A new variant of the heat shock protein GRP78 as target for antibody- treatment of pancreatic cancer

Abstract

21173 Background: Pancreatic malignancies belong to the top-five killers among all cancers worldwide. The 5-year survival rate with conventional therapy is below 5%. This shows that there is a big need for new therapeutical approaches. The fully human monoclonal antibody SAM-6 is a germ-line coded IgM, isolated from a cancer patient by TRIOMA technology. SAM-6 antibody binds to a modified O-linked carbohydrate moiety expressed on a membrane-bound variant of GRP78, which is a member of the HSP70 family. Heat-shock proteins (HSPs) are critical components of a cell's defense mechanism against injury associated with adverse stresses. They can protect cells against subsequent, otherwise lethal, outcome. Although HSPs are very beneficial to the normal cell, cancer cells often over-express HSPs on the membrane. They use them in response to stresses associated with various therapies, diminishing the treatment effects. Methods: In vitro and in vivo assays were used to investigate the apoptotic effects of antibody SAM-6 on pancreas cancer cells. Results: Binding of SAM-6 antibody to GRP78 induces an overfeeding of malignant cells with oxidized LDL. The cancer cells over-accumulate depots of cholesterol and triglyceride esters and finally undergo apoptosis. The deadly effect of SAM-6 could be demonstrated in vitro and in vivo in experimental animal models. Conclusions: These data show that cancer-specific modifications of cell surface protection molecules are ideal targets for immuno-therapeutical approaches. No significant financial relationships to disclose.