IC50 were determined by interpolation from your dose-response curves


IC50 were determined by interpolation from your dose-response curves. L858R point mutation), which account for about 16% of advanced NSCLC patients, result sensitive to the first- and second-generation EGFR tyrosine kinase inhibitors (EGFR-TKIs) gefitinib, erlotinib, and afatinib, respectively [1, 2]. However, EGFR-TKIs therapies are not curative: most patients with mutant NSCLC treated with EGFR-TKIs develop resistance within 9C14 months [1C3]. Mechanisms of resistance to first-generation EGFR-TKIs are widely known and include for the majority of cases the onset of the second-site mutation substituting threonine for methionine at position 790 in exon 20 (T790M), the activation of other cellular signaling such as MET [4], ERBB2, AXL [5], Hedgehog (Hh) [6] or of downstream escape mediators (BRAF, PIK3CA) and histological changes as epithelial-to-mesenchymal transition (EMT) and small cell lung malignancy (SCLC) [7, 8]. A strategy that has exhibited significant activity in overcoming acquired resistance to erlotinib and gefitinib is the dual inhibition of EGFR with the second-generation EGFR tyrosine kinase inhibitor (EGFR-TKI) afatinib and the anti-EGFR monoclonal antibody cetuximab, which induces tumor regression of T790M+ transgenic mouse lung tumors [9, 10]. The addition of cetuximab to afatinib results in simultaneous depletion of phospho- and total EGFR levels [9]. In a subsequent phase Ib clinical trial of afatinib cetuximab, a 29% response rate was observed in patients with acquired Lesopitron dihydrochloride resistance to gefitinib or erlotinib, regardless of T790M status [10]. Thus, a substantial portion of cetuximab has already been observed in patients, a total understanding of the spectrum of resistance mechanisms is currently lacking. A recent breakthrough in the treatment of T790M mutant cancers occurred with the development of mutant selective pyrimidine based third-generation Hhex EGFR-TKIs, which include the WZ4002, CO-1686, osimertinib and HM61713 inhibitors which have exhibited tumor responses in 50% of patients harboring T790M mutation [11C14]. Additionally, their reduced affinity for wild type provokes less toxicity than other EGFR-TKIs. However, resistance will also occur for this class of EGFR inhibitors [11]. As these new compounds become widely available for clinical use, patients will be treated with multiple lines of EGFR-targeted therapies with increasing frequency. However, the effect of sequential treatment with numerous anti-EGFR brokers on tumor development and drug resistance in model of EGFR acquired resistance was obtained by treating nude mice xenografted with HCC827, a human NSCLC cell collection harboring the activating mutation (del ex lover19), with a sequence of first-generation EGFR-TKIs (erlotinib and gefitinib) (step 1 1), second-generation EGFR-TKIs (afatinib) plus/minus cetuximab, Lesopitron dihydrochloride anti-EGFR monoclonal antibody (step 2 2) and third-generation EGFR-TKIs (osimertinib) (step 3 3) (Physique ?(Figure11). Open in a separate window Physique 1 Schematic representation of the whole experiments In the first step, two cohorts of 5 mice each with established HCC827 tumors have been treated with escalating doses of erlotinib or gefitinib over 6 months to derive erlotinib- or gefitinib-resistant tumors (defined as 25% re-growth from maximum reduction). For monitoring tumor responses to therapy, we measured volumetric changes and used an arbitrary classification method partially based on clinical research (15): total response (CR) was defined as no clinical evidence of tumor when mice were sacrificed; partial response (PR) was defined as a decreased of at least 30% in tumor volume with respect to the baseline tumor volume; progression disease (PD) was defined as an increase of at least 20% in the tumor Lesopitron dihydrochloride volume with respect to the.