Could Chicken Eggs Be a Low-Cost Option for Cancer Studies?

Researchers from King’s College London (KCL) suggest that fertilized chicken eggs could provide a low-cost option for cancer imaging studies, potentially helping to resolve some ethical and economic issues. The study is published in npj Imaging.

Fertilized chicken eggs for imaging studies

Positron emission tomography (PET) scans produce 3D pictures of the human body and are commonly used to monitor the effectiveness of cancer treatments. They create images by detecting radiation from an injectable radioactive chemical called a radiotracer, which typically collects within tumors.

Experimental mouse models are used extensively in cancer research studies and are particularly useful for PET imaging studies. However, experimental mice are also very costly, low-throughput and limited in their use by animal welfare considerations.

Researchers are now trying to find alternatives to experimental mice that could resolve some of these issues. One possible solution is to use chicken eggs, as the fertilized eggs contain a membrane rich in blood vessels called the chorioallantoic membrane (CAM).

Chick CAM provides an ideal environment for tumor growth and has been used in studies of cancer spread (metastasis) and blood vessel growth (angiogenesis) previously.

Pivoting towards chick CAM follows the 3R principles (replacement, reduction and refinement) of using animals in research, as they are not recognized as a “protected species” until day 14 of embryonic development.

KCL researchers in the current study wanted to determine whether fertilized chicken eggs could be a viable option instead of mice for pre-clinical cancer imaging studies.

In-egg imaging

The research team was led by Dr. Tim Witney, senior author and a reader in molecular imaging at KCL’s School of Biomedical Engineering and Imaging Studies. The team added non-small cell lung cancer cells to the chick CAM to grow and produce a tumor. To enable PET imaging, they designed a simplified method to cannulate the CAM blood vessels using an ultra-sharp needle that allowed delivery of the radiotracer. This new method had a success rate of ~75%.

They then compared PET imaging in mouse models and chick CAM using the gold-standard radiotracer, ¹⁸F-FDG, and observed a high tumor-to-background signal in the chick CAM, similar to the mouse models.

However, Witney and colleagues also observed that ¹⁸F-FDG tumor uptake was consistently higher in the egg models compared to the mouse models – possibly because ¹⁸F-FDG clearance is much slower in the chick embryo.

“This work supports the case for the use of chick CAM as a more sustainable, low-cost substitute to mouse models of cancer, with results showing that it is possible to cultivate tumors for imaging in seven days using this approach,” said Witney.

A low-cost alternative

“Testing new imaging agents in cancer cells in culture is a useful first step, but it only gets us so far – it’s hard to know how an imaging agent that works in a Petri dish would work in the body,” explained Dr. Richard Southworth, co-author of the study and a reader in cardiac molecular imaging at KCL. “Growing tumors in a chicken egg is an interesting intermediate step that could accelerate imaging agent development at a fraction of the cost. I’m very pleased to see this work published – the endless egg puns have been no yolk.”

Using the chicken eggs led to 97% maintenance cost savings compared to similar mouse models.  “But more importantly, these eggs provided exquisite tumor images that allowed us to assess delivery of tumor-targeting drugs and the effects of radiation therapy. I initially thought all we’d produce is scrambled eggs, but this model was robust and versatile!” Witney added.

Reference: Smith LM, Greenwood HE, Tyrrell WE, et al. The chicken chorioallantoic membrane as a low-cost, high-throughput model for cancer imaging. npj Imaging. 2023;1(1):1-12. doi: 10.1038/s44303-023-00001-3

This article is a rework of a press release issued by King's College London. Material has been edited for length and content.