Surface plots of tumor cell proliferation versus the concentration of Aβ40 and Aβ42 in the CM. Second-order polynomial was used to approximate the relationship between the tumor cell proliferation and Aβ40 (A), Aβ42 (B) concentrations. Using the derived polynomial, the tumor cell proliferation from minimum Aβ40 and Aβ42 concentrations to maximum concentrations at a step size of 5 was calculated. The Matlab® command "surf" was used to plot the proliferation of three tumor cell lines as a function of the Aβ40 and Aβ42 concentrations. The region of high cell proliferation (red zone) lies at low Aβ concentrations.