Figure 1.

HER2 delays intraluminal apoptosis and GFs induce invasive arm formation by MCF10A spheroids grown in extracellular matrix. (a) MCF10A and MCF10A/HER2 monolayers (50 000 cells) were plated on Matrigel-coated Transwell chambers and incubated for 12 h in the presence or absence of EGF (20 ng/ml). Thereafter, the opposite face of the Transwell filter was stained using crystal violet. The lower part presents quantification of the number of cells that migrated to the other side of the filter. (b) MCF10A and MCF10A/HER2 cells were suspended in 5% Matrigel and 2000 cells were plated on a Matrigel-coated Transwell filter separating two compartments of a Transwell chamber. After 18 days of incubation in the absence or presence of EGF, spheroids were removed from the upper face of the filter, whereas cells located on the lower face were observed using fluorescence microscopy. The lower part shows quantification of the number of invading colonies per field. Bars represent s.d. of triplicate determinations. (c) Confocal microscopy images of acini of MCF10A and MCF10A/HER2 cells plated in Matrigel for the indicated times in the absence or presence of EGF or neuregulin (NRG)-1β (each at 20 ng/ml). Each series represents time-lapse images from the same acinus (bar, 50 μm). (d) Flow diagrams of RNA sampling for microarray analyses. The schemes present multicellular structures exhibited by MCF10A and MCF10A/HER2 cells grown in extracellular matrix, in the absence or presence of EGF. RNA was isolated at the indicated time points and used for hybridization to DNA arrays.