R-Ras-expressing cells produced few tumors (that is, tumors only formed at 2 out of 13 allograft sites), and tumors that did form were <2 mm in diameter and appeared avascular, consistent with previous observations with R-Ras (Figure 5b, Table 1).13, 14, 43, 44 In contrast, R-Ras-tH cells produced tumors at 50% of injection sites, and average tumor mass in these cases was ~2.3-fold higher than those generated by cells expressing R-Ras, indicating that fusion of the tH domain enhances tumorigenesis by R-Ras. This evidence concerns the gene RRAS and neoplasm.