Childhood cancer mutagenesis caused by transposase-derived PGBD5

Genomic rearrangements are a hallmark of most childhood tumors, including medulloblastoma, one of the most common brain tumors in children, but their causes remain largely unknown. Here, we show that PiggyBac transposable element derived 5 (Pgbd5) promotes tumor development in multiple developmentally accurate mouse models of Sonic Hedgehog (SHH) medulloblastoma. Most Pgbd5-deficient mice do not develop tumors, while maintaining normal cerebellar development. Ectopic activation of SHH signaling is sufficient to enforce cerebellar granule cell progenitor-like cell states, which exhibit Pgbd5-dependent expression of distinct DNA repair and neurodevelopmental factors. Mouse medulloblastomas expressing Pgbd5 have increased numbers of somatic structural DNA rearrangements, some of which carry PGBD5-specific sequences at their breakpoints. Similar sequence breakpoints recurrently affect somatic DNA rearrangements of known tumor suppressors and oncogenes in medulloblastomas in 329 children. This identifies PGBD5 as a medulloblastoma mutator and provides a genetic mechanism for the generation of oncogenic DNA rearrangements in childhood cancer.

A road map for the treatment of pediatric diffuse midline glioma

Recent clinical trials for H3K27-altered diffuse midline gliomas (DMGs) have shown much promise. We present a consensus roadmap and identify three major barriers: (1) refinement of experimental models to include immune and brain-specific components; (2) collaboration among researchers, clinicians, and industry to integrate patient-derived data through sharing, transparency, and regulatory considerations; and (3) streamlining clinical efforts including biopsy, CNS-drug delivery, endpoint determination, and response monitoring. We highlight the importance of comprehensive collaboration to advance the understanding, diagnostics, and therapeutics for DMGs.

Case report: A novel biallelic FTO variant causing multisystem anomalies with severe epilepsy, widening the spectrum of FTO syndrome

The fat mass and obesity-associated gene (FTO) codes for a DNA/RNA demethylase. Pathological variants in this gene are rare, with only three reports in the literature, all with mutations in the catalytic domain. We report the first biallelic human variant in fat mass and obesity-associated gene (c.287G>C, p.Arg96Pro/R96P) outside the catalytic site, causing numerous abnormalities across multiple organ systems, affecting respiratory, cardiovascular, and neurological function. Biochemical assays of cells with the patient's variant were performed to further quantify the effect of the variant on function. Loss-of-function resulting from the patient's R96P missense variant was demonstrated with in vitro biochemical characterization of demethylase activity, resulting in a 90% reduction in function of the fat mass and obesity-associated protein compared to wild-type. Our findings demonstrate a novel fat mass and obesity-associated gene non-catalytic site variant with a unique patient phenotype of bilateral multifocal epilepsy and multisystem congenital anomalies.

Abstract 1992: P-selectin-targeted delivery of intracranial therapeutics across an intact BBB in Sonic Hedgehog medulloblastoma

Medulloblastoma (MB) is the most common malignant pediatric brain tumor with ~30% mediated by Sonic hedgehog (SHH) signaling. While SHH effector Smoothened inhibition is promising, therapeutic index is reduced by high systemic doses required for sufficient intracranial drug concentrations. Treatment-related toxicities associated with radiation therapy result in lifelong morbidity, and SHH pathway inhibition in children notably results in permanent bone defects. Here, we found that nanoparticle-mediated P-selectin targeting on tumor vasculature induces caveolin-1-dependent transcellular passage across the blood-brain barrier. A vismodegib nanocarrier that targets P-selectin exhibited striking efficacy and markedly reduced both bone-related toxicities and drug exposure to healthy brain. These findings demonstrate a potent strategy and novel mechanism for targeted intracranial pharmacodelivery that overcomes the restrictive endothelial barrier to achieve enhanced tumor-selective penetration and has therapeutic implications for other diseases within the central nervous system.

