An antimelanoma-barley ribosome inactivating protein conjugate is cytotoxic to melanoma cells in vitro

The ribosome inactivating protein (BRIP) from barley is a single polypeptide chain (Mr = 32,000 Dalton) and is nontoxic to intact cells. The BRIP has been purified to homogeneity by modifications of the methods of Roberts and Selitrennikoff and crosslinked to monoclonal antibodies by Succinimidyl-3 (2-pyridyldithio)-propionate (SPDP) and by the cystamine-EDAC methods. The resulting hybrids were purified from the free BRIP by gel filtration on Sephadex G-75 column. The suicide transport agents were assayed against melanoma cells; K-562 cells were used as control. The hybrids were found to be selectively toxic to melanoma cells in a dose dependent manner.