Figure 5. Loss of Rb promotes hypoxia-dependent invasiveness in MCF7 cells in a Matrigel Invasion Assay - MCF7 cells were transfected with scrambled siRNA (SCX) or Rb siRNA as described above.

Twenty-four hours after siRNA transfection, the cells were subjected to the Matrigel invasion assay. Plates were incubated in normoxic (20% O₂) or hypoxic conditions (1% O₂) at 37°C for 24 h and invading cells were fixed and visualized with toluidine blue. (A) Photomicrographs of matrigel-embedded MCF7 cells. (B) Numerical representation of relative invasion of matrigel-embedded MCF7 cells after treatment with SCX or siRb and exposure to normoxic or hypoxic conditions (n = 6), (C) Knock-down of Rb in MCF7 cells does not alter cell proliferation in response to CoCl₂. Cells were transfected with siRNA’s as described above. Twenty-four h after transfection, cells were treated with vehicle or 100 µM CoCl₂ to activate HIF1α and cells were counted at 0, 6, 12, 24, 36 48, and 72 h later. Error bars represent ± S.E.M. *p<0.01.