Ki67 and CD31 staining of histological tissue sections revealed a greater number of proliferating cells (Figure 2E–2F) and CD31 positive vessels (Figure 2G–2H) in tumour biopsies from mice injected with MDA-231 cells over-expressing IKKβ, indicative of enhanced tumour growth and angiogenesis, respectively. The gene discussed is PECAM1; the disease is neoplasm.