The evidence for involvement of type C RNA tumor viruses in human acute leukemia.

Abstract

RNA- and reverse transcriptase (R.T.)-containing viruses have been etiologically related to leukemia in several species of animals. There is no convincing report of isolation of a similar virus from man. In the past few years, however, biochemical evidence for three components thought to be characteristic of type C viruses has been detected in human acute leukemic cells. This includes the following: 1) An enzyme with physical and biochemical properties so far indistinguishable from viral R.T. has been purified from these cells. It was also recently shown that this enzyme is immunologically closely related to R.T. purified from type C primate RNA tumor viruses, much less to murine virus R.T., and not at all to avian or feline. 2) RNA has been detected in these cells with some nucleotide sequence relatedness to the genomic RNA of some murine and primate type-C viruses. 3) The DNA product of the endogenous R.T. of human leukemic cells has nucleotide sequences related to murine and especially primate type C sarcoma viruses. Thus, certain virus-like components exist in human leukemic cells in a functional form within ribonucleoprotein particles which resemble animal type C viruses. However, if they represent virus, they are defective—not released under ordinary conditions—and a causal relationship to human neoplasia, if any, has not been shown and may be impossible to prove.