APOBEC3C-Mediated NF-κB Activation Enhances Clear Cell Renal Cell Carcinoma Progression

Academic Background

Clear cell renal cell carcinoma (CCRCC) is the most common subtype of kidney cancer, accounting for approximately 75% of all kidney cancer cases. Although immunotherapy has shown some potential in treating CCRCC, the treatment of metastatic CCRCC remains a significant challenge. Therefore, a deeper understanding of the molecular mechanisms underlying CCRCC progression is crucial for developing new therapeutic strategies. The nuclear factor kappa B (NF-κB) signaling pathway plays an important role in various cancers, particularly in inflammation and immune responses. However, the specific mechanisms of NF-κB in CCRCC have not been fully elucidated. Additionally, the role of RNA-binding proteins (RBPs) in post-transcriptional regulation has gradually gained attention, but their functional studies in CCRCC are still limited.

APOBEC3C (A3C) is a member of the APOBEC3 family, known for its cytidine deaminase activity, which can edit DNA and RNA, potentially inducing mutations. Although A3C plays an important role in inhibiting viral replication, its role in cancer remains unclear. This study aims to explore the function of A3C in CCRCC and its impact on the NF-κB signaling pathway, with the goal of providing new therapeutic targets for CCRCC.

Source of the Paper

This paper was co-authored by Nora Hase, Danny Misiak, Helge Taubert, Stefan Hüttelmaier, Michael Gekle, and Marcel Köhn. The authors are affiliated with the Medical Faculty of Martin Luther University Halle-Wittenberg, the Institute of Molecular Medicine, the Department of Urology and Pediatric Urology, and the Institute of Physiology in Germany. The paper was published online on August 26, 2024, in the journal Molecular Oncology, with the DOI 10.¹⁰⁰²⁄₁₈₇₈-0261.13721.

Research Process and Results

1. Expression of A3C in CCRCC and Its Clinical Significance

The study first analyzed kidney cancer data from the TCGA database and found that A3C was significantly upregulated in CCRCC tissues (p < 0.0001). Further clinical data analysis showed that high expression of A3C was associated with disease progression and poor prognosis (p = 0.0001). The study also validated the high expression of A3C in CCRCC tissues and cell lines through RNA sequencing and Western blot.

2. Impact of A3C Knockout on the NF-κB Signaling Pathway

To explore the function of A3C in CCRCC, the research team used CRISPR/Cas9 technology to knockout the A3C gene in the 786-O cell line and analyzed gene expression changes through RNA sequencing. The results showed that A3C knockout led to significant downregulation of 645 genes and upregulation of 656 genes. Gene set enrichment analysis (GSEA) indicated that A3C knockout significantly affected the expression of genes related to the NF-κB signaling pathway.

3. Interaction Between A3C and NF-κB Signaling Pathway Regulators

Through RNA immunoprecipitation (RIP) experiments, the research team found that A3C binds to the mRNAs of multiple NF-κB signaling pathway regulators, including CDK6 and IKBKA. Further experiments showed that A3C knockout significantly reduced the mRNA and protein levels of these regulators, thereby affecting the nuclear translocation and activity of NF-κB subunits.

4. Role of A3C in Tumor Cell Stress Response

The study also found that A3C expression was upregulated under stress conditions such as increased tumor cell density, low attachment conditions, and serum deprivation. A3C knockout significantly reduced the survival rate of tumor cells under stress conditions, while re-expression of A3C restored cell stress tolerance. Additionally, 3D spheroid culture and mouse xenograft experiments demonstrated that A3C knockout significantly inhibited tumor growth.

Conclusions and Significance

This study is the first to reveal the important role of A3C in CCRCC, showing that A3C promotes tumor cell survival and growth by regulating the NF-κB signaling pathway. The high expression of A3C is associated with poor prognosis in CCRCC, suggesting that it may serve as a potential therapeutic target. Furthermore, the study found that A3C plays a key role in tumor cell stress responses, further emphasizing its importance in tumor progression.

Research Highlights

1. High Expression of A3C is Associated with Poor Prognosis in CCRCC: Through clinical data analysis, the study for the first time linked high expression of A3C with disease progression and poor prognosis in CCRCC.
2. A3C Regulates the NF-κB Signaling Pathway: The study revealed the molecular mechanism by which A3C enhances NF-κB activity by binding and stabilizing the mRNAs of NF-κB signaling pathway regulators.
3. Role of A3C in Tumor Cell Stress Response: The study found that A3C expression is upregulated under stress conditions and plays a critical role in maintaining cell survival and tumor growth.

Other Valuable Information

The study also explored the potential application value of A3C in CCRCC treatment. Preliminary experiments showed that A3C knockout enhanced the sensitivity of CCRCC cells to tyrosine kinase inhibitors (such as pazopanib and sunitinib), suggesting that A3C inhibitors may be used in combination with existing treatment regimens to improve therapeutic efficacy.

This study provides new insights into the molecular mechanisms of CCRCC and lays a theoretical foundation for developing therapeutic strategies targeting A3C.