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PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Differential expression analysis was performed using the libraries DESeq2 version 1.36.0 (The R Foundation for Statistical Computing, Vienna, Austria) in R software version 4.2.1 (The R Foundation for Statistical Computing, Vienna, Austria).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
All volcano plots showed results of RNAseq as the statistical significance (adjusted p-value or q-value) versus the log2 FC and were generated using the libraries from ggplot2 version 3.3.36 in R software version 4.2.1.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Genes with an adjusted p-value (q-value) ≤ 0.01 and an absolute log 2-fold change (abs log2 FC) > 0.5 were considered to be statistically significant.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The ferroptosis database used for the analysis was retrieved on http://www.zhounan.org/ferrdb/ (accessed on 19 September 2022).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cell samples were lysed for 2 h at 4 °C in extraction buffer 5X PTR, purchased from Abcam (ab193970, Cambridge, United Kingdom), supplemented with extraction enhancer buffer 50X (Abcam, Cambridge, United Kingdom, Cat# ab193971) and EDTA-free protease inhibitor complete™ (Roche, Indianapolis, IN, USA, Cat# 11873580001).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The total protein concentration was measured based on the Bradford assay using the Bio-Rad Protein Assay Kit II (Bio-Rad, Hercules, CA, USA, Cat# 5000002).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Proteins were denatured in Laemmli sample buffer (Bio-Rad, Hercules, CA, USA, Cat# 1610747), heated at 95 °C for 5 min, separated by SDS-PAGE on 12% or 15% polyacrylamide gel, and transferred on a 0.2 μm nitrocellulose membrane (Bio-Rad, Hercules, CA, USA, Cat# 1620168).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Each membrane was blocked with Intercept blocking buffer PBS (Li-Cor, Lincoln, NE, USA, Cat# 927-70001).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Primary antibodies raised in different species and secondary antibodies, coupled with different fluorochromes (800 Li-Cor and 680 Li-Cor), were sequentially imaged on an Azure c500 imaging system (Azure Biosystems, Dublin, CA, USA) and displayed in green and red, respectively.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Image Lite Studio quantification software (version 5.2.5, LI-COR Biosciences, Lincoln, NE, USA) was used to quantify the fluorescence signals.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
A list of antibodies used is given in Table S6.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
All the whole western blot figures can be found in the Supplementary Materials.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Glutathione contents were measured using Glutathione Colorimetric Assay Kit (BioVision, CA, USA, Cat# K261).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
GIST882 cells were seeded at 500,000 cells/well and GIST48 cells at 300,000 cell/well in 6-well plates.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cells were treated with DMSO, CA3 (0.670 µM), or VP (2 µM for GIST882 cells and 0.5 µM for GIST48 cells) for 24 h and then harvested.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cell pellets were washed twice in ice-cold 0.01M PBS pH 7.4 and then lysed in ice-cold glutathione buffer for 20 min on ice.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cell lysates were centrifuged for 10 min at 13,000 rpm at 4 °C and each supernatant was transferred to a new tube.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
A small volume from the supernatant was taken for protein quantification.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Next, 5% sulfosalicylic acid (SSA) was added to the supernatant to precipitate and remove proteins from the sample and to protect GSH oxidation.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Each sample was then centrifuged at 8000× g for 10 min at 4 °C and the supernatant was transferred to a new tube for the next steps, according to the instructions in the kit.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The absorbance was read at 415 nm on a plate reader (iMark Microplate Absorbance Reader, BioRad, Hercules, CA, USA).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The content of GSH of each sample was calculated using a standard curve and normalized to the protein content in the lysate (µg GSH/mg protein).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Results are shown as scatter plots and are expressed as means ± SD of fold changes (treated samples normalized to untreated cells).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Ferrous iron was measured using the colorimetric QuantiChrom Iron Assay Kit (BioAssay Systems, CA, Cat# DIFE-250).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Briefly, cells were seeded in six-well plates (500,000 GIST882 cells or 300,000 GIST48 cells per well) 72 h before the start of the assay.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cells were treated for 24 h with VP or CA3 using concentrations mentioned above.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The next day, cells were washed with PBS and lysed on ice for 20 min in 55 µL of lysis buffer containing 1% Triton X-100 (PBS + 1% Triton X-100 + cOmplete EDTA-free protease inhibitor cocktail (Roche, Cat# 11873580001)).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cell lysates were centrifuged at 4 °C for 15 min at 13,000 rpm, and each supernatant was transferred to a new 1.5 mL tube.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
From the supernatant, 2 µL was taken aside for protein quantification and the remaining material was used for ferrous iron measurements following instructions of the kit.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The absorbance was read at 595 nm on a plate reader (iMark Microplate Absorbance Reader, BioRad, Hercules, CA, USA).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Ferrous iron concentration was calculated using a standard curve and normalized to the protein content of the lysate (µM/mg protein) for each sample.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Results are shown as scatter plots and are expressed as means ± SD of fold changes (treated samples normalized to untreated cells).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Flow cytometry analysis of C11-BODIPY green fluorescence was used as a readout for membrane lipid peroxidation, a hallmark of ferroptosis.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
When C11-BODIPY is oxidized, its emission fluorescence shifts from 591 nm (red) to 510 nm (green) .
