Figure 2 from DIPG Harbors Alterations Targetable by MEK Inhibitors, with Acquired Resistance Mechanisms Overcome by Combinatorial Inhibition

Abstract

<p><i>PIK3R1</i> and <i>NF1</i> mutations drive the sensitivity of DIPG cells to trametinib. <b>A,</b> Cartoon representing the protein domains of <i>PIK3R1</i> showing the mutant residue for the observed hotspot N564D mutation observed in ICR-B181. <b>B,</b> Cartoon representing the protein domains of <i>NF1</i> showing the mutant residue for the observed I1824S missense mutation observed in ICR-B184. Generated in ProteinPaint (pecan.stjude.cloud/proteinpaint). <b>C,</b> Dose–response validation curves for trametinib tested against ICR-B181 cells <i>in vitro</i> grown in 3-D (<i>PIK3R1</i><sup>N564D</sup>, blue) and 2-D (<i>PIK3R1</i> wild-type, gray). <b>D,</b> Dose–response curves for trametinib tested against ICR-B184 cells <i>in vitro</i> grown in 3-D (<i>NF1</i><sup>I1824S</sup>, blue) and 2-D (<i>NF1</i> wild-type, gray). Concentration of compound is plotted on a log scale (<i>x</i>-axis) against cell viability (<i>y</i>-axis). Mean plus standard error are plotted from at least <i>n</i> = 3 experiments. ****, <i>P</i> < 0.0001, AUC <i>t</i> test. <b>E,</b> Bar plot of quantitative capillary phospho-protein assessment of phospho-ERK1/2<sup>T202/Y204</sup>, plotted as a ratio to total ERK1/2, and normalized to the 2-D (MAPK wild-type) model in each case. <b>F,</b> VAF (<i>y</i>-axis) of <i>PIK3R1</i><sup>N564D</sup> in ICR-B181 cells grown in 3-D (blue) and 2-D (gray) over time, as measured by ddPCR. Passage number of cells assessed is given on the <i>x</i>-axis. <b>G,</b> Survival curves for ICR-B181-CDX models, separated by mice implanted with cells grown as either 2-D (gray) or 3-D (blue). <b>H,</b> Anti–human nuclear antigen (HNA), staining for ICR-B181-CDX derived from cells grown in 3-D, with extensive tumor cell infiltration. Sagittal sections, counterstained with hematoxylin. <b>I,</b> Sagittal T<sub>2</sub>-weighted image (day 246 postimplantation) for ICR-B181-CDX derived from cells grown in 3-D, showing hyperintense tumor throughout the cerebellum and upper pons (indicated by arrow). <b>J,</b> Hematoxylin and eosin–stained section of ICR-B181–3-D CDX, showing histology consistent with high-grade glioma. Scale bar, 200 μm.</p>

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