A thorough understanding of the mechanisms underlying chemotherapy sensitivity is crucial for enhancing outcomes in bladder cancer. Nevertheless, there remains a gap in comprehensive research on hub genes related to chemotherapy resistance. Therefore, we systematically investigated the biomarkers and potential mechanisms of chemotherapy resistance in bladder cancer patients through bioinformatics analyses.
In this study, DEGs between chemo-resistant and chemo-sensitive bladder cancer patients were identified using the limma package in the Gene Expression Omnibus (GEO) dataset GSE77883. A total of 4042 up-regulated and 1355 down-regulated genes were identified. Random survival forest analysis of the DEGs from The Cancer Genome Atlas Bladder Cancer (TCGA-BC) cohort revealed six genes that met the threshold, namely RNF19A, PCGF5, UNC5CL, CCDC146, APBA3, and NDUF A3. RNF19A, PCGF5, UNC5CL, and CCDC146 were found to be significantly associated with the survival of bladder cancer patients and identified as hub genes in the study. GSVA and GSEA analysis showed that RNF19A, PCGF5, UNC5CL, and CCDC146 have varying expression levels that impact cancer-related signaling pathways. These genes were also linked to tumor immune infiltration, immune-related genes, sensitivity to chemotherapeutic drugs, and the expression of disease-related genes such as APC and EGFR. A nomogram was created to predict bladder cancer outcomes based on these genes and clinical characteristics. The nomogram accurately predicted overall survival in bladder cancer patients. Additionally, significant binding motifs and transcription factors for hub genes were identified using RcisTarget. We developed an mRNA-miRNA regulatory network and utilized single cell analysis to investigate the cellular heterogeneity of hub gene expression.
The gene RNF19A, also referred to as RNF144B, functions as an E3 ubiquitin-protein ligase that plays a role in regulating multiple cellular processes such as protein degradation, DNA damage response, and cell cycle regulation.14,15 Numerous studies have indicated that aberrant expression of RNF19A is linked to tumorigenesis and treatment outcomes in various cancer types.16–18 In recent years, scholarly attention has been directed towards elucidating the role of RNF19A in conferring resistance to chemotherapy. Research findings have demonstrated a correlation between elevated RNF19A levels and resistance to a range of chemotherapeutic agents, including taxanes, platinum-based compounds, and tyrosine kinase inhibitors.19 RNF19A facilitates chemoresistance through various mechanisms, such as promoting drug efflux, suppressing apoptosis, and activating DNA repair pathways.18 Given its significant impact on tumor prognosis and chemoresistance, RNF19A is increasingly recognized as a promising target for therapeutic intervention. To the best of our knowledge, there has been no investigation into the role of RNF19A in the development of chemo-resistance in bladder cancer.
The gene PCGF5, also referred to as RNF110, is a member of the polycomb group (PcG) protein family, which plays a role in epigenetic regulation and transcriptional repression.20 Previous research has revealed PCGF5 promoted NKX6-3 activation in B-cell development and lymphomas.21 Previous research has also reported that PCGF5 repressed transcription of NKL homeobox gene MSX1 in T-ALL cells.22 The gene UNC5CL, alternatively referred to as PPP1R74, is a member of the UNC5 family of netrin receptors and plays a role in axonal guidance and neuronal development.23 A recent study showed that UNC5CL is recognized as a prognostic indicator and gemcitabine-resistance genes in bladder cancer.22 Three genome-wide association studies in Chinese populations identified variants at UNC5CL as new OSCC susceptibility loci.24 Accordingly, the gene CCDC146, also known as KIAA0427, is a member of the coiled-coil domain-containing protein family and is involved in a variety of cellular processes, such as cellular adhesion and signal transduction.25 CCDC146 was a potential therapeutic strategy for lymph node metastasis of breast cancer.26 CCDC146 has also showed good diagnostic potential and clinical relevance as molecular markers for clinical diagnosis, treatment and prognosis of thyroid cancer.27 Nonetheless, the present study was the first to recognize these hub genes as a prognostic indicator in bladder cancer.
Evidence has demonstrated that the effectiveness of chemotherapy is not solely attributed to its direct cytotoxic effects, but also relies on the concurrent stimulation of anti-tumor immune responses. Furthermore, previous study revealed significant variations in the responses to anticancer drugs among closely related cells within the same tumor.28 The hub genes identified in our study were found to have strong correlations with immune infiltrating cells and immune-related genes in bladder cancer. Single cell analysis demonstrated differential expression levels of the hub genes across various cell types. Additionally, coexpression was observed between the hub genes and TP53, a commonly mutated gene. The TP53 mutation, along with its related pathways, may act as driver mutations in bladder cancer, thereby promoting disease progression and influencing cancer prognosis and therapeutic strategy.29BMC These findings suggest that immunity plays a significant role in chemoresistance and may elucidate the underlying mechanisms of chemoresistance and the potential efficacy of combining chemotherapy with immunotherapy in bladder cancer.
Nevertheless, it is important to acknowledge the limitations and deficiencies present in our current research efforts. Initially, the sample sizes obtained from the TCGA and GEO databases were limited in scope. Additionally, the outcomes lacked experimental verifications both in vivo and in vitro. Notwithstanding these limitations, the preliminary investigation still yielded significant and constructive insights. Subsequent research endeavors will aim to substantiate the involvement of the key genes RNF19A, PCGF5, UNC5CL, and CCDC146 in the development of chemoresistance in bladder cancer through a series of comprehensive experiments. The study will examine the impact of the overexpression and knockdown of RNF19A, PCGF5, UNC5CL, and CCDC146 on various cellular processes such as cell cycle distribution, proliferation, colony-forming ability, apoptosis, and invasiveness following chemotherapy in human bladder cancer cell lines and in vivo models. Additionally, the investigation will encompass an analysis of the relevant signaling pathways and the regulatory network involving the transcription factor and disease‑related genes.