Figure 2.

Cancer genes adopt the IGF1 signaling pathway. IGF1 is regarded as a non-genotoxic growth factor, i.e., it is unable, in itself, to induce mutations or transformation. However, once an oncogenic event has occurred, IGF1 can enhance proliferation and survival of already transformed cells. In the context of the ‘two hit hypothesis’, IGF1 action is regarded as a second, or permissive, hit. Multiple cancer genes, including oncogenes and anti-oncogenes, adopt the IGF1 signaling pathway. In agreement with this notion, cells devoid of the IGF1R usually do not undergo transformation.