Figure 7
c-Myb delays mammary tumor growth and prevents the formation of pulmonary metastases. The tumor growth and spontaneous metastatic ability of the myb-less vector-transfected (control) 4T1 and 4T1M-M5 cell variant (MYBup) were determined following orthotopic inoculation into the mammary fat pads of BALB/c mice. (A) Tumor growth was monitored twice a week by measuring the tumor length (l) and width (w). Tumor volume was calculated using the equation l × w2/2. The mice injected with the MYBup 4T1 variants (n = 9) and control 4T1 cells (n = 9) were euthanized when the mean tumor diameter was approximately 1.2 cm. (B) Lungs were removed, rinsed in water, and fixed in Bouin's solution. Liver and bones were harvested and fixed in 10% buffered formalin. The number of lungs with surface metastases was determined using dissecting microscopy, and metastases in liver and bones were determined by histological examination of H&E-stained sections. Percentage of the mice with metastases (mts) developed in lung, liver and bones, respectively, is shown. (C) The surface metastatic nodules per lungs (mts) exemplified under the graph were enumerated by examination using dissecting microscopy. Asterisks indicate significant (p < 0.01) differences in the number of lung metastases in the mice injected with MYBup 4T1 variants and control 4T1 cells as determined by the t-test. Error bars indicate standard deviations. Representative samples of Bouin's solution-fixed tissues are shown. (D) Tissues were processed for paraffin embedding, sectioned, and stained with H&E. Bones were decalcified overnight before embedding. The lung, liver, and bone metastases were identified by light microscopy (arrows).