Transparent Zebrafish Show Breast Cancer Cells Invading Bloodstream in Study Using Video

Transparent Zebrafish Show Breast Cancer Cells Invading Bloodstream in Study Using Video

A Georgetown Lombardi Comprehensive Cancer Center research team has published a paper that details — in words and through video — the steps allowing scientists to track cancer cell invasion and metastasis in real time, using transparent zebrafish embryos. The approach was developed using breast cancer cells capable of entering the bloodstream.

The paper, “Testing the Vascular Invasive Ability of Cancer Cells in Zebrafish (Danio Rerio),” and published online in the Journal of Visualized Experiments (JoVE).

The method may replace mice models in studies of cancer biology and for drug development, the researchers said, because of its speed and effectiveness at capturing cancer cell movement. Zebrafish, a tropical freshwater minnow, are commonly used in many research areas, but are only beginning to be of interest in cancer studies.

“Invasion of the blood system is a significant step towards the metastatic spread of cancer cells, which is a significant threat to patients with cancer,” Anton Wellstein, MD, PhD, co-senior investigator in the study and Georgetown professor and deputy director, said in a press release. “This method uses human cancer cells in zebrafish and can reveal distinct invasive properties of cancer cells, help identify genes that drive vascular invasion as well as to allow to test drugs that inhibit it.”

Zebrafish are “increasingly used in oncology research, but the technique, which has a lot of moving parts, hadn’t been written up,” Wellstein added.

Researchers in his lab worked with Eric Glasgow, PhD, director of Georgetown’s zebrafish lab, to explain their approach. They evaluated seven different lines of breast cancer cells to determine which ones invaded the blood system, and how aggressively.

To visualize the work, they injected fluorescent cancer cells into the precardiac sinus of 2-day-old zebrafish embryos, “whose vasculature is marked by a contrasting fluorescent reporter.” Then, at time points 24 to 96 hours later, they used fluorescence microscopy to see the cells entering the blood and spreading. The technique, they reported, can be modified for different research needs by switching the injection site to the embryonic yolk sac.

“Together, these methods can evaluate a hallmark behavior of cancer cells and help uncover mechanisms indicative of malignant progression to the metastatic phenotype,” the researchers wrote.

“One could envision using this model system in the future to test how aggressive an individual person’s cancer is, and what treatments might work best against it,” said Eric Berens, a PhD student and study co-author.

The team previously published two zebrafish studies, looking at tumor aggressiveness, in the journal Oncogene.

One, a 2015 study, demonstrated that cancer cells grown at tight density in a culture are more likely to be invasive cells. Another, published this year, used a screening methodology to identify an unstudied gene, the keratin-associated protein 5-5 (Krtap5-5), and to suggest that it served as a “switch” toward malignancy.