Abstract
Nongenetic adaptive resistance to chemotherapy, driven by transcriptional rewiring, is emerging as a significant mechanism in tumor survival. In this study we combined longitudinal transcriptomics with temporal pattern analysis to investigate patient-specific mechanisms underlying acquired resistance in breast cancer. Matched tumor biopsies (pretreatment, posttreatment, and adjacent normal) were collected from breast cancer patients who received neoadjuvant chemotherapy. Transcriptomes were analyzed by longitudinal gene-pattern classification to track patient-specific gene expression alterations that occur during treatment. Our findings reveal that resistance-associated genes were already dysregulated in primary tumors, suggesting the presence of a preexisting drug-tolerant state. While each patient displayed unique resistance-associated gene rewiring, these alterations converged into a limited number of dysregulated functional modules. Notably, patients receiving the same treatment exhibited distinct rewiring of genes and pathways, revealing parallel, individualized routes to resistance. In conclusion, we propose that tumor cells survive chemotherapy by sustaining or amplifying a preexisting drug-tolerant state that circumvents drug action. We suggest that individualized "chemoresistome maps" could identify cancer vulnerabilities and inform personalized therapeutic strategies to overcome or prevent resistance.