Can dietary methionine restriction increase the effectiveness of chemotherapy in treatment of advanced cancer?

Most metastatic tumors, such as those originating in the prostate, lung, an d gastrointestinal tract, respond poorly to conventional chemotherapy. Nove l treatment strategies for advanced cancer are therefore desperately needed . Dietary restriction of the essential amino acid methionine offers promise as such a strategy, either alone or in combination with chemotherapy or ot her treatments. Numerous in vitro and animal studies demonstrate the effect iveness of dietary methionine restriction in inhibiting growth and eventual ly causing death of cancer cells. In contrast, normal host tissues are rela tively resistant to methionine restriction. These preclinical observations led to a phase I clinical trial of dietary methionine restriction for adult s with advanced cancer. Preliminary findings from this trial indicate that dietary methionine restriction is safe and feasible for the treatment of pa tients with advanced cancer. In addition, the trial has yielded some prelim inary evidence of antitumor activity. One patient with hormone-independent prostate cancer experienced a 25% reduction in serum prostate-specific anti gen (PSA) after 12 weeks on the diet, and a second patient with renal cell cancer experienced an objective radiographic response. The possibility that methionine restriction may act synergistically with other cancer treatment s such as chemotherapy is being explored. Findings to date support further investigation of dietary methionine restriction as a novel treatment strate gy for advanced cancer.