MDK and neoplasm: We first analyzed midkine expression at both mRNA and protein level in vitro and in vivo, and the results showed that reduced midkine expression was observed in Huh7 cells with IGF-1R inhibition and in tumor tissues of nude mice inoculated intratumorally with lentivirus-IGF-1R siRNA compared with their negative controls or blank controls (Figure 9A–9C).