Evolution of MET and NRAS gene amplification as acquired resistance mechanisms in EGFR mutant NSCLC.

EGFR mutant non-small cell lung cancer patients' disease demonstrates remarkable responses to EGFR-targeted therapy, but inevitably they succumb to acquired resistance, which can be complex and difficult to treat. Analyzing acquired resistance through broad molecular testing is crucial to understanding the resistance mechanisms and developing new treatment options. We performed diverse clinical testing on a patient with successive stages of acquired resistance, first to an EGFR inhibitor with MET gene amplification and then subsequently to a combination EGFR and MET targeted therapies. A patient-derived cell line obtained at the time of disease progression was used to identify NRAS gene amplification as an additional driver of drug resistance to combination EGFR/MET therapies. Analysis of downstream signaling revealed extracellular signal-related kinase activation that could only be eliminated by trametinib treatment, while Akt activation could be modulated by various combinations of MET, EGFR, and PI3K inhibitors. The combination of an EGFR inhibitor with a MEK inhibitor was identified as a possible treatment option to overcome drug resistance related to NRAS gene amplification.

Oncogenic and drug-sensitive NTRK1 rearrangements in lung cancer.

We identified new gene fusions in patients with lung cancer harboring the kinase domain of the NTRK1 gene that encodes the high-affinity nerve growth factor receptor (TRKA protein). Both the MPRIP-NTRK1 and CD74-NTRK1 fusions lead to constitutive TRKA kinase activity and are oncogenic. Treatment of cells expressing NTRK1 fusions with inhibitors of TRKA kinase activity inhibited autophosphorylation of TRKA and cell growth. Tumor samples from 3 of 91 patients with lung cancer (3.3%) without known oncogenic alterations assayed by next-generation sequencing or fluorescence in situ hybridization demonstrated evidence of NTRK1 gene fusions.

Phospho-regulation of synaptic and extrasynaptic N-methyl-d-aspartate receptors in adult hippocampal slices.

Recent evidence demonstrates that N-methyl-d-aspartate receptor (NMDAR) trafficking contributes to synaptic plasticity in the hippocampus. Phosphorylation of tyrosine residues, especially NR2B tyrosine 1472, appears to be a mechanism by which NMDAR endocytosis is prevented, suggesting that the tyrosine phosphorylation and surface expression of NMDARs are positively correlated. Previous work from our laboratory and others has confirmed that modulation of tyrosine phosphatase and kinase activity alters the surface expression of NMDARs. However, the changes in NMDAR surface expression described in those studies were in terms of total surface membrane versus intracellular receptors. Within the plasma membrane of glutamatergic synapses, distinct populations of NMDARs exist. Namely, receptors at the surface can be differentiated into synaptic and extrasynaptic pools based on their association with the post-synaptic density (PSD) and availability to glutamate. In the present study, we utilized a subcellular fractionation approach coupled with detergent extraction to prepare synaptic and extrasynaptic NMDARs from adult rat hippocampal slices. Using this method, we examined how tyrosine phosphatase and Src-family tyrosine kinase (SFK) inhibitors modulate the phosphorylation and localization of these different pools of NMDARs. We found that both synaptic and extrasynaptic NMDARs were modulated by tyrosine phosphatase and SFK inhibitors; however subunit- and residue-specific effects were observed. Specifically, phosphorylation of NR2B tyrosine 1472 was associated with enrichment of synaptic NMDARs, whereas phosphorylation of NR2B tyrosine 1336 was associated with enrichment of extrasynaptic NMDARs. Using electrophysiological methods, we also reveal that the biochemical modifications produced by these inhibitors were associated with corresponding changes in NMDAR function.