After treating with M1557 peptide for 48 hours, cancer cell proliferation was inhibited by about 15% with significant effects at doses of 0.01 μM onward. Again, this inhibition was in a dose responsive manner (A). To detect whether cellular proliferation inhibition was the result of interference with IGF-I signalling, two further experiments were performed with serum free medium. In the first set of experiments cells were treated with different concentrations of recombinant human IGF-I and it can be seen that IGF-I increased cancer cell proliferation in serum free medium. The increase was in a dose responsive manner (B). In the second set, cells were also treated the same as in the first set of experiments, but also with addition of 2 μM M1557 peptide in all samples. It can be seen that with M1577 inclusion, the IGF-I enhancing- proliferation dose response curve vanished (C). Significance value: * P < 0.05; ** P < 0.001.