Did it need double glazing? (Image: Jacco van Rheenen)

A window into the soul is poetic, but a window into the abdominal cavity may be more useful. A glass porthole implanted into the abdomen of mice has allowed researchers to observe the spread of cancer in intimate detail.

Tumour metastasis occurs when cancer cells spread from a primary tumour to other parts of the body, where they group together and form secondary tumours.

The migration of tumour cells is not well understood, partly because it is not easy to observe the spread of cancer inside the body. Advanced imaging techniques like multiphoton fluorescence microscopy only penetrate to a depth of half a millimetre or so – far too small to look at common sites of metastasis, including organs such as the liver.


So Jacco van Rheenen at the Hubrecht Institute for Developmental Biology and Stem Cell Research in Utrecht, the Netherlands, and colleagues tried a new approach: implanting a 12-millimetre titanium ring containing a panel of glass into the abdominal wall of mice. “It’s just like a window in a ship or a plane,” says van Rheenen. This porthole gives a clear view of the internal organs, including the kidneys, small intestine and liver.

Tracking cancer

The team was then able to track individual tumour cells, marked with fluorescent dye, over the course of two weeks as they spread around the abdomen. Surprisingly, after the cells had migrated to their final destination – but before they condensed into secondary tumours – they appeared to move randomly about the local area. Nobody had realised that cancer cells move around like this before they form secondary tumours, says van Rheenen. “We found new stuff that we didn’t imagine before.”

The team used drugs to suppress the mobility of the cancer cells after they had reached their destination, and found that this led to a lower rate of tumour growth and fewer secondary tumours. “By suppressing the movement, you block progress to full metastasis,” says van Rheenen.

“This is a great technical feat,” says Peter Kuhn, who studies metastasis at the Scripps Research Institute in La Jolla, California. “Putting windows into animals is an important development.” But he cautions against drawing quick conclusions from animal models. “It is really important to distinguish between cancer in a mouse and cancer in a human.”

Journal reference: Science Translational Medicine, DOI: 10.1126/scitranslmed.3004394