PHOTODYNAMIC THERAPY/ONCOLOGY: Targeted PDT method completely eradicates some cancer models

"There are already drugs in clinical use which target tumor blood vessels, but these only inhibit growth rather than completely kill the tumor," explains Ross Boyle from University of Hull's (England) Department of Chemistry.

“There are already drugs in clinical use which target tumor blood vessels, but these only inhibit growth rather than completely kill the tumor,” explains Ross Boyle from University of Hull’s (England) Department of Chemistry. Boyle, who designs and creates light-sensitive molecules, is part of a team involving researchers from ETH Zurich (Switzerland) as well as Hull that has linked light-sensitive molecules with antibodies to target tumor blood vessels. The porphyrin-based photosensitizer molecules, when irradiated with light, create particles known as reactive oxygen species, which in high numbers cause irreparable damage to cells. In this way, the researchers starved mouse model cancer tumors of oxygen and nutrients and caused them to disappear completely, with no re-growth during the following 100 days.

“By using this form of targeted photodynamic therapy, we were able to completely kill the tumor in our models. Though this is still a long way from being used on patients, it does hold exciting potential for the treatments of some of the most common skin cancers,” he explains.

Importantly, the tumor was completely eradicated only when ‘natural killer cells’—a key part of the immune system—were present. When the production of these was blocked, the tumor reduced in size, but did not disappear. The team thinks that further research to determine the exact role of the immune system in the process would benefit treatment progress.

Targeting light-sensitive molecules to a tumor site ensures that the treatment should be more effective even at smaller doses, improving outcomes and reducing potential side effects to patients. The technique could potentially replace more invasive forms of treatment, such as surgery and radiotherapy.

1. A. Palumbo et al., British Journal of Cancer 104, 1106–1115 (2011).

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