Figure 1. IL-22 promotes growth of breast cancer cells in vivo. (A–C) 4T1 cells (2×105) were injected into a single mammary fat pad of BALB/c mice (n=6). (D–F) MCF7 cells (2×106) and (G–I) MDA-MB-231 cells (2×106) were inoculated subcutaneously to BALB/c Nude mice (n=6). From day 3 post cell inoculation, mice were injected with PBS or recombinant murine IL-22 (rmIL-22, 20 μg/kg) or recombinant human IL-22 (rhIL-22, 20 μg/kg) thrice weekly for up to 3 weeks. (A, D, G) Tumor size was measured continuously. (B, E, H) 4T1 tumors were collected on day 15. MCF7 and MDA-MB-231 tumors were collected on day 30. Histological analyses were performed by H&E staining and Ki-67 immunohistochemical staining. Scale bar: 500 μm. (C, F, I) Percent of Ki-67-positive cells were counted (n=4). Data are from two independent experiments. Data are presented as mean ± SD, compared using unpaired t test. *p < 0.05.