Pre-clinical evaluation of biomarkers for the early detection of nephrotoxicity following alpha-particle radioligand therapy

PURPOSE

Cancer treatment with alpha-emitter-based radioligand therapies (α-RLTs) demonstrates promising tumor responses. Radiolabeled peptides are filtered through glomeruli, followed by potential reabsorption of a fraction by proximal tubules, which may cause acute kidney injury (AKI) and chronic kidney disease (CKD). Because tubular cells are considered the primary site of radiopeptides' renal reabsorption and potential injury, the current use of kidney biomarkers of glomerular functional loss limits the evaluation of possible nephrotoxicity and its early detection. This study aimed to investigate whether urinary secretion of tubular injury biomarkers could be used as an additional non-invasive sensitive diagnostic tool to identify unrecognizable tubular damage and risk of long-term α-RLT nephrotoxicity.

METHODS

A bifunctional cyclic peptide, melanocortin 1 ligand (MC1L), labeled with [203Pb]Pb-MC1L, was used for [212Pb]Pb-MC1L biodistribution and absorbed dose measurements in CD-1 Elite mice. Mice were treated with [212Pb]Pb-MC1L in a dose-escalation study up to levels of radioactivity intended to induce kidney injury. The approach enabled prospective kidney functional and injury biomarker evaluation and late kidney histological analysis to validate these biomarkers.

RESULTS

Biodistribution analysis identified [212Pb]Pb-MC1L reabsorption in kidneys with a dose deposition of 2.8, 8.9, and 20 Gy for 0.9, 3.0, and 6.7 MBq injected [212Pb]Pb-MC1L doses, respectively. As expected, mice receiving 6.7 MBq had significant weight loss and CKD evidence based on serum creatinine, cystatin C, and kidney histological alterations 28 weeks after treatment. A dose-dependent urinary neutrophil gelatinase-associated lipocalin (NGAL, tubular injury biomarker) urinary excretion the day after [212Pb]Pb-MC1L treatment highly correlated with the severity of late tubulointerstitial injury and histological findings.

CONCLUSION

Urine NGAL secretion could be a potential early diagnostic tool to identify unrecognized tubular damage and predict long-term α-RLT-related nephrotoxicity.

Structural modifications toward improved lead-203/lead-212 peptide-based image-guided alpha-particle radiopharmaceutical therapies for neuroendocrine tumors

PURPOSE

The lead-203 (203Pb)/lead-212 (212Pb) elementally identical radionuclide pair has gained significant interest in the field of image-guided targeted alpha-particle therapy for cancer. Emerging evidence suggests that 212Pb-labeled peptide-based radiopharmaceuticals targeting somatostatin receptor subtype 2 (SSTR2) may provide improved effectiveness compared to beta-particle-based therapies for neuroendocrine tumors (NETs). This study aims to improve the performance of SSTR2-targeted radionuclide imaging and therapy through structural modifications to Tyr3-octreotide (TOC)-based radiopharmaceuticals.

METHODS

New SSTR2-targeted peptides were designed and synthesized with the goal of optimizing the incorporation of Pb isotopes through the use of a modified cyclization technique; the introduction of a Pb-specific chelator (PSC); and the insertion of polyethylene glycol (PEG) linkers. The binding affinity of the peptides and the cellular uptake of 203Pb-labeled peptides were evaluated using pancreatic AR42J (SSTR2+) tumor cells and the biodistribution and imaging of the 203Pb-labeled peptides were assessed in an AR42J tumor xenograft mouse model. A lead peptide was identified (i.e., PSC-PEG2-TOC), which was then further evaluated for efficacy in 212Pb therapy studies.

RESULTS

The lead radiopeptide drug conjugate (RPDC) - [203Pb]Pb-PSC-PEG2-TOC - significantly improved the tumor-targeting properties, including receptor binding and tumor accumulation and retention as compared to [203Pb]Pb-DOTA0-Tyr3-octreotide (DOTATOC). Additionally, the modified RPDC exhibited faster renal clearance than the DOTATOC counterpart. These advantageous characteristics of [212Pb]Pb-PSC-PEG2-TOC resulted in a dose-dependent therapeutic effect with minimal signs of toxicity in the AR42J xenograft model. Fractionated administrations of 3.7 MBq [212Pb]Pb-PSC-PEG2-TOC over three doses further improved anti-tumor effectiveness, resulting in 80% survival (70% complete response) over 120 days in the mouse model.

CONCLUSION

Structural modifications to chelator and linker compositions improved tumor targeting and pharmacokinetics (PK) of 203/212Pb peptide-based radiopharmaceuticals for NET theranostics. These findings suggest that PSC-PEG2-TOC is a promising candidate for Pb-based targeted radionuclide therapy for NETs and other types of cancers that express SSTR2.

