Abstract Purpose: The Achilles' heel of all conventional and targeted anticancer treatments is intrinsic or acquired resistance. The era of precision medicine where tumors are selected for specific treatments based on their genetic alterations is revolutionary, but unfortunately prolonged responses are rarely observed due to rapid emergence of resistant clones. We recently developed a new concept of DNA repair inhibitor (Dbait) acting by activating enzymes involved in DNA damage signaling. We tested how such agonist activity would be prone to induce resistance to Dbait treatment. Experimental design: We performed repeated cycles of treatment with various targeted therapy agents (Imatinib, Olaparib, 6-thioguanine and the clinical form of Dbait, AsiDNATM). We analyzed the specific sensitivity of independent cultures after each treatment cycle. The study was performed in different tumor cell lines ((MDAMB231, MDAMB468, HCC1143, THP1, U937, KBM7) and in two non-malignant breast cell lines (MCF10A, MCF12A). Extensive transcriptome and genome studies were performed on MDAMB231 breast cancer cell lines. Results: Resistant clones appeared at a frequency of 1.45% for Olaparib, 0.62% for imatinib, and 1.66% for 6-thioguanine. Similar protocol did not select for resistance to AsiDNA. Unexpectendly, tumor cells became more sensitive to AsiDNA after each cycle of treatment. This behavior was specific of AsiDNA and was not observed with other treatments. The six tumor cell lines tested developed AsiDNA autosensitisation and no resistance. Non tumoral cells were not affected by repeated treatments. The acquired sensitivity of the treated tumor populations was conserved for months after end of treatment Transcriptional and genetic analysis of independently treated MDAMB-231 populations reveals that all evolved similarly. They display a few conserved genome modifications and a large deregulation of 1160 genes resulting in an overexpression of luminal associated genes and a decrease in mesenchymal associated genes. Conclusion: Our results indicate a phenomenon of “autosensitisation”, along treatment which has never been described for anticancer treatment and could prevent development of resistance during treatment. Citation Format: Maria Kozlac, Wael Jdey, Pierre-Marie Girard, Françoise Bono, Marie Dutreix. The evolution of tumor cells under AsiDNA treatment results in “autosensitization” [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2851.
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