In his presentation, Joseph Tario Jr., predoctoral research affiliate at the Roswell Park Cancer Institute, explored a new way of exploiting the power of flow cytometry in a practical, clinical research setting. Tario and his colleagues developed an assay for assessing cytotoxicity by flow cytometry, using components easily accessible to most laboratories.
Cytotoxicity assays are useful in cancer research because they can monitor whether a drug or therapeutic intervention can render the immune system capable of killing tumor cells. This contrasts to other readouts such as the measurement of immune cell numbers or their phenotypic activation status. While such investigations are meaningful, they provide little information as to whether the cells are capable of eliminating disease.
“Cytotoxicity is an important metric in determining the success of an immune response. Conversely, the absence of cytotoxicity when it is expected to occur may indicate that there’s a suppressive environment that is being imparted upon the cell system,” Tario pointed out.
Restoring the immune system’s ability to kill cancer cells is an important strategy in developing anticancer therapies. Flow cytometric methods of measuring cytotoxicity have been shown to compare favorably to the current prevailing methodology, the chromium release assay, which requires the use of dangerous radioactive reagents, often exhibits high backgrounds, and is entirely uniparametric.
In the flow cytometric assay, effector and target cell populations were discriminated from one another with two different lipophilic dyes and viability was assessed with a DNA intercalating reagent. Samples were normalized to controls via the use of fluorescent enumeration beads, and data was acquired on a 14-color LSRII flow cytometer from BD.
The assay gives an accurate readout of cytotoxicity, but its true power comes from the ability to combine cytotoxicity with additional simultaneous and correlated measurements such as antigen-expression profiles and cytokine production in order to more fully elucidate how an intervention affects immune cells.
“Our work on the improved cytotoxicity assay is a step in a process that represents a paradigm shift toward the increasing role of flow cytometry in the laboratory, Tario concluded. “Due to its multiparametric nature, flow cytometry yields data that is inherently more useful than uniparametric technologies such as chromium release. Furthermore, flow cytometry is logistically more feasible than many of the technologies it is capable of replacing.”