Construction of a human X-chromosome-enriched phage library which facilitates analysis of specific loci.

A human X-chromosome-enriched MboI-partial-digest recombinant library in phage lambda Charon30 has been constructed. Twelve out of the thirteen X-chromosome DNA sequences that were tested were present in the library. Most regions were covered in overlapping phage inserts; mean insert size was 13.7 kb. One phage from the library allowed detection of a 225-bp insertion of DNA into a region near the Duchenne muscular dystrophy (DMD) locus. Another recombinant phage represents an expansion of a region which exhibits extensive and varying homology with other human chromosomes, including the Y, as well as with rodent DNA. The present library should have widespread use for examining DNA sequences on the human X chromosome.

Trisomy 1q, 2, and 20 in a case of hepatoblastoma: possible significance of 2q35-q37 and 1q12-q21 rearrangements.

Combined cytogenetic, chromosome painting, and spectral karyotyping (SKY) analyses in a case of hepatoblastoma revealed a karyotype of 49,XY,+Y,+der(2)t(2;3)(q35;q25),der(3)t(1;3)(q12; q25),+20. Trisomy 1q, 2, and 20 identified in the present case are consistent with the previously reported cytogenetic alterations in hepatoblastoma. The breakpoints at 1q12 and 2q35 identified in this case have also been reported previously as nonrandom changes. The frequent occurrence of these rearrangements in hepatoblastoma suggests that they may be of pathogenic significance.

Exogenous calcitonin gene-related peptide causes gubernacular development in neonatal (Tfm) mice with complete androgen resistance.

It has been proposed that testicular descent is controlled indirectly by androgens acting on the central nervous system to mediate migration of the gubernaculum to the scrotum. Accumulating evidence suggests that the genitofemoral nerve may release a newly described neurotransmitter, calcitonin gene-related peptide (CGRP) to stimulate gubernacular motility during migration. This study aimed to determine whether exogenous CGRP could stimulate gubernacular migration in mice with complete androgen resistance (testicular feminization mouse [Tfm]). CGRP was injected into the right groin of neonatal Tfm mice at 2-day intervals until 2 weeks of age, when the length of the processus vaginalis was measured under a dissecting microscope. The processus vaginalis length in normal male littermates was 5.9 +/- 1.8 mm (mean +/- SD) while in the female it was 1.2 +/- 0.9 mm. Exogenous CGRP had no effect on either of these. In Tfm males CGRP caused a significant increase in the length of the processus vaginalis on the injected side (2.3 +/- 0.8 mm) compared with the uninjected side (1.4 +/- 1.0 mm). These results are consistent with the hypothesis that CGRP can replace, at least partially, the effect of androgens on gubernacular migration.

Prenatal androgen blockade with flutamide inhibits masculinization of the genitofemoral nerve and testicular descent.

Prenatal androgen blockade with the antiandrogen flutamide inhibits the inguinoscrotal phase of testicular descent. The evidence suggests that androgens may act indirectly via the sexually dimorphic genitofemoral nerve (GFN) to control this phase. Rats were exposed to flutamide on gestational days 16 through 19. Seven-day-old rats were subjected to retrograde fluorescent labelling of the GFN combined with immunohistochemistry for calcitonin gene-related peptide (CGRP), a neurotransmitter found in the GFN. Fluorescent-labelled and CGRP-immunoreactive neurons in the GFN spinal nucleus were quantified. Sexual dimorphism of the GFN nucleus was absent in the flutamide-treated rats but obviously present in control rats. Furthermore, control male nuclei had 24% more CGRP-immunoreactive neurons and 12% more fluorescent-labelled neurons than did flutamide-treated male nuclei. This study shows that prenatal androgen blockade with flutamide inhibits masculinization of the GFN, with significant reduction of its CGRP content. This supports the proposal that androgens act via the GFN, with CGRP as the second messenger, to control inguinoscrotal testicular descent.