Citation Format: Daniel A. Heller, Daniel Tylawsky, G. Praveen Raju. P-selectin-targeted delivery of intracranial therapeutics across an intact BBB in Sonic Hedgehog medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1992.

P-selectin-targeted nanocarriers induce active crossing of the blood-brain barrier via caveolin-1-dependent transcytosis

Medulloblastoma is the most common malignant paediatric brain tumour, with ~30% mediated by Sonic hedgehog signalling. Vismodegib-mediated inhibition of the Sonic hedgehog effector Smoothened inhibits tumour growth but causes growth plate fusion at effective doses. Here, we report a nanotherapeutic approach targeting endothelial tumour vasculature to enhance blood-brain barrier crossing. We use fucoidan-based nanocarriers targeting endothelial P-selectin to induce caveolin-1-dependent transcytosis and thus nanocarrier transport into the brain tumour microenvironment in a selective and active manner, the efficiency of which is increased by radiation treatment. In a Sonic hedgehog medulloblastoma animal model, fucoidan-based nanoparticles encapsulating vismodegib exhibit a striking efficacy and marked reduced bone toxicity and drug exposure to healthy brain tissue. Overall, these findings demonstrate a potent strategy for targeted intracranial pharmacodelivery that overcomes the restrictive blood-brain barrier to achieve enhanced tumour-selective penetration and has therapeutic implications for diseases within the central nervous system.

Abstract 3401: Whole genome cell-free tumor DNA mutational signatures for noninvasive monitoring of pediatric brain cancers

Introduction: Liquid biopsy offers a noninvasive approach to monitor cancer burden during therapy and surveillance period. However, in pediatric brain cancers, liquid biopsy methods from the blood have been unsuccessful due to a low tumor burden and low number of mutations in coding regions. We hypothesized that a whole genome sequencing (WGS)-derived patient specific mutational signature from a matched tumor-normal WGS can provide a sensitive and specific approach to detect mutations in circulating cell free tumor DNA (ctDNA) and provide blood-based monitoring in pediatric patients with brain tumor.

Methods: All tumors were analyzed and molecularly subclassified using whole genome DNA methylation profiling and machine learning classifier. Tumor DNA was extracted from pathology tissue and normal germline DNA from the white blood cells, while ctDNA was extracted from 1-2 mL of post-surgery or follow-up plasma samples, WGS was applied to sequence DNA from matched tumor-normal and plasma samples. WGS coverage was 40x for matched tumor-normal DNA and 20x for ctDNA. Using the C2i assay, we derived a personalized mutational pattern for each tumor and used an AI-based error suppression model for quantification and ultra-sensitive detection of ctDNA in plasma samples. A patient-specific personalized genome-wide compendium of somatic mutations was established and ctDNA tested at 1 to 3 available time points during the therapy or surveillance period. An AI-based error suppression model was implemented to filter out the noise in the cell free DNA (cfDNA) while the personalized mutational signature was used to detect the ctDNA in the cfDNA and to amplify the somatic signal contained in it. The ctDNA Tumor Fraction (TF) was compared to the clinical status and MR-based imaging.

Results: We profiled 7 pediatric brain tumors, including 2 medulloblastomas (one Group 3, one Group 4), 3 pediatric glioblastomas IDH wild-type, 1 ependymoma PFA subtype and one low grade ganglioglioma. Tumor specific signatures were identified and detected in the plasma of 5 patients with clinical disease with a TF range 0.02-0.0005 but not in 2 patients with no tumor at the time of blood collection. In two children with a medulloblastoma and glioblastoma, the decrease of tumor fraction in ctDNA over 2 (TF: 0.002 to 0.0009) and 3 time points (TF: 0.0005 to undetectable), respectively, correlated with response to therapy based on imaging.

Conclusions: Patient-specific WGS tumor signature in ctDNA from blood can be used for sensitive monitoring of children with brain tumors.

