Background

KRAS mutations are the most frequent oncogenic drivers in various solid tumors, including non-small cell lung cancer. For decades, they were considered undruggable targets, but recently, the commercialization of targeted therapies that selectively inhibit mutant proteins has significantly shifted the treatment paradigm.

However, in clinical practice, the limitation of cancer recurrence after a certain period following drug administration continues to be observed. This is because acquired resistance is induced in residual cancer cells that survive without undergoing cell death, despite many patients showing initial tumor shrinkage responses. Until now, secondary mutations or genetic variations in other bypass signaling pathways have been identified as the primary causes. On the other hand, the specific impact of non-genetic resistance mechanisms, by which cells alter their properties and withstand drugs without genetic mutations—particularly the process by which cancer cells maintain or change their original tissue identity from which they originated—on tolerance has not been clearly elucidated.

Key Findings

The research team constructed a genetically engineered mouse model (GEMM) that mimics KRAS-mutant lung cancer and tracked the molecular biological changes in cancer cells following the administration of targeted inhibitors.

Analysis revealed that lineage fidelity, which indicates how faithfully tumor cells maintain the characteristics inherent to their original tissue, is a critical factor directly regulating drug responsiveness and survival mechanisms. Tumor cells that robustly maintain the differentiated state and gene expression patterns of normal alveolar epithelial cells were highly dependent on KRAS signaling. These cells exhibited high sensitivity, leading to rapid cell death upon inhibitor administration.

In contrast, the group of cancer cells that deviated from the differentiation trajectory and lost phylogenetic fidelity exhibited entirely different behavior. Rather than dying immediately upon drug administration, these cells survived in a state of drug-tolerant residual disease. The researchers confirmed that under the pressure of inhibitor treatment, phenotypic plasticity is activated, causing tumor cells to evolve along distinct resistance trajectories. Cells that had lost their original differentiation markers acquired persistent drug resistance by rewiring metabolic pathways or activating alternative survival circuits even in the absence of oncogenic signaling.

Significance and Prospects

This study demonstrated that the residual lesions and acquired resistance, which are the biggest obstacles in KRAS-targeted therapy, do not arise merely from genetic mutations but from the loss of cellular differentiation identity and plasticity. This achievement elucidates the mechanistic causal relationship that the target of existing targeted therapies is neutralized at the moment cancer cells deviate from their original lineage.

These findings herald a paradigm shift in therapeutic strategies. They underscore the rationale for combination therapies that not only inhibit onkogenesis with single agents but also prevent epigenetic reprogramming of cancer cells, thereby enforcing lineage fidelity or fundamentally blocking the trajectory toward acquired plasticity. However, a subsequent challenge remains to determine whether the cellular trajectories observed in mouse models are equally reproduced within the diverse tumor microenvironment and immune interactions of actual human lung cancer. This is a point where precise validation through clinical patient biopsy samples must be followed by the discovery of safe drugs targeting lineage plasticity.