Protoporphyrin IX is a twin inhibitor of p53/MDM2 and p53/MDM4 interactions and induces apoptosis in B-cell power lymphocytic leukemia cells

Reagents and cell strains

PpIX and nutlin had been bought from Sigma-Aldrich (Munich, Germany) and re-constituted in 100% DMSO (Sigma-Aldrich, Munich, Germany) to 2 mg/ml or 10 mM, respectively. PpIX was saved in amber eppendorf tubes at room temperature and nutlin was aliquoted and saved at −20 °C. RITA was bought from Calbiochem (Solna, Sweden) reconstituted in 100% DMSO to zero.1 M, aliquoted and saved at −20 °C.

Cisplatin (CDDP) (Sigma-Aldrich, Munich, Germany) was ready in zero.9% NaCl resolution to 1 mM, shielded from gentle and saved at −20 °C. MG132 was from Sigma-Aldrich (Munich, Germany) reconstituted in 100% DMSO to 10 mM and saved at −20 °C. IgG and protein A agarose beads had been from Santa Cruz Biotechnology (Solna, Sweden), protease inhibitors had been ready from tablets cOmplete® Roche to 100× focus (Sigma-Aldrich, Munich, Germany), MTT was from Sigma-Aldrich (Munich, Germany).

Rabbit polyclonal anti-MDMX was from Imgenex (Cambridge, UK), rabbit polyclonal anti-TAp73 (A300-126A) (Bethyl Laboratories, TX, USA), anti-PUMA (ABC158; Merck, MA, USA), anti-BAX (N-20; Santa Cruz Biotechnology, Germany), anti-BID (FL-195; Santa Cruz Biotechnology, TX, USA), anti-PARP (F-2; Santa Cruz Biotechnology), anti-β-ACTIN (A2228; Sigma-Aldrich), regular mouse IgG (sc-2025) had been from Santa Cruz Biotechnology. Anti-mouse HRP and anti-rabbit HRP secondary antibodies had been from (Jackson ImmunoResearch Inc., Ely, UK) Reverse transcription iScript cDNA synthesis equipment and SSo Superior Common SYBR Inexperienced equipment had been from Bio-Rad (Solna, Sweden)24.

Cell strains

EHEB (wt-p53) power B cell leukemia cells had been kindly offered by Dr. Anders Österborg, Karolinska Institutet (supply ATCC). HL-60 (p53-null) acute promyelocytic leukemia cell strains had been offered by Dr. Sören Lehmann, Karolinska Institutet (supply ATCC). PBMCs had been offered by Dr. Noemi Nagy, Karolinska Institutet and separated as described beforehand25. HCT 116 cells had been a sort reward from Dr. Bert Vogelstein, The Johns Hopkins College College of Medication26.

Leukemic cells and PBMCs had been cultured in RPMI-1640 (Roswell Park Memorial Institute) medium (Sigma-Aldrich, Munich, Germany) and HCT 116 cells in DMEM medium with 10% fetal calf serum (Sigma-Aldrich) and penicillin/streptomycin (10 models/ml) (Sigma-Aldrich) at 37 °C in a humidified 5% CO2/95% air environment.

Cell viability assay

The viability of EHEB, HL60 and PBMCs after 72-hour remedy with PpIX was assessed by the Three-(four,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in line with producer’s protocol. Briefly, 5 mg/ml MTT resolution was ready in PBS buffer and filter-sterilized. Cells had been washed as soon as with RPMI-1640 medium and 1 × 105 cells/ml had been transferred to eppendorf tubes and handled with zero.5% DMSO or the investigated compounds. Subsequent, cells had been seeded onto 96-well plates on the density of 1 × 104 cells/properly and incubated for 72 h at 37 °C. After this time, MTT reagent was added to every properly to a ultimate focus of 10% and the plates had been incubated for Three h at 37 °C in a humidified 5% CO2/95% air environment. The supernatant was eliminated and 200 μl DMSO/properly was added. The plates had been incubated at 37 °C for 30 min and the absorbance of the formazan was measured at 560 nm in a Perkin-Elmer (Waltham, MA, USA) microplate reader.

Untreated EHEB cells, RPMI 1640 medium and RPMI 1640 medium with 20 μg/ml PpIX had been used as background controls. The experiments had been carried out in triplicates and in no less than three unbiased repeats.