Citation Format: Ivy Tran, Kristyn Galbraith, Guisheng Zhao, Robyn Borsuk, Joyce Varkey, Sharon Gardner, Jeffrey Allen, David Harter, Jeffrey Wisoff, Eveline T. Hidalgo, Sunil Deochand, Dillon Maloney, Danielle Afterman, Tomer Lauterman, Noah Friedman, Imane Bourzgui, Nidhi Ramaraj, Zohar Donenhirsh, Ronel Veksler, Jonathan Rosenfeld, Ravi Kandasamy, Iman Tavassoly, Boris Oklander, G. Praveen Raju, Theodore Nicolaides, Asaf Zviran, Matija Snuderl. Whole genome cell-free tumor DNA mutational signatures for noninvasive monitoring of pediatric brain cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3401.

A tumor suppressor role for EZH2 in diffuse midline glioma pathogenesis

Pediatric high-grade gliomas, specifically diffuse midline gliomas, account for only 20% of clinical cases but are 100% fatal. A majority of the DMG cases are characterized by the signature K27M mutation in histone H3. The H3K27M mutation opposes the function of enhancer of zeste homolog 2 (EZH2), the methyltransferase enzyme of the polycomb repressor complex 2. However, the role of EZH2 in DMG pathogenesis is unclear. In this study, we demonstrate a tumor suppressor function for EZH2 using Ezh2 loss- and gain-of-function studies in H3WT DMG mouse models. Genetic ablation of Ezh2 increased cell proliferation and tumor grade while expression of an Ezh2 gain-of-function mutation significantly reduced tumor incidence and increased tumor latency. Transcriptomic analysis revealed that Ezh2 deletion upregulates an inflammatory response with upregulation of immunoproteasome genes such as Psmb8, Psmb9, and Psmb10. Ezh2 gain-of-function resulted in enrichment of the oxidative phosphorylation/mitochondrial metabolic pathway namely the isocitrate dehydrogenase Idh1/2/3 genes. Pharmacological inhibition of EZH2 augmented neural progenitor cell proliferation, supporting the tumor suppressive role of EZH2. In vivo 7-day treatment of H3K27M DMG tumor bearing mice with an EZH2 inhibitor, Tazemetostat, did not alter proliferation or significantly impact survival. Together our results suggest that EZH2 has a tumor suppressor function in DMG and warrants caution in clinical translation of EZH2 inhibitors to treat patients with DMG.

Extracellular Vesicle and Particle Biomarkers Define Multiple Human Cancers

There is an unmet clinical need for improved tissue and liquid biopsy tools for cancer detection. We investigated the proteomic profile of extracellular vesicles and particles (EVPs) in 426 human samples from tissue explants (TEs), plasma, and other bodily fluids. Among traditional exosome markers, CD9, HSPA8, ALIX, and HSP90AB1 represent pan-EVP markers, while ACTB, MSN, and RAP1B are novel pan-EVP markers. To confirm that EVPs are ideal diagnostic tools, we analyzed proteomes of TE- (n = 151) and plasma-derived (n = 120) EVPs. Comparison of TE EVPs identified proteins (e.g., VCAN, TNC, and THBS2) that distinguish tumors from normal tissues with 90% sensitivity/94% specificity. Machine-learning classification of plasma-derived EVP cargo, including immunoglobulins, revealed 95% sensitivity/90% specificity in detecting cancer. Finally, we defined a panel of tumor-type-specific EVP proteins in TEs and plasma, which can classify tumors of unknown primary origin. Thus, EVP proteins can serve as reliable biomarkers for cancer detection and determining cancer type.

SCIDOT-41. NANOTHERAPEUTIC TARGETING OF TUMOR ENDOTHELIUM FOR ENHANCING DRUG DELIVERY PAST THE BLOOD-BRAIN BARRIER

OBJECTIVE

The Sonic Hedgehog (SHH) medulloblastoma subgroup accounts for ~25% of all cases and has an intermediate prognosis. Current conventional therapies result in devastating morbidities including intellectual disability and secondary malignancies. Although molecularly targeted agents that inhibit the SHH pathway have demonstrated clinical efficacy, recent studies have shown on-target secondary toxicities on bone development suggesting new therapeutic approaches are needed.

