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• Patient-derived xenografts (PDXs) are important preclinical tool for cancer research as they preserve molecular, histological, and drug response features of patient tumors. • However, PDX establishment from patient tumor specimens is resource intensive and engraftment success rates for resectable lung adenocarcinoma (LUAD) is approximately 20 %. • Our analyses on the clinical, imaging, molecular and pathology features of 254 LUAD that were used to establish PDX models show that solid appearance of the tumors on preoperative CT images, solid predominant histology subtype, and KRAS or TP53 mutations were significantly associated with PDX growth in LUAD. • Our findings reveal a cost-effectiveness approach to enhance the success rates of LUAD PDX establishment. Patient-derived xenografts (PDXs) are increasingly utilized in preclinical drug efficacy studies due to their ability to retain the molecular, histological, and drug response characteristics of patient tumors. This study aimed to investigate the factors influencing the successful engraftment of PDXs. Lung adenocarcinoma PDXs were established using freshly resected tumor tissues obtained through surgery. Radiological data of pulmonary nodules from this PDX cohort were analyzed, categorizing them into solid tumors and tumors with ground-glass opacity (GGO) based on preoperative CT images. Gene mutation status was obtained from next generation sequencing data and MassARRAY panel. A total of 254 resected primary lung adenocarcinomas were utilized for PDX establishment, with successful initial engraftment in 58 cases (22.8 %); stable engraftment defined as at least three serial passages was observed in 43 cases (16.9 %). The stable engraftment rates of PDXs from solid tumors and tumors with GGO were 22.1 % (42 of 190 cases) and 1.6 % (1 of 64 cases), respectively (P < 0.001). Adenocarcinomas with advanced stage, poor differentiation, solid histologic subtype, and KRAS or TP53 gene mutations were associated with stable PDX engraftment. Avoiding tumors with GGO features could enhance the cost-effectiveness of establishing PDX models from early-stage resected lung adenocarcinomas. [ABSTRACT FROM AUTHOR]

Highlights • The treatment strategy for NSCLC with HER2 exon 20 insertion remains unclear. • Poziotinib showed potent activity against HER2 exon 20 insertions in vitro model. • C805S was identified as a mechanism underlying acquired resistance to poziotinib. • HSP90 inhibitors were able to overcome this resistant clone. Abstract Objectives Oncogenic HER2 mutations are present in 2–4% of lung adenocarcinomas, but the relevant clinical trials are unsatisfactory. The novel HER2 inhibitor poziotinib was recently developed and clinical trials are ongoing. We compared poziotinib with nine tyrosine kinase inhibitors (TKIs), and derived poziotinib-resistant clones to investigate the resistant mechanism. Materials and methods We introduced three common HER2 mutations A775_G776insYVMA (YVMA), G776delinsVC (VC) and P780_Y781insGSP (GSP), which account for 94% of HER2 exon 20 insertions in the literature, into Ba/F3 cells. We then compared the activity of poziotinib with that of nine TKIs (erlotinib, afatinib, dacomitinib, neratinib, osimertinib, AZ5104, pyrotinib, lapatinib, and irbinitinib), determined the 90% inhibitory concentration (IC 90) through a growth inhibition assay, and defined a sensitivity index (SI) as IC 90 divided by the trough concentration at the recommended dose as a surrogate for drug activity in humans. We also generated resistant clones by exposure to poziotinib in the presence of N-ethyl -N- nitrosourea, and HER2 secondary mutations that might serve as a resistance mechanism were searched. Results YVMA showed resistance to all tested drugs except neratinib, poziotinib and pyrotinib. Poziotinib was the only drug with an SI less than 10 for YVMA, the most common HER2 exon 20 insertion. We established 62 poziotinib-resistant clones, and among these, only C805S of HER2, which is homologous to C797S of the EGFR, was identified as a secondary mutation in 19 clones. We also revealed that heat shock protein (HSP) 90 inhibitors show potent anti-growth activity to the C805S secondary mutant clone. Conclusions Poziotinib showed the most potent activity against HER2 exon 20 mutations. We identified the secondary C805S at the covalent binding site of HER2 to poziotinib as a potential mechanism of acquired resistance. HSP90 inhibitors might be a therapeutic strategy for the C805S secondary mutation. [ABSTRACT FROM AUTHOR]

