The γ-isozyme is predominantly expressedin neurons and neuroendocrine cells, including neuroendocrine tumorssuch as small-cell lung cancer (SCLC).30,31 NSE has beenreported to be a promising tumor marker for the diagnosis and follow-upof SCLC.32 A bottom-up LC-MS assay hasalready been developed to quantify this biomarker.11 However, the development of an intact top-down LC-MS methodcould lead to a simplified method for the possible incorporation ofPTMs in the analysis. This evidence concerns the gene ENO2 and small cell lung carcinoma.