METHODS

We investigated the efficacy of the SHH pathway inhibitor, Vismodegib packaged in a fucoidan-based nanoparticle (Fi-Vis) that targets P-selectin, a protein overexpressed on vascular endothelial cells and induced by low-dose ionizing radiation (XRT) in a time- and dose-dependent manner. This P-selectin targeting nanoparticle drug delivery system shows selectivity toward tumor vasculature and not normal brain vasculature in a genetic SHH medulloblastoma mouse model as assessed by ex vivo infrared imaging and two-photon intravital imaging.

RESULTS

Quantitative RT-PCR analysis of SHH medulloblastoma tissue following single dose XRT and Fi-Vis treatment (10mg/kg) showed a synergistic inhibition of Gli1 expression (>90% target inhibition). Furthermore, we demonstrate that very low dose XRT (0.25Gy) can induce P-selectin expression specifically within MB tumor vasculature and synergize with low dose Fi-Vis (10mg/kg) to significantly enhance mouse survival (p<0.01) when compared to radiation or Fi-Vis alone. Furthermore, assessment of bone toxicity using micro-CT and histological analysis following Fi-Vis administration in postnatal (P10) mice shows no bone toxicity when compared to free Vismodegib. Finally, in vitro studies using mouse brain endothelial cells suggest at least in part a caveolin-1 mediated transcytosis mechanism of crossing the endothelial blood-brain barrier.

CONCLUSIONS

These data suggest applicability of combined XRT and tumor vasculature-targeted nanotherapeutic dose de-escalation strategies for SHH medulloblastoma with implications for other pediatric and adult brain tumors.

In vivo Mn-enhanced MRI for early tumor detection and growth rate analysis in a mouse medulloblastoma model

Mouse models have increased our understanding of the pathogenesis of medulloblastoma (MB), the most common malignant pediatric brain tumor that often forms in the cerebellum. A major goal of ongoing research is to better understand the early stages of tumorigenesis and to establish the genetic and environmental changes that underlie MB initiation and growth. However, studies of MB progression in mouse models are difficult due to the heterogeneity of tumor onset times and growth patterns and the lack of clinical symptoms at early stages. Magnetic resonance imaging (MRI) is critical for noninvasive, longitudinal, three-dimensional (3D) brain tumor imaging in the clinic but is limited in resolution and sensitivity for imaging early MBs in mice. In this study, high-resolution (100 μm in 2 hours) and high-throughput (150 μm in 15 minutes) manganese-enhanced MRI (MEMRI) protocols were optimized for early detection and monitoring of MBs in a Patched-1 (Ptch1) conditional knockout (CKO) model. The high tissue contrast obtained with MEMRI revealed detailed cerebellar morphology and enabled detection of MBs over a wide range of stages including pretumoral lesions as early as 2 to 3 weeks postnatal with volumes close to 0.1 mm³. Furthermore, longitudinal MEMRI allowed noninvasive monitoring of tumors and demonstrated that lesions within and between individuals have different tumorigenic potentials. 3D volumetric studies allowed quantitative analysis of MB tumor morphology and growth rates in individual Ptch1-CKO mice. These results show that MEMRI provides a powerful method for early in vivo detection and longitudinal imaging of MB progression in the mouse brain.

Rapid reversal of uremic neuropathy following renal transplantation in an adolescent

Clinical and pathologic studies on adults with uremic neuropathy are numerous, but less is known about this disorder in children and adolescents. We report the clinical, electrophysiologic, and pathologic findings in an adolescent female with uremic neuropathy. Electrophysiologic findings were consistent with a primarily axonal sensorimotor polyneuropathy. Sural nerve biopsy revealed areas of focal depletion in myelin sheaths and loss of axons. Axonal degeneration with secondary myelin changes appears to be the characteristic pathology in this case, one of the youngest to our knowledge for which nerve biopsy data are available. Our patient experienced dramatic recovery after renal transplantation, similar to the reports of older patients.

