Electroporation of AMO-1 cells with a 6-FAM-labelled siRNA oligonucleotide.

<p>Left column: Fluorescence of AMO-1 cells electroporated with the siERK2-6-FAM oligonucleotide (green curve) in relation to mock transfected cells (blue curve) at different time points post-electroporation. Right: Western analysis for ERK2 knockdown at days 3, 5, 7 post-electroporation. One representative experiment from a total of three is shown. Anti-ERK1/2 antibody: CST.</p

Voltage dependence of electroporation and knockdown efficiency in AMO-1 cells.

<p>Transfection of AMO-1 cells across a range of voltages using an expression vector for EGFP (pEGFP-N3) and a stealth siRNA against ERK2 (stERK2) in the electroporation mixture. Top panel: increases of the fractions of EGFP-expressing as well as of dead cells with higher voltages (top row). Cells taken in culture after OptiPrep-mediated debris removal reflect only the increase in transfection efficiency for the EGFP expression plasmid (bottom row). Middle panel: purified AMO-1 cells (those shown in the upper panel, bottom row) after culture for another 4 days. Top row: EGFP expression. Bottom row: annexin V-PromoFluor 647/PI staining. Even for the highest voltage used (320 V) the purified live cell fraction did not fare worse in subsequent culture than cells electroporated under milder conditions. Bottom panel: Western analysis of ERK2 knockdown at days 3 and 5 post-electroporation from the same cultures from which the FACS panels were derived. Efficient siRNA-mediated ERK2 knockdown was achieved at voltages significantly lower than required for the best levels of plasmid electroporation. However, a lower limit for successful knockdown was reached between the settings for 160 and 200 V. Shown is a representative experiment of two complete sets (Western blotting included). Anti-ERK1/2 antibody: CST.</p

Electroporation and knockdown efficiencies in “easy-to-transfect” vs. “hard-to-transfect” MM cell lines.

<p>Left-hand panel: MM cell lines were electroporated with an expression vector for EGFP (pEGFP-N3; 10 µg/ml) and stealth siRNAs against either ERK2 (stERK2; 3 µM) or against no specific target (control; 3 µM). The FACS-measurements represent the cell cultures at day 1 post-electroporation after debris removal with OptiPrep. Right-hand panel: Knockdown of ERK2 and intrinsic levels of phospho-ERK2 (cells from the cultures represented on the left were harvested at day 3 post-electroporation for Western blotting). Good knockdown of ERK2 and lowered levels of phospho-ERK2 were found for all four MM cell lines tested. Shown is a representative experiment of two complete sets (Western blotting included). Anti-ERK1/2 antibody: Santa Cruz Biotechnology.</p

Electroporation of MM cell lines and subsequent purification of transfected cells.

<p>Shown is a representative example of the procedure using the well-transfectable MM cell line JJN-3. This standard column purification has now been performed hundreds of times in our laboratory and is also easily applicable for MM cell lines INA-6, KMS-11, L-363, MM.1S and U-266 (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0097443#pone-0097443-t001" target="_blank">Table 1</a>). a) Cell culture one day after electroporation with expression plasmids for enhanced green fluorescent protein (EGFP) and CD4Δ, showing about a quarter of cells strongly positive for EGFP. b)-e) Enrichment of strongly transfected cells by selection for CD4 surface expression (CD4 MicroBead column selection). b) Column runthrough of cell culture shown in a). Of note is the similar look with a), but with depletion of the strongest transfected cells in b). c) Column eluate of the cell culture shown in a). Untransfected cells (EGFP- and CD4Δ-negative) have effectively been removed, but the column procedure tends to retain significant amounts of dead cells (EGFP-negative, PI-positive). d) Floating fraction of the column eluate as shown in c) after “density gradient” (more properly: density step) treatment using OptiPrep, consisting mostly of viable and strongly transfected cells. e) Pelleted fraction of the column eluate as shown in c) after “density gradient” treatment using OptiPrep, consisting mostly of debris. f) Removal of debris by OptiPrep treatment from the cell culture as shown in a) without prior column separation, leaving two main fractions which are either EGFP-negative, or distinctly EGFP-positive. See Methods section for further details.</p

Electroporation of INA-6 cells stably expressing enhanced green fluorescent protein with an siRNA oligonucleotide against EGFP.

<p>INA-6-EGFP cells were electroporated with a solution containing a stealth siRNA targeting EGFP as well as an expression plasmid for CD4Δ. One day post-electroporation one half of the cell culture was purified according to the column procedure (red curves, also see Fig. 1b)–e)), whereas the other half only underwent debris removal with OptiPrep (blue curves, also see Fig. 1f)). Purified cells were further cultured and FACS-analysed for EGFP expression at the times indicated. Only the live cell fraction (as demarcated in the forward/sideward scatter) was analysed and plotted against similarly treated INA-6-EGFP cells (green curves) transfected with a non-EGFP targeting siRNA. Knockdown efficiency was essentially identical in strength and over time between both purification approaches. One representative experiment from a total of three is shown.</p

Knockdown efficiency in MM cells.

<p>Knockdown of ERK2 in different MM cell lines after transfection with either a short-hairpin expression vector (pSU-ERK2) or the “corresponding” target sequence synthesised as 25 bp stealth siRNA (stERK2; see Methods and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0097443#pone.0097443-Chatterjee1" target="_blank">[21]</a>). At day 1 post-electroporation half of the transfected culture was subjected to the column purification method (also see Fig. 1b)–e)) (resp. cell sorting for AMO-1 cells) and the other half to debris removal only (also see Fig. 1f)). Cells were harvested for Western blotting at the times indicated. Empty pSUPER vector (pSU) transfected cells served as controls. The blots show that the ERK2 knockdown efficiency for stealth siRNA is virtually identical between cells that only underwent debris removal and those that were subjected to the column purification procedure. ERK2 knockdown using the short-hairpin expression vector was less efficient in debris-removal-only samples compared with their cognate column purification complements (see JJN-3, L-363). Representative experiments (JJN-3: n = 3; L-363: n = 2, AMO-1: n = 2) are shown. Anti-ERK1/2 antibody: CST.</p

Functional titration of IKK inhibitors.

