Author(s): Lizhi Liu, Weiming Xu
Nitric oxide (NO) is a pleiotropic signali ng molecule, and may be a contributing factor to the hypoxia encountered in a variety of solid tumors. Previously we reported that increased NOS expression resulted in a concomitant increase in expression of the glucose - regulated protein 78 (GRP78) in huma n embryonic kidney 293 cells. In the present study, we found that GRP78 was expressed on the cell membrane after nitric oxide induction. In order to isolate membrane - bound GRP78, we have designed a novel scFv library screening method, based on alternative screening with recombinant protein and cell surface - expressed antigen. After first routine screen using GRP78 protein, we used NO - induced cell surface GRP78 as a bait to subtract the none - membrane binding phages. We have successful isolated a panel of scFv specific for GRP78. Treatment of cells with one of the scFv (scFv - GRP78 - H19) attenuated the GRP78 - mediated protection against thapsigargin, a selective ER Ca 2+ - ATPase inhibitor. Furthermore, it synergized with ionomycin (IM) to promote apoptosis in prost ate cancer cells and inhibited the glucose - deprivation - mediated etoposide resistance in human colon and prostate cancer. The work presented here has highlighted the possibility that anti - GRP78 antibodies have the potential to be used therapeutically for th e treatment of cancer.