Signal Transduction and Targeted Therapy | Hypoxia-induced VEGF secretion mediates resistance to bispecific T-cell engagers

This study reveals the critical role of hypoxia-induced VEGF secretion in mediating resistance to bispecific T-cell engagers (BITEs) and proposes a combination therapeutic strategy with VEGF inhibitors. The research provides new insights into the resistance mechanisms and identifies potential targets for optimizing ovarian cancer immunotherapy.

 

Literature Overview

This article, titled 'Hypoxia-induced VEGF secretion promotes resistance to bispecific T-cell engagers', published in the journal 'Signal Transduction and Targeted Therapy', systematically reviews and summarizes the resistance mechanisms of bispecific T-cell engagers (BITEs) in ovarian cancer. The study found that hypoxia can induce VEGF secretion, leading to epithelial-mesenchymal transition (EMT) and downregulation of MUC16/CA125 expression on tumor cells, which affects the efficacy of BITEs. It also demonstrated that VEGF inhibitors (such as bevacizumab) can restore BITE-mediated cytotoxic effects in hypoxic conditions. These findings offer new directions for developing treatment strategies for drug-resistant ovarian cancer.

Background Knowledge

Bispecific T-cell engagers (BITEs) are an emerging immunotherapeutic strategy that targets tumor-associated antigens (such as MUC16/CA125) and activates polyclonal T cells to attack tumors. However, their efficacy in solid tumors is limited by resistance mechanisms. High-grade serous ovarian cancer (HGSOC) is a highly aggressive tumor that frequently develops resistance to conventional therapies upon recurrence. MUC16/CA125 is highly expressed in HGSOC and represents a potential therapeutic target. Although BITEs have been approved for hematologic malignancies, their application in solid tumors faces challenges, including hypoxic tumor microenvironment, antigen downregulation, and T cell functional suppression. This study, based on samples from patients with clinical disease progression, investigates the role of hypoxia and VEGF secretion in BITE resistance, providing a mechanistic basis for overcoming resistance in solid tumors.

 

 

Research Methods and Experiments

The research team collected serum, peripheral blood mononuclear cells (PBMCs), and ascites samples from ovarian cancer patients who experienced disease progression after receiving MUC16-targeted BITE therapy. Using techniques such as Western blot, ELISA, and flow cytometry, they analyzed MUC16/CA125 expression levels, epithelial-mesenchymal transition (EMT) marker changes, and VEGF secretion. Furthermore, CRISPR/Cas9 technology was employed to knockout MUC16/CA125 and VEGF genes to verify their role in hypoxia-induced resistance. The study also assessed the impact of proteasome inhibitors and VEGF inhibitors on MUC16/CA125 expression and BITE-mediated cytotoxicity.

Key Conclusions and Perspectives

• Hypoxic tumor microenvironment induces VEGF secretion, which promotes downregulation of MUC16/CA125 expression, ultimately reducing BITE efficacy.
• Ovarian cancer patients in progressive stages exhibit reduced MUC16/CA125 expression and increased EMT markers such as N-cadherin and vimentin.
• Patients' serum shows elevated levels of inflammatory cytokines (e.g., IL18, IFN-α, IL8, CCL5) and immunosuppressive factors (e.g., IL4, IL5, IL10).
• OVCAR3 and OVCAR4 cells cultured under hypoxic conditions show reduced CA125 expression and adopt an EMT phenotype.
• CRISPR/Cas9 knockout of MUC16/CA125 in OVCAR3 and OVCAR4 cells enhances migration and invasion and leads to resistance to BITEs.
• VEGF secretion is significantly increased in hypoxic cells, and VEGF levels negatively correlate with BITE cytotoxicity.
• Bevacizumab (anti-VEGF antibody) restores BITE-mediated cytotoxicity under hypoxic conditions, whereas anti-PD-1 treatment does not.
• Proteasome inhibitors (e.g., MG132) partially restore MUC16/CA125 expression but do not fully recover BITE activity.
• Hypoxia-induced HIF-1α does not directly regulate MUC16/CA125 downregulation, suggesting the involvement of other mechanisms.
• Patient-derived PBMCs remain effective in killing tumor cells in vitro, indicating that resistance is primarily driven by the tumor microenvironment.

Research Significance and Prospects

This study highlights the critical role of the hypoxic tumor microenvironment in mediating BITE resistance, particularly through VEGF secretion affecting T cell function and cytotoxicity. These findings provide a rationale for novel combination strategies in ovarian cancer immunotherapy, such as using anti-VEGF therapy to restore BITE efficacy. Additionally, the study underscores the importance of hypoxia-inducible factors and the inflammatory microenvironment in resistance mechanisms, offering new directions for future research. Targeting VEGF or modulating the hypoxic tumor microenvironment may enhance BITE efficacy in solid tumors and provide theoretical support for the design of clinical trials.

 

 

Conclusion

In summary, this study systematically demonstrates that the hypoxic tumor microenvironment induces VEGF secretion, which leads to downregulation of MUC16/CA125 expression and consequently results in resistance to bispecific T-cell engagers (BITEs). Using CRISPR/Cas9 knockout and VEGF inhibition experiments, the research team further confirmed the central role of VEGF in mediating resistance. These findings provide new insights into combination immunotherapeutic strategies for solid tumors, such as the addition of VEGF inhibitors to BITE therapy to restore anti-tumor immune responses. Future studies should assess the impact of hypoxic microenvironment on resistance in other solid tumors and explore personalized therapeutic strategies targeting hypoxia or VEGF signaling to improve BITE efficacy in solid tumor treatment.

 

Mengyao Xu, Syem K Barakzai, Raj Kumar, David R Spriggs, and Oladapo O Yeku. Hypoxia induced VEGF secretion promotes resistance to bispecific T-cell engagers. Signal Transduction and Targeted Therapy.