Poly(A)polymerase activity levels in breast tumour cytosols

The enzyme poly(A) polymerase (PAP) catalyses the polyadenylation of mRNA a nd its activity levels vary within the cell cycle. The levels of activity o f this enzyme were measured in the cytosol of breast tumours from 62 untrea ted patients and compared to clinical prognostic parameters as well as othe r biological markers. The enzyme levels measured ranged from 3 to 46 units/ mg protein. A statistically significant association was observed between hi gh PAP activity values and the TNM stage of the disease as well as node inv asiveness. Furthermore, there was a positive correlation between PAP activi ty values and c-erbB-2 overexpression but not with its amplification. No si gnificant correlation was observed with c-myc amplification or overexpressi on and cathepsin D levels. A direct relationship between steroid receptor c ontent and PAP activity levels, which was more prominent in the case of the progesterone receptor, was observed. However, also on the basis of previou s data PAP activity may prove to be indicative of aggressive disease. Furth ermore, measurements of PAP activity may contribute to the definition of th e biological profile of tumour cells.