Since all primary mammary tumors were approximately the same size when they were collected, and mice bearing 231MXRA8KO-O and 231MXRA8KO-V tumors had more time to metastasize (90 and 65 days, respectively) compared to 231MXRA8Con tumors (44 days), this observation truly represents a decrease in lung metastases in MXRA8-knockout tumors. The gene discussed is MXRA8; the disease is breast cancer.