Comparing programmed cell death in cultured primary and tumor cells in inquiry-based cell biology laboratory exercises

ABSTRACT

Programmed cell death, or apoptosis, is a cellular pathway by which individual cells self-destruct for the benefit of the organism. In this practical paper, we describe laboratory exercises with an inquiry-based learning (IBL) approach in which undergraduate students compared apoptosis among different types of cultured cells. Ultraviolet (UV) radiation was used to induce apoptosis in mouse primary cells and in Chinese hamster ovary (CHO) tumor cells. Students hypothesized that, because tumor cells evade apoptosis, CHO cells would exhibit less apoptosis compared to primary cells. Treated and control cells were labeled for two hallmarks of apoptosis, fragmented DNA and active caspase-3 enzyme, and all nuclei were visualized with DAPI. Cell counts were conducted using fluorescence microscopy. Exposure to UV light induced apoptosis in both cell types compared to controls, but no significant difference in the proportions of labeled cells was observed between UV-treated primary and CHO cells. Optimal parameters for UV exposure and labeling techniques are presented. This exercise provides instructors with methodology for allowing students to use a basic cell culture system and microscopy to formulate a hypothesis and design experiments related to apoptosis. Students incorporated their work into a research paper, which served as the main mode of assessment.

KEYWORDS:

• Apoptosis
• DNA fragmentation
• caspase
• CHO cells
• inquiry-based learning

Acknowledgments

The authors thank Dr. Margaret Richey for comments on the manuscript, Drs. Jeffrey Heath, Kelly O’Quin and Ellen Swanson for help with statistical analysis of the data, and Dr. Stephanie Dew for seminal discussions of this work. This work was supported by institutional funds from Centre, including the H.W. Stodghill, Jr. and Adele H. Stodghill Professorship to SEA.

Disclosure statement

No potential conflict of interest was reported by the authors.

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