IFNL1 and neoplasm: On the other hand, a direct intratumoural injection of Ad/IFN-λ1 or Ad/IFN-λ2, or injection of Ad/IFN-λ2 or Ad/IFN-λ2-infected P6X cells into established YES-2 tumours produced little anti-tumour effects (data not shown), which could be due to inefficient Ad-mediated transduction efficacy and Ad retention at the tumour sites or due to a poor migration activity of the transduced P6X cells into YES-2 tumours.