NOTCH1 and cancer: To validate the mechanism of the density-dependent features of malignant cancer cells, various pharmaceutical inhibitors targeting inter-cellular contact (GSI against Notch1, β-GA against gap junction, RGDFV against integrin αvβ3/αvβ5, and A205804 against ICAM-1/E-selectin) were tested for the effects on U251-MG cells grown to high density.