Abstract 1418: Dll4-Fc, an inhibitor of Dll4-notch signaling, suppresses liver metastasis of small cell lung cancer cells through down-regulation of NF-kappa-B activity

Abstract

Abstract Purpose: The Notch signaling regulates cell-fate decisions during development and postnatal life. Recent studies have demonstrated that the signaling through Notch and its ligand Dll4 in tumor endothelial cells plays an important role in cancer angiogenesis. Little is known, however, about the role of Dll4-Notch signaling between cancer cells, and how it affects on cancer metastasis. We therefore assessed the importance of cancer cell Dll4-Notch signaling in cancer metastasis produced by human small lung cancer cells. Experimental Design: On the basis of previous studies, we generated retroviral vectors encoding a soluble dimerized form of Dll4 fused to the human IgG1 Fc constant region (Dll4-Fc) that acts as a blocker of Dll4-Notch interactions. Dll4-Fc was introduced into human small cell lung cancer cell lines that express high level of Dll4 and Notch (SBC-3 and H1048 cells), and low level of Dll4 (SBC-5 cells). The cells were intravenously inoculated to natural killer cell-depleted SCID mice, and the multiple-organ metastases were evaluated. Result: The number of liver metastasis in the mice inoculated with SBC-3 and H1048 cells expressing Dll4-Fc were significantly lower than that of liver metastasis formed by control transfectant cells. However, the number of liver metastasis formed by SBC-5 cells was not significantly different between Dll4-Fc expressing and control cells, suggesting that Dll4-Notch signaling in cancer cells plays important role in liver metastasis of small cell lung cancer. Metastatic colonies in other organ such as lung, kidney and bone were not affected by Dll4-Fc overexpression in each cell lines. In order to study the molecular mechanism of the effect of Dll4-Fc on liver metastasis, genes associated with metastasis were screened by PCR array system. Seven genes (MMP7, IL1B, MMP1, S100A4, MMP10, CXCR4, SERPINE1) were down-regulated in Dll4-Fc-overexpressing SBC-3 and H1048, but not SBC-5 cells, compared with control transfectant cells. Since most of the selected genes were NF-kappa-B target genes, we explored whether NF-kappa-B is involved in cancer cell Dll4-Notch signaling. By using luciferase assay, we observed that NF-kappa-B activity was down-regulated in Dll4-Fc-overexpressing SBC-3 and H1048 cells, but not SBC-5 cells, compared with control transfectant cells, indicating that Dll4-Fc inhibits NF-kappa-B activity in small cell lung cancer cells by suppressing Dll4-Notch signaling. Conclusion: These results suggest that Dll4-Notch signaling in cancer cells plays a critical role in liver metastasis of small cell lung cancer, by regulating the NF-kappa-B signaling. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1418. doi:1538-7445.AM2012-1418