DKK1 and cancer: The expression levels of 5 cytokine genes commonly involved in cancer growth [33–35], including Dickkopf WNT signaling pathway inhibitor 1 (DKK1), transforming growth factor-β (TGF-β), interferon-β (IFN-β), interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α) in CH-hMSCs and PL-hMSCs were determined by quantitative real-time PCR.