Abstract 3158: DLL3 regulates migration and invasion of small cell lung cancer

Abstract

Abstract Background: Delta-like protein 3 (DLL3) is a ligand of Notch signaling, which is reported to be a tumor suppressor in small cell lung cancer (SCLC). Previous studies suggest that DLL3 might be associated with neuroendocrine tumorigenesis through inhibition of Notch signaling unlike other activating ligands. Moreover, DLL3 was highly expressed in SCLC, but not in normal lung tissue. However, little is known about function of DLL3 in SCLC. In this study, we examine the effect of DLL3 in tumorigenesis of SCLC. Methods: The mRNA expression levels and proteins of DLL3, Notch receptors (Notch1, Notch2, Notch3 and Notch4), Hes1 and EMT markers (E-cadherin, Snail and Vimentin) were examined using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blot in 9 SCLC cell lines (SBC-3, SBC-5, MS-1, RERF-LC-MA, H69, H82, H209, H529 and H1688). We used small interfering RNA (siRNA) to down-regulate the expression of DLL3 in SCLC cell lines. Anchorage-dependent and anchorage-independent cell growth was measured by MTT assay and migration and invasion were assessed by transwell assay. Results: The mRNA of DLL3 was expressed in all of 9 SCLC cell lines. The expression of DLL3 was especially higher in H82, H69, H209, H529 and H1688 cells. Notch1 protein was expressed in SBC-3, SBC-5, MS-1 and H82. Based on DLL3 expression analysis data, we used H82 and H69 in the following experiments. The suppression of DLL3 by siRNA resulted in the moderate inhibition of cell growth of H82 cells in both anchorage-dependent and anchorage-independent cell proliferation. The depletion of DLL3 prevented migration and invasion in the two cell lines. The expressions of Notch1 and Notch target gene, Hes1 were downregulated by DLL3 knockdown in both SCLC cells. Because Notch pathway was reported to regulate EMT, we evaluated the EMT markers when DLL3 was inhibited in SCLC cells. Snail was downregulated in DLL3 knockdown SCLC cells, while protein expression levels of E-cadherin and Vimentin were not changed in these DLL3 knockdown cells compared to control cells. Conclusions: DLL3 promotes the migration and invasion in SCLC cells by modulating Notch1 and Snail. Citation Format: Megumi Furuta, Jun Konishi Sakakibara, Tetsuaki Shoji, Yuta Takashima, Hajime Kikuchi, Eiki Kikuchi, Junko Kikuchi, Ichiro Kinoshita, Hirotoshi Dosaka Akita, Masaharu Nishimura. DLL3 regulates migration and invasion of small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3158.