Pre-clinical Evaluation of Biomarkers for Early Detection of Nephrotoxicity Following Alpha-particle Radioligand Therapy

Purpose

Cancer treatment with alpha-emitter-based radioligand therapies (α-RLTs) demonstrates promising tumor responses. Radiolabeled peptides are filtered through glomeruli, followed by potential reabsorption of a fraction by proximal tubules, which may cause acute kidney injury (AKI) and chronic kidney disease (CKD). Because tubular cells are considered the primary site of radiopeptides' renal reabsorption and potential injury, the current use of kidney biomarkers of glomerular functional loss limits the evaluation of possible nephrotoxicity and its early detection. This study aimed to investigate whether urinary secretion of tubular injury biomarkers could be used as additional non-invasive sensitive diagnostic tool to identify unrecognizable tubular damage and risk of long-term α-RLTs nephrotoxicity.

Methods

A bifunctional cyclic peptide, melanocortin ligand-1(MC1L), labeled with [ 203 Pb]Pb-MC1L, was used for [ 212 Pb]Pb-MC1L biodistribution and absorbed dose measurements in CD-1 Elite mice. Mice were treated with [ 212 Pb]Pb-MC1L in a dose escalation study up to levels of radioactivity intended to induce kidney injury. The approach enabled prospective kidney functional and injury biomarker evaluation and late kidney histological analysis to validate these biomarkers.

Results

Biodistribution analysis identified [ 212 Pb]Pb-MC1L reabsorption in kidneys with a dose deposition of 2.8, 8.9, and 20 Gy for 0.9, 3.0, and 6.7 MBq injected [ 212 Pb]Pb-MC1L doses, respectively. As expected, mice receiving 6.7 MBq had significant weight loss and CKD evidence based on serum creatinine, cystatin C, and kidney histological alterations 28 weeks after treatment. A dose-dependent urinary Neutrophil gelatinase-associated lipocalin (NGAL, tubular injury biomarker) urinary excretion the day after [ 212 Pb]Pb-MC1L treatment highly correlated with the severity of late tubulointerstitial injury and histological findings.

Conclusion

urine NGAL secretion could be a potential early diagnostic tool to identify unrecognized tubular damage and predict long-term α-RLT-related nephrotoxicity.

Preclinical Evaluation of a Lead Specific Chelator (PSC) Conjugated to Radiopeptides for 203Pb and 212Pb-Based Theranostics

203Pb and 212Pb have emerged as promising theranostic isotopes for image-guided α-particle radionuclide therapy for cancers. Here, we report a cyclen-based Pb specific chelator (PSC) that is conjugated to tyr3-octreotide via a PEG2 linker (PSC-PEG-T) targeting somatostatin receptor subtype 2 (SSTR2). PSC-PEG-T could be labeled efficiently to purified 212Pb at 25 °C and also to 212Bi at 80 °C. Efficient radiolabeling of mixed 212Pb and 212Bi in PSC-PEG-T was also observed at 80 °C. Post radiolabeling, stable Pb(II) and Bi(III) radiometal complexes in saline were observed after incubating [203Pb]Pb-PSC-PEG-T for 72 h and [212Bi]Bi-PSC-PEG-T for 5 h. Stable [212Pb]Pb-PSC-PEG-T and progeny [212Bi]Bi-PSC-PEG-T were identified after storage in saline for 24 h. In serum, stable radiometal/radiopeptide were observed after incubating [203Pb]Pb-PSC-PEG-T for 55 h and [212Pb]Pb-PSC-PEG-T for 24 h. In vivo biodistribution of [212Pb]Pb-PSC-PEG-T in tumor-free CD-1 Elite mice and athymic mice bearing AR42J xenografts revealed rapid tumor accumulation, excellent tumor retention and fast renal clearance of both 212Pb and 212Bi, with no in vivo redistribution of progeny 212Bi. Single-photon emission computed tomography (SPECT) imaging of [203Pb]Pb-PSC-PEG-T and [212Pb]Pb-PSC-PEG-T in mice also demonstrated comparable accumulation in AR42J xenografts and renal clearance, confirming the theranostic potential of the elementally identical 203Pb/212Pb radionuclide pair.

Dosimetry of [212Pb]VMT01, a MC1R-Targeted Alpha Therapeutic Compound, and Effect of Free 208Tl on Tissue Absorbed Doses

[²¹²Pb]VMT01 is a melanocortin 1 receptor (MC1R) targeted theranostic ligand in clinical development for alpha particle therapy for melanoma. ²¹²Pb has an elementally matched gamma-emitting isotope ²⁰³Pb; thus, [²⁰³Pb]VMT01 can be used as an imaging surrogate for [²¹²Pb]VMT01. [²¹²Pb]VMT01 human serum stability studies have demonstrated retention of the ²¹²Bi daughter within the chelator following beta emission of parent ²¹²Pb. However, the subsequent alpha emission from the decay of ²¹²Bi into ²⁰⁸Tl results in the generation of free ²⁰⁸Tl. Due to the 10.64-hour half-life of ²¹²Pb, accumulation of free ²⁰⁸Tl in the injectate will occur. The goal of this work is to estimate the human dosimetry for [²¹²Pb]VMT01 and the impact of free ²⁰⁸Tl in the injectate on human tissue absorbed doses. Human [²¹²Pb]VMT01 tissue absorbed doses were estimated from murine [²⁰³Pb]VMT01 biodistribution data, and human biodistribution values for ²⁰¹Tl chloride (a cardiac imaging agent) from published data were used to estimate the dosimetry of free ²⁰⁸Tl. Results indicate that the dose-limiting tissues for [²¹²Pb]VMT01 are the red marrow and the kidneys, with estimated absorbed doses of 1.06 and 8.27 mGy_{RBE = 5}/MBq. The estimated percent increase in absorbed doses from free ²⁰⁸Tl in the injectate is 0.03% and 0.09% to the red marrow and the kidneys, respectively. Absorbed doses from free ²⁰⁸Tl result in a percent increase of no more than 1.2% over [²¹²Pb]VMT01 in any organ or tissue. This latter finding indicates that free ²⁰⁸Tl in the [²¹²Pb]VMT01 injectate will not substantially impact estimated tissue absorbed doses in humans.

