Metastatic tumor burden and proliferative capacity are decreased in the presence of mCAT. Surface area of metastatic foci in lungs of PyMT/WT mice (A) was significantly larger than metastatic foci in lungs of PyMT/mCAT mice (B). Arrows indicate metastatic tumors. Original magnification was at 2.5×. C. Ki-67 staining of PyMT metastatic tumor cells negative for mCAT showed a labeling percent of 23. D. Ki-67 staining of PyMT metastatic tumor cells positive for mCAT showed a labeling per cent of 6. The difference in ki-67 labeling between mCAT positive and mCAT negative PyMT metastatic tumor cells was significant at p ≤ 0.01.