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Leptomeningeal metastasis (LM) is a fatal complication of advanced non-small-cell lung cancer (NSCLC). The aim of this study was to evaluate the utility of cerebrospinal fluid (CSF) as a medium for epidermal growth factor receptor (EGFR) mutation testing in clinical practice. We prospectively enrolled patients with EGFR-mutant NSCLC who underwent CSF sampling for suspected LM. The supernatant of CSF after routine cytology examination was collected. The diagnosis of LM was established according to EANO-ESMO criteria. CSF and plasma cell-free DNA (cfDNA) were retrieved for EGFR mutation testing. Fifty-one patients with a median age of 62.7 years were enrolled. The median duration from initial diagnosis to CSF sampling was 23.0 months and most patients (94.1%) had received at least one EGFR-tyrosine kinase inhibitor. Adenocarcinoma cells were found in 37 CSF samples (72.5%), and 48 (94.1%) patients had confirmed or probable LM. Thirty-five of these 48 patients (72.9%) had valid EGFR mutation-testing results using CSF cfDNA and tended to have higher white blood cell counts and positive cytology in their CSF compared to those with invalid mutation testing results. The overall detection rate of EGFR mutation in CSF cfDNA was 68.8%, and the T790M detection rate was 14.6%. In 37 patients with paired CSF and plasma samples, the concordance rate of the EGFR mutation results was 29.7%. For patients with EGFR-mutant NSCLC with LM, CSF supernatant is a valuable source for EGFR mutation testing and may provide important information.

Glucocorticoids (GCs) and progesterone have been employed as immunosuppressive agents during pregnancy for many years. Intracellular acidification by GCs is due to a rapid non-genomic inhibition of membrane Na(+)/H(+)-exchange 1 (NHE1) activity and is followed by immunosuppression of PHA-stimulated proliferation. NHE1 is tethered to the cortical actin cytoskeleton through ezrin/radixin/moesin (ERM) proteins within lipid rafts; these regulate cell shape, migration and resistance to apoptosis. We explored whether mifepristone (RU486), an antagonist of GCs in T cells, is able to completely block rapid non-genomic responses, namely NHE1 activity and the phosphorylation C-terminal residues of ERM proteins at threonine (cp-ERM). GCs stimulate a rapid non-genomic cp-ERM response in cells within 5min. RU486 antagonized the GC-induced rapid decrease in NHE1 activity, and arrested PHA-stimulated T cells at G0/G1 phase but had no effect on the rapid increase in cp-ERM, which persisted for 24h. However, the cp-ERM response was blocked by staurosporine in both resting and GC stimulated cells. The results of RU486 antagonized the GC induced rapid decrease in NHE1 ion transport activity, but not the increase cp-ERM. This suggests that RU486 in T cells exerts its antagonistic effects at NHE1 containing plasma membrane sites and not where cp-ERM links lipid rafts to cortical cytoskeletons.