The Role and Mechanism of STEAP3 in Cervical Cancer

Background

Cervical cancer (CC) is the fourth most common cancer among women globally, with approximately 600,000 new cases and 300,000 deaths annually. Although the five-year survival rate for early-stage cervical cancer patients exceeds 85% through treatments such as surgery, radiotherapy, and chemotherapy, the prognosis for patients with advanced, recurrent, or metastatic cervical cancer remains poor, with a five-year survival rate of only 16.5%. Therefore, identifying more effective therapeutic targets is crucial for improving the prognosis of cervical cancer patients.

In recent years, immunotherapy has made significant progress in cervical cancer treatment, particularly the application of anti-PD-1 (Programmed Death Receptor 1) therapy. However, the positive rate of PD-L1 (Programmed Death Ligand 1) is only 58.1%, indicating that a considerable number of patients do not benefit from it. Consequently, researchers have begun to focus on other potential molecular targets, especially genes related to tumor proliferation and metastasis.

STEAP3 (Six-Transmembrane Epithelial Antigen of Prostate 3) is an essential member of the STEAP family of proteins, known to promote tumor proliferation and metastasis in various cancers. However, the specific role of STEAP3 in cervical cancer remains unclear. This study aims to explore the function of STEAP3 in cervical cancer and its underlying mechanisms, providing new therapeutic targets for cervical cancer treatment.

Source of the Paper

This paper was co-authored by Zouyu Zhao, Panpan Yu, Yan Wang, and others, affiliated with the Department of Obstetrics and Gynecology, First Affiliated Hospital of Shihezi University, and the Department of Physiology, School of Medicine, Shihezi University. The paper was published in 2024 in the journal Cancer & Metabolism, titled “Silencing of STEAP3 suppresses cervical cancer cell proliferation and migration via JAK/STAT3 signaling pathway.”

Research Process and Results

1. Expression of STEAP3 in Cervical Cancer and Its Relationship with Prognosis

Experimental Process

The researchers first detected the expression level of STEAP3 protein in 111 cervical cancer tissues and 29 normal cervical tissues using immunohistochemistry (IHC). Additionally, they analyzed the mRNA expression level of STEAP3 in cervical cancer using the TCGA, GSE7803, and GENT2 databases. Furthermore, the relationship between STEAP3 expression and patient prognosis was evaluated using Kaplan-Meier survival analysis.

Results

The study found that STEAP3 expression was significantly higher in cervical cancer tissues compared to normal tissues, and high STEAP3 expression was associated with poor prognosis. Specifically, 58.6% of cervical cancer samples showed high STEAP3 expression, while only 10.3% of normal tissues exhibited high expression. Survival analysis indicated that patients with high STEAP3 expression had significantly lower overall survival (OS) and progression-free survival (PFS).

2. DNA Methylation Analysis of STEAP3

Experimental Process

To explore the mechanism of STEAP3 upregulation, the researchers analyzed the DNA methylation level of the STEAP3 promoter region using the Ualcan database and evaluated the relationship between the methylation status of CpG sites in the STEAP3 gene and patient prognosis using the MethSurv tool. Additionally, reduced representation bisulfite sequencing (RRBS) was used to detect DNA methylation levels in cervical cancer tissues and adjacent normal tissues.

Results

The results showed that the DNA methylation level of STEAP3 in cervical cancer tissues was significantly lower than in normal tissues, and the methylation levels of multiple CpG sites were associated with patient prognosis. Specifically, the methylation levels of 12 CpG sites were significantly reduced in cervical cancer, with 6 sites associated with poor prognosis and 4 sites associated with better prognosis.

3. The Impact of STEAP3 on Cervical Cancer Cell Proliferation, Migration, and Invasion

Experimental Process

The researchers knocked down STEAP3 expression in cervical cancer cell lines (Hela and Siha) using lentiviral infection and assessed the effects of STEAP3 knockdown on cell proliferation, migration, and invasion through CCK-8 assays, EdU assays, Transwell assays, and wound healing assays. Additionally, the expression levels of epithelial-mesenchymal transition (EMT)-related proteins were detected using Western blot.

Results

STEAP3 knockdown significantly inhibited the proliferation, migration, and invasion of cervical cancer cells. Western blot results showed that STEAP3 knockdown reduced the expression of N-cadherin and Vimentin while increasing E-cadherin expression, indicating that STEAP3 promotes cervical cancer metastasis by regulating the EMT process.

4. STEAP3 Regulates Cervical Cancer Progression via the JAK/STAT3 Signaling Pathway

Experimental Process

To further explore the mechanism of STEAP3, the researchers analyzed gene expression changes in cervical cancer cells after STEAP3 knockdown using RNA sequencing. KEGG pathway enrichment analysis revealed significant enrichment of the JAK/STAT3 signaling pathway. Subsequently, the phosphorylation levels of JAK2 and STAT3 were detected using Western blot, and functional validation was performed using the STAT3 activator Colivelin and the JAK2/STAT3 inhibitor WP1066.

Results

RNA sequencing results showed that STEAP3 knockdown led to the upregulation of 151 genes and the downregulation of 91 genes, with KEGG analysis indicating significant enrichment of the JAK/STAT3 signaling pathway. Western blot results demonstrated that STEAP3 knockdown significantly reduced the phosphorylation levels of JAK2 and STAT3. Colivelin treatment reversed the inhibitory effects of STEAP3 knockdown on cell proliferation, migration, and EMT-related protein expression, while WP1066 further suppressed these processes.

5. STEAP3 and Cervical Cancer Cell Resistance to Oxaliplatin

Experimental Process

The researchers evaluated the effect of STEAP3 knockdown on the sensitivity of cervical cancer cells to oxaliplatin using CCK-8 assays.

Results

STEAP3 knockdown significantly increased the sensitivity of cervical cancer cells to oxaliplatin, suggesting that STEAP3 may influence cervical cancer treatment outcomes by regulating chemoresistance.

Conclusion and Significance

This study found that STEAP3 is highly expressed in cervical cancer and is associated with poor prognosis. STEAP3 promotes the proliferation, migration, and invasion of cervical cancer cells by regulating the JAK/STAT3 signaling pathway and may facilitate tumor metastasis by modulating the EMT process. Additionally, STEAP3 affects the sensitivity of cervical cancer cells to oxaliplatin. These findings suggest that STEAP3 may serve as a potential therapeutic target for cervical cancer, particularly for patients with advanced or recurrent disease.

Research Highlights

1. High STEAP3 Expression is Associated with Poor Prognosis in Cervical Cancer: This study systematically explored the expression of STEAP3 in cervical cancer and its relationship with prognosis for the first time, providing a new biomarker for cervical cancer prognosis assessment.
2. STEAP3 Regulates Cervical Cancer Progression via the JAK/STAT3 Signaling Pathway: The study revealed that STEAP3 promotes cervical cancer cell proliferation and metastasis by activating the JAK/STAT3 signaling pathway, offering new molecular insights for cervical cancer treatment.
3. STEAP3 Influences Cervical Cancer Cell Sensitivity to Chemotherapy: The study found that STEAP3 knockdown increased the sensitivity of cervical cancer cells to oxaliplatin, suggesting that STEAP3 may be a potential target for overcoming chemoresistance.