A study published by Wang et al in the journal Carcinogenesis has identified new factors accompanying previous findings that frequent consumption of peanuts by patients with cancer could increase the risk of metastasis.
Relationship Examined
The results show that peanut agglutinin—a carbohydrate-binding protein that rapidly enters the bloodstream after peanuts are eaten—interacts with endothelial cells to produce molecules called cytokines. The cytokines in question—IL-6 and MCP-1—are well-known promoters of cancer metastasis. The increased cytokine production causes other endothelial cells to express more cell surface adhesion molecules, making them more attractive to the circulating tumor cells and thus potentially promoting metastasis.
In an earlier study, members of the same research team reported that circulating PNA binds to a special sugar chain, which occurs mainly on precancerous and cancer cells, and interacts with a larger protein expressed on the surface of tumor cells in the bloodstream. This interaction triggers changes in the larger protein, resulting in underlying adhesion molecules on the surface of the cancer cell to become exposed, making the cancer cells stickier and easier to attach themselves to the blood vessels. It also allows the cancer cells to form small clumps that prolong the survival of cancer cells in the body’s circulation.
Photo credit: Getty
Commentary
Corresponding author Lu-Gang Yu, PhD, of The University of Liverpool, said, “Although further research and investigation are still needed, these studies suggest that very frequent consumption of peanuts by patients [with cancer] might increase the risk of metastatic spread.”
He continued, “Reassuringly though, a large U.S. study reported no significant impact of peanut consumption on cancer mortality. In another study, peanut consumption was reported to have no significant effect on prognosis in men with established prostate cancer. In our previous healthy volunteer study, substantial blood concentrations of peanut agglutinin were only seen transiently 1 hour or so after consumption of a large dose (250 g) of peanuts, so it may be that ‘normal’ peanut consumption yielding lower peanut agglutinin concentrations is harmless.”
“Nevertheless, the possibility remains that circulating peanut agglutinin—at least at the relatively high levels found shortly after a large ‘dose’ of peanuts, could have a significant biological effect on tumor cells circulating at that time, with a potential for increased risk of metastasis. Heavy or very frequent peanut consumption therefore might be better avoided by patients with cancer,” Dr. Yu concluded.
The possible impact of heavy peanut consumption by patients with cancer on survival will need to be investigated in further population-based epidemiologic studies.
Disclosure: This study was supported by the American Institute for Cancer Research. For full disclosures of the study authors, visit academic.oup.com/carcin.