All angiogenesis is not the same: Distinct patterns of response to antiangiogenic therapy in experimental neuroblastoma and Wilms tumor.

BACKGROUND/PURPOSE: Neuroblastoma and Wilms tumor exhibit different patterns of metastasis, invasion, and therapeutic response. Vascular endothelial growth factor (VEGF) is an angiogenic factor expressed in both tumors. The authors hypothesized that because the clinical behavior of these tumors differs, the response to anti-VEGF therapy would be distinct, and tumor vascular architectures would reflect this distinction. METHODS: Xenografts were induced by intrarenal injection of cultured cells in athymic mice. After 1 week, anti-VEGF antibody or vehicle were administered for 5 weeks before sacrifice. Additional animals were maintained for 3 weeks after termination of antibody injections to assess rebound growth of tumors. Fluorescein angiography was performed in selected animals. RESULTS: Neuroblastoma control and treated tumor weights were not significantly different (1.48 g v 0.77 g, P =.34). By comparison, as previously reported, antibody-treated Wilms tumors were growth inhibited. Angiograms of treated (but not control) neuroblastomas displayed novel rounded structures at vessel branches, which the authors term terminal vascular bodies (TVBs). Wilms tumor vessels displayed no such alteration. CONCLUSIONS: Neuroblastoma xenografts are less effectively suppressed by anti-VEGF antibody than Wilms tumors. Neuroblastoma vascular architecture displays a novel alteration during antibody administration, which attenuates when antibody is withdrawn. These studies suggest that angiogenesis is differently regulated in experimental neuroblastoma and Wilms tumor.

Highly specific antiangiogenic therapy is effective in suppressing growth of experimental Wilms tumors.

BACKGROUND/PURPOSE: Pathologic angiogenesis in tumors is a potential target for novel therapies. Vascular endothelial growth factor (VEGF) is an angiogenic promoter present in a wide variety of human tumors. VEGF is expressed as 4 isoforms; one of these, VEGF165, predominates in human tumors. The authors hypothesized that antagonism of VEGF165 by a specific aptamer would block tumor growth in an experimental model of Wilms tumor. METHODS: VEGF isoform expression in clinical (n = 2) and experimental tumors were evaluated by reverse transcription polymerase chain reaction (RT-PCR). Tumors were induced in NCR nude mice (n = 32) by intrarenal injection of 10(6) cultured Wilms tumor cells. At 1 week, aptamer (n = 16) or vehicle (n = 16) treatment was started and continued daily for 5 weeks. RESULTS: At 6 weeks tumors weighed 84% less in treated versus control animals (0.69 v 4.41 g; P <.028), without observed adverse effects and similar to suppression previously reported using nonisoform-specific anti-VEGF antibody (94% to 96%). CONCLUSIONS: Anti-VEGF165 aptamer effectively suppressed primary tumor growth in experimental animals with no observed adverse effects. Development of highly specific antiangiogenic therapies may be of particular benefit to pediatric patients.

Combination antiangiogenic therapy: increased efficacy in a murine model of Wilms tumor.

BACKGROUND/PURPOSE: Antibody to vascular endothelial growth factor (anti-VEGF) suppresses tumor growth and metastasis in experimental Wilms tumor. However, tumor growth accelerates if antibody is withdrawn. As recently shown, low-dose, frequently administered topotecan, a topoisomerase-1 inhibitor, has anti-angiogenic activity. The authors hypothesized that combined topotecan/anti-VEGF therapy would suppress tumor growth and metastasis more durably than either agent alone. METHODS: Xenografts were induced by intrarenal injection of human Wilms tumor cells in athymic mice (n = 59). Mice were divided into control (n = 10), anti-VEGF (n = 16), topotecan (n = 17), and topotecan plus anti-VEGF (n = 16) groups. All control and half the treated mice were killed at week 6. Remaining ("rebound") mice were maintained without treatment until week 8. Tumor vasculature was mapped by fluorescein angiography/PECAM immunostaining. Endothelial apoptosis was assessed by TUNEL assay. RESULTS: 6 weeks: Tumor weights were reduced significantly in treated mice (P <.003 v control). Seven of ten control and 1 of 25 treated mice displayed lung metastases (P <.003). Rebound tumors were largest in topotecan-only, intermediate in antibody-treated, and smallest in combination-treated mice. Immunostaining and angiography results showed sparse vascularity in treated xenografts. Endothelial apoptosis was observed only in treated tumors. CONCLUSION: Combination low-dose topotecan and anti-VEGF antibody therapy is antiangiogenic and suppresses tumor growth and metastasis in experimental Wilms tumor more durably than either agent alone.

