Influence of Subcellular Localization on the Cytotoxicity of Targeted α-Therapy

Area of Science:

• Radiopharmaceutical therapy
• Molecular targeting
• Cancer treatment

Background:

• Targeted alpha-therapy (TAT) utilizes radiopharmaceuticals to target cancer cells.
• The impact of subcellular target localization on TAT's effectiveness remains unclear.
• Understanding localization effects is crucial for optimizing TAT efficacy.

Purpose of the Study:

• To investigate whether localizing alpha-emitters closer to DNA enhances cytotoxicity in targeted alpha-therapy.
• To determine the influence of subcellular localization on the cytotoxic effects of alpha-emitters.
• To guide the development of novel TAT agents by elucidating the role of target proximity to DNA.

Main Methods:

• Engineered human mesothelioma (I45) and ovarian adenocarcinoma (SKOV3) cell lines for subcellular protein localization (DNA, nucleus, cytoplasm, plasma membrane).
• Utilized [211At]At-trimethoprim (TMP) for targeted alpha-therapy, localizing it via engineered fusion proteins.
• Assessed in vitro cytotoxicity, performed subcellular dosimetry, and evaluated in vivo biodistribution and antitumor efficacy.

Main Results:

• [211At]At-TMP targeting DNA and nucleus demonstrated the highest in vitro cytotoxicity per decay.
• Cytotoxic advantage persisted after dose normalization, indicating a significant role for alpha-recoil effects.
• Plasma membrane targeting showed comparable cytotoxicity to cytoplasmic targeting, suggesting membrane damage contributes to cell death.
• In vivo studies showed similar responses for nuclear versus cytoplasmic targeting, supporting the relevance of subcellular localization for tumor treatment.

Conclusions:

• Alpha-emitter proximity to DNA significantly increases cytotoxicity, a key factor for future TAT drug development.
• This finding can improve the treatment of microscopic metastases and macroscopic disease, potentially enhancing clinical outcomes.
• Subcellular dosimetry is vital for predicting TAT efficacy at the cellular level, especially for small tumor clusters.