MASTR: a technique for mosaic mutant analysis with spatial and temporal control of recombination using conditional floxed alleles in mice

Mosaic mutant analysis, the study of cellular defects in scattered mutant cells in a wild-type environment, is a powerful approach for identifying critical functions of genes and has been applied extensively to invertebrate model organisms. A highly versatile technique has been developed in mouse: MASTR (mosaic mutant analysis with spatial and temporal control of recombination), which utilizes the increasing number of floxed alleles and simultaneously combines conditional gene mutagenesis and cell marking for fate analysis. A targeted allele (R26(MASTR)) was engineered; the allele expresses a GFPcre fusion protein following FLP-mediated recombination, which serves the dual function of deleting floxed alleles and marking mutant cells with GFP. Within 24 hr of tamoxifen administration to R26(MASTR) mice carrying an inducible FlpoER transgene and a floxed allele, nearly all GFP-expressing cells have a mutant allele. The fate of single cells lacking FGF8 or SHH signaling in the developing hindbrain was analyzed using MASTR, and it was revealed that there is only a short time window when neural progenitors require FGFR1 for viability and that granule cell precursors differentiate rapidly when SMO is lost. MASTR is a powerful tool that provides cell-type-specific (spatial) and temporal marking of mosaic mutant cells and is broadly applicable to developmental, cancer, and adult stem cell studies.

Arsenic: a potentially useful poison for Hedgehog-driven cancers

Dysregulated Hedgehog (Hh) signaling has been implicated in a growing number of human cancers. To date, most antagonists of this signaling pathway that have been developed target the Hh receptor Smoothened. However, these are predicted to have minimal effect when the pathway is activated as a result of dysregulation downstream of this receptor. In this issue of the JCI, Beauchamp and colleagues provide preclinical evidence that arsenic trioxide, a drug FDA approved for the treatment of acute promyelocytic leukemia, inhibits the growth of Ewing sarcoma and medulloblastoma cells by targeting GLI family zinc finger (GLI) proteins, which are Hh signaling pathway components downstream of Smoothened.

Germinal matrix hemorrhage in Zellweger syndrome

A term male newborn was noted to have severe diffuse hypotonia, hyporeflexia, hepatosplenomegaly, and characteristic abnormal facies of Zellweger syndrome, the diagnosis of which was confirmed by identification of 2 mutations including Nt2098insT, a frameshift with premature stop codon in exon 13, as well as a novel second mutation at Nt3038G→A (Arg1013His) on skin fibroblast testing. His brain magnetic resonance imaging (MRI) demonstrated bilateral germinolytic cysts with unilateral hemorrhagic transformation. Germinolytic cysts are one of the characteristic radiographic features of Zellweger syndrome, but germinal matrix hemorrhage has never been reported. Germinal matrix hemorrhage is common in premature infants, but found in only 4% of normal term infants. Germinal matrix hemorrhage was seen in a case of Zellweger syndrome with a novel mutation.

Postvaricella acute transverse myelitis in a previously vaccinated child

We describe a 14-year-old boy with acute transverse myelitis after breakthrough varicella infection, despite immunization with the Varicella zoster virus vaccine 8 years earlier. He recovered fully after treatment with intravenous corticosteroids and acyclovir. To our knowledge, there are no previously reported cases of postvaricella acute transverse myelitis in vaccinated individuals. Our report emphasizes that the Varicella zoster virus booster vaccine may be necessary to prevent not only acute varicella, but also its postinfectious neurologic complications.

