title: Influence of freeze-drying on the recovery of the tumour invasion markers uPA and PAI-1 from prostate cancer resections.
abstract: BACKGROUND
  Urokinase plasminogen activator (uPA) and its inhibitor (PAI-1) have been shown to be of merit as biomarkers for a variety of cancers. Prostate tissue resections from patients with prostate cancer (PCa) and benign prostatic hyperplasia were analysed to determine the influence of freeze-drying on the recovery of uPA and PAI-1 and their predictive performance.
  
  
  METHODS
  Prostate tissue was frozen in liquid nitrogen and homogenised into a fine powder in a precooled stainless steel punch homogeniser. One aliquot of the powder was extracted directly, and a second aliquot was freeze-dried overnight and then extracted. The extracts were analysed by FEMTELLE assay to determine the concentrations of uPA and PAI-1. uPA/PAI-1 ratios were calculated for each sample, and the mean ratios for the frozen and the lyophilised tissue were compared.
  
  
  RESULTS
  The concentrations of uPA measured for the frozen and lyophilised samples are strongly correlated (R = 0.90 ± 0.05). The same applies to the PAI-1 measured (R = 0.89 ± 0.03). The uPA/PAI-1 ratios for the lyophilised and frozen samples were strongly correlated. The uPA/PAI-1 ratios for frozen and lyophilised samples were found to be essentially the same with values of 0.0344 ± 0.0066 and 0.0340 ± 0.0068, respectively (P = 0.9633).
  
  
  CONCLUSIONS
  The recovery of uPA and PAI-1 from a deep frozen prostate tissue homogenate followed by freeze-drying proceeds with a loss of 10 and 11%, respectively, with no influence on the uPA/PAI-1 ratio. Lyophilisation is a safe procedure for the preservation of frozen prostate tissue samples as it permits recovery of the markers without compromising their use for diagnostic purposes.
authors.affiliation: Division of Radiobiology, Department of Medical Imaging and Clinical Oncology, Faculty of Medicine and Health Sciences, Stellenbosch University, Tygerberg, South Africa.
authors.forename: A M
authors.initials: AM
authors.lastname: Serafin
authors.affiliation: Division of Radiobiology, Department of Medical Imaging and Clinical Oncology, Faculty of Medicine and Health Sciences, Stellenbosch University, Tygerberg, South Africa.
authors.forename: J M
authors.initials: JM
authors.lastname: Akudugu
authors.affiliation: Division of Radiobiology, Department of Medical Imaging and Clinical Oncology, Faculty of Medicine and Health Sciences, Stellenbosch University, Tygerberg, South Africa lbohm@telkomsa.net.
authors.forename: L
authors.initials: L
authors.lastname: Bohm
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis*; D005612:Freeze Drying / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000473:pathology; D017395:Plasminogen Activator Inhibitor 1 / Q000032:analysis*; D011471:Prostatic Neoplasms / Q000473:pathology; D014568:Urokinase-Type Plasminogen Activator / Q000032:analysis*
chemical_list: D014408:Biomarkers, Tumor; D017395:Plasminogen Activator Inhibitor 1; C051321:SERPINE1 protein, human; D014568:Urokinase-Type Plasminogen Activator
keywords: Cancer; clinical studies; tumour markers