Biliary atresia.

Biliary atresia, a progressive obliterative process involving the bile ducts, has its onset in the newborn period. It is characterized by worsening cholestasis, hepatic fibrosis, and cirrhosis, which lead to portal hypertension and a decline in hepatic synthetic function. Untreated, the outcome is uniformly fatal. The two major milestones toward improved treatment of this disease have been the Kasai portoenterostomy and orthotopic liver transplantation. There has been discussion regarding transplantation as primary therapy, but portoenterostomy remains the standard of care as first-line intervention. Hepatic transplantation, done more frequently for biliary atresia than for any other cause of liver failure in the pediatric population, offers improved survival and quality of life to those for whom the Kasai operation fails. The etiology of biliary atresia remains poorly understood. Working toward a better understanding of this disease, recent investigations target more precise characterization of the hepatic pathology and seek to identify possible causative agents and predictors of favorable outcome. Recent advances in the understanding of biliary atresia published between December 1995 and November 1996 are the focus of this review.

The relationship among calcitonin gene-related peptide, androgens and gubernacular development in 3 animal models of cryptorchidism.

The relationship among calcitonin gene-related peptide (CGRP), a neurotransmitter in the genitofemoral nerve, androgens and gubernacular development was studied using rats treated prenatally with the antiandrogen flutamide and the mutant cryptorchid TS rat. We compared these 2 groups with the testicular feminization mouse with androgen insensitivity. Gubernacula from male TS rats and flutamide-treated rats were maintained in organ culture and examined for contractile response to CGRP. Controls were gubernacula from normal rats and vehicle-treated rats, respectively. TS rat gubernacula have an inhibited contractile response to CGRP, whereas flutamide-treated rat gubernacula have an exaggerated response. A similar exaggerated response to CGRP has previously been demonstrated in testicular feminization mouse gubernacula. These results revealed abnormalities in gubernacular contractile response to CGRP in these cryptorchid animal models, implying that CGRP and gubernacular contractility may have key roles in mediating normal inguinoscrotal testicular descent.

Specific cloning of DNA fragments absent from the DNA of a male patient with an X chromosome deletion.

A method that allows the specific cloning of DNA fragments absent from patients homozygous or hemizygous for chromosomal deletions is described. The method involves phenol-accelerated competitive DNA reassociation and subsequent molecular cloning of appropriately reassociated molecules. The deletion DNA sample utilized in the competition was isolated from a patient with a minute interstitial deletion in the short arm of the X chromosome. Sheared DNA isolated from a male child, who was diagnosed as having Duchenne muscular dystrophy, chronic granulomatous disease, and retinitis pigmentosa, was combined in a 200-fold excess with Mbo I-cleaved DNA isolated from a 49, XXXXY human lymphoid cell line, and the mixture was subjected to a phenol-enhanced reassociation technique. Analysis of 81 unique segments derived from cloned reassociated DNA molecules has led to the identification of 4 (5%) human DNA fragments that are absent from the male patient's DNA. The 4 clones were localized, on the basis of hybridization with restriction nuclease-digested genomic DNA from a panel of human and human-rodent hybrid cell lines, into three regions surrounding band 21 of the short arm of the normal human X chromosome. These clones are potential linkage markers for the diseases affecting this boy. Each clone, as well as others obtainable by this approach, may also serve as a starting point in the eventual cloning of these three X-linked-disease loci. Extension of this approach to other loci, including human tumors potentially homozygous for small deletions, should also be possible.

