Imaging tumors with an albumin-binding Fab, a novel tumor-targeting agent.

Association with albumin as a means to improve biodistribution and tumor deposition of a Fab was investigated using AB.Fab4D5, a bifunctional molecule derived from trastuzumab (HERCEPTIN) capable of binding albumin and tumor antigen HER2 (erbB2) simultaneously. AB.Fab4D5 was compared with trastuzumab and a trastuzumab-derived Fab (Fab4D5) for the ability to target tumors overexpressing HER2 in mouse mammary tumor virus/HER2 allograft models. Biodistribution was monitored using intravital microscopy, histology, and integrated single-photon emission computed tomography/computed tomography analysis. Fab4D5 tumor deposition was characterized by rapid but transient appearance in tumor at 2 h with little retention, followed by rapid accumulation in kidney by 6 h. Trastuzumab was slow to accumulate in tumors and slow to clear from normal tissues, although significant tumor deposition was achieved by 24 h. In contrast, AB.Fab4D5 was observed at 2 h in tumor and its presence was sustained beyond 24 h similar to trastuzumab. Intravital microscopy revealed that at peak tumor accumulation, tumor cell staining by AB.Fab4D5 was more uniform than for Fab4D5 or trastuzumab. Similar tumor deposition was achieved for both AB.Fab4D5 and trastuzumab at 48 h (35.9 +/- 1.8% and 38.2 +/- 3.1% injected dose/g); however, AB.Fab4D5 targeted tumors more rapidly and quickly cleared from blood, leading to a lower overall normal tissue exposure. Importantly, unlike Fab4D5, AB.Fab4D5 did not accumulate in kidney, suggesting that association with albumin leads to an altered route of clearance and metabolism. Rapid targeting, excellent tumor deposition and retention, coupled with high tumor to blood ratios may make AB.Fab an exceptional molecule for imaging and cancer therapy.

The effects of anesthetic agent and carrier gas on blood glucose and tissue uptake in mice undergoing dynamic FDG-PET imaging: sevoflurane and isoflurane compared in air and in oxygen.

PURPOSE: We sought to identify an anesthetic regime that, unlike isoflurane in air, would maintain glucose homeostasis in mice undergoing Positron emission tomography (PET) imaging with 2-deoxy-2-[18F]fluoro-D: -glucose (FDG). MATERIALS AND METHODS: FDG uptake was also measured in normal and tumor tissues. Athymic and Balb/c nude mice were studied. Blood glucose levels were measured before and after 30 min of FDG PET imaging under isoflurane or sevoflurane carried in air or oxygen. FDG uptake was quantified as a percentage of the injected dose and using Patlak analysis yielding Ki values. RESULTS: Blood glucose levels were more stable under sevoflurane than under isoflurane, especially in the athymic nude mice. Under isoflurane, FDG uptake into myocardium was higher than under sevoflurane and was strongly correlated with the intrascan change in blood glucose. CONCLUSION: Sevoflurane should be preferred for physiologic imaging in mice, minimizing changes in glucose and, for FDG PET, reducing signal spillover from the myocardium.

Loss of the serine/threonine kinase fused results in postnatal growth defects and lethality due to progressive hydrocephalus.

The Drosophila Fused (Fu) kinase is an integral component of the Hedgehog (Hh) pathway that helps promote Hh-dependent gene transcription. Vertebrate homologues of Fu function in the Hh pathway in vitro, suggesting that Fu is evolutionarily conserved. We have generated fused (stk36) knockout mice to address the in vivo function of the mouse Fu (mFu) homologue. fused knockouts develop normally, being born in Mendelian ratios, but fail to thrive within 2 weeks, displaying profound growth retardation with communicating hydrocephalus and early mortality. The fused gene is expressed highly in ependymal cells and the choroid plexus, tissues involved in the production and circulation of cerebral spinal fluid (CSF), suggesting that loss of mFu disrupts CSF homeostasis. Similarly, fused is highly expressed in the nasal epithelium, where fused knockouts display bilateral suppurative rhinitis. No obvious defects were observed in the development of organs where Hh signaling is required (limbs, face, bones, etc.). Specification of neuronal cell fates by Hh in the neural tube was normal in fused knockouts, and induction of Hh target genes in numerous tissues is not affected by the loss of mFu. Furthermore, stimulation of fused knockout cerebellar granule cells to proliferate with Sonic Hh revealed no defect in Hh signal transmission. These results show that the mFu homologue is not required for Hh signaling during embryonic development but is required for proper postnatal development, possibly by regulating the CSF homeostasis or ciliary function.