• Several HER2/4 VUS were identified in lung SCC patients in the LUX-Lung 8 trial. • We examined the transforming ability of these HER2/4 VUS and sensitivity to TKIs. • HER2 mutations E395K, G815R, and R929W showed transforming ability in Ba/F3 models. • 2G/3G TKIs, but not erlotinib, were active for Ba/F3 cells with these mutations. • These results suggest that HER2 mutations may be therapeutic targets in lung SCC. The LUX-Lung 8 randomized trial (LL8) demonstrated a prolonged progression-free survival (PFS) in patients with metastatic squamous cell carcinoma (SCC) of the lung after treatment with afatinib compared with erlotinib. A secondary analysis of the LL8 reported that the presence of rare HER2/HER4 mutations may be partly responsible for this result. Patients with HER2 (hazard ratio [HR] 0.06/ p-value 0.02) or HER4 (HR 0.21/ p-value unreported) mutations had longer PFS after treatment with afatinib. However, the biological function of these mutations is unclear. Ten HER2 and 13 HER4 point mutations that were detected in the secondary analysis were transduced into the mouse pro-B cell line (Ba/F3) to determine changes in interleukin-3 (IL-3) dependence and sensitivity to six EGFR or pan-HER tyrosine kinase inhibitors (TKIs), including afatinib and erlotinib. The efficacy of the six TKIs was compared using a sensitivity index, defined as the 50% inhibitory concentration divided by trough concentration of each drug at clinically recommended doses. Seven out of 10 Ba/F3 clones expressing HER2 mutations and all 13 Ba/F3 clones expressing HER4 mutations did not grow in the absence of IL-3, indicating these mutations were non-oncogenic. Three Ba/F3 clones expressing the HER2 mutations E395K, G815R, or R929W acquired IL-3-independent growth. The sensitivity indices for afatinib were ≤ one-fifth of those for erlotinib in all three lines. Other second/third-generation (2G/3G) TKIs showed high efficacy against clones expressing these HER2 mutations. The majority of HER2/4 mutations detected in lung SCC from LL8 were not oncogenic in the Ba/F3 models, suggesting that the presence of HER2/4 mutations were not responsible for the superior outcomes of afatinib in the LL8 study. However, SCC of the lung in some patients may be driven by rare HER2 mutations, and these patients may benefit from 2G/3G pan-HER-TKI treatment. [ABSTRACT FROM AUTHOR]

• The inducibility of drug tolerant cells depended on the type of cell line. • Acquisition of DTC phenotype was a cellular response to high dose of EGFR-TKI. • High expression of RYK was a molecular mechanism of the drug-tolerant state. Emergence of acquired resistance is almost inevitable during EGFR-tyrosine kinase inhibitor therapy for non-small-cell lung cancer (NSCLC) harboring EGFR mutations. Drug tolerance, a reversible state of drug insensitivity in the early phases of tyrosine kinase inhibitor therapy, is considered to serve as the basis of recurrent disease. Therefore, it is important to elucidate the molecular mechanisms of drug tolerance. Five EGFR -mutated NSCLC cell lines were used in this study. We established drug-tolerant cells (DTCs) via 72 h treatment with osimertinib (600 nM) or afatinib (60 nM). Acquisition of drug tolerance was evaluated by growth inhibitory assay, and the molecular mechanisms of drug tolerance were analyzed by phospho-RTK array. DTCs were successfully induced in PC9, HCC4006, and H1975 cells against osimertinib and in PC9 cells against afatinib. We observed that a high drug concentration was required to induce DTCs, and HCC4006 cells become tolerant when a higher dose of afatinib (>180 nM) was used. In the analysis of HCC4006 DTCs against osimertinib, we observed increased receptor-like tyrosine kinase (RYK) expression, and siRNA-mediated RYK knockdown inhibited the proliferation of DTCs. These results suggest that induction of DTCs is dose-dependent, and increased RYK expression was the mechanism of drug tolerance in HCC4006 cells against osimertinib. [ABSTRACT FROM AUTHOR]

