MKI67 and neoplasm: In agreement with the observation that reduced ABCC5 levels did not negatively influence primary tumor growth (Additional file 9), we did not observe statistically significant differences in the percentage of Ki67-positive nuclei in primary tumors derived from 1833-BM1 or 4T1 cells, possessing normal or shRNA-reduced levels of ABCC5 (see Additional file 11A and B).