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X. Liu

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    MA 12 - Circumventing EGFR Resistance (ID 665)

    • Event: WCLC 2017
    • Type: Mini Oral
    • Track: Advanced NSCLC
    • Presentations: 1
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      MA 12.09 - EGFR T790M Co-Exist with Sensitive Mutation in the Same Cell Group in Lung Adenocarcinoma Patients (ID 9414)

      11:00 - 12:30  |  Author(s): X. Liu

      • Abstract
      • Presentation
      • Slides

      EGFR TKI therapy has improved lung adenocarcinoma patients’ prognosis tremendously, but almost all of the patients inevitably develop acquired resistance, and EGFR T790M mutation is the major contributors. T790M restores the EGFR tyrosine kinase domain affinity to ATP, and therefore gefitinib is displaced from the binding pocket, and the ‘driving’ signal for proliferation is switched on again. Previous work has shown that after TKI therapy, lung adenocarcinoma patients kept the sensitive mutation and acquired resistance mutation simultaneously by sequencing methods or in vitro cell line experiments. Whether the two different type mutations are in the same cell group or in two different cell groups is unknown. None of them has observed what was happening in the tumor cells after TKI therapy.

      RNA in situ hybridization methods was employed to examined EGFR T790M and L858R mutation in lung adenocarcinoma cancer tissues which was obtained before and after TKI therapy. EGFR expression was examined by immunohistochemistry. EGFR mutation were detected by ARMS PCR methods.

      Twenty five patients were enrolled in this study which were divided into 3 groups. Group 1: 5 patients who had concurrent primary T790M and sensitive EGFR mutation. Group 2: 14 patients who acquired T790M mutation after receiving TKI therapy. Among them, 6 patients had biopsy tissues before and after TKI therapy. 8 patients only own tissues after TKI therapy. Group 3: 6 patients who had sensitive EGFR mutation and received TKI therapy, but re-biopsy tissues didn’t had EGFR T790M. We found that the results of RNA ISH and ARMS PCR methods was identical in the majority of the examined tissues. Only one repeated biopsy tissue didn’t identify EGFR T790M after TKI therapy by PCR in group 3, while the RNA ISH method detected T790M in this tissue which contain only 150 tumor cells. In the serial cut slides, we observed that T790M and L858R mutations were in the same cell group, not only in the primary resistance cases, but also in the acquired resistance cases. For the two cases which had tissues available after receiving third generation TKI therapy, we observed that T790M disappeared in the repeated biopsy specimen, leaving the sensitive mutation which existed from the beginning.

      In the primary and acquired resistance tissues, EGFR sensitive mutation and T790M co-exist in the same cell groups. EGFR sensitive mutation is a trunk and drive mutation, while T790M is a passenger mutation during the treatment process by TKI therapy.

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