Increased dosage of wild-type KRAS protein drives KRAS-mutant lung tumorigenesis and drug resistance

Almost 30% of lung adenocarcinomas are driven by activating KRAS mutations. The heterogeneous clinical behavior observed in these cancers could be due to the imbalance of wild-type and oncogenic KRAS alleles. However, the role of RAS dysregulation at the protein level needs to be further explored. A genome-wide global protein stability screen identified the CUL3 ubiquitin ligase adaptor LZTR1, as a major proteostatic regulator of wild-type but not mutant KRAS. In KRAS-mutant lung adenocarcinoma, shallow deletion of LZTR1 is observed in up to 50% of patients and is associated with hypoxic signatures and poorer progression-free disease survival. In a Kras-mutant lung cancer mouse model, heterozygous loss of Lztr1 promoted tumor growth, led to peritumoral vascular remodeling, and limited the response to the KRAS-G12D inhibitor MRTX1133. The vascular alteration in LZTR1-depleted lung cancer was mediated by increased wild-type KRAS protein dosage, which promoted mTOR pathway activation and a subsequent increase in VEGFA secretion. The inhibition of the PI3K/mTOR pathway using dactolisib normalized tumor vasculature, improved drug delivery, and overcame resistance to KRAS-G12D inhibitors. In summary, the dysregulation of RAS proteostasis contributes to lung tumorigenesis, and targeting wild-type KRAS signaling is crucial to overcome intrinsic resistance to inhibitors of mutant KRAS. ### Competing Interest Statement The authors have declared no competing interest.