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Updated: Apr 23, 2026
Measurement of Natural Killer Cell-Mediated Cytotoxicity and Migration in the Context of Hepatic Tumor Cells
Published on: February 22, 2020
Quantitative analysis of resistance to natural killer attacks reveals stepwise killing kinetics
Paul J Choi1, Timothy J Mitchison
1Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA. paulchoi@post.harvard.edu.
Abstract:
Molecular mechanisms can protect cancer cells from immune attacks. At the level of bulk tissue, these survival mechanisms are often indistinguishable and simply appear as reduced cell death. However, by tracking individual cell survival and death times, we found broad variation in the kinetics of immune evasion. In response to attacks by natural killer cells, we observed that some cancer lines exhibited exponential survival time distributions. Slowly killed cancer lines had reduced exponential rate constants. In contrast, a line engineered to express the serpin protein PI-9, which is known to promote resistance to immune killing, exhibited a markedly nonexponential survival time distribution. By following the histories of individual cancer cells with multiplexed reporters, we obtained evidence that two or more immune attacks are likely required to kill serpin-expressing cells. Thus, resistance is a finite and measurable quantity, with a distinct kinetic signature. A quantitative model based on independently measured parameters is consistent with our conclusions.
Insights
Cancer cells evade immune attacks through varied survival kinetics. A specific protein, PI-9, confers resistance by requiring multiple immune cell attacks for cancer cell death.
Area of Science:
- Immunology
- Cancer Biology
- Cellular Kinetics
Background:
- Cancer cells possess molecular mechanisms for immune evasion, often appearing as reduced cell death at the tissue level.
- Individual cell survival and death kinetics during immune attack show significant variation.
- Natural killer (NK) cell cytotoxicity is a key component of the immune response against cancer.
Purpose of the Study:
- To investigate the kinetics of immune evasion in cancer cells.
- To characterize the survival time distributions of cancer cells under immune attack.
- To determine if resistance to immune killing is a measurable quantity with a distinct kinetic signature.
Main Methods:
- Tracking individual cancer cell survival and death times using multiplexed reporters.
- Analyzing survival time distributions (exponential vs. nonexponential) in response to natural killer cell attacks.
- Developing and validating a quantitative model based on independently measured parameters.
Main Results:
- Observed broad variation in immune evasion kinetics among different cancer cell lines.
- Identified exponential survival time distributions in some cancer lines, with slower killing correlating to reduced rate constants.
- Demonstrated a nonexponential survival time distribution in serpin protein PI-9-expressing cancer cells, indicating increased resistance.
- Provided evidence that PI-9-expressing cells require multiple immune attacks for elimination.
Conclusions:
- Cancer cell resistance to immune attack is not uniform and exhibits distinct kinetic signatures.
- The serpin protein PI-9 significantly enhances cancer cell resistance to immune-mediated killing.
- Resistance to immune attack is a finite and quantifiable property of cancer cells.
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