Seems irresponsible of USA Today to have a story with the heading "Could cutting asparagus from your diet stop the spread of cancer?" . Imagine the financial impact on growers.
Asparagine is found in many foods. The body needs it, but can make what it needs, so we could safely eliminate it from the diet.
"A study of lab mice found lowering levels of asparagine "dramatically" reduced the spread of triple-negative breast cancer."
"Cedars-Sinai Hospital's Simon Knott, an author on the study, said the research adds to mounting evidence a person's diet "can influence the course of the disease." He said should the same finding be made in humans, curbing asparagine intake could assist with cancer treatment, and not just in breast cancer."
The story is based on a study paper published in Nature this week .
But the important finding IMO was that:
"... asparagine synthetase expression in a patient's primary tumour was most strongly correlated with later metastatic relapse"
Asparagine synthetase is the enzyme that is needed to synthesize asparagine. We can restrict asparagine intake, but if cancer wants to make it, the enzyme will be upregulated.
"An epithelial to mesenchymal transition was mimicked in metastatic cells by adapting PC-3 prostate cancer cells from adherent to suspension culture and then examined to investigate changes in gene expression concurrent with this adaption to suspension. It was found that the asparagine synthetase expression was sixfold greater in the suspension cells than in the adherent cells. In xenografts from a human breast cancer cell line in an established metastatic mouse model, asparagine synthetase was elevated in circulating tumor cells isolated from the mouse blood compared with the parental cell line. When these circulating tumor cells were returned to an in vitro culture and exposed to hypoxia, they showed higher basal expression and greater induction of asparagine synthetase than their parental cell line. These circulating tumor cells were also found to have an increased capacity for colony formation in soft agar assays under hypoxic conditions and grew faster when reimplanted as xenografts. The increased prevalence of asparaginase synthetase in the metastatic cells suggests that its activity may be beneficial for circulating tumor cell survival."
The chemo drug "Asparaginase is an enzyme that is used as a medication ... to treat acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), and non-Hodgkin's lymphoma. It is given by injection into a vein, muscle, or under the skin. A pegylated version is also available...
Common side effects when used by injection include allergic reactions, pancreatitis, blood clotting problems, high blood sugar, kidney problems, and liver dysfunction. Use in pregnancy may harm the baby... Asparaginase works by breaking down the amino acid known as asparagine ..." 
The secondary study finding was that:
"increased dietary asparagine ... promotes metastatic progression"
That's what the media is jumping on.
It seems odd to me that cancer cells that do not express asparagine synthetase would respond to dietary asparagine in this way, but that's what the authors claim. So perhaps we should cut out:
- whole grains
- & asparagus