Of anticancer silver bullets, Trojan horses and ticking time bombs

The phrase "a silver bullet for cancer" has been bandied about for many years, it’s a neat phrase in "journalese" that at once casts cancer as somehow evil rather than merely a disease. It flags it as a werewolf, a witch, the baddie in the black hat. Silver bullets, after all, are essential munitions for the dispatching of such evils.

A quick Google search reveals almost half a million pages using the phrase "silver bullet" in association with cancer. Often, the results are alternative medicine quackery or some promotional material for an antioxidant supplement but there are also numerous mentions in the scientific literature itself. Indeed, I have written about proclaimed silver bullets, although I don’t recall using that specific phrase in earnest during my 25 years in science communication. There are many research threads, often interwoven, that claim to have found a way to target specific cancerous cells and tissues in the body. There have been polymeric  carriers, supramolecular cages with spring-loaded doors, viral capsids, nanoparticles and many others.

As I understand it, nothing works more effectively against the myriad diseases we refer to as cancer than simply cytotoxic and DNA-damaging chemicals, radiation and surgical excision, usually all in combination. This is despite several decades of research and development attempting to fashion that proverbial silver bullet. Nevertheless, it is always interesting to see new science being undertaken enthusiastically in excellent research establishments, such as the Edinburgh Cancer Research UK Centre at the MRC Institute of Genetics and Molecular Medicine at the University of Edinburgh.

Rather than attempting to fire a silver bullet at cancer, Asier Unciti-Broceta and colleagues in Edinburgh have engineered palladium-coated implants that can target cancer cells and hopefully eradicate the usual side effects of chemotherapy, including hair loss, fatigue, nausea, and immune system compromise. Asier’s technique is described by colleague Carmen Torres-Sánchez of Loughborough University as "bioorthogonal", the technology hinging on the activation of a pro-drug by palladium catalyzed dealkylation. The approach is thus another medical metaphor, not a silver bullet, but a "ticking time bomb" secreted into the tumor and ready to be detonated, or as Torres-Sánchez has it a Trojan Horse..

"In our vision we implant the engineered catalyst carrier first," explains Torres-Sánchez. "Then, by a selective activation via oral drugs, we produce the chemo-destructive effect with maximum effect on the targeted area, and minimal negative effects (i.e. death) on healthy tissue." She told me that she thinks this high impact work is generating a lot of excitement as a new anti-cancer strategy. As with most experimental treatments, however, it will be several years before the technology has matured through testing and clinical trials.

It is always the way, cancer and most other diseases are complex, treating them is complex, there are not quick fixes, there are no silver bullets. We can hope that targeted therapies will eventually provide the means to treat specific types of tumor and materials science is usually there to augment and assist the chemistry.

David Bradley blogs at http://ift.tt/1dXIL6e and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".

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