Solid tumor therapy by selectively targeting stromal endothelial cells

Area of Science:

• Oncology
• Molecular Biology
• Biotechnology

Background:

• Engineered anthrax lethal toxin proteins show promise in suppressing solid tumor growth.
• Toxins utilize tumor endothelium marker-8 and capillary morphogenesis protein-2 (CMG2) receptors, often found on tumor endothelium.
• Previous studies suggested these receptors are crucial for tumor growth.

Purpose of the Study:

• To investigate the mechanism of engineered toxin efficacy against solid tumors.
• To determine the role of CMG2 and tumor endothelium in toxin-mediated tumor suppression.
• To evaluate the potential for repeated toxin administration for durable antitumor effects.

Main Methods:

• Utilized tissue-specific loss-of-function and gain-of-function genetic models in mice.
• Assessed toxin sensitivity of tumor cells in vitro and in vivo.
• Investigated the role of CMG2 expression on host-derived tumor endothelial cells.
• Administered an immunosuppressive regimen to allow for multiple toxin dosages.

Main Results:

• Neither tumor endothelium marker-8 nor CMG2 is required for tumor growth.
• Tumor cells resistant in vitro become highly sensitive to toxins when implanted in vivo.
• In vivo toxin sensitivity is dependent on CMG2 expression on host-derived tumor endothelial cells.
• Engineered toxins suppressed the proliferation of isolated tumor endothelial cells.
• Multiple toxin dosages, facilitated by immunosuppression, produced a strong and durable antitumor effect.

Conclusions:

• Engineered anthrax toxins specifically target tumor endothelial cells via CMG2, leading to tumor growth suppression.
• The in vivo sensitivity of tumor cells is mediated by host endothelial CMG2.
• A strategy of repeated toxin administration with immunosuppression can achieve durable antitumor effects.
• This approach holds potential for treating a wide range of solid tumors.