Figure 6.

Combined PLX3397 and PTX treatment inhibits metastasis in a CD8-dependent manner. A and B, improved outcome following PLX3397/PTX treatment dependent on CD8⁺ T cells. A, 85-day-old MMTV-PyMT mice were treated with PTX or PLX3397 or both, as well as anti-CD8 IgG. Total tumor burden per animal was assessed every 5 days. B, orthotopic PyMT-derived tumors were grown to a median diameter of 1.0 cm, at which time mice were treated with PTX or PLX3397 or both in combination with anti-CD8 or control IgG for 21 days, and total tumor burden per animal was assessed every 2 to 3 days. Treatment regimens are depicted along with SEM; *, statistically significant differences between mice treated with PTX alone and those treated with PLX3397/PTX. **, significant differences between mice treated with PLX3397/PTX and those treated with anti-CD8 and PTX/PLX3397/control IgG. C, histologic stage analysis of MMTV-PyMT tumors. Tumors from 100-day-old MMTV-PyMT mice treated with anti-CD8 IgG or with PTX and/or PLX3397 were assessed for presence of premalignant tissue and early- and late-stage carcinoma; data expressed as mean percentage of total gland area ±SEM. D, quantification of cleaved caspase-3–positive cells in mammary tumors of MMTV-PyMT mice treated with anti-CD8 IgG or with PTX and/or PLX3397 versus control (vehicle). Graph depicts mean positive cells per µm² of tumor tissue. E, quantification of metastatic foci per lung section per mouse from 100-day-old MMTV-PyMT mice treated with PTX and/or PLX3397 and/or anti-CD8 IgG, versus controls. Each lung was serially sectioned, 6 sections 100 µm apart were stained with hematoxylin and eosin (H&E), and the total number of metastatic foci (>8 cells) was quantified per mouse (n ≥10 mice per cohort). SEM is depicted. *, Statistically significant differences (P < 0.05, Mann-Whitney). Representative photomicrographs of lung tissue sections reveal metastatic foci from 100-dayold MMTV-PyMT mice treated with vehicle or with PTX and/or PLX3397. Scale bar, 500 µm.