<p>(A,B) HT29 cells were pretreated for 1 h with the indicated concentrations of TPCA-1 and Bay 11-7082 and were subsequently challenged with TNF (50 ng/ml) for 3 and 10 min (A) or with Flag-TWEAK (200 ng/ml) for 8 hours (B). Total cell lysates were finally analyzed by Western blotting with respect to TNF-induced phosphorylation and degradation of IκBα (A) and TWEAK-induced p100 processing (B). (C) HT29 cells (40,000/chamber) were grown on glass slides and were pretreated with Bay 11-7082 (30 µM) or TPCA-1 (20 µM) for 30 min. Cells were then challenged with 100 ng/ml TNF for 1 h. After immunofluorescence staining for p65, the ratio of nuclear to cytoplasmic fluorescence intensity (FI) was determined. Data shown corresponds to 95–111 analyzed cells per experimental condition derived from a total of four independent experiments. (D) HT29 cells (20,000/well, 96 well-plate, triplicate values) were pretreated with the IKK inhibitors Bay 11-7082 (30 µM) or TPCA-1 (20 µM) for 30 min and were then stimulated with 100 ng/ml TNF for 6 h. The IL8 content of supernatants was subsequently determined by ELISA. To minimize the background signal related to constitutive IL8 production, medium was changed prior to inhibitor treatment. (E) The effects of TPCA-1 and Bay 11-7082 on TNF-induced phosphorylation and degradation of IκBα were analyzed in KMS-12-BM myeloma cells as described under “A”; n.s. = non specific. (F) Equivalent analysis on TNF-induced IL8 production as described in “D” using the RPMI8226 MM cell line. For statistical analysis of data shown in C, D and F one-way ANOVA with a Tukey post-test was performed. Asterisks indicate p-values≤0.01.</p

SGK3 knockdown in the broader context of MEK1,2/PI3K blockade.

<p>MM cells were electroporated with stealth siRNAs against EGFP or SGK3 and drugs were added at day 2 post-electroporation for a further 3-day incubation. Cell death was measured by annexin V/PI staining and FACS analysis. Error bars denote s.e.m. based on 3 independent experiments. The survival rates were calculated relative to DMSO-treated cells. The absolute survival rates for the experimental pairs in these experiments (DMSO treated stEGFP vs. DMSO treated stSGK3 transfected cells) were 92.7% vs. 93.6% (AMO-1) and 92.7% vs. 91.9% (L-363), i.e. there was no substantial difference between control cells and SGK3 knockdown cells. Titration of BYL-719 and choice of its concentration are detailed in [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0122689#pone.0122689.ref015" target="_blank">15</a>]. Of note, the strong synergistic effect observed in AMO-1 cells for the combination of PI3K-p110α inhibitor BYL-719 and MEK1,2 inhibitor PD0325901 is not observed when the PI3K-p110α inhibitor is substituted with an Akt inhibitor (MK-2206 or Akti1,2), but it is also not mirrored by the combination of MEK1,2 inhibition and SGK3 depletion.</p

The mechanism of Bay 11-7082-induced MM cell death involves necrosis.

<p>(A) MM.1S and KMS-12-BM cells were treated with 30 µM Bay 11-7082 and analyzed by time-lapse video microscopy. Pictures shown represent typical stages of cells undergoing Bay 11-7082-induced cell death within 3 h. (B) Cells were pretreated for 30 min with BHA (50 µM), necrostatin-1 (90 µM) or remained untreated and were then challenged with 30 µM Bay 11-7082 for 2 h. Cells were finally photographed (B, arrows indicate swollen cells and the plasma membrane). (C) MM cells were either left untreated or pretreated for 1 h with BHA (50 µM), necrostatin-1 (90 µM), z-VAD-fmk (100 µM) or both necrostatin-1 and z-VAD-fmk. Cells were then challenged with 15 µM Bay 11-7082 for 1 h (KMS-12-BM) or 2 h (MM.1S) followed by annexin V-FITC/PI staining and FACS analysis. (D) MM.1S and KMS-12-BM cells were pretreated in triplicates for 30 min with the indicated combinations of BHA (50 µM), necrostatin-1 (90 µM) and z-VAD-fmk (100 µM), exposed for 2 h to 30 µM Bay 11-7082 and then analyzed for viability using the MTT assay. For statistical analysis a one-way ANOVA with a Tukey post-test was performed. Experimental settings that display significant protection against Bay 11-7082 induced cell death (p-values≤0.01) are indicated by asterisks.</p

SGK3 expression in relation to (activated) signalling components of the PI3K/Akt system in MM cell lines.

<p>Shown are Western blots for PI3K pathway-associated signalling proteins or for their phosphorylated forms. Cells from the MM cell lines indicated were harvested from standard cell culture, the signals are thus representative of steady-state levels in culture. One cell lysate per line was used to load multiple gels. The representative β-actin control derives from the same blot on which SGK3 and P-FOXO1/3A were also stained. Note: the strong phospho-STAT3 signal in INA-6 cells results from permanent supplementation of the culture with recombinant human IL-6.</p