Specifically, Hu et al. employed human umbilical cord CD34+ stem cells transfected with the pIRES2-IL-21-EGFP plasmid, carrying the anti-tumour cytokine IL-21, and demonstrated a therapeutic effect in ovarian cancer xenografts, possibly due to tumour-specific NK cytotoxicity, as a result of elevated levels of IFN-γ and TNF-α. Here, IL21 is linked to ovarian cancer.