Regenerating Islet Derived Protein 3 Beta (REG3b) also known as PAP-I and HIP is bactericidal C-type lectin which acts against several intestinal Gram-positive bacteria and Gram-negative bacteria. The Reg family proteins have been implicated in a range of physiological processes including acting as acute phase reactants, lectins, survival/growth factors for insulin-producing pancreatic beta-cells, neural cells, and epithelial cells of the digestive system. To test the effect of REG3b on cell proliferation of SK-N-SH, SK-N-SH cells were seeded into triplicate wells of 96-well plates at a density of 5,000 cells/well and allowed to attach overnight, then the medium was replaced with serum-free standard DMEM?prior to the addition of various concentrations of REG3b. After incubated for 72h,?cells were observed by inverted microscope and cell proliferation was measured by Cell Counting Kit-8 (CCK-8). Briefly, 10μL of CCK-8 solution was added to each well of the plate, then measure the absorbance at 450nm using a microplate reader after incubating the plate for 1-4 hours at 37°C .Cell proliferation of SK-N-SH cells after incubation with REG3b for 72h observed by inverted microscope was shown in Figure 1.

The dose-effect curve of REG3b was shown in Figure 2. It was obvious that REG3b significantly promoted cell proliferation of SK-N-SH cells. The ED50 for this effect is typically3.685-84.37ng/mL.