Contributed by Cory Schlesener, B.S.
When conducting biological assays using mammalian cell tissue culture, the cell line used is crucial. It is a given to choose cells derived from the tissue of interest to study. However, as immortalized cell lines are not entirely normal, lines derived from the same tissue types can ultimately have differences in their regulatory networks. These changes can lead to differences in the way different lines behave in an assay. This can be particularly true if studying regulatory genes involved in cancer formation, as immortalized cells are already caner-like.
A somewhat recent example of this is in a publication (reference below) on the effect a bacterial pathogen has on mammalian cells when injecting a cytotoxin. Specifically, they observed the effect on a particular regulatory gene’s expression, which can potentially lead to oncogenesis. The study showed multiple assays using different mammalian cell lines. Interestingly, the baseline expression of the protein of interest and its partner protein were at very different levels between the cell lines. Further, the ratios of expression between the proteins were also variable between cell lines. Choosing a subset of the lines from their working set, they characterized the cellular morphology and the changes in abundance of their protein of interest after the pathogenic bacteria were introduced. In the assay the three lines showed different increases in expression from ~1.4-2.3x baseline, which can significantly impact the statistical power. Additionally, the cell morphology drastically changes, measured at 24 hours. There was some variation in the proportion of cells that changed morphology, however one cell line reached this percentage morphology after 5 hrs (~25%), while the other lines remain below 15% of cells changed. These observed variations show how cell lines can behave differently, and their sensitivities (underlying regulatory and gene expression patterns) determine the phenotype observed for assay.
Tiffon et al. “TAZ Controls Helicobacter pylori-Induced Epithelial–Mesenchymal Transition and Cancer Stem Cell-Like Invasive and Tumorigenic Properties.” Cells 9, no. 6 (2020): 1462.