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. SignificanceOur study highlights the impact of RAS proteostasis on lung cancer development and progression. Vascular normalization achieved by suppressing wild-type KRAS signaling improved the delivery and response to MRTX1133 in KRAS-mutant lung cancer with shallow LZTR1 deletion.