Extinction of the UPR sensors induces the autophagic cell death of MM cells.

<p>A. NCI-H929 cells were serum-starved or transfected with the non-targeting or PERK siRNAs for 24 h then stained with MDC and examined by fluorescence microscopy. B. NCI-H929 cells cultured as in A, in the presence or absence of 3-MA, were stained with MDC and analyzed by flow cytometry. C and D, NCI-H929 cells were serum-starved (C) or transfected either with the non-targeting or the PERK siRNAs (D). All cultures were conducted with or without bafilomycin A1. Accumulation of autophagosomes was visualized by the conversion of endogenous LC3-I (18 kDa) to LC3-II (16 kDa). E. Average proportion of MDC⁺ cells in NCI-H929 cells 24 h after transfection with the targeting or non-targeting siRNAs or 24 h after culture in serum-starved conditions. All cultures were conducted with or without 3-MA. Results are expressed as the mean ± SD percentages of positive cells as calculated from duplicate determinations. The data shown are representative of two independent experiments. F. NCI-H929 cells were cultured as in E. Membrane alterations were estimated by Annexin V staining after 24 h of culture. Results are expressed as the mean ± SD percentages of positive cells as calculated from duplicate determinations and are representative of three independent experiments. (* <i>p</i><0.05; ** <i>p</i><0.01; ***<i>p</i><0.005; <i>ns</i> = non significant).