Xenograft Tumors Derived From Non-Smallcell Lung Cancer Patients As Model To Explore Targeted Therapy Drug Resistances

Background: EGFR mutation or ALK fusion non-small cell lung cancer(NSCLC)patients receiving specific tyrosine kinase inhibitors(TKIs)get dramatic responses.But after 10-12 months,some secondary mutations contribute to resistance.We generated patient-derived xenografts(PDX)in mice using NSCLC cells isolated from the pleural fluid of two NSCLC patients to investigate mechanisms of TKI resistance.Methods: The genotypes of the patient biopsies and the PDX tumors were determined by whole exome sequencing(WES).Based on the respective genotypes the patients and mice bearing the PDX tumors received target treatment using crizotinib or osimertinib.The PDX were also treated for prolonged periods to identify the development of drug resistance.Response to treatment in the PDX model was determined based on tumor size.The pathology of the patients’ biopsies and the PDX tumors were compared by hematoxylin and eosin staining.Results: The histological characteristics and chemotherapy response of the PDX tumors were similar to those of the patients’ tumors.WES showed that the genotypes of tissues from the PDX and patients’ tumors were similar(EML4-ALK gene fusion in Patient/PDX CTC15035;EGFR L858 R and T790 M gene mutations in Patient/PDX CTC15063).After inducing resistance by continuous treatment with crizotinib or osimertinib,WES data suggested that ALK E1210 K conferred crizotinib resistance in the CTC15035 PDX clone,Crizotinib-6.WES data also showed that acquired osimertinib resistance in the CTC15063 PDX clone,Osimertinib-3,was conferred by a decrease in the frequencies of EGFR L858 R and T790 M and the occurrence of BRAF(G7V)and PIK3C2A(A86fs).Conclusions: Using renowned microfluidic technology,we successfully developed a new method to generate drug resistant PDX model from liquid biopsy.Such drug resistant PDX model is a feasible tool to understand the mechanism of drug resistance in NSCLC patients.