New Enzyme Prodrug and Methionine-Depletion Combination Therapy of Breast Cancer Designed for Effective Delivery to the Tumor.

摘要

Recombinant L-methioninase-annexin V and cytosine deaminase-annexin V fusion proteins have been produced in good purity and yield from E. coli. As indicated by measuring the dissociation constant (Kd), both purified FPs bind strongly to human endothelial cells, MCF-7 breast cancer cells, and MDA-MB-231 breast cancer cells grown in vitro. In vitro tests of both enzyme prodrug systems showed that significant killing of endothelial cells, MCF-7 cells, and MDA-MB-231 cells (approximately 80% confluent) was obtained with very little or no effect of the prodrug when the FP was not present. The L-methioninase-annexin V/SeMet enzyme prodrug system, where SeMet is converted to methylselenol, was tested in vivo in SCID mice with implanted MDA-MB-231/GFP cancer cells using i.p. injection of the FP and the prodrug. The result was that tumor growth was arrested or greatly slowed during the 11-day treatment period, but tumor growth resumed at the end of treatment. These results indicate that the use of an enzyme prodrug system targeted to the tumor vasculature that yields a drug with a longer half-life than methylselenol may be more effective in treating breast tumors.