Retinoic Acid Mediates Regulation of Network Formation by COUP-TFII and VE-Cadherin Expression by TGFβ Receptor Kinase in Breast Cancer Cells
Figure 4
COUP-TFII is necessary for network formation while TGFβR1 activity is necessary for cell fusion.
Low power images (20×) of control siRNA transfected untreated SKBR-3 cells show that they grow as clusters of individual cells in Matrigel (a) without any cell fusion (inset, 40×). Upon RA treatment, the cells begin to form networks (b) with cell fusion (inset). Loss of VE-cadherin expression using VE-cadherin siRNA does not affect untreated SKBR-3 cells (c, inset). However, a loss of VE-cadherin expression with concomitant RA treatment results in a preservation of network formation (d), but a loss of cell fusion (inset). Like the VE-cadherin siRNA treatment, COUP-TFII siRNA treatment does not affect the growth patterns of untreated SKBR-3 cells (e, inset). However, treatment with COUP-TFII siRNA does not affect the fusion of RA treated SKBR-3 cells (f, inset), but it does inhibit network formation (f). Untreated SKBR-3 cells also grow as clusters of unfused individual cells in the absence of RA treatment (g, inset), and RA treatment results in network formation and cell fusion (h, inset). Pre-treatment with 50 µM SB431542 does not affect the growth patterns of untreated SKBR-3 cells (i, inset). Pre-treatment with SB431542 prior to RA treatment does not alter network formation (j), but inhibits cell fusion (j, inset).