New substance that improves the photodetection of bladder cancer gains marke...( Georges Wagnires and colleagues at the...),Health

Georges Wagnires and colleagues at the EPFL and is part of a slightly different cystoscopy technique. First, HAL as part of Hexvix is applied to bladder tissue where it is selectively metabolized by cancer cells into a fluorescent compound. About a half hour later, the physician examines the inside of the bladder with a cystoscope, using blue light instead of white light. With the help of a filter placed on the camera, the fluorescent tumors stand out as bright red spots, impossible to miss. Patients screened using this process are far more likely to be diagnosed correctly, and because the cancerous tissue is easy to identify, very small tumors are not likely to be overlooked. Even flat lesions, previously so difficult to detect, are easily spotted and removed. The lower recurrence rates reported with this technique in turn greatly reduce the likelihood of local or distant metastasis.

Exploiting a cellular manufacturing cycle

Van den Bergh and Wagnires' group developed this molecule by exploiting naturally occurring cellular processes. Protoporphyrine IX (PPIX), a naturally occuring photoactive porhyrine produced normally as an intermediate step in the cellular manufacture of hemoglobin, is fluorescent, albeit ephemerally. In healthy cells the effect quickly disappears as the molecule takes on an iron atom.

It turns out that cancer cells slightly overproduce photoactive porhyrins, and the enzyme responsible for the next step, adding the iron atom, is also inhibited. These two effects combine in cancerous cells to produce an accumulation of the fluorescent molecule.

Although this naturally occurring accumulation is too feeble to be exploited clinically, van den Bergh and Wagnires' group used it as a starting point in designing a substance that would increase the basic ingredients needed for its synthesis in the cell. The molecule they came up with, hexaminolevulinate (HAL) causes cells to over-manufacture photoactive porhyrins, an
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Contact: Mary Parlange, science writer
mary.parlange@epfl.ch
41-21-693-7022
Ecole Polytechnique Fdrale de Lausanne
2-Mar-2005

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