Analysis of DLL3 and ASCL1 in Surgically Resected Small Cell Lung Cancer (HOT1702)

Background: Delta-like protein 3 (DLL3) is a Notch ligand that has an important role in the tumorigenesis of small cell lung cancer (SCLC). Recently, rovalpituzumab tesirine (Rova-T), a DLL3-targeted antibody-drug conjugate, has been developed for treating SCLC. DLL3 is a transcriptional target of the achaete-scute homolog-1 (ASCL1) transcription factor, which is involved in pulmonary neuroendocrine cell development. However, the relationship between DLL3 and/or ASCL1 expression and the clinical features of SCLC remains unknown, especially for early-stage resected SCLC. This study aimed to investigate the expression of DLL3 and ASCL1 in resected SCLC samples using immunohistochemical analysis. Materials and Methods: We collected 95 surgically resected SCLC samples, which were formalin fixed and paraffin embedded. Immunohistochemistry staining was performed to investigate the correlation between the expression of either DLL3 or ASCL1 and clinicopathological features of study patients. Results: Seventy-seven (83%) of 93 immunohistochemically evaluable samples were positive for DLL3 (expression in ≥1% of tumor cells), and DLL3-high expression (≥75%) was observed in 44 samples (47%). Sixty-one (64%) of 95 samples were positive for ASCL1 (expression in ≥5% of tumor cells). A positive correlation was observed between DLL3 and ASCL1 expression. DLL3 and ASCL1 expression were not associated with survival in SCLC patients. DLL3 was more prevalent in patients with advanced clinical disease. Conclusion: DLL3 and ASCL1 were highly expressed in patients with surgically resected SCLC. DLL3 and ASCL1 may be targets for the treatment of SCLC. Implications for Practice: This article examines the relationship between delta-like protein 3 (DLL3) and achaete-scute homolog-1 (ASCL1) protein expression with the clinical features of 95 surgically resected small cell lung cancer (SCLC). DLL3 is attracting attention because rovalpituzumab tesirine (Rova-T), a DLL3-targeted antibody-drug conjugate, was developed recently. DLL3 and ASCL1 were highly expressed in patients with surgically resected SCLC. DLL3 and ASCL1 may be targets for the treatment of early-stage SCLC, including with Rova-T.