PurposeSmall cell lung cancer (SCLC) is one of the malignant cancers with aggressive progression and poor prognosis. Bronchoalveolar lavage fluid (BALF) has been arising recently as a potential source of biomarkers for lung cancers. In this study, we performed quantitative BALF proteomic analysis to identify potential biomarkers for SCLC.Experimental designBALF were collected from tumor‐bearing lungs and non‐tumor lungs of five SCLC patients. Then, BALF proteomes were prepared for a TMT‐based quantitative mass spectrometry analysis. Differentially expressed proteins (DEP) were identified when considering individual variation. Potential SCLC biomarker candidates were validated by immunohistochemistry (IHC). A public database of multiple SCLC cell lines was used to evaluate the correlation of these markers with SCLC subtypes and chemo‐drug responses.ResultsWe identified 460 BALF proteins in SCLC patients and observed considerable individual variation among the patients. Immunohistochemical analysis and bioinformatics resulted in the identification of CNDP2 and RNPEP as potential subtype markers for ASCL1 and NEUROD1, respectively. In addition, CNDP2 was found to be positively correlated with responses to etoposide, carboplatin, and irinotecan.Conclusions and clinical relevanceBALF is an emerging source of biomarkers, making it useful for the diagnosis and prognosis of lung cancers. We characterized the proteomes of paired BALF samples collected from tumor‐bearing and non‐tumor lungs of SCLC patients. Several proteins were found elevated in tumor‐bearing BALF, and especially CNDP2 and RNPEP appeared to be potential indicators for ASLC1‐high and NEUROD1‐high subtypes of SCLC, respectively. The positive correlation of CNDP2 with chemo‐drug responses would help to make decisions for treatment of SCLC patients. These putative biomarkers could be comprehensively investigated for a clinical use towards precision medicine.

N-ethylmaleimide (NEM) inhibits peripheral nerve degeneration (PND) by targeting Schwann cells in a hydrogen sulfide (H2S)-pathway-dependent manner, but the underlying molecular and pharmacological mechanisms are unclear. We investigated the effect of NEM, an α,β-unsaturated carboxyl compound, on H2S signaling in in vitro- and ex vivo-dedifferentiated Schwann cells using global proteomics (LC-MS) and transcriptomics (whole-genome and small RNA-sequencing (RNA-seq)) methods. The multi-omics analyses identified several genes and proteins related to oxidative stress, such as Sod1, Gnao1, Stx4, Hmox2, Srxn1, and Edn1. The responses to oxidative stress were transcriptionally regulated by several transcription factors, such as Atf3, Fos, Rela, and Smad2. In a functional enrichment analysis, cell cycle, oxidative stress, and lipid/cholesterol metabolism were enriched, implicating H2S signaling in Schwann cell dedifferentiation, proliferation, and myelination. NEM-induced changes in the H2S signaling pathway affect oxidative stress, lipid metabolism, and the cell cycle in Schwann cells. Therefore, regulation of the H2S signaling pathway by NEM during PND could prevent Schwann cell demyelination, dedifferentiation, and proliferation.