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Published on: November 5, 2013
In vivo imaging of drug-induced mitochondrial outer membrane permeabilization at single-cell resolution
Sarah Earley1, Claudio Vinegoni, Joshua Dunham
1Center for Systems Biology, Massachusetts General Hospital, Boston 02114, USA.
Abstract:
Observing drug responses in the tumor microenvironment in vivo can be technically challenging. As a result, cellular responses to molecularly targeted cancer drugs are often studied in cell culture, which does not accurately represent the behavior of cancer cells growing in vivo. Using high-resolution microscopy and fluorescently labeled genetic reporters for apoptosis, we developed an approach to visualize drug-induced cell death at single-cell resolution in vivo. Stable expression of the mitochondrial intermembrane protein IMS-RP was established in human breast and pancreatic cancer cells. Image analysis was then used to quantify release of IMS-RP into the cytoplasm upon apoptosis and irreversible mitochondrial permeabilization. Both breast and pancreatic cancer cells showed higher basal apoptotic rates in vivo than in culture. To study drug-induced apoptosis, we exposed tumor cells to navitoclax (ABT-263), an inhibitor of Bcl-2, Bcl-xL, and Bcl-w, both in vitro and in vivo. Although the tumors responded to Bcl-2 inhibition in vivo, inducing apoptosis in around 20% of cancer cells, the observed response was much higher in cell culture. Together, our findings show an imaging technique that can be used to directly visualize cell death within the tumor microenvironment in response to drug treatment.
Insights
Researchers developed a new imaging method to directly observe cancer cell death within tumors. This technique reveals how cancer drugs affect cells in vivo, offering more accurate insights than traditional cell cultures.
Area of Science:
- Oncology
- Cell Biology
- Biomedical Imaging
Background:
- Studying cancer drug responses in the tumor microenvironment in vivo is challenging.
- Cell culture models do not accurately reflect in vivo cancer cell behavior.
- Accurate visualization of drug-induced cell death in vivo is crucial for cancer therapy development.
Purpose of the Study:
- To develop and validate a high-resolution imaging technique for visualizing single-cell apoptosis in vivo.
- To compare in vivo and in vitro responses of cancer cells to targeted drug treatment.
- To assess the utility of a novel genetic reporter for monitoring cell death.
Main Methods:
- Utilized high-resolution microscopy and fluorescently labeled genetic reporters (IMS-RP) for apoptosis.
- Established stable expression of IMS-RP in human breast and pancreatic cancer cells.
- Quantified IMS-RP release into the cytoplasm to detect apoptosis and mitochondrial permeabilization.
- Administered navitoclax (ABT-263), a Bcl-2 family inhibitor, to tumors in vivo and in vitro.
Main Results:
- Breast and pancreatic cancer cells exhibited higher basal apoptotic rates in vivo compared to cell culture.
- Navitoclax treatment induced apoptosis in approximately 20% of cancer cells in vivo.
- In vitro drug response was significantly higher than observed in vivo, highlighting differences in cellular environments.
- The developed imaging technique successfully visualized drug-induced cell death at single-cell resolution within the tumor microenvironment.
Conclusions:
- The novel imaging approach enables direct visualization of drug-induced cell death in vivo at single-cell resolution.
- Significant discrepancies exist between in vitro and in vivo cancer cell drug responses.
- This technique provides a valuable tool for evaluating targeted cancer therapies within the complex tumor microenvironment.
