Antibody discovery could lead to more targeted cancer scans

In collaboration with the Press Association
A PET scan of a patient with nasopharyngeal carcinoma (via Wikimedia Commons)

US laboratory research has potentially opened the door to far more sensitive PET scans for cancer.

The new technique attaches a radioactive molecule to specialised proteins – called antibodies - that can recognise different types of cell. 

And experts said it could lead to a more precise way of visualising tumours inside cancer patients.

A mouse with immune tissues visualised by PET​PET – which stands for ‘positron emission tomography’ – is routinely used by doctors to visualise cancer and monitor the extent of a patient’s disease. 

It relies on giving patients a radioactive molecule, or ‘tracer’ - most commonly a form of sugar called 18F-2-deoxyfluoroglucose, or FDG.

FDG lights up cells that are burning sugars particularly quickly – such as cancer cells. 

But other tissues can burn sugar quickly too, and so show up on PET scans. And this background ‘noise’ can lead to difficulties in interpreting patients’ scans.

As a result, researchers have been looking for ways to develop better tracer molecules that are more specific to cancer cells.

Several key issues have hampered progress: FDG is difficult to chemically link to other molecules, it’s unstable, and it loses radioactivity quickly – so even successful attempts to chemically alter it need to be quick to carry out.

Writing in the journal ACS Chemical Science, a team at the Whitehead Institute for Biomedical Research in Massachusetts in the US have now developed a quick and reliable way to chemically attach FDG to antibodies – proteins made by the immune system target specific molecules.

The team tested the technique in mice with pancreatic cancer.

Using their modified FDG-antibodies, they successfully used PET scans to track immune cells as they moved to the tumours located around the mice’s bodies.

Antibody fragments expand what PET imaging can ‘see’ in mice

They were able to spot even very tiny tumours the might not ordinarily be spotted by conventional scans.

While their technique is only in the early stages of development, the researchers believe it could ultimately be combined with conventional PET to offer new information about a patient’s disease. 

The researchers said this would represent a “powerful addition” to doctors toolkits.

UK experts said it was “an impressive development”.

“This could ultimately open up new ways to visualise cancer in a patient’s body,” said Professor Katherine Vallis, a Cancer Research UK expert in imaging, based in Oxford.

“What’s particularly interesting is that it could be used to create new imaging systems tailored to different types of cancer or, potentially, even patients’ individual tumours.

“But there’s still work to do to translate this important laboratory development into something that can be reliably used in the clinic to help improve things for patients with cancer,” she added.

References

  • Rashidian, M., Keliher, E., Dougan, M., Juras, P., Cavallari, M., Wojtkiewicz, G., Jacobsen, J., Edens, J., Tas, J., Victora, G., Weissleder, R., & Ploegh, H. (2015). Use of F-2-Fluorodeoxyglucose to Label Antibody Fragments for Immuno-Positron Emission Tomography of Pancreatic Cancer ACS Central Science DOI: 10.1021/acscentsci.5b00121

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