TP53 mutations in triple-negative breast cancer cells confer sensitivity to ASCT2 inhibition via arginine uptake.

Targeting dysregulated glutamine metabolism via ASCT2 inhibition has therapeutic potential in cancer, but its clinical translation is hindered by tumor metabolic heterogeneity and the lack of predictive biomarkers. This study aims to define genetic determinants of ASCT2 inhibitor sensitivity and uncover compensatory resistance mechanisms to enable precision therapeutic strategies. We systematically evaluated ASCT2 inhibitor responses across molecular subtypes of breast cancer via in vitro and in vivo models. Mechanistic studies integrated transcriptomics, metabolomics, and functional validation of candidate pathways. Using genetic and pharmacological tools, including TP53 isogenic lines and ASCT2 inhibitors, we mapped the metabolic compensation networks. This approach revealed that TP53-mutant triple-negative carcinomas were more sensitive to ASCT2 monotherapy than any other subtype. In TP53 wild-type tumors, ASCT2 inhibition triggered SLC7A3-mediated arginine uptake, destabilizing the CASTOR1-GATOR2 complex to sustain mTORC1-driven proliferation. Cotargeting ASCT2 and SLC7A3 overcame resistance in TP53 wild-type models, inducing metabolic collapse and tumor reduction. This work establishes the TP53 mutational status as a potential predictive biomarker for ASCT2 inhibitor responsiveness and defines the SLC7A3-arginine-mTORC1 axis as a targetable compensatory pathway. Therefore, we propose a genotype-guided therapeutic strategy, recommending ASCT2 monotherapy for TP53-mutant tumors and combined ASCT2 and SLC7A3 inhibition for TP53 wild-type cancers. These findings advance precision in targeting glutamine metabolism while providing a blueprint to counter adaptive resistance through rational drug combinations.