In vitro Inhibition of Human Melanoma Cells by Immunotoxin Luffin B-Ng76.

Luffin B, a plan single-chain ribosome inactivating protein, was purified from seeds of Luffa cylindrica by Blue Sepharose CL-6B affinity chromatography. An immunotoxin was constructed with luffin B and Ng76, a monoclonal antibody to human melanoma cell M(21). Luffin B-Ng76 showed 4 000-fold more cytotoxic to target melanoma cells than free luffin B. The IC(50) of luffin B-Ng76 for M(21) cells and non-target HeLa cells was 2.5x10(-11) mol/L and 3.0x10(-8) mol/L, respectively. The results suggest that luffin B is a new potent immunotoxin effector.

Isolation, Purification and Characterization of a Group of Novel Small Molecular Ribosome Inactivating Protein -- LuffinS from Seeds of Luffa cylindrica.

A group of novel RIPs--LuffinS(1), LuffinS(2), LuffinS(3) (MW about 8 kD) were purified by ammonia sulfate precipitation, CM-52 chromatography, HRLC size chromatography and Mono S FPLC. LuffinS(1), LuffinS(2) and LuffinS(3) have similar weight of about 8kD, and their N-terminal amino acid is Ala, Pro and Thr respectively. The N-terminal nine amino acid sequence of LuffinS(2) was determined as Pro-Arg-Arg-Gly-Gln-Glu-Ala-Phe-Asp. The reaction mechanism of LuffinSs is the same as that of TCS, which is RNA N glycosidases. LuffinSs are more toxic than TCS, with IC(50) of 1.3x10(-11), 1.0x10(-10) and 6.3x10(-11) mol/L respectively in a cell-free protein synthesis system. It is promising that LuffinSs may be used as the efficient toxin moiety of immunotoxins.