Figure 2

KIF5B-RET fusion kinase is constitutively active and enhances cell proliferation in vitro. A. KIF5B-RET fusion kinase is constitutively active. A549 lung cancer cells were transfected with an empty vector, wild-type RET (RET) or KIF5B-RET variants1 or 2 expression plasmids, and cultured without GDNF for 48 hour. The level of phosphorylated Tyr905 (pTyr905) RET in cell lysates was analyzed by western blots. B. Expression of KIF5B-RET fusion protein enhances positive cell proliferation in vitro. A549 cells carrying KIF5B-RET,RET or empty vector were seeded in 6-well plates and cultured for 7 days, and cell numbers were obtained at the indicated time (^*P < 0.05, ^**P < 0.01, Student’s t test). C. Expression of KIF5B-RET fusion protein enhances the colony forming ability of positive cells in vitro. A549 cells carrying KIF5B-RET, RET or empty vector were seeded in 6-well plates, and cultured for 14 days. The total number of colonies, each containing more than 40 cells, were determined (^*P < 0.05, ^**P < 0.01, Student’s t test).