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New human Escherichia coli heat-stable peptide (ST(h)) analogues containing a DOTA chelating group were synthesized by sequential and selective formation of disulfides bonds in the peptide. This synthetic approach utilizes three orthogonal thiol-protecting groups, Trt, Acm, and t-Bu, to form three disulfide bonds by successive reactions using 2-PDS, iodine, and silyl chloride-sulfoxide systems. The DOTA-ST(h) conjugates exhibiting high guanylin/guanylate cyclase-C (GC-C) receptor binding affinities were obtained with >98% purity. In vitro competitive binding assays, employing T-84 human colon cancer cells, demonstrated the IC(50) values of <2 nM for GC-C receptor binding suggesting that the new synthetic ST(h) analogues are biologically active. In vitro stability studies of the (111)In-DOTA-Phe(19)-ST(h) conjugate incubated in human serum at 37 degrees C under 5% CO(2) atmosphere revealed that this conjugate is extremely stable with no observable decomposition at 24 h postincubation. HPLC analysis of mouse urine at 1 h pi of the (111)In-DOTA-Phe(19)-ST(h) conjugate showed only about 15% decomposition suggesting that the (111)In-DOTA-Phe(19)-ST(h) conjugate is highly stable, even under in vivo conditions. In vivo pharmacokinetic studies of the (111)In-DOTA-Phe(19)-ST(h) conjugate in T-84 human colon cancer derived xenografts in SCID mice conducted at 1 h pi showed an initial tumor uptake of 2.04 +/- 0.30% ID/g at 1 h pi with efficient clearance from the blood pool (0.23 +/- 0.14% ID/g, 1 h pi) by excretion mainly through the renal/urinary pathway (95.8 +/- 0.2% ID, 1 h pi). High tumor/blood, tumor/muscle, and tumor/liver ratios of approximately 9:1, 68:1, and 26:1, respectively, were achieved at 1 h pi The specific in vitro and in vivo uptake of the radioactivity by human colonic cancer cells highlights the potential of radiometalated-DOTA-ST(h) conjugates as diagnostic/therapeutic radiopharmaceuticals.

Lipofibromatosis is a rare, benign fibrofatty tumor of childhood. Since the tumor was first characterized in 2000, only a few additional cases have been reported. The classic presentation of lipofibromatosis is a slow-growing mass arising in a distal extremity, with boys more commonly affected than girls. We report a 16-month-old girl who presented with a lipofibromatosis in her left scapular region that increased 30% in size during a 6-week period. Although previous case reports of lipofibromatosis have emphasized immunohistological findings, this paper focuses on imaging findings and discusses the utility of imaging in the differential diagnosis of pediatric soft-tissue tumors.

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