RBC numbers found in the lung parenchyma were lower in 40-week-old mice compared to 20-week-old mice suggesting impaired pulmonary capillary perfusion and were consistent with higher HIF1α levels in 40-week-old mice compared to 20-week-old mice after the injection of 4T1 breast cancer cells (Figure 8B). This evidence concerns the gene HIF1A and breast carcinoma.