Historical overview of the use of polynucleotides in cancer

A search for effective inducers of interferon lead to the discovery of polyinosinic-polycytidylic acid [poly(I,C)], which was effective in rodents but not primates. Stabilization of poly(I,C) with poly-L-lysine and carboxymethyl-cellulose produced a derivative that is much more effective as an inducer in humans, but also more toxic. The ability of modified poly(I,C) to induce interferon in primates appears to be at least partly related to its ability to resist hydrolysis by nucleases. As the ability to induce interferon in primates increases, so does the toxicity. Several investigations have emphasized increasing the ease of hydrolysis in order to minimize toxicity. The inducers should not be considered just as a readily available source of interferon, as there are a number of differences between the biologic effects of the inducers and exogenous interferon.