Cancers pick up GLUT of vitamin C.

Leukemia cells, prostate tumors, and breast cancers are among malignancies that like to stock up on copious amounts of ascorbate, also known as vitamin C, a new study finds.

"We presume cancers do this because it gives them some advantage," speculates one of the authors, David W. Golde of Memorial Sloan-Kettering Cancer Center in New York City.

Earlier test-tube studies by Golde's team showed that tumor cells can't take up ascorbate. At a loss to reconcile this with data by others showing vitamin C in tumors, the Sloan-Kettering scientists implanted mice with human cancers and then probed the role of the host in the tumor's vitamin uptake.

In the Sept. 15 CANCER RESEARCH, they report that nearby stromal cells help the tumors by oxidizing vitamin C. In its new form, this material readily enters cancer cells' glucose transporters, or GLUTs. Golde notes that tumor cells have unusually high numbers of these pores, which normally regulate sugar's entry. Once inside a cancer cell, the oxidized material converts back to normal ascorbate, the new data show.

Radiation and many chemotherapy drugs kill cancers through oxidative mechanisms. Because ascorbate is a powerful antioxidant, Golde worries "that vitamin C [supplementation] might make cancer treatment less effective."