Tracking Breast Cancer Tumor Growth and Angiogenesis with Perfluorocarbon Microbubbles

Abstract

Objective: In this study, I have directly tracked the progression of angiogenesis for three different types of breast cancer cell lines; MDA-MB-231, MCF-7, and MDA-MB-468. Each of these cell lines is known to overexpress different receptors, which may affect a tumor’s growth rate and perhaps its ability to undergo angiogenesis. Here, I measure and compare the growth, extent, and time of onset for angiogenesis. Methods: I used SCID mice to profile each of the different breast cancer cell lines. The growth rate of each tumor, along with its blood vessel development, was monitored and imaged using lipid-coated microbubbles and contrast-enhanced ultrasound (CEUS). A Vevo 2100 pre-clinical ultrasound machine was used for the imaging experiments. To track development of angiogenesis, mice were injected with perfluorobutane gas microbubbles of 1-2 microns diameter. Bubble perfusion into the tumor is an indicator of the presence of blood vessel formation. A custom image analysis program was developed in Matlab™ to eliminate breathing artifacts and track microbubble motion based on their high temporal frequency signature ("flicker"). Results: My experiments demonstrated that, although different cell lines grow at different rates, microbubbles begin to penetrate the tumor when it reaches approximately a size of approximately 3 mm in diameter. Therefore, the onset of angiogenesis occurred at different times (MCF-7 occurring first at around 9 days, MDA-MB-468 occuring at 12 days post inoculation, and MDA-MB-231 occurring at 17 days post tumor cell inoculation). Matlab™ analysis demonstrates consistent angiogenic behavior among the three cell lines. Conclusion: For all cell lines, angiogenesis started when the volume of the tumor was approximately 21.76 mm³, consistent with previous studies. As angiogenesis progressed, there was a drop in tumor blood flow. This can be explained by the sudden influx of oxygen when angiogenesis first begins. This momentarily inhibits new blood vessel formation while the tumor continues to steadily grow. After this sudden drop, tumor vascularization resumes a steady increase.