The Clinical Significant Of EGFR Mutation In Non-small Cell Lung Cancer

BackgroundNon-small cell lung cancer (NSCLC) becomes a worldwide problem, due to its higher and higher mobidity and mortality. In recent years, the targeted therapy provides a new treatment thoughts for NSCLC patients. The epidermal growth factor receptor (EGFR) mutations is the key to effectiveness of targeted therapy. Tyrosine kinase inhibitors (TKIs) can extend the progress survival (PFS) of patients with common sensitive mutations (del-19, L858R). Nevertheless, The sensitivity of EGFR uncommon mutations L861Q to targeted medication TKIs is unclear, which needs further research.Objective1 To obtain a large number of the wild type and mutant EGFR protein with high purity.2 To explore the combination between the small molecule drug TKIs and EGFR-L861Q mutation protein.3 To explore the kinase activity of EGFR-L861Q mutation protein and the inhibition effect of the small molecule drug TKIs.4 To explore the clinical characteristics and prognosis of NSCLC patients with L861Q mutation.5 To explore the sensitivity of targeted therapy to the TKIs drugs in NSCLC patients with L861Q mutation.Methods1 In the basic experiment, the truncated gene of wild type EGFR protein 696-1022 regions was searched from NCBI. We used PCR amplification to get the targeted gene, then connected it to the carrier plasmid. Designing the mutant gene primers, we used PCR to obtain the recombinant plasmid containing the targeted genes. Next, Bac-to-Bac(?) Baculovirus Expression system enabled the efficient production of recombinant baculovirus for expression testing in insect sf9 cells. The sf9 cells could express the target protein a lot. Breaking the sf9 cells, we can get a lot of target protein, which was purified by Nickel column and molecular sieve. Next, using the target protein, we proceeded the SPR affinity experiment and the protein kinase activity experiment.2 In the clinical follow-up, we reviewed data from 5125 nationwide NSCLC patients with gene mutation detection in 2009-2012 and 489 lung cancer cases from PUMC in 2009-2014. And identify 6 patients with L861Q mutation in EGFR. Patients’ characteristics including gender, age, smoking history, pathological type, tumor staging, treatment and survival were collected.Results1 Through purification and enrichment, we obtained the target protein:500ul of 2.5mg/ul of wild type EGFR protein,500ul of 200ug/ul of EGFR-L858R mutant protein,800ul of 500ug/ul of EGFR-L861Q mutant protein,500ul of 315ug/ul EGFR-L861Q/G719A mutant protein. The protein kinase activity experiment confirmed that all kinds of EGFR target proteins have phosphorylated kinase activity, and active order from high to low was:L858R> L861Q/G719A> L861Q> G719A> WT.2 Through follow-up of 5125 nationwide NSCLC patients and 489 PUMC cases, we summarized the EGFR mutation rate was 36.2%(1854/5125) and 44.2%(216/489), among which coexisting mutation rate was 7.2%(160/2208) and 6.02%(13/216). L861Q mutation in proportion to the total EGFR mutation was 0.27%(5/1854) and 0.46%(1/216). All the L861Q mutations were coexisting mutation forms. The most common joint mutation of L861Q was L861Q/G719A, accounted for 66.7%(4/6). The NSCLC patients with L861Q mutation benefited from targeted therapy, but appeared resistance after 4-5 months.Conclusion1 A lot of target protein with high purity was obtained.2 The EGFR-L861Q mutant protein have phosphorylated kinase activity. And L861Q mutation is oncogene.3 The NSCLC patients with L861Q mutation can benefit from TKIs targeted therapy, but quickly appear resistance after 4-5 months. After then, other TKIs are invalid.