Extracellular Vesicular Delta-Like Ligand 3 and Subtype Transcription Factors for Small Cell Lung Cancer Diagnosis

Small cell lung cancer (SCLC) is associated with high mortality and limited therapeutic options. There is increasing recognition that SCLC harbors molecular heterogeneity. Using a new liquid biopsy assay, it is demonstrated that SCLC subtypes, as determined by patient tumor tissue staining and cell lines, can be accurately identified by measuring the mRNA expression of subtype transcription factors (ASCL1, POU2F3, and NEUROD1) in circulating exosome-rich extracellular vesicles (Exo). Additionally, upregulation of Delta-like ligand 3 (DLL3) mRNA in Exo and its membrane protein (mProtein) in extracellular vesicles associated with tumor (tEV) may distinguish both limited- and extensive-stage SCLC patients from high-risk smokers, with AUC/ROC values of 0.836 and 0.839, respectively. By incorporating Exo-ASCL1 and Exo-POU2F3 mRNA expression with DLL3 Exo-mRNA/tEV-mProtein expression, the classifier enhances the AUC/ROC to 0.912 and 0.963 for limited- and extensive-stage SCLC patients, respectively.