Novel use of an established agent: Topotecan is anti-angiogenic in experimental Wilms tumor.

BACKGROUND/PURPOSE: Antiangiogenic agents offer a new approach to the treatment of aggressive neoplasms, yet very few agents are available for current use. The authors have shown previously the efficacy of antiangiogenic therapy in experimental Wilms tumor, using an investigative antibody. They hypothesized that topotecan, administered in a regimen targeting endothelial cells, would suppress tumor growth and angiogenesis in experimental Wilms tumor. METHODS: Experimental tumors were induced in the left kidneys of athymic mice by injection of cultured Wilms tumor cells. Topotecan (0.36, 0.6, 1.0, 2.0, and 3.0 mg/kg) or vehicle was injected intraperitoneally in 2 cycles over a 6-week period. Fluorescein angiograms and platelet endothelial cell adhesion molecule-1 staining of primary tumors were performed to ascertain vascular architecture. Endothelial apoptosis was assessed by TdT-mediated dUTP nick end labeling assay. RESULTS: Tumor weights were reduced significantly in treated versus control animals, even in the lowest-dose group. Endothelial cell staining and angiography results showed relatively sparse vascularity in treated xenografts. Endothelial apoptosis was observed in treated but not control tumors. CONCLUSIONS: Topotecan, delivered in an "antiangiogenic" regimen, even at very low doses, significantly inhibited growth of experimental Wilms tumors. No adverse effects were noted at low doses. Thus, the established chemotherapy agent topotecan may be useful in a novel role: as antiangiogenic therapy. J Pediatr Surg 36:1781-1784.

Detection of deletions spanning the Duchenne muscular dystrophy locus using a tightly linked DNA segment.

The Duchenne muscular dystrophy (DMD) locus has been localized to the short arm of the human X chromosome (Xp21) by detection of structural abnormalities and by genetic linkage studies. A library highly enriched for human DNA from Xp21 was constructed using DNA isolated from a male patient who had a visible deletion and three X-linked disorders (DMD, retinitis pigmentosa and chronic granulomatous disease). Seven cloned DNA probes from this library and the probe 754 (refs 5, 8) are used in the present study to screen for deletions in the DNA isolated from 57 unrelated males with DMD. Five of these DMD males are shown to exhibit deletions for one of the cloned DNA segments and at least 38 kb of surrounding DNA. In addition, two subclones from the same region detect four restriction fragment length polymorphisms which exhibit no obligate recombination with DMD in 34 meiotic events. These new DNA segments will complement the existing Xp21 probes for use in carrier detection and prenatal diagnosis of DMD. Elucidation of the end points of the five deletions will help delineate the extent of the DMD locus and ultimately lead to an understanding of the specific sequences involved in DMD.

Analysis of deletions in DNA from patients with Becker and Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is an X-linked recessive genetic disorder for which the biochemical defect is as yet unknown. Recently, two cloned segments of human X-chromosome DNA have been described which detect structural alterations within or near the genetic locus responsible for the disorder. Both of these cloned segments were described as tightly linked to the locus and were capable of detecting deletions in the DNA of boys affected with DMD. In an attempt to determine more precisely the occurrence of these deletions within a large population of DMD patients and the accuracy of one of the segments, DXS164 (pERT87), in determining the inheritance of the DMD X chromosome, the subclones 1, 8 and 15 were made available to many investigators throughout the world. Here we describe the combined results of more than 20 research laboratories with respect to the occurrence of deletions at the DXS164 locus in DNA samples isolated from patients with DMD and Becker muscular dystrophy (BMD). The results indicate that the DXS164 locus apparently recombines with DMD 5% of the time, but is probably located between independent sites of mutation which yield DMD. The breakpoints of some deletions are delineated within the DXS164 locus, and it is evident that the deletions at the DMD locus are frequent and extremely large.