Related Experiment Video
Updated: Jul 3, 2026
Quantifying Antibody-Dependent Cellular Cytotoxicity in a Tumor Spheroid Model: Application for Drug Discovery
Published on: April 26, 2024
Effect of antigen turnover rate and expression level on antibody penetration into tumor spheroids
Margaret E Ackerman1, David Pawlowski, K Dane Wittrup
1Department of Biology, Massachusetts Institute of Technology Building E19-551, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
Abstract:
Poor tissue penetration is a significant obstacle to the development of successful antibody drugs for immunotherapy of solid tumors, and diverse alterations to the properties of antibody drugs have been made to improve penetration and homogeneity of exposure. However, in addition to properties of the antibody drug, mathematical models of antibody transport predict that the antigen expression level and turnover rate significantly influence penetration. As intrinsic antigen properties are likely to be difficult to modify, they may set inherent limits to penetration. Accordingly, in this study, we assess their contribution by evaluating the distance to which antibodies penetrate spheroids when these antigen properties are systematically varied. Additionally, the penetration profiles of antibodies against carcinoembryonic antigen and A33, two targets of clinical interest, are compared. The results agree well with the quantitative predictions of the model and show that localizing antibody to distal regions of tumors is best achieved by selecting slowly internalized targets that are not expressed above the level necessary for recruiting a toxic dose of therapeutic. Each antibody-bound antigen molecule that is turned over or present in excess incurs a real cost in terms of penetration depth-a limiting factor in the development of effective therapies for treating solid tumors.
Insights
Antibody drug penetration into solid tumors is limited by antigen properties. Selecting slowly internalized targets optimizes antibody drug delivery for effective cancer immunotherapy.
Area of Science:
- Oncology
- Immunology
- Biomedical Engineering
Background:
- Poor antibody drug penetration hinders solid tumor immunotherapy.
- Mathematical models suggest antigen expression and turnover impact drug penetration.
Purpose of the Study:
- To assess the influence of antigen properties on antibody drug penetration into solid tumors.
- To compare penetration profiles of antibodies targeting carcinoembryonic antigen (CEA) and A33.
Main Methods:
- Systematic variation of antigen expression levels and turnover rates in spheroids.
- Evaluation of antibody penetration distances within these spheroids.
- Comparison of penetration profiles for anti-CEA and anti-A33 antibodies.
Main Results:
- Results align with mathematical model predictions.
- Antibody penetration depth is significantly influenced by antigen turnover rate and expression level.
- Slowly internalized targets with optimal expression levels facilitate deeper antibody penetration.
Conclusions:
- Antigen properties, specifically internalization rate and expression level, are critical determinants of antibody drug penetration.
- Selecting slowly internalized targets with non-excessive expression is key for effective antibody drug delivery in solid tumors.
- Optimizing antigen targeting can overcome penetration limitations in cancer immunotherapy.
