ROR1P808A has impaired capacity to induce activation of Rac1/2 or to enhance leukemia cell proliferation. (A) Activated Rac1, Rac2 (B), and RhoA (C) were measured in MEC1-Ctrl, MEC1-ΔPRD, MEC1-ROR1, or MEC1 cells expressing any 1 of the mutated forms of ROR1, as indicated on the top. The numbers above each lane are ratios of band IOD of GTP-Rac1/2 vs total Rac1/2. The numbers between 2 lanes are ratios of band IOD of GTP-Rac1/2 vs total Rac1/2, or GTP-RhoA vs total-RhoA. (D) Mean numbers of MEC1-Ctrl (blue), MEC1-ROR1 (red), or MEC1 cells expressing each of the mutated forms of ROR1 (colors indicated in the legend) at the days indicated below the graph. Data are shown as mean ± SD from 5 independent experiments. Longitudinal mixed effects model analysis was performed to get a global P value for the differences in proliferation rate compared with control. This model takes into account growth overtime (baseline is day 0 and then subsequent measurements were on days 1, 2, and 3), as well as cell type; this showed ROR1, P874A, P826A, and P841A each grew significantly more rapidly compared with Ctrl cells (P < .0001); ΔPRD and P808A cells did not differ from Ctrl cells (P = .60 and .26, respectively).
