the tumor microenvironment(31). Therefore, cancer-associated fibroblasts and related genes can be used as promising prognostic indicators and potential targets for bladder cancer immunotherapy.
Overall, we created an innovative prognostic model strongly linked to the OS of bladder cancer patients by investigating the biological function and prognostic significance of genes involved in the cytoskeleton. This study's key drawback is the limited number of clinical samples used for validation, which calls for additional research. We also have to conduct experimental tests to confirm this theory. Our results imply that prognostic indicators based on cytoskeleton-related genes may be a reliable predictive tool for the prognosis of patients with bladder cancer, despite the limitations that still remain.