TKT and neoplasm: IHC staining for myeloid cells and blood vessels in tumor tissues (Figure 5A) revealed that tk/GCV treatment significantly increased the number of infiltrating CD11b+ myeloid cells (32.1% to 61.4%), and F4/80+ TAMs (15.0% to 36.1%), but not Gr-1+ granulocytes (6.9% to 3.6%) (Figure 5B–D) when compared with the control group (Figure 3).