MAPK3 and neoplasm: Phosphorylation of the mitogen Erk1/2 in tumor cells in response to CM exposure, however, was not sensitive to siRNA mediated targeting of HS in the CM (Figure 4B), implying that the activation of chemokine-mediated migration-associated pathways (i.e., p-FAK, p- GSK3β) in the tumor cells appears to be more sensitive to the HS alteration than the effect on activation of a major mitogen (i.e., p-Erk1/2) pathway.