Targeting KRAS: Light at the End of the Tunnel
Mariano Barbacid
Centro Nacional de Investigaciones Oncológicas (CNIO), Madrid, Spain.
KRAS, an oncogene responsible for one fourth of all human cancers, was discovered four decades ago. Yet, the first selective inhibitor could not be not approved until 2021. In spite of this long-awaited breakthrough, current KRAS inhibitors only block one of the multiple oncogenic isoforms, KRASG12C an isoform primarily present in lung adenocarcinomas. Moreover, tumor resistance to these KRAS inhibitors appears to be a significant issue in the clinic (Awad et al., N Engl J Med, 2021; Zhao et al., Nature 2021). In an effort to provide experimental information that might help to improve current KRAS targeting strategies, we have generated two genetically engineered mouse models of Kras/Trp53-driven lung adenocarcinoma to (i) interrogate the mechanisms of drug resistance that appear in KRASG12C driven tumors and (ii) compare the therapeutic consequences of eliminating, instead of inhibiting, KRAS oncoproteins. Our results indicate that Kras gene amplification along with activation of drug metabolic pathways are major components of the mechanisms responsible for the acquisition of resistance. More importantly, genetic evidence strongly supports the concept that Kras ablation provides superior therapeutic benefits than Kras inhibition, thus arguing for the development of Kras degron strategies. In addition, I will discuss alternative strategies to block KRAS oncogenic signaling by targeting downstream effectors, mainly RAF1 (Sanclemente et al., Cancer Cell, 2018; Sanclemente et al. Cancer Cell 2021; ;Garcia-Alonso et al., Mol. Cell, 2022).