To validate the protein synthesis rate (PSR) measured in human brain tumors using L-[1-(11)C]tyrosine (TYR) PET, the PSR was compared to histopathological parameters that reflect proliferation and protein synthesis.
Methods: We studied 20 patients who had a brain biopsy and who also underwent a PET study with TYR. Paraffin sections were stained with the monoclonal antibody MIB 1, targeted against the core antigen Ki-67, and nucleolar organizer regions (NORs) were measured as argyrophilic NORs (AgNORs). The TYR uptake was measured by PET, and with a kinetic model, the PSR was determined.
Results: PSR (nmol/ml/min) ranged from 0.44 to 1.99 (mean, 0.97), Ki-67 labeling indices (%) ranged from 0.9 to 33.5 (mean, 9.5) and AgNOR area (mm2/cm2) ranged from 0.13 to 0.85. No relationship was found between PSR and Ki-67 labeling index or AgNOR area.
Conclusion: It seems that the PSR and proliferation, as measured by Ki-67, are independent processes. The role of the PSR is uncertain, but it is likely that it can be seen as a marker for the homeostasis of the cell.