FIGURE 6.

Tumor-suppressive effects of the Pcdhβ cluster. A, wild-type her-2 tumor cells and MDA-MB231 cells were transfected with either Pcdhβ4 or Pcdhβ19 cDNA and grown in selection medium for 2–3 weeks for colony formation. The number of colonies in six random fields was counted and expressed as the mean with error bars indicating ±1 S.D. * represents Student's t test, p < 0.001. B, transfected cells were grown in soft agar for 2–3 weeks, and the number of colonies in six random fields was counted and expressed as the mean with error bars indicating ±1 S.D. *, p < 0.05. C, Pcdhβ4-transfected wild-type her-2 tumor cells (2 × 10⁶) were injected into mammary fat pads of SCID mice (n = 5), and secondary tumor growth was observed for up to 8 weeks. *, p < 0.05. D, secondary tumors in SCID mice formed by injection of Pcdhβ4-expressing cells were dissected at week 8 and photographed (left panel), and the weight of tumors was quantified and expressed as the mean with error bars indicating ±1 S.D. (n = 5; right panel). *, p < 0.05. E, ALDEFLUOR assays of Pcdhβ4-expressing her-2 tumor cells (left panel) and xenografts formed by injection of Pcdhβ4-expressing her-2 cells (right panel) were performed, and the percentage of ALDEFLUOR-positive cells (tumor initiating cells) was determined using similar gating criteria. Data are representative of two independent experiments. DEAB, diethylaminobenzaldehyde.