A new study presented at the annual Era of Hope Conference has reported that the marine omega-3 fatty acid docosahexaenoic acid (DHA) reduces bone metastasis in a mouse model of breast cancer. The other major marine omega-3 fatty acid found in fish oil is eicosapentaenoic acid (EPA). Fat in bone marrow is suspected to influence bone metastasis and osteolysis (bone resorption). Previous animal experiments have reported that high omega-6 corn oil enriched diets increase obesity and also adipocytes (fat cells) in bone marrow, whereas omega-3 fatty acid-enriched diets result in reduced fat cells and reduced inflammation. These and other observations led the authors to carry out animal studies using diets with concentrated eicosapentaenoic acid and docosahexaenoic acid. Groups of four-week-old nude mice were fed either a standard rat diet (control diet), a 10% EPA-enriched diet, or a 10% DHA-enriched diet for one month. Mice in each group were injected in the heart with MDA-231BO breast cancer cells. The MDA-231BO cell line was derived from bone metastases that formed after injection of triple negative MDA-MB-231 cells in mice. These cancer cells reliably metastasizes in bone after being injected in the heart. After four weeks, all of the mice were x-rayed to assess bone resorption. This was followed by evaluation of both leg joints to measure tumor proliferation.

Mice fed DHA were found to have very minimal proliferation and bone resorption. CD44 expression in the bone was also found to be lower in DHA-fed mice. Breast cancer stem cells expressing CD44 have been shown to possess the most metastatic potential. The authors comment that it is encouraging to see these results, which for the first time demonstrate that DHA inhibits metastasis and bone resorption after injection of cancer cells known to result in bone metastases. Planned future studies include feeding 4% and 2% DHA, as well as the FDA-approved Lovaza (which is made from fish oil) to examine their chemotherapeutic potential when administered in conjunction with low doses of bisphosphonates to prevent both metastasis and bone resorption in nude mice. The study findings might lead to clinical studies of breast cancer patients to prevent onset of metastasis and bone pain in later years.