Intratumoral administration of NDV-ICOSL into B16-F10 tumours resulted in ICOSL upregulation in ∼2% of tumour cells at 24 h (Fig. 2f), which was consistent with the number of tumour cells predicted to be infected after the first cycle of viral replication (18 h) due to initial infection primarily taking place at the tumour periphery. This evidence concerns the gene ICOSLG and neoplasm.