Abstract 3171: Analysis of "drug addiction" mechanisms in the drug-resistant ROS1-rearranged cancer cells

Abstract

Abstract ROS1-rearranged non-small-cell lung cancer (NSCLC) is observed in approximately 1% of lung cancer patients. Crizotinib, ALK/ROS1/cMET tyrosine kinase inhibitor (TKI), showed high effect against ROS1-rearranged NSCLC in the clinical trials and is approved in US and EU. However, the cancers inevitably relapse due to the acquired resistance such as ROS1-G2032R mutation. We previously reported that cabozantinib could overcome those secondary mutations mediated crizotinib-resistance. Based on this finding, we tried to establish cabozantinib-resistant ROS1 mutant cells by ENU mutagenesis screening. Surprisingly, we found out a few CD74-ROS1 mutant clones that only grew in the presence of low-dose cabozantinib. Namely, these mutant clones were “addicted” to cabozantinib. When the fluorescent labeled cabozantinib addicted ROS1 mutant cells were co-cultured with non-addicted CD74-ROS1-WT-BaF3 cell in the presence or absence of low-dose cabozantinib, the drug-addicted cells became dominant in the low-dose cabozantinib, and CD74-ROS1-WT cells became dominant in the absence of it. To analyze the molecular mechanism of “drug-addiction” in the addicted CD74-ROS1 mutant cells, we performed comprehensive analysis such as inhibitor screening, cDNA microarray, and phosphoproteome analysis. As the result, we observed that the expression and phosphorylation of CD74-ROS1 in the addicted cells were excessively upregulated within 24 hours after removal of cabozantinib or other ROS1 inhibitors, such as crizotinib or lorlatinib. We also observed that the apoptosis was induced in these cells upon ROS1 inhibitor removal, whereas ROS1 mediated growth signaling were simultaneously activated. Consistent with this, cDNA microarray analysis revealed that the expression of both cell survival and cell death related genes were changed by ROS1 inhibitor removal. Furthermore, we identified that several proteins were highly phosphorylated by excessive ROS1 activation originated from ROS1 inhibitor removal. These observations suggest that these drug-addicted cells were died by excessive oncogenic signaling, and the appropriate oncogene signaling by low-dose TKI made them survive and grow without inducing apoptosis. Thus, the excessive oncogene signaling has “double-edged sword” characteristics for cancer cell viability and those characteristics could be a new therapeutic target. Citation Format: Hayato Ogura, Jun Adachi, Takeshi Tomonaga, Naoya Fujita, Ryohei Katayama. Analysis of "drug addiction" mechanisms in the drug-resistant ROS1-rearranged cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3171. doi:10.1158/1538-7445.AM2017-3171