The downstream response to pharmacologically induced endoplasmic reticulum stress in two human cell lines.

Abstract Endoplasmic reticulum stress and the unfolded protein response are implicated in a number of diseases, from cancer to ankylosing spondylitis. Understanding the mechanisms underlying this response and how these may differ between cell types is important in beginning to address potential pharmacological therapies. This thesis investigated the effect of the pharmacological endoplasmic reticulum stress inducer tunicamycin, and the isoflavine tyrosine kinase inhibitor genistein on the downstream pathways of the subsequent unfolded protein response. This was investigated in the two human cell lines HeLa and HT1080. The investigations in this thesis found that tunicamycin induced differential activation of downstream unfolded protein response pathways in the two cell lines. The first main finding was that the HT1080 cells exhibited chronic activation of stress related phosphorylation pathways in comparison to the more transient response of the HeLa cells. Both cell lines showed a peak expression of the pro-survival proteins after 10 minutes of tunicamycin treatment, as well as showing longer-term responses to stress with later induction of the phosphorylated-Stat3 protein. This indicates that both acute and chronic effects of ER stress occur in both cell types, but that HT1080 cells had a more consistent expression of stress related proteins. From live cell imaging data, HeLa cells were much more sensitive to tunicamycin induced motility inhibition than the HT1080 cells, which may reflect a state of resistance to stress induced changes in motility in the HT1080 cells. Genistein decreased the phosphorylation of stress related phosphoproteins slightly. These findings reveal that consideration of the cell type must be made when devising pharmacological routes to address conditions where endoplasmic reticulum stress is a pathological factor. The differential response of cell lines to pharmacologically induced ER stress could be exploited to create selective therapies specific to individual cell types.