A case of congenital glycogen storage disease type IV with a novel GBE1 mutation

Glycogen storage disease type IV (Andersen disease) is a rare metabolic disorder characterized by deficient glycogen branching enzyme activity resulting in abnormal, amylopectin-like glycogen deposition in multiple organs. This article reports on an infant with the congenital neuromuscular subtype of glycogen storage disease type IV who presented with polyhydramnios, hydrops fetalis, bilateral ankle contractures, biventricular cardiac dysfunction, and severe facial and extremity weakness. A muscle biopsy showed the presence of material with histochemical and ultrastructural characteristics consistent with amylopectin. Biochemical analysis demonstrated severely reduced branching enzyme activity in muscle tissue and fibroblasts. Genetic analysis demonstrated a novel deletion of exon 16 within GBE1, the gene associated with glycogen storage disease type IV. Continued genetic characterization of glycogen storage disease type IV patients may aid in predicting clinical outcomes in these patients and may also help in identifying treatment strategies for this potentially devastating metabolic disorder.

Oxcarbazepine in children with nocturnal frontal-lobe epilepsy

Nocturnal frontal-lobe epilepsy is characterized by paroxysmal arousals, motor seizures with dystonic or hyperkinetic features, and episodic nocturnal wanderings. Carbamazepine is effective for seizure control in some of these patients, but seizures may be refractory to multiple antiepileptic drugs. We report on eight children between ages 4-16 years with nocturnal frontal-lobe epilepsy who had a dramatic response to oxcarbazepine at standard recommended doses, some of whom were refractory to previous antiepileptic medications. Brain magnetic resonance imaging, routine electroencephalogram, and prolonged, continuous video-electroencephalogram telemetry were performed in all children. Nocturnal frontal-lobe epilepsy was diagnosed by demonstrating ictal electroencephalogram changes originating from the frontal lobes. The children were followed for response of seizures to oxcarbazepine, side effects, and routine blood tests, including serum 10-monohydroxide derivative levels. The mean oxcarbazepine dose was 30.4 mg/kg/day +/- 11.7 (mean +/- SD); the mean 10-monohydroxide level was 23.1 microg/mL +/- 8.6 (mean +/- SD). Seizures improved within 4 days of oxcarbazepine initiation in six children, whereas two children required higher doses. Their follow-up has ranged from 12 to 24 months, without seizure recurrence or serious side effects. Our patients demonstrate the efficacy of oxcarbazepine for nocturnal hyperkinetic seizures in children with nocturnal frontal-lobe epilepsy.

Neonatal subependymal giant cell astrocytoma: new case and review of literature

Subependymal giant cell astrocytomas are one of the three major intracranial lesions found in tuberous sclerosis complex. Subependymal giant cell astrocytomas are typically slow-growing tumors of mixed glioneuronal lineage which can become aggressive and cause obstructive hydrocephalus usually in older children and adolescents. Neonatal subependymal giant cell astrocytomas are extremely rare, and their natural history and prognosis are poorly understood. This report investigates an extremely large neonatal subependymal giant cell astrocytoma which was initially identified in utero at 19 weeks of gestation in a high-risk pregnancy with no family history of tuberous sclerosis complex.

SANE, a novel LEM domain protein, regulates bone morphogenetic protein signaling through interaction with Smad1

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-beta (TGF-beta) superfamily that play important roles in bone formation, embryonic patterning, and epidermal-neural cell fate decisions. BMPs signal through pathway specific mediators such as Smads1 and 5, but the upstream regulation of BMP-specific Smads has not been fully characterized. Here we report the identification of SANE (Smad1 Antagonistic Effector), a novel protein with significant sequence similarity to nuclear envelop proteins such as MAN1. SANE binds to Smad1/5 and to BMP type I receptors and regulates BMP signaling. SANE specifically blocks BMP-dependent signaling in Xenopus embryos and in a mammalian model of bone formation but does not inhibit the TGF-beta/Smad2 pathway. Inhibition of BMP signaling by SANE requires interaction between SANE and Smad1, because a SANE mutant that does not bind Smad1 does not inhibit BMP signaling. Furthermore, inhibition appears to be mediated by inhibition of BMP-induced Smad1 phosphorylation, blocking ligand-dependent nuclear translocation of Smad1. These studies define a new mode of regulation for intracellular BMP/Smad1 signaling.

