HISTONE MESSENGER-RNA IN-SITU HYBRIDIZATION IN ASTROCYTOMAS - A COMPARISON WITH PCNA, MIB-1 AND MITOSES IN PARAFFIN-EMBEDDED MATERIAL

Aims: Non-isotopic histone mRNA in-situ hybridization (HmRNA NISH) all ows detection of cells in the S phase of the cell cycle in paraffin-em bedded tissue. The aim of this study was to evaluate the technique in measuring the proliferative activity of astrocytic neoplasms, and to c ompare the results with other proliferation estimates and patient surv ival. Methods and results: The proliferative activity of 71 routinely fixed and paraffin-embedded astrocytomas was studied by light microsco pic HmRNA NISH, proliferating cell nuclear antigen (PCNA), Ki67(MIB-1) and mitoses, A significant correlation was found between the labellin g indices of histone mRNA (the percentage of histone-positive tumour c ells: HmRNA-LI), immunohistochemical proliferation marker labelling in dices (PCNA-LI: r=0.64 and Ki67(MIB-1)-LI: r = 0.44) and mitotic indic es (r = 0.45), The results were reproducible as judged by intra-and in terobserver agreement (HmRNA/10 HPF (high power fields): r = 0.91 and r = 0.75, respectively, and HmRNA-LI: r = 0.61 and r = 0.62, respectiv ely), The fraction of the cells in the most active cell cycle phases, as suggested by the HmRNA/Ki67 and mitotic index/Ki67 ratios, increase d significantly with malignancy grade, In the univariate analysis the association of HmRNA-LI with survival was highly significant (P<0.0001 ). Multivariate survival analysis showed that HmRNA-LI was an independ ent prognostic marker. Conclusions: Non-isotopic histone mRNA in-situ hybridization assay offers an alternative and reproducible method for measuring proliferative activity (S phase) in tumours under morphologi cal control.