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.