Plasmacytoma tumor cells, mouse

Purther evidence that cellular mRNA is not degraded after infection came from experiments using cellular mRNA extracted from infected cells to prime protein synthesis in extracts. From mouse plasmacytoma tumor cells Lawrence and Thach (26) isolated a poly(A)-containing 10S RNA fraction which in extracts was translated into a protein found in plasmacytoma cells, as determined by co-electrophoresis and tryptic mapping. This messenger RNA, when isolated from infected cells, was less active in translation than when isolated from uninfected cells by about However, mRNA... 

With Potter s development of experimental plasmacytoma in mice, it was established that the turnover of paraprotein (N2), or more simply the serum level (08), was directly related to the weight of solid soft-tissue plasmacytoma. In our laboratory an ascitic form of plasmacytoma has been studied, and using isotope dilution it has been possible to estimate the actual total number of plasmacytoma cells in a mouse. At the same time the serum level of paraprotein was measured and a simple correlation was shown (F2). To the best of my knowledge, this was the first time that the serum level of a tumor product had been directly related to the actually counted number of tumor cells. Incidentally it was noted that the paraprotein could be first detected in the serum, when a 23 g mouse had 3 million tumor cells. 

Recently, we have demonstrated the existence of a poly(ADPR) polymerase activity associated with cytoplasmic free messenger ribonucleoprotein particles (mRNP) isolated from mouse plasmacytoma cells [4]. The enzyme does not require DNA for activity and is able to produce an ADP-ribosylation of some of the mRNP proteins. We have extended our observations to Krebs II ascites-tumor cells and to rat liver. In the present report, we will discuss some properties of this enzyme, particularly the activation by RNase A. 

Table 1 summarizes the poly(ADPR) polymerase activities measured in free mRNP isolated from mouse plasmacytoma, Krebs II ascites-tumor cells or rat liver. In contrast to the tumoral cells, the activity associated to rat liver free mRNP is very low nevertheless, it is twelvefold higher than the activity associated with the microsomal-ribosomal fraction reported by Burzio et al. [3]. The addition of calf thymus DNA induces only an increase of about 20% in enzymatic activity. 

ADP-Ribosylation in Cytoplasmic Ribonucleoprotein Particles Which Contain Silent mRNA. We demonstrated that ADP-ribosyl transferase activity is associated with cytoplasmic free mRNP isolated from a variety of organs and tumor cells mouse plasmacytoma, rat liver, rat brain, Krebs n cell rat brain cultured neurons and astrocytes (25-28). Table 1 summarizes the mRNP poly(ADP-ribose) polymerase activity. On a protein basis, in contrast to the tumor cells, the activity associated with rat liver and whole rat brain free mRNP is very low. Nevertheless, it is 12 fold higher than the activity associated with the microsomal ribosomal fraction reported by Burizo et al. (19). In brain mRNP and mainly in neuronal mRNP die activity is much higher than in the rat liver mRNP on a DNA basis (not shown). 

Park et al. (1971) compared the effects of ascorbate on mouse plasmacytoma cells with that on normal bone marrow cells forming granulocytic colonies. Only the plasmacytoma cells responded with marked proliferation. This, however, does not imply that myeloic stem cells in general are unresponsive to ascorbate. The growth of the human promyeloic tumor cell line HL-60 was stimulated by ascorbate (Alcain et al., 1990). Similarly, bone marrow cells from a variety of acute myeloid leukemia patients responded with growth, or growth inhibition or remained unaffected (Park et al, 1992). In this context it should be stressed that inhibition of... 

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