Response to HER2 Inhibition in a Patient With Brain Metastasis With EGFR TKI Acquired Resistance and an HER2 Amplification

Acquired Concurrent EGFR T790M and Driver Gene Resistance From EGFR-TKIs Hampered Osimertinib Efficacy in Advanced Lung Adenocarcinoma: Case Reports

The acquired resistance of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) is inevitable and heterogeneous. The strategies to overcome acquired resistance are significant. For patients with secondary T790M-positive after early generation EGFR-TKIs, osimertinib is the standard second-line therapy. In patients resistant to prior early generation EGFR-TKIs, the acquired T790M mutation overlaps with other driver gene resistance, such as HER2-and MET amplification, accounting for 4–8%. The efficacy of osimertinib is unclear in patients with concurrent multiple driver gene resistance. We here report a patient who acquired EGFR T790M, STRN-ALK fusion, and EGFR amplification after gefitinib progression and subsequent MET amplification acquired from osimertinib. The other patient acquired EGFR T790M and MET amplification post-dacomitinib and acquired CCDC6-RET fusion after osimertinib treatment. Besides, subsequent new bypass activations were the possible resistance mechanisms to second-line osimertinib. Both patients had progression-free survival (PFS) less than 4 months and limited benefits from osimertinib second-line therapy. The T790M accompanying driver gene resistance will be a new subtype after EGFR-TKIs progression, needing effective treatment options.

Overcoming the acquired resistance to gefitinib in lung cancer brain metastasis in vitro and in vivo

In our previous work, PC-9-Br, a PC-9 brain seeking line established via a preclinical animal model of lung cancer brain metastasis (LCBM), exhibited not only resistance to epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) gefitinib in vitro, but also chemotherapy regimens of cisplatin plus etoposide in vivo. Using this cell line, we investigated novel potential targeted therapeutics for treating LCBM in vitro and in vivo to combat drug resistance. Significant increases in mRNA and protein expression levels of Bcl-2 were found in PC-9-Br compared with parental PC-9 (PC-9-P), but no significant changes of Bcl-XL were observed. A remarkable synergistic effect between EGFR-TKI gefitinib and Bcl-2 inhibitors ABT-263 (0.17 ± 0.010 µM at 48 h and 0.02 ± 0.004 µM at 72 h), or ABT-199 (0.22 ± 0.008 µM at 48 h and 0.02 ± 0.001 µM at 72 h) to overcome acquired resistance to gefitinib (> 0.5 µM at 48 h and 0.10 ± 0.007 µM at 72 h) in PC-9-Br was observed in MTT assays. AZD9291 was also shown to overcome acquired resistance to gefitinib in PC-9-Br in MTT assays (0.23 ± 0.031 µM at 48 h and 0.03 ± 0.008 µM at 72 h). Western blot showed significantly decreased phospho-Erk1/2 and increased cleaved-caspase-3 expressions were potential synergistic mechanisms for gefitinib + ABT263/ABT199 in PC-9-Br. Significantly decreased protein expressions of phospho-EGFR, phospho-Akt, p21, and survivin were specific synergistic mechanism for gefitinib + ABT199 in PC-9-Br. In vivo studies demonstrated afatinib (30 mg/kg) and AZD9291 (25 mg/kg) could significantly reduce the LCBM in vivo and increase survival percentages of treated mice compared with mice treated with vehicle and gefitinib (6.25 mg/kg). In conclusion, our study demonstrated gefitinib + ABT263/ABT199, afatinib, and AZD9291 have clinical potential to treat LCBM.

Significant Benefits of Afatinib and Apatinib in a Refractory Advanced NSCLC Patient Resistant to Osimertinib: A Case Report

EGFR-tyrosine kinase inhibitors (TKIs) have revolutionized the treatment for NSCLC. However, acquired drug resistance often occurs after treatment with EGFR-TKIs. EGFR T790M and C797S mutations are the most common resistance mechanism in patients who failed from first- and third- generation EGFR TKI treatments, respectively. However, there is no standard of care for NSCLC harboring EGFR T790M and C797S in-cis. The present case reports a 69-year-old Chinese man with advanced NSCLC harboring EGFR exon 19-deletion, T790M, cis-C797S, and HER2 amplification who was heavily pre-treated. The patient was then given a combination of afatinib and apatinib and achieved a PFS of more than 10 months. This case showed that afatinib plus apatinib may be a promising therapy for patients with EGFR 19Del-T790M-cis-C797S mutant and HER2 amplified NSCLC.

Drug resistance occurred in a newly characterized preclinical model of lung cancer brain metastasis

Background

Cancer metastasis and drug resistance have traditionally been studied separately, though these two lethal pathological phenomena almost always occur concurrently. Brain metastasis occurs in a large proportion of lung cancer patients (~ 30%). Once diagnosed, patients have a poor prognosis surviving typically less than 1 year due to lack of treatment efficacy.

Methods

Human metastatic lung cancer cells (PC-9-Br) were injected into the left cardiac ventricle of female athymic nude mice. Brain lesions were allowed to grow for 21 days, animals were then randomized into treatment groups and treated until presentation of neurological symptoms or when moribund. Prior to tissue collection mice were injected with Oregon Green and ¹⁴C-Aminoisobutyric acid followed by an indocyanine green vascular washout. Tracer accumulation was determined by quantitative fluorescent microscopy and quantitative autoradiography. Survival was tracked and tumor burden was monitored via bioluminescent imaging. Extent of mutation differences and acquired resistance was measured in-vitro through half-maximal inhibitory assays and qRT-PCR analysis.

Results

A PC-9 brain seeking line (PC-9-Br) was established. Mice inoculated with PC-9-Br resulted in a decreased survival time compared with mice inoculated with parental PC-9. Non-targeted chemotherapy with cisplatin and etoposide (51.5 days) significantly prolonged survival of PC-9-Br brain metastases in mice compared to vehicle control (42 days) or cisplatin and pemetrexed (45 days). Further in-vivo imaging showed greater tumor vasculature in mice treated with cisplatin and etoposide compared to non-tumor regions, which was not observed in mice treated with vehicle or cisplatin and pemetrexed. More importantly, PC-9-Br showed significant resistance to gefitinib by in-vitro MTT assays (IC50 > 2.5 μM at 48 h and 0.1 μM at 72 h) compared with parental PC-9 (IC50: 0.75 μM at 48 h and 0.027 μM at 72 h). Further studies on the molecular mechanisms of gefitinib resistance revealed that EGFR and phospho-EGFR were significantly decreased in PC-9-Br compared with PC-9. Expression of E-cadherin and vimentin did not show EMT in PC-9-Br compared with parental PC-9, and PC-9-Br had neither a T790M mutation nor amplifications of MET and HER2 compared with parental PC-9.

Conclusion

Our study demonstrated that brain metastases of lung cancer cells may independently prompt drug resistance without drug treatment.