title: Single-cell imaging of the heat-shock response in colon cancer cells suggests that magnitude and length rather than time of onset determines resistance to apoptosis.
abstract: Targeting the proteasome is a valuable approach for cancer therapy, potentially limited by pro-survival pathways that are induced in parallel to cell death. Whether these pro-survival pathways are activated in all cells, show different activation kinetics in sensitive versus resistant cells or interact functionally with cell death pathways is unknown. We monitored activation of the heat-shock response (HSR), a key survival pathway induced by proteasome inhibition, relative to apoptosis activation in HCT116 colon cancer cells expressing enhanced green fluorescent protein (EGFP) under the control of the HSP70 promoter. Single-cell and high-content time-lapse imaging of epoxomicin treatment revealed that neither basal activity nor the time of onset of the HSR differed between resistant and sensitive populations. However, resistant cells had significantly higher and prolonged reporter activity than those that succumbed to cell death. p53 deficiency protected against cell death but failed to modulate the HSR. By contrast, inhibition of the HSR significantly increased the cytotoxicity of epoxomicin. Our data provide novel insights into the kinetics and heterogeneity of the HSR during proteasome inhibition, suggesting that the HSR modulates cell death signalling unidirectionally.
authors.affiliation: Centre for Systems Medicine and Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland.
authors.forename: Lavanya
authors.initials: L
authors.lastname: Ramapathiran
authors.forename: Tytus
authors.initials: T
authors.lastname: Bernas
authors.forename: Franziska
authors.initials: F
authors.lastname: Walter
authors.forename: Linda
authors.initials: L
authors.lastname: Williams
authors.forename: Heiko
authors.initials: H
authors.lastname: Düssmann
authors.forename: Caoimhín G
authors.initials: CG
authors.lastname: Concannon
authors.forename: Jochen H M
authors.initials: JH
authors.lastname: Prehn
mesh_terms: D017209:Apoptosis / Q000235:genetics*; D002470:Cell Survival; D003110:Colonic Neoplasms / Q000378:metabolism / Q000473:pathology*; D045325:HCT116 Cells; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics* / Q000648:ultrastructure; D018869:Heat-Shock Response / Q000235:genetics; D006801:Humans; D059010:Single-Cell Analysis; D059008:Time-Lapse Imaging
chemical_list: D018840:HSP70 Heat-Shock Proteins
keywords: Apoptosis; Colon cancer; Heat-shock protein; Hsp70; Proteasome; Single-cell imaging