• Heterogeneity of EGFR-TKI resistance mechanisms will affect treatment strategy. • We found ten of 24 autopsied NSCLC patients developed heterogeneous resistance. • Patients with heterogeneous resistance mechanisms had shorter TTF (p = 0.0004). • T790M was frequently detected in locoregional lesions than distant metastases. • Three lost chance to use osimertinib; T790M (-) at biopsy but T790M (+) at autopsy. Overcoming acquired resistance against targeted therapies to improve outcomes of lung cancer patients harboring driver mutations is a critical issue. While drug therapy oriented to a resistance mechanism appears attractive, spatial heterogeneity of resistance mechanisms in each patient will diminish treatment efficacy. However, the frequency, clinical backgrounds, clinical implications, and patterns of spatial heterogeneity in resistance mechanisms to EGFR tyrosine kinase inhibitors (TKIs) are largely unknown. This study included 128 specimens from 24 autopsied patients with lung adenocarcinoma harboring EGFR mutation. Acquired resistance mechanisms reported as relatively frequent in lung cancer, e.g. , T790 M and other secondary EGFR mutations, MET and ERBB2 gene amplification, and histological transformation, were retrospectively examined. All patients had received 1st/2nd generation EGFR-TKI and showed acquired resistance to the drug before death. No patient received osimertinib. No resistance mechanism was identified in two patients. T790M mutation was detected in 20 patients (83 %); however, nine of these patients also had lesions without T790M mutation. Among 22 patients whose resistance mechanisms were identified, ten had spatial heterogeneity of resistance mechanisms (45 %), and these patients had significantly shorter time-to-treatment failure compared with those without heterogeneity (median 4.7 months vs. 14.7 months, p = 0.0004). We observed significant spatial heterogeneity of acquired resistance mechanisms to EGFR-TKIs in lung adenocarcinoma. Our results also indicate that the incidence of resistance mechanisms may vary based on the biopsied tumor locations. [ABSTRACT FROM AUTHOR]

Highlights • Possible secondary resistant mutations against front-line osimertinib were examined. • Together with Del 19, only C797S conferred significant resistance to osimertinib. • Together with L858R, C797 and L718 mutations conferred resistance to osimertinib. • TKI sensitivities depended on combinations of secondary and activating mutations. Abstract Objectives Non-small cell lung cancers (NSCLCs) that harbor activating mutations for epidermal growth factor receptor (EGFR) show remarkable initial response to EGFR-tyrosine kinase inhibitors (TKIs), but inevitably acquire resistance, half of which are due to a T790 M secondary mutation when first-generation (1 G) or 2 G EGFR-TKIs are used. Osimertinib, a 3 G EGFR-TKI, is a standard of care in this situation, but eventually also evokes resistance, reportedly due to some tertiary EGFR mutations. However, the FLAURA trial showed the superiority of osimertinib over 1 G EGFR-TKIs in treatment-naïve patients, thus providing an option of first-line osimertinib treatment. Resistance in this setting is also inevitable, but its mechanism is unclear. We investigated whether resistance mutations that emerged with T790 M were responsible for the osimertinib resistance in the first-line setting; i.e. without T790 M, and if so, what treatment option was available. Materials and Methods We used literature search to identify EGFR mutations at codons L718, G724, L792, G796, and C797 as mechanisms of osimertinib resistance in the presence of T790 M. These mutations were introduced into Ba/F3 cells in cis with activating EGFR mutations but not with T790 M; inhibitory effects of five EGFR-TKIs were evaluated. Results Only C797S conferred significant resistance against osimertinib when exon 19 deletion was the activating mutation. However, co-existence of L858R with C797S, C797 G, L718Q, or L718 V mutations all conferred resistance to osimertinib. Erlotinib showed the greatest activity for C797S-mediated resistance. However, 2 G EGFR-TKIs (afatinib or dacomitinib) were effective for other resistance mutations. Conclusion After first-line osimertinib failure, 1 G or 2 G EGFR-TKIs are effective, depending on combinations of secondary and activating mutations. [ABSTRACT FROM AUTHOR]