Fig. 3.

LMS⁺ primary tumors intravasate upon reaching larger tumor sizes. (A) Mice bearing parental or LM2 tumors grown in the mammary gland to various sizes were killed and bled via cardiac puncture. Mouse blood was lysed and plated in culture. Tumor cell colonies were scored and plotted as a function of tumor volume. (B) A suspension of 200 LM2 or parental MDA-MB-231 cells expressing luciferase were injected into the tail vein of mice. The development of lung metastasis was monitored over the indicated time course by using noninvasive luciferase bioluminescence imaging and quantitated by measuring photon flux. Values are the mean of four animals ± SEM. Representative mice from each group are shown.