Effect of chloroplast-derived IGF-1 on HU-3 cell proliferation. IGF-1 was added to HU-3 cells; 48 hours later, cell proliferation was measured by the Cy-QUANT NF Cell proliferation assay (Invitrogen) and by hemocytometer counting. Proliferation was measured by fluorescence determination of DNA replication based on intercalation of a fluorescent dye into double stranded DNA. Cell proliferation was determined according to the instructions supplied by the manufacturer. Red (chloroplast derived IGF-1), blue (Sigma IGF-1), and green (negative control) lines represent the best fit of the respective data points for each proliferation assay treatment. Top row shows concentration (ng/ml) of IGF-1 (Sigma). Bottom numbers are dilution factor of chloroplast-derived IGF-1. Negative control is the dilution of the TS buffer.