ARHGAP5 and neoplasm: Analysis of BrdU incorporation, a marker of S phase, indicated that proliferation rates were similar in p190B transgenic and control tumors (4.1 +/- 0.13% vs. 4.9 +/- 0.49%, P > 0.05, n =6 tumors/group, a minimum of 5,000 cells/tumor were counted) (Figure 2a, c).