Neither AT2 cell number nor their ability to incorporate BrdU was altered in Npc2+/hypo BVE mice at the pre-senescent stage of tumour development (5 weeks p.p.; Supplementary Fig S9), demonstrating that NPC2 does not regulate the intrinsic growth of the pre-malignant tumour cells, at least at the pre-senescent stage. This evidence concerns the gene NPC2 and neoplasm.