Therapeutic Discovery Dll4-Fc, an Inhibitor of Dll4-Notch Signaling, Suppresses Liver Metastasis of Small Cell Lung Cancer Cells through the Downregulation of the NF-kB Activity

Notch signaling regulates cell-fate decisions during development and postnatal life. Little is known, however, about the role of Delta-like-4 (Dll4)-Notch signaling between cancer cells, or how this signaling affects cancer metastasis. We, therefore, assessed the role of Dll4-Notch signaling in cancer metastasis. We generated a solubleDll4 fused to the IgG1 constant region (Dll4-Fc) that acts as ablocker ofDll4-Notch signaling and introduced it into human small cell lung cancer (SCLC) cell lines expressing either high levels (SBC-3 and H1048) or low levels (SBC-5) ofDll4. The effects ofDll4-Fc onmetastasis of SCLCwere evaluatedusing amouse model. Although Dll4-Fc had no effect on the liver metastasis of SBC-5, the number of liver metastasis inoculated with SBC-3 and H1048 cells expressing Dll4-Fc was significantly lower than that injected with control cells. To study the molecular mechanisms of the effects of Dll4-Fc on liver metastasis, a PCR array analysis was conducted. Because the expression of NF-kB target genes was affected by Dll4-Fc, we conducted an electrophoretic mobility shift assay and observed that NF-kB activities, both with and without stimulation by TNF-a, were downregulated inDll4-Fc–overexpressing SBC-3 andH1048 cells comparedwith control cells. Moreover, Dll4-Fc attenuates, at least in part, the classical and alternative NF-kB activation pathway by reducingNotch1 signaling. These results suggest thatDll4-Notch signaling in cancer cells plays a critical role in liver metastasis of SCLC by regulating NF-kB signaling. Mol Cancer Ther; 11(12); 1–10. 2012 AACR.