Resumen de Ribosome-Inactivating proteins (RIPs) and their aplication in the construction of immunotoxins for the experimental therapy of cancer
The ribosome �inactivating proteins (RIPs) are protein synthesis inhibitors that trigger the irreversible inactivation of ribosomes. The most known RIPs are those from plants being ricin the most studied one. The molecular mechanism of action of RIPs is the depurination of the largest rRNA (28 S rRNA in mammalian). RIPs act also on other substrates like DNA, viral genomic RNA and some synthetic polynucleotides which become multidepurinated. Some RIPs display antiviral activity on plant and animal viruses and also have a topological activity on double stranded DNA. We have found a novel kind of RIP that we named non-toxic type 2 RIP. Among these RIPs are nigrin and basic nigrin b from Sambucus nigra and ebulin from Sambucus ebulus. The new RIPs are between 1.000 and 10.000 times less toxic for cultured human cells and mice than ricin. The most noteworthy application of RIPs is the construction of conjugates and immunotoxins for the experimental therapy of human cancer. We have prepared conjugates active on colon cancer cells and immunotoxins active on CD105+ cells which are characteristic of the tumoral neovasculature.
