Nanomedicines, considered as providing an efficient way to transcend the limits of standard cancer treatments, could also have unintended and harmful side effects like accelerating cancer spread, say researchers.

The findings caution against possible side effects of cancer nanomedicines, which are designed to kill cancer cells, and other common nanoparticles but paves the way for safer design and better treatment strategies.

Using breast cancer as a model, researchers from the National University of Singapore (NUS) discovered that common nanoparticles made from gold, titanium dioxide, silver and silicon dioxide - and also used in nanomedicines - widen the gap between blood vessel cells, making it easier for other cells, such as cancer cells, to go in and out of "leaky" blood vessels.

The phenomenon, named 'nanomaterials induced endothelial leakiness' (NanoEL), accelerates the movement of cancer cells from the primary tumour and also causes circulating cancer cells to escape from blood circulation.

This results in faster establishment of a bigger secondary tumour site and initiates new secondary sites previously not accessible to cancer cells, the team explained.

"For a cancer patient, the direct implication of our findings is that long term, pre-existing exposure to nanoparticles - for instance, through everyday products or environmental pollutants - may accelerate cancer progression, even when nanomedicine is not administered," said David Leong, Associate Professor at NUS.

"The interactions between these tiny nanomaterials and the biological systems in the body need to be taken into consideration during the design and development of cancer nanomedicine.

"It is crucial to ensure that the nanomaterial delivering the anti-cancer drug does not also unintentionally accelerate tumour progression. As new breakthroughs in nanomedicine unfold, we need to concurrently understand what causes these nanomaterials to trigger unexpected outcomes," he noted in the study, published in the journal Nature Nanotechnology.

The NUS researchers are harnessing the NanoEL effect to design more effective therapies.

For example, nanoparticles that induce NanoEL can potentially be used to increase blood vessel leakiness, and in turn promote the access of drugs or repairing stem cells to diseased tissues that may not be originally accessible to therapy.