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cumene hydroperoxide (CumOOH), a strong oxidant, was used as a positive control for lipid peroxidation.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cells were seeded in a 6-well plate (TPP Techno Plastic Products AG, Trasadingen, Switzerland) at a cell density of 300,000 or 500,000 per well for GIST48 and GIST882 cells, respectively, supplemented with 2 mL of medium.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
After drug treatment, 1 µM of BODIPY™ 581/591 C11 (Invitrogen, OR, USA, Cat# D3861) was added to the well and incubated at 37 °C for 30 min.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cells were treated with either 50 µM of CumOOH for 45 min (GIST882 cells) or 100 µM for 30 min (GIST48) (Figures S1 and S2).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cells were washed twice with PBS 1x (Gibco, CA, USA, Cat# 10010-056) and trypsinized in trypsin-EDTA (0.25%) (Gibco, CA, USA, Cat# 25200-056).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cells were harvested and centrifuged for 2 min at 3000 rpm.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The pellet was resuspended in 500 µL of cold PBS/FBS 2%.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Hoechst 33342 (Invitrogen, OR, USA, Cat# H3570) was added prior to flow cytometry to exclude dead cells.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Flow cytometry was performed using a BD LSRFortessa™ X-20 cell analyzer (BD Bioscience).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Green fluorescence was detected using a 488 nm wavelength laser with a 505 nm dichroic mirror and a band-pass emission filter (530/30 nm), and blue fluorescence was detected using a 405 nm wavelength laser with a band-pass emission filter (450/50 nm).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Apoptosis was detected by flow cytometry using the FITC Active Caspase-3 Apoptosis Kit (BD Biosciences Pharmingen, SanDiego, CA and Lexington, KY, USA, Cat# 550480).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Briefly, GIST48 cells were seeded in 6-well plates at a cell density of 300,000 cells/ well.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cells were treated with 1 µM of staurosporine (STS) as a positive control for 4 h or with CA3 (0.670 µM) or VP (0.5 µM) for 24 h. Cells were collected, centrifuged, and resuspended in PBS.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Then, 250,000 cells per test were transferred to a new vial and then centrifuged.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Supernatants were removed and 100 µL of BD cytofix–cytoperm was added to each pellet for 30 min on ice.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cells were washed with BD Perm/Wash buffer (1x) and pelleted.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Supernatants were removed and caspase-3 active antibody was added to each tube at a concentration of 1/15 (diluted in BD Perm/Wash buffer 1x) for an incubation time of 1 h at room temperature.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cells were washed with BD Perm/Wash buffer (1x), pelleted, resuspended in PBS/FBS 2%, and analyzed by flow cytometry.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Flow cytometry was performed using a BD LSRFortessa™ X-20 cell analyzer (BD Bioscience).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Green fluorescence was detected using a 488 nm wavelength laser with a 505 nm dichroic mirror and a band-pass emission filter (530/30 nm).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Data from the flow cytometry experiment were saved in the proprietary *.fsc file format.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Analysis was performed using FlowJo 10.5.3 software (BD Biosciences, NJ, USA).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Cells were selected for granularity (SSC-A x FSC-A) and singlets (FSC-W x FSC-H).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Living cells were selected (Hoechst x FSC-A) and represented as a FITC-A histogram.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Data were exported as CSV channel values.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
On the upper panel, Cumming estimation plots display all data points, presented as a swarm plot, and their distribution .
