library_construction_protocol: On day 21, tumors were harvested. One half was fixed in 10% neutral buffered formalin for 24h, followed by transfer to 70% ethanol before paraffin embedding. Samples were then embedded in paraffin and sectioned for downstream GeoMx DSP spatial transcriptomics analysis. The freshly cut sections were then processed within two weeks of sectioning following the Nanostring GeoMx DSP Automated RNA Slide Preparation user manual (MAN-10151-04, section “Fully Automated RNA Slide Preparation protocol for FFPE”). ISH hybridization was performed using NanoString Mouse Whole Transcriptome Atlas probe mix (>20,000 genes). Acquisition runs of four slides (one slide of each study group) were performed on the Nanostring GeoMx DSP instrument. For each tumor, we defined 3 compartments (“Leading Edge”, “Tumor” and “Necrosis”) based on morphological markers and H&E staining. For each compartment, we then harvested 8 circular (250μm in diameter) ROIs, so a total of 24 per tumor (23 ROIs per tumor for the isotype control group as the first well on each collection plate was dedicated to the no-template control). ROI placement for each compartment was done within the tumor boundaries, including for the “Leading Edge” one. Libraries were prepared from released tags according to the Nanostring GeoMx DSP NGS readout user manual (MAN-10153-02). Library quality was assessed using Agilent 4200 Tapestation system and the D1000 DNA ScreenTape (Agilent Technologies, catalog# 5067-5582). Library concentration was assessed using Qubit™ Flex Fluorometer and Qubit™ 1X dsDNA BR Assay Kit (ThermoFisher Scientific, catalog# Q33262). Libraries were sequenced on the NovaSeq 6000 platform (Illumina) using Illumina v1.5 reagent kits with a read length of 27 for both reads and i5 reverse sequence orientation.