Improved imaging of prostate cancer proteins in single cells is possible thanks to scientists at the University of Manchester. The UK researchers identified and investigated an optical illusion in the imaging of single cells that gave inconsistent results.

'Developing the use of infrared spectroscopy in cancer diagnosis' is the aim of the UK team led by Peter Gardner. 'Prostate cancer, if it remains localised, is a manageable condition and patients can survive for many years,' Gardner said. 'However, the cancer can spread, particularly to the bone, and this is almost always fatal.' Gardner's team, in collaboration with Noel Clark, a consultant urologist at the Christie Hospital and Paterson Institute for Cancer Research, have therefore been studying how cancer cells move through tissue.

They study cancer cells by sending a beam of infrared (IR) radiation through the cancer cell and what it is growing on (its biological support generally called the substrate). The beam then bounces off an IR reflective surface and reflects back into the detector, measuring how much is absorbed. A map of the absorption creates an image of the cancer cell proteins.

The problem seen by Gardner's team was that, with some high protein substrates, they sometimes saw negative images of the cells. This illusion was caused by the IR radiation being scattered by the nucleus of the cancer cell. As it scatters in all directions, some goes directly into the detector resulting in more radiation being recorded, indicating that less has been absorbed. This gives the illusion of a negative image of the cancer cell.

Deducing the origin of these optical illusions 'contributes significantly to the debate concerning "anomalies" observed in infrared-microscopy mapping of single cells,' according to John Chalmers of VS Consulting, Stokesley, UK. The Manchester researchers cautioned that 'people using infrared spectroscopy to study cells on biological supports must be careful how they interpret their results'.

Wendy Crocker