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Updated: Jul 11, 2026
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Published on: November 1, 2021
Imaging and modulating antisense microdistribution in solid human xenograft tumor models
Joseph D Mocanu1, Kenneth W Yip, Julia Skliarenko
1Division of Applied Molecular Oncology, Ontario Cancer Institute, Canada.
Purpose:
The tumor microenvironment is complex and heterogeneous, populated by tortuous irregular vasculature, hypoxic cells, and necrotic regions. These factors can all contribute to the biodistribution difficulties encountered by most cancer therapeutic agents. Antisense oligodeoxynucleotides (ASO) are a class of therapeutics where limited information is available about their distribution within a solid tumor environment.
Experimental Design:
To assess ASO distribution, a fluorescein-labeled phosphorothionated ASO based on the G3139 mismatch control was injected systemically (i.v.) into tumor-bearing severe combined immunodeficient mice. Hoechst 33342 was injected i.v. to visualize active vasculature. Unstained sections were imaged through tiled fluorescence stereomicroscopy and then quantitated using novel algorithms. Tumor sections from four human tumor models were examined (CaSki, DU-145, C666-1, and C15) for hypoxia, apoptosis/necrosis, and morphology.
Results:
For all four tumors, ASO accumulated within regions of hypoxia, necrosis, and apoptosis. Scatter plots of ASO versus active vasculature generated for each individual tumor revealed a consistent pattern of distribution of the ASO within each model. In C666-1 xenografts, the slopes of these scatter plots were significantly reduced from 0.41 to 0.16 when pretreated with the antivascular agent ZD6126 48 h before ASO injection. This was accompanied by the formation of large disseminated necrotic regions in the tumor, along with a 13.1 mmHg reduction in interstitial fluid pressure.
Conclusions:
These data suggest the possibility that these algorithms might offer a generalizable and objective methodology to describe the distribution of molecular therapeutic agents within a tumor microenvironment and to quantitatively assess distribution changes in response to combination therapies.
Insights
Antisense oligodeoxynucleotides (ASO) accumulate in hypoxic and necrotic tumor regions. Novel algorithms quantify ASO distribution, showing reduced accumulation in vasculature after antivascular therapy, aiding combination therapy assessment.
Area of Science:
- Oncology
- Pharmacology
- Biomedical Engineering
Background:
- The tumor microenvironment (TME) presents significant challenges for cancer therapeutics due to its heterogeneity, including irregular vasculature, hypoxia, and necrosis.
- Understanding the biodistribution of therapeutic agents within the TME is crucial for optimizing treatment efficacy.
- Antisense oligodeoxynucleotides (ASO) are a promising class of therapeutics, but their distribution in solid tumors remains poorly characterized.
Purpose of the Study:
- To investigate the distribution patterns of systemically administered antisense oligodeoxynucleotides (ASO) within solid tumors.
- To evaluate the utility of novel quantitative algorithms for assessing ASO biodistribution in relation to tumor microenvironment characteristics.
- To examine the impact of antivascular therapy on ASO distribution within the TME.
Main Methods:
- Fluorescein-labeled ASO and Hoechst 33342 were administered intravenously to tumor-bearing mice.
- Tiled fluorescence stereomicroscopy and novel quantification algorithms were employed to analyze ASO distribution in tumor sections.
- Tumor sections from four human xenograft models were analyzed for hypoxia, apoptosis/necrosis, and vascularization.
Main Results:
- ASO consistently accumulated in hypoxic, necrotic, and apoptotic regions across all four tumor models.
- A distinct pattern of ASO distribution relative to active vasculature was observed in each tumor model.
- Pretreatment with the antivascular agent ZD6126 significantly reduced ASO accumulation in the vasculature of C666-1 xenografts, correlating with increased necrosis and reduced interstitial fluid pressure.
Conclusions:
- The developed algorithms provide a generalizable and objective method for characterizing molecular therapeutic agent distribution within the TME.
- Quantitative assessment of ASO distribution can be effectively achieved using these algorithms.
- These methods can be utilized to evaluate the effects of combination therapies, such as antivascular agents, on drug delivery within tumors.
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