がん：パーム油に含まれる脂肪酸がマウスの腫瘍転移を促進する

Exposure to high concentrations of a dietary fatty acid contained in palm oil promotes the metastasis of mouth and skin cancer cells in mice, according to a paper published in Nature.

Changes in the uptake and metabolism of fatty acids have been linked to cancer metastasis — the process by which cancer cells spread to other parts of the body. However, it is unclear which dietary fatty acids in particular might be responsible for these changes, and the biological mechanisms involved.

Salvador Benitah and colleagues exposed human mouth and skin cancer cells to one of three types of dietary fatty acid — palmitic acid (the main saturated fatty acid in palm oil), oleic acid or linoleic acid — for four days, before introducing them into corresponding tissues in mice fed a standard diet. Although tumour initiation was not found to be influenced by any of the fatty acids studied, palmitic acid significantly increased both the penetrance and size of existing metastatic lesions. No such significant effect was observed for oleic or linoleic acid.

Pro-metastatic cancer cells also retained ‘memory’ of exposure to high levels of palmitic acid. For example, tumours from mice fed a palm-oil-rich diet for only ten days or tumour cells exposed to palmitic acid in the laboratory transiently for four days (before returning to normal medium) remained highly metastatic even when transplanted into mice fed on a normal diet. This process is associated with epigenetic changes — molecular modifications that alter patterns of gene expression without the DNA itself being altered — in metastatic cells that are suggested to mediate the long-term stimulation of metastasis.

The findings may aid in the identification of new therapies, the authors conclude.