Growth hormone and colorectal carcinoma: localization of receptors

Growth hormone (GH) plays a crucial role in stimulating and controlling the growth, metabolism and differentiation of many mammalian cell types by modulating the synthesis of multiple mRNA species and a paracrine or autocrine mechanism of action has been proposed. These effects are mediated by the binding of GH to its membrane-bound receptor and involve a phosphorylation cascade that results in the modulation of numerous signaling pathways. To address the side/mode of action through which GH exerts its effects, a panel of well characterized monoclonal antibodies, directed against the hormone binding side of the receptor, was applied to immunohistochemically determine growth hormone receptor (GH-receptor) expression in poorly- moderate- to well differentiated col.orectal adenocarcinomas (n = 40) from the rectum, transverse-, ascending-, descending and sigmoid colons. Of five anti-growth hormone receptor monoclonal antibodies used, human GH- receptor specific Mab 263 consistently resulted in strong receptor expression in colorectal carcinoma tumour cells. Heterogeneity of immunoreactivity was found in primary and secondary tumour lesions with a variable range of positive cells. Staining was mainly intracellular, showing either a monotonous or granular pattern, with some nuclei also reactive. The presence of intracellular GH-receptors has been previously documented and is a result of endoplasmic reticulum and Golgi localization. Immunoreactivity in surface columnar cells, independent from pathological tissue, was weak to moderate. Epithelial cells from normal tissue, adjacent to tumour lesions, were of variable intensity. Goblet and mucous cells located at the crypt base immunostained faintly or were negative for the GH-receptors. Crypt base columnar cells strongly expressed the GH-receptor, but oligomucous cells were less reactive. In conclusion, this study indicates that receptor expression may be associated with malignancy of colorectal carcinoma and supports the hypothesis that GH may act locally in colorectal tissue. The demonstration of the presence of receptors for GH will be useful for site-specific studies of the evolution of gastrointestinal tract tumours, providing valuable information concerning cellular growth kinetics and tumour prognosis. It also raises questions regarding the administration of GH to cancer-induced cachexia patients and the possible oncogenic potential of the GH-receptor.

In utero cardiac gene transfer via intraplacental delivery of recombinant adenovirus

BACKGROUND

The relationship among the maternal, placental, and uniquely shunted embryonic circulation was explored to provide access to the embryonic cardiovascular system in utero. Manipulation of gene expression in the developing heart would be particularly useful for studying the effects of altered gene expression on cardiac development and in the etiology of congenital cardiac anomalies.

METHODS AND RESULTS

Dye studies demonstrated that intraplacental injection allows direct access to the embryonic cardiac and systemic circulation. To evaluate the efficacy of cardiac gene transfer using this approach, replication-deficient recombinant adenoviral vectors encoding luciferase or beta-galactosidase as reporter genes were injected intraplacentally into embryonic day (E)12.5 murine embryos, an age at which the mass of the heart was observed to be large compared with other organs. Embryos were assayed for transgene expression at E15.5 and at birth. Survival rates at these times were similar among vector-injected and control groups. At E15.5 and at birth, luciferase activity within the heart was 9- and 23-fold higher, respectively, than in the remainder of the embryo, although levels of expression were generally lower at birth than during embryonic life. Beta-galactosidase expression was observed within all regions of the embryonic heart and was localized to approximately 15% of atrial and ventricular cells.

CONCLUSIONS

Intraplacental delivery of adenovirus at embryonic day 12.5 results in somatic gene transfer to the murine embryonic heart, which persists at least until birth. The combination of intraplacental injection to directly access the fetal coronary circulation and injection at E12.5 when the mass of the heart is large compared with other organs results in transgene expression in cardiac cells. Intraplacental injections early in embryonic life may thus be useful to study the effects of temporal manipulation of gene expression on cardiac development and disease.