The bee products significantly decreased tumour growth and spreading of the cancer (metastasis) in mice when they were applied orally or by injection, reports the team from the University of Zagreb in this month's issue of the Journal of the Science of Food and Agriculture.
Nada Orsolic and colleagues tested both the preventative and curative effects of the bee products on tumour models in mice. In the prevention studies, the products were administered before inoculation with the tumour cells. In the curative studies, the products were administered after tumour inoculation.
"The effects of the tested compounds were demonstrated either by inhibition of tumour growth or metastases (secondary tumour) formation and by increased survival of the animals," said Dr Orsolic.
Propolis, a resin-like substance used in the construction of honeycombs, and a chemical found in propolis called caffeic acid significantly reduced subcutaneous tumour growth and prolonged the survival of mice. Honey also inhibited the spread of the tumour when applied before tumour cell inoculation in the lungs.
Royal jelly, used as food for young bee larvae made by worker bees, also significantly inhibited tumour spread when injected at the same time as tumour cells. When bee venom was injected intratumourally, tumour shrinkage occurred, and the delay of tumour growth was evident.
Meanwhile mice treated with bee venom survived longer than control mice.
The way in which the bee products work to combat the tumours is not clear, but the authors suggest the chemicals cause apoptosis (cell suicide) or necrosis of the cancerous cells, or that they exert directly toxic or immunomodulatory effects. They may also reduce harmful oxyradicals in cells or body fluids, said the Croatian team.
Their findings could be supported by further trials on humans they add.
"These results suggest the benefits of potential clinical trials using propolis or honey, combined with chemotherapeutic agents," said Dr Orsolic.