Immunoprecipitation and western blot

Immunoprecipitation was carried out utilizing a modified protocol described beforehand27. Briefly, HCT 116 cells had been seeded in 10 cm dish at four × 106 cells, allowed to stick in a single day and handled with the compounds for eight h adopted by Three h with 20 μM MG132. Cells had been washed 2× with ice-cold PBS and solubilized in IP buffer: 25 mM Tris-HCl, pH, 150 mM NaCl, and zero.5% Nonidet P-40 supplemented with protease inhibitors and lyzed on ice for 30 min and 1 mg of complete protein in IP buffer was added to 30 μl mouse protein A agarose beads and 1 μg mouse anti-p53 DO-1 antibody or 1 μg regular mouse IgG and immunoprecipitated for 16 h at four °C. The beads had been washed 3 times with buffer 1 (50 mM Tris-HCl, pH 7.5, 5 mM EDTA, 500 mM NaCl, and zero.5% Nonidet P-40) and one time with buffer 2 (50 mM Tris-HCl pH 7.5, 5 mM EDTA, 150 mM NaCl). The beads had been resuspended in 15 μl of lysis buffer and 5 μl of 5× Laemmli buffer and boiled previous to western blot evaluation.

For western blot, complete proteins had been transferred to HyBond membrane (GE healthcare), blocked with 5% milk in PBS for 20 min and incubated with the related antibodies. After washing in PBS membranes had been incubated with secondary antibodies (1:3000 in 5% milk) for two h at room temperature. The protein alerts had been detected utilizing Tremendous Sign West Dura Prolonged Length Substrate (Bio-Rad, Solna, Sweden) and ChemiDoc (Bio-Rad).

PBMCs had been cultured in RPMI 1640 supplemented with 10% fetal calf serum and penicillin/streptomycin (10 models/ml) with out supplementation with progress elements at 37 °C for 3 days earlier than remedy with compounds.

Quantitative PCR

Quantitative PCR was carried out as described beforehand24,28. Briefly, cells had been handled with 2.5 μg/ml PpIX for eight h. qPCR was carried out utilizing following primers pairs:

Fluorescence activated cell sorting (FACS)

Cells had been cultured in 6-well plates with eight × 105 (Okay562 and HL60) and 1 × 106 PBMC cells and a couple of ml media/properly and handled with the compounds. Propidium iodide (PI) and FITC-Annexin V (each from BD Biosciences, CA, USA) staining was carried out in line with the producer’s protocols. For PBMCs, cells had been washed and stuck with 500 μl ice-cold 70% ethanol and saved at four °C. Subsequent, cells had been washed and stained in 300 μl PI resolution for 30 min. Cells had been then centrifuged at 300g for five min and supernatant was eliminated and re-suspended in 200 μl PBS. FACS was carried out utilizing the CELLQuest software program (CELLQuest, NJ, USA) as described beforehand29.

Yeast-based reporter assay

The yeast-based purposeful assay was performed as beforehand described30. Briefly, the p53-dependent yeast reporter pressure yLFM-PUMA containing the luciferase cDNA cloned on the ADE2 locus and expressed below the management of PUMA promoter31 was transfected with pTSG-p5332, pRB-MDM2 (generously offered by Dr. R. Brachmann, College of California, Irvine, CA, USA), or pTSG-p53 S33/37 mutant and chosen on double drop-out media for TRP1 and HIS3. Luciferase exercise was measured 16 h after the shift to galactose-containing media31 upon the addition of two and 10 μg/ml PpIX or 10 or 50 μM nutlin (Alexis Biochemicals, Sant Diego, CA, USA), or DMSO. Offered are common relative gentle models and the usual errors obtained from three unbiased experiments every containing 5 organic repeats.


The assay was developed and carried out as described beforehand33,34. Briefly, F2H®-analysis (ChromoTek GmbH, Planneg-Martinsried, Germany) was carried out to evaluate PpIX potential to disrupt p53/MDM2 and p53/MDM4 interactions in U2OS cells, when MDM2 or MDM4 was tethered within the nucleus. U2OS cells had been co-transfected with LacI-GFP-MDM2 or MDM4 and RFP-p53 for eight h after which incubated with 1 or 10 μM of PpIX or nutlin for 16 h. Management interplay values in every unbiased experiment are normalized to 100%. Averaged interplay values for the handled cells had been plotted for p53/MDM2 and p53/MDM4 interactions on the graph. Knowledge is offered as imply ± s.e.m., n = 6, PpIX—p < zero.01, nutlin—p < zero.001, Pupil’s t-test.

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