The ability of cancer cells to transition between epithelial and mesenchymal states, a process known as epithelial-to-mesenchymal transition (EMT), is a key driver of cancer metastasis and therapy resistance. While ataxia telangiectasia and Rad3-related (ATR) kinase was originally characterized as a responder to DNA damage and replication stress, recent discoveries implicate a critical role for ATR in EMT and metastasis. Two pivotal studies published in this issue of JCI provide key insights into how ATR intersects with EMT transcriptional reprogramming. Patel et al. demonstrated that ATR prevented R-loop accumulation at EMT-related gene loci, thereby facilitating the transcriptional reprogramming necessary for EMT as well as tumor growth and metastasis. Tu et al. further uncovered a role for ATR in ECM stiffness–induced EMT, which was associated with an immunosuppressive tumor microenvironment. Together, these studies highlight important therapeutic implications for ATR targeting in the context of metastasis and therapy resistance.
Epidermal growth factor receptor-targeted therapies such as afatinib provide clinical benefits to patients with advanced-stage non-small cell lung cancer (NSCLC); however, acquired resistance frequently develops, with the underlying mechanisms remaining undefined in 20–30% of cases. The present study established afatinib-resistant (AR) NSCLC cell lines and confirmed their resistance phenotype using Cell Counting Kit-8 (CCK-8) cell viability assays. Notably, these cells also exhibited cross-resistance to osimertinib. To elucidate the molecular basis of resistance acquisition, the time-resolved transcriptomic profiling of A549 cells was performed across three stages: Parental, afatinib-exposed (adaptive phase) and stable resistant cells. The analyzed results revealed the persistent upregulation of ABLIM3, HTR1D and HSPA1A, which was validated by reverse transcription-quantitative polymerase chain reaction. The meta-analysis of hazard ratios from The Cancer Genome Atlas demonstrated that the elevated expression level of the three-gene signature was significantly associated with tumor progression and an increased risk of disease recurrence. These transcriptional alterations were accompanied by the sustained activation of the MAPK/ERK signaling pathway, as evidenced by increased ERK1/2 phosphorylation detected using western blot analysis, which was positively associated with the expression level of the three-gene signature. Functional analyses further demonstrated that the pharmacological inhibition of MAPK/ERK signaling using selumetinib effectively re-sensitized AR cells to both afatinib and osimertinib, as demonstrated by restored drug sensitivity in CCK-8 assays. Collectively, these findings suggest that MAPK/ERK signaling contributes to the transition from adaptive tolerance to stable resistance to afatinib and highlight a tractable therapeutic vulnerability for overcoming resistance to tyrosine kinase inhibitors in NSCLC.
