Surface antigens/receptors for targeted cancer treatment: The GnRH receptor/binding site for targeted adenocarcinoma therapy

Colon, breast and lung adenocarcinomas - three of the major malignancies occurring in humans, together with ovarian, endometrial, kidney and liver adenocarcinomas, account for more then 50% of cancer-related death. As the number of cancer-related deaths has not decreased in recent years, major efforts are being made to find new and more specific drugs for cancer treatment. One of the approaches developed in recent years for targeted cancer therapy is the construction and use of chimeric proteins. Chimeric cytotoxins are a class of targeted molecules designed to recognize and specifically destroy cells over-expressing specific receptors. These molecules, designed and constructed by gene fusion techniques, comprise both the cell-targeting and the cell-killing moieties. Our laboratory has developed a number of chimeric proteins based on an analog of Gonadotropin Releasing Hormone (GnRH) as their targeting moiety. These chimeras recognize a GnRH-binding site that, we found, was over-expressed on a surprisingly wide variety of cancers, all confined to the adenocarcinoma type. A GnRH analog was fused to a large number of killing moieties, including bacterial or human pro-apoptotic proteins. All GnRH-based chimeric proteins selectively killed adenocarcinoma cells both in vitro and in vivo. Utilizing GnRH-based chimeric proteins for targeted therapy could open up new vistas in the fight against adenocarcinomas in humans. This review summarizes the latest developments in the area of targeted cancer therapy via specific antigens/receptors, as well as our latest findings in targeting GnRH-binding sites using GnRH-based chimeric proteins for specific and targeted adenocarcinoma therapy in humans.