MAPK3 and neoplasm: Even though the activation of ERK1/2 was also increased in C4-HI tumors as compared to C4-HD tumors (Figure 1A), the role of the RAS-RAF-MEK-ERK1/2 pathway in tumor growth does not seem to be pivotal since PD98059 treatment did not interfere with either C4-HD or C4-HI tumor growth (Figure 1C).