Radiologists look virtually from the inside out

THE LANCET

SCIENCE AND MEDICINE

Radiologists look virtually from the inside out clinicians with surgical planning. One developing application for VE is virtual angioscopy, which allows

Elliot Fishman, Johns Hopkins University

irtual endoscopy (VE), most commonly used to examine the colon and the bronchial tree noninvasively, is now being used to provide internal images of other organs and tissues. Some of the latest advances were described at the Radiological Society of North America meeting in Chicago, IL, USA (Nov 30–Dec 5). Intraluminal structures within the body can be visualised in three dimensions (3D) by using VE based on either computed tomography (CT) or magnetic resonance imaging (MRI) datasets. VE readily detects mass lesions, but is often quite nonspecific. Thus, explained Emanuele Neri (Pisa, Italy), VE is likely to complement rather than replace existing diagnostic methods. But, by allowing the anatomy of whole structures to be visualised, VE should assist

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Looking up the aorta with helical CT

physicians to view blood vessels noninvasively from within their lumen (figure). Such representations are of

considerable use when viewing aortic dissections, permitting careful definition of the extent of the flap and a more accurate assessment of the involvement of aortic branches, explained Elliot Fishman (Baltimore, MD, USA). These images—by allowing the true and false lumens to be more easily identified—may also, in time, aid the radiological placement of intra-aortic stents. Virtual angioscopy, based on MRI data, has been used to assess intracranial aneurysms (K Eberhardt, Erlangen, Germany). Here, the technique is especially useful in deciding where vessel branches exit aneurysm sacs. Identification of the neck of giant aneurysms is also possible with VE, suggesting that the technique might help in pre-operative planning. Eldon D Lehmann

Pregnancy hormone acts on AIDS-related Kaposi’s sarcoma—or does it?

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uman chorionic gonadotrophin (hCG) has previously been shown to have activity against AIDS-related Kaposi’s sarcoma (KS) in vivo. But now, as US researchers report a phase-I trial of hCG in patients with KS, UK experts suggest that this clinical effect may not all be due to hCG. Parkash Gill (University of Southern California School of Medicine, Los Angeles, CA, USA) and colleagues studied three groups of six HIV-1-positive men with KS given crude hCG (made from the

urine of pregnant women). Two patients given 5000 IU hCG daily and two given 10 000 IU three times a week had at least a 50% reduction in tumour burden. Two patients given 10 000 IU daily had complete remission. Disease stabilised in nine other patients (J Natl Cancer Inst 1997; 89: 1797–1802). But in other studies, purified or recombinant hCG has had no antiKS effects. New work by Suzanne Griffiths (University of Leeds, UK) and co-workers may explain this paradox (Nature 1997; 390: 568).

They report the purification from a commercial hCG preparation of a ribonuclease which has “potent dose-dependent killing activity” against a KS cell line. A related amphibian enzyme, onconase, is in phase-III trials for pancreatic carcinoma. It may be possible, say the authors, to use the antineoplastic properties of human urinary ribonuclease “as part of a new regime for the treatment of AIDSrelated KS and other tumours”. Kelly Morris

Infant acute lymphoblastic leukaemia arises in utero cientists have published the first direct evidence that infant acute lymphoblastic leukaemia (ALL) arises in utero. Researchers at the Institute of Cancer Research (London, UK) compared blood samples taken from children at birth with samples taken after diagnosis of leukaemia. Cells carrying the mutation found in the children’s leukaemic cells were present at birth. Infant ALL is characterised by chromosomal translocations involving the MLL gene. Mel Greaves and co-workers report that a specific genomic fusion sequence, MLL-AF4, was present and detectable in neonatal blood samples from three children diagnosed with ALL between

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Vol 350 • December 13, 1997

the ages of 5 months and 2 years (Proc Natl Acad Sci USA 1997; 94: 13950–54). Greaves’ team identified the MLL mutation in each patient and then used PCR to search for rare leukaemia cells in stored neonatal blood samples. Twin studies also indicate that infant ALL may arise in utero, explains Greaves. Although the precise MLL mutation varies between patients, malignant cells in twins with this form of leukaemia have identical, non-inherited MLL rearrangements. “60% of identical twins share the same placenta. This suggests that the mutation arises in a single cell in one fetus, and that clonal progeny then pass to the other twin within the pla-

centa”. Older twins with leukaemia often have different mutations, adds Greaves, but they can also have malignant clones in common which “points strongly towards a fetal origin for leukaemia more generally”. The next step will be to test neonatal blood samples of older children with leukaemia to see if the mutations in their malignant cells were present at birth. Developing a screening test for a disease that only affects 1 in 60 000 children would not be practical, notes Greaves. But, “if the risk of leukaemia in general could be spotted at birth then developing a test makes greater sense”. Janet Fricker

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