ABSTRACT
The radiolabelled growth factor [(123/125)I] I-hEGF is evaluated in vitro and in vivo to monitor the acute effects on the EGFR of R115777, a farnesyl transferase inhibitor (FTI). Upregulation of the EGFR after incubation with R115777 correlated linearly with FTI induced acute growth inhibition. Receptor mediated [125I] I-hEGF internalization decreased following R115777 treatment. Preliminary data suggest that the net in vivo effect is a decrease of [123I] I-hEGF uptake in the tumour. These findings suggest the possible use of radioiodinated hEGF as a radiodiagnosticum to investigate EGFR status changes as a predictor for eventual FTI chemotherapy outcome in vivo.
Subject(s)
Alkyl and Aryl Transferases/antagonists & inhibitors , Enzyme Inhibitors/pharmacology , ErbB Receptors/drug effects , Animals , Cell Line , Epidermal Growth Factor/chemistry , Epidermal Growth Factor/metabolism , Farnesyltranstransferase , Humans , Iodine Radioisotopes/chemistry , Magnetic Resonance Imaging , Male , Mice , Mice, Nude , Neoplasm Transplantation , Quinolones/pharmacology , Radiopharmaceuticals/chemical synthesis , Regression Analysis , Tissue DistributionABSTRACT
PURPOSE: Using a model tablet, the influence of breakability methodology on mass uniformity of half- and quarter-tablets as well as the comparison of different data acquisition and evaluation approaches were investigated. Moreover, different breakability evaluation criteria were compared based upon distribution as well as distribution-free models. METHODS: A cross-scored tablet, i.e. having two break-marks, was broken by different methods by different persons, and the masses determined for the whole (unbroken) tablets, the half-tablets and quarter-tablets. RESULTS: Beside the possible interaction between the methodology and the person breaking the tablets, the major factor significantly influencing the mass uniformity of broken tablets is the breakability methodology. The best results, i.e. smallest loss and smallest variability, are obtained when the breaking force applied by the thumbs is directed towards the score side of the tablet, i.e. by "opening" the score. Using our model tablet, significant differences between the different evaluation criteria are observed, with the USP/NF approach being best in line with the detailed analysis of all broken tablets. CONCLUSIONS: Assuming that for this model tablet the variance is a linear function of the break-line length, the standard deviation of quarter-tablets is theoretically calculated to be 0.87 times the standard deviation of the half-tablets. As the absolute standard deviation, expressed in mass units, will thus remain approximately identical, the relative standard deviation will nearly double as the mean mass of the quarter-tablets will be half of the mean mass of the half-tablets. This was experimentally confirmed.