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The number of events (single cells) analyzed is indicated in the figure.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The size effect (mean difference) is presented as a bootstrap sampling distribution and depicted as a dot with a 95% confidence interval (95% CI), indicated by the ends of the vertical error bars on the lower axis (Figures S1 and S2).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The mean difference in green fluorescence intensity of treated cells compared to untreated cells (DMSO) for multiple independent experimental replicates are shown as scatter plots ± SD, generated using Prism 9 software (GraphPad Software, Inc., La Jolla, CA, USA).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Estimation statistics were used for flow cytometry analysis to focus on the magnitude of the effect (effect size) and its precision. “
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Data Analysis by Estimation Statistics” (DABEST) software (https://www.estimationstats.com/#/ (accessed on 22 July 2022)) was used as a Python script (https://github.com/ACCLAB/DABEST-python, accessed on 22 July 2022), running on a local PC to generate Cumming plots, for experiments that share one reference control group.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
For all other experiment, statistical analysis was performed with Prism 9 software (GraphPad Software, Inc., La Jolla, CA, USA), using ordinary one-way ANOVA, followed by Tukey’s test for ferrous iron and GSH measurements, the Pearson normality test, repeated-measures one-way ANOVA with Geisser–Greenhouse correction and Tukey’s multiple comparisons test for Western blot experiments, and multiple-ratio paired t-test for qPCR.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Contingency tables and Freeman–Halton extensions of Fisher’s test were performed to study the relationship between TFRC expression and non-continuous variables, such as tumor location, sex, mitotic figures, histological type, risk classification, YAP-ir, YAP activation, and KIT-ir.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The Kruskal–Wallis test was used to compare the mean of tumor size between the TFRC+++, TFRC++, and TFRC+ GIST samples.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
A p-value smaller than 0.05 was regarded as statistically significant for iron and GSH measurements and for Western blot quantifications.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
For the qPCR experiment, and for biological relevance, a higher stringency was applied and a p-value smaller 0.01 was regarded as statistically significant.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
All data are presented as mean ± SD.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Figures were prepared with Adobe Illustrator (Version 26.3.1, Adobe Inc., San Jose, CA, USA).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Imatinib-sensitive (GIST882) and imatinib-resistant (GIST48) cells were treated with class II FIN RSL3, a direct GPX4 inhibitor for 3 h. We first assessed the cell viability.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
RSL3 drastically reduced GIST882 and GIST48 cell viability (Figure 1A,B).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Liproxstatin (Lip), an antioxidant and ferroptosis inhibitor, protected GIST882 and GIST48 cells from RSL3 viability reduction.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
We next investigated lipid peroxidation, the main hallmark of ferroptosis by flow cytometry using C11-BODIPY 581/591.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
RSL3 increased the mean difference in green fluorescence intensity (FITC-channel) after 3 h in a dose-dependent manner in both GIST882 and GIST48 cells (Figure 2A).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The antioxidant Lip (from 0.1 µM to 4 µM) completely abolished lipid peroxidation induced by RSL3 (150 nM) in both GIST882 and GIST48 cells (Figure 2B).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Deferoxamine (DFO), another ferroptosis inhibitor, acting through the chelation of iron, also prevented lipid peroxidation in both GIST882 and GIST48 cells (Figure 2C).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
We conclude that RSL3 is a potent ferroptosis inducer in both GIST882 and GIST48 cells.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
To investigate a potential link between ferroptosis and YAP, cell viability was assessed in GIST882 and GIST48 cells after 24 h of treatment with the combination of VP, an inhibitor of YAP , and the two ferroptosis inhibitors, Lip and DFO.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
We observed that Lip had a minor effect on viability reduction induced by VP in GIST882 and GIST48 cells, with a slight increase in IC50 values compared to the VP alone (Figure 3A).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Interestingly, DFO increased the viability of VP-treated GIST882 and GIST48 cells, as reflected by higher IC50 values (Figure 3B).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
These data indicate that ferroptosis plays a role in VP-induced cell death and that iron is important in this mechanism.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
VP is a photosensitizer used to treat macular degeneration and has been shown to inhibit YAP-TEAD interaction independently of light .
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
However, ambient light can induce VP cytotoxicity through the formation of protein cross-linked oligomers and high-molecular-weight complexes or by ROS production, as suggested in the patient-derived xenograft of acute lymphoblastic leukemia .
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Although all experiments with VP were sheltered from ambient light to minimize possible photoactivation, we also tested CA3, a compound with a chemical structure distinct from VP, recently coined as a YAP inhibitor .
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
To investigate the effect of CA3 on GIST882 and GIST48 cell viability after 24, 48, and 72 h, we performed viability assays (Figure 4A).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
CA3 drastically reduced viability in both cell lines at 24, 48, and 72 h, as shown by their respective IC50 values.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
We then tested whether the antioxidant Lip and the iron chelator DFO reversed a reduction in viability induced by CA3 in GIST882 and GIST48 after 24 h (Figure 4B,C).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
Both Lip and DFO increased IC50 values when combined with CA3, as compared to CA3 alone.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
However, DFO was a more potent ferroptosis inhibitor than Lip to reverse the effect of CA3 on viability reduction.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
These data suggest that ferroptosis is the major cell death mechanism induced by CA3 in GIST882 and GIST48 cells.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
We next assessed lipid peroxidation in both GIST882 and GIST48 cells (Figure 5, left and right panels).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
We observed that VP increased the mean difference in green intensity fluorescence (FITC-channel) in GIST882 and GIST48 cells (Figure 5A) in a dose-dependent manner, corresponding to an increase in lipid peroxidation.
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The addition of different Lip and DFO concentrations halved the mean differences in green intensity fluorescence in GIST882 (Figure 5B,C, left panels) and GIST48 (Figure 5B,C, right panels).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
We next tested lipid peroxidation in GIST882 and GIST48 cells treated by CA3 for 24 h. CA3 also induced lipid peroxidation in a dose-dependent manner in GIST882 and GIST48 cells (Figure 5D).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The antioxidant Lip completely abolished lipid peroxidation in GIST882 and GIST48 cells (Figure 5E).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
The iron chelator DFO also prevented GIST882 and GIST48 from lipid peroxidation induced by CA3 (Figure 5F).
PMC9599726
Ferroptosis Induction and YAP Inhibition as New Therapeutic Targets in Gastrointestinal Stromal Tumors (GISTs)
These data suggest that VP largely, albeit not exclusively, induces cell death, whereas CA3 seems to exert its cytotoxicity entirely through ferroptosis.