Hyperhomocysteinemia is a risk factor for cancer and a new potential tumor marker

Plasma homocysteine (Hcy), a well-known independent risk factor for coronary heart disease, is also a risk factor for cancer. Results from our studies indicate that Hcy could be used as a tumor marker. We found elevated circulating total homocysteine (tHcy) in cancer patients even though they were not treated with anti-folate drugs. In serial specimens from cancer patients undergoing treatment, the change of tHcy coincided with the concentration of tumor markers. The rapid proliferation of tumor cells contributed to the much higher concentrations of circulating tHcy. Both concentrations of tHcy and tumor marker would increase in parallel during the growth of tumor cell, but only the Hcy concentration would decline in response to tumor cell death. Several biochemical changes, including folate deficiency, oxidative stress, aberrant DNA methylation, and production of homocysteine thiolactone have been identified in association with hyperhomocysteinemia, which explained why elevated homocysteine eventually led to carcinogenesis. Conceivably, tHcy may be used as a more accurate tumor marker for monitoring cancer patients during treatment, and hyperhomocysteinemia as a risk factor for carcinogenesis.