Interestingly, the number of GFP-positive cells was significantly increased in the bevacizumab-resistant tumours (Fig. 4a,b), and the collagen type I+/CXCR4+ cells were also GFP-positive (Fig. 4c), suggesting that the origin of the collagen type I+/CXCR4+ cells was the bone marrow. The gene discussed is CXCR4; the disease is neoplasm.