Abstract 1586: Evaluation of AXL expression on circulating tumor cells from EGFR mutated lung cancer patients who have relapsed after the EGFR TKI treatment

Abstract

Abstract Background: The EGFR (epidermal growth factor receptor) TKI (tyrosine kinase inhibitor) has become the standard treatment in lung cancer patients with EGFR mutations. When these patients are treated with EGFR TKI, 80~90% of the patients show responses to the drug. However the tumor begins to progress again following the development of resistance about 1 year later on average. About a half of resistance mechanisms are caused by the additional mutation of the EGFR gene (T790M), and the other half of the resistance mechanisms are caused by various mechanisms, with one of them being the overexpression of the AXL protein. Confirming AXL overexpression in circulating tumor cells (CTCs) can be an alternative method for tissue biopsy, but almost no research has been conducted on this so far. Here, we evaluate the AXL expression in CTC in case resistance occurs after the EGFR inhibitor treatment. Materials and Methods: The blood samples (10 ml) were collected from 10 EGFR TKI treated and relapsed lung cancer patients (TKI group) and 10 non-treated patients (control group). The blood samples were processed through Cytogen protocol to enrich CTCs. The enriched cells were immunofluorescent stained for CTC markers (EpCAM or Vimentin), AXL and WBC marker (CD45). The immunofluorescent stained cells were analyzed for each markers using Image Analysis program. Result: CTCs were detected by CTC markers in all patients from TKI group (range 0-210) and control group (range 1-42). AXL positive CTCs were detected in 9 out of 10 cases from TKI group and in all cases from control group. Interestingly, the quantification of AXL staining intensity in CTCs showed that AXL overexpression (3 fold or greater than baseline) was in 50% of TKI group and 20 % of control group. Conclusion: We have tested a new approach to evaluate the AXL overexpression in tumor cells of EGFR TKI resistant patients, and showed the feasibility of the this method. Most of lung cancer patients who undergo biopsy require hospitalization and some degree of complication due to biopsy is inevitable. Here we suggested that the blood-based method as a good alternative to the tissue biopsy in patients with tolerance. Citation Format: Young Hun Kim, Myoung Shin Kim, Jun Sup Lee, Hyun Kyung Lee, Jae Hyuk Lee, Young Woong Sohn, Koichi Tazaki, Kenji Nakamaru, Kenichi Wakita, Byung Hee Jeon, Seokhyung Kim, Se-Hoon Lee. Evaluation of AXL expression on circulating tumor cells from EGFR mutated lung cancer patients who have relapsed after the EGFR TKI treatment [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 1586.