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. 2018 Apr 17;9(29):20265–20281. doi: 10.18632/oncotarget.24750

Figure 1. cSCC cell lines can be highly sensitive to a pulse of bortezomib.

Figure 1

(A-C) Cells were continuously incubated with the proteasome inhibitor bortezomib for 72 hours (Continuous) or treated with bortezomib for 8 hours and then maintained in drug-free medium for a further 64 hours (Pulse). Cell viability (live cell number) expressed as a percentage of carrier alone and the percentage of dead cells were assayed by real-time imaging. Values are the mean -/+ SEM of 3 independent experiments. (A) Normal keratinocytes from an RDEB patient (RDEBK) and cSCC cell lines derived from primary tumours from RDEB patients (SCCRDEB 2, 3 and 4) and from an RDEB cSCC metastasis (SCCRDEBMet). (B) Normal human keratinocytes (NHK) and cSCC lines derived from paired primary tumours and metastases from immunocompetent (SCCIC1 and SCCIC1Met) and transplant patients (SCCT and SCCTMet). (C) Relative EC50 values (μM) for reducing cell viability (live cell number) and for promoting cell death. There was little cSCC selectivity with continuous exposure to bortezomib but the majority of cSCC cell lines were more sensitive to a pulse of bortezomib than normal keratinocytes. (D) The three proteolytic activities of the proteasome were assayed 8 hours after the addition of bortezomib. The results were expressed as a percentage of the activity with carrier alone. Values are the mean -/+ SEM of 3 independent experiments. The cSCC cells lines most sensitive to pulse of bortezomib were killed at bortezomib concentrations that strongly inhibit both the chymotrypsin and caspase-like activities of the proteasome.