Preventing the spread of cancer is a major step in the battle against the disease. Researchers at Beth Israel Deaconess Medical Center have conducted research on cells within tumors that regulate cancer growth and metastasis. Their findings indicate that a common treatment targeting a specific type of cell, pericytes, prevents tumor growth but increases the aggressive spread of cancer in the body. Lab tests revealed that tumors lacking pericytes had weakened vasculature, which reduced the amount of oxygen that the tumor was able to receive. In response to the lack of oxygen in the tumor, surrounding cancer cells began small mutations called epithelial-to-mesenchymal transition (EMT), which enabled easier movement to other nearby locations in the body. Lab results were compared with pericyte levels in 130 breast cancer samples of varying stages and sizes. Samples with low pericytes in the tumor vasculature were consistent with deeply invasive cancers.