Extracellular niche and tumor microenvironment enhance the impact of KRAS inhibitors in pancreatic cancer models [DSP]
Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease for which new therapeutic interventions are needed. Here, we assessed the cellular response to pharmacological KRAS inhibition, targeting the central oncogenic factor in PDAC. In a panel of PDAC cell lines, pharmaceutical inhibition of the KRASG12D allele with MRTX1133 yields variable efficacy in the suppression of cell growth and downstream gene expression programs in 2D culture. CRISPR-Cas9 loss-of-function screens identified ITGB1 as a novel driver for enhanced therapeutic response that regulates mechanotransdcution signaling and YAP/TAZ expression, which is further confirmed by gene specific knockdowns and combinatorial drug synergy. Interestingly, MRTX1133 is considerably more efficacious in the context of 3D cell cultures. Moreover, MRTX1133 elicits a more pronounced cytostatic effect in controlling the in vivo tumor growth in PDAC patient-derived xenografts. In syngeneic models, KRASG12D inhibition leads to potent tumor regression that did not occur in immune-deficient hosts. Digital spatial profiling on tumor tissues indicates that MRTX1133-mediated KRAS inhibition enhances interferon-? signaling and induces antigen presentation that modulates the tumor microenvironment. Further investigation on the immunological response using single-cell sequencing and multispectral imaging reveals that tumor regression is associated with suppression of neutrophils and influx of effector CD8+ T-cells. Thus, both tumor cell-intrinsic and extrinsic events contribute to response and credential KRASG12D inhibition as a promising strategy for a large percentage of PDAC tumors. Overall design: Digital spatial profiling (DSP) was performed on tumor tissues that were derived from AKB6 xenografts developed in  C57BL/6 strain. Mice were treated with vehicle and MRTX1133 (30 mg/kg) once a day via IP administration. The DSP analysis was performed on vehiclle (n=2) and MRTX1133 treated (n=4) tissues. A total of 6 ROIs  were selected from vehicle treted tissues and 23 ROIs were selected from MRTX1133 treated tissues.