Study on mice found palmitic acid promoted metastasis in mouth and skin cancers
Hannah Devlin Science correspondent
Wed 10 Nov 2021 17.31 GMT
Scientists have shown how a fatty acid found in palm oil can encourage the spread of cancer, in work that could pave the way for new treatments.
The study, on mice, found that palmitic acid promoted metastasis in mouth and skin cancers. In future, this process could be targeted with drugs or carefully designed eating plans, but the team behind the work cautioned against patients putting themselves on diets in the absence of clinical trials.
“There is something very special about palmitic acid that makes it an extremely potent promoter of metastasis,” said Prof Salvador Aznar-Benitah, of the Institute for Research in Biomedicine (IRB), Barcelona. “I think it is too early to determine which type of diet could be consumed by patients with metastatic cancer that would slow down the metastatic process.”
The study adds to emerging evidence that diet can be used to enhance existing cancer treatments because certain nutrients are disproportionately relied on by tumour cells, or are required at critical stages such as metastasis.
The study built on previous work by the same team showing that, within a tumour, just a small subset of cells have the capacity to spread by travelling out of the tumour, reaching other organs and colonising them. These specialised cancer cells appeared to rely particularly heavily on fatty acids and the latest work narrowed this down to palmitic acid, which is found in palm oil – but also in a wide variety of foods such as butter and olive oil.
The study, published in Nature, found that when palmitic acid was supplemented into the diet of mice, mouth and skin cancers were more likely to spread. Other fatty acids called oleic acid and linoleic acid – omega-9 and omega-6 fats found in foods such as olive oil and flaxseeds – did not show the same effect. Neither of the fatty acids tested increased the risk of developing cancer in the first place.
The study suggested that exposure to palmitic acid caused changes to the function of genes in cancer cells that allowed them to sense fatty acids and consume them more efficiently. The presence of palmitic acid also appeared to send cancer cells into a “regenerative state” allowing them to form signalling networks beyond the tumour, which is known to be a crucial step towards spreading.
Metastasis of cancer remains the main cause of death in cancer patients and the vast majority of people with metastatic cancer can only be treated, but not cured.
By understanding what cancer cells need to make this leap, the scientists also identified ways to block the process and are planning a clinical trial of proteins that interfere with the tumour response to palmitic acid.
“That is a much more realistic approach in terms of a real therapy, that doesn’t depend on whether a patient likes Nutella or pizza,” said Aznar-Benitah. “Playing with diets is so complicated.”
Prof Greg Hannon, director of the Cancer Research UK Cambridge Institute, said: “This is a rigorous and comprehensive study that suggests that exposure to a major constituent of palm oil durably changes the behaviour of cancer cells, making them more prone to progress from local to potentially lethal metastatic disease. Given the prevalence of palm oil as an ingredient in processed foods, this study provides strong motivation for further study on how dietary choices influence the risk of tumour progression.”
Helen Rippon, chief executive at Worldwide Cancer Research, said: “This discovery is a huge breakthrough in our understanding of how diet and cancer are linked and, perhaps more importantly, how we can use this knowledge to start new cures for cancer. Metastasis is estimated to be responsible for 90% of all cancer deaths – that’s around 9 million deaths a year globally. Learning more about what makes cancer spread and – importantly – how to stop it is the way forward to reduce these numbers.”