Targeted Alpha-Particle Radiotherapy and Immune Checkpoint Inhibitors Induces Cooperative Inhibition on Tumor Growth of Malignant Melanoma

Simple Summary

Radiation therapy and immune checkpoint inhibitors (ICIs) have been demonstrated to cooperatively activate adaptive anti-tumor immunity with curative potential in preclinical models of melanoma. Receptor-targeted radionuclide therapy can be systemically injected to selectively deliver ionizing radiation to tumor sites throughout the body, potentially rendering all tumor sites more susceptible to anti-tumor immune response. In this study, we demonstrated the feasibility of delivering alpha-particle radiation to murine melanoma tumors using a ²¹²Pb radiolabeled peptide [²¹²Pb]VMT01 that targets the melanocortin 1 receptor (MC1R). Our data showed anti-tumor cooperation between [²¹²Pb]VMT01 and ICIs in melanoma, mediated by induction of tumor-specific immunity. The immunogenicity of [²¹²Pb]VMT01 in melanoma was also evidenced by enhanced tumor infiltrating lymphocytes and tumor vaccination assays.

Abstract

Radiotherapy can facilitate the immune recognition of immunologically “cold” tumors and enhance the efficacy of anti-PD-1 and anti-CTLA-4 immune checkpoint inhibitors (ICIs) in melanoma. Systemic administration of receptor-targeted radionuclide therapy has the potential to selectively deliver radionuclides to multiple tumors throughout the body in metastatic settings. By triggering immunologic cell death and increasing the immune susceptibility of surviving tumor cells in these locations, targeted radionuclide therapies may overcome resistance to ICIs and render immunologically “cold” tumors throughout the body responsive to ICIs and immunologically “hot”. Here, we show the anti-tumor cooperation of targeted α-particle radionuclide therapy (α-TRT) and ICIs in preclinical models of melanoma. Melanocortin 1 receptor (MC1R)-targeted radiopeptide [²¹²Pb]VMT01 was employed to deliver α-radiation to melanoma tumors in mice. A single injection of 4.1 MBq [²¹²Pb]VMT01 significantly slowed the tumor growth of B16-F10 melanoma and the combination of [²¹²Pb]VMT01 and ICIs induced a cooperative anti-tumor effect leading to 43% complete tumor response with no sign of malignancy on autopsy. Animals with complete response developed anti-tumor immunity to reject further tumor inoculations. This therapeutic cooperation was completely abolished in RAG1 KO mice, which are deficient in T-cell maturation. In addition, the anti-tumor cooperation was compromised when fractionated [²¹²Pb]VMT01 was used in the combination. We also demonstrated that [²¹²Pb]VMT01 induced immunogenic cell death in tumor vaccination assays and in vitro exposure to [²¹²Pb]VMT01 sensitized immunotolerant melanoma to ICIs treatment in vivo. Enhanced tumor infiltrating CD3⁺, CD4⁺, CD8⁺ lymphocytes were observed following injection of 1.4 MBq [²¹²Pb]VMT01. Overall, we demonstrated anti-tumor cooperation between α-TRT and ICIs in melanoma that is mediated by tumor specific immunity.

203/212Pb Theranostic Radiopharmaceuticals for Image-guided Radionuclide Therapy for Cancer

Receptor-targeted image-guided Radionuclide Therapy (TRT) is increasingly recognized as a promising approach to cancer treatment. In particular, the potential for clinical translation of receptor-targeted alpha-particle therapy is receiving considerable attention as an approach that can improve outcomes for cancer patients. Higher Linear-energy Transfer (LET) of alpha-particles (compared to beta particles) for this purpose results in an increased incidence of double-strand DNA breaks and improved-localized cancer-cell damage. Recent clinical studies provide compelling evidence that alpha-TRT has the potential to deliver a significantly more potent anti-cancer effect compared with beta-TRT. Generator-produced 212Pb (which decays to alpha emitters 212Bi and 212Po) is a particularly promising radionuclide for receptor-targeted alpha-particle therapy. A second attractive feature that distinguishes 212Pb alpha-TRT from other available radionuclides is the possibility to employ elementallymatched isotope 203Pb as an imaging surrogate in place of the therapeutic radionuclide. As direct non-invasive measurement of alpha-particle emissions cannot be conducted using current medical scanner technology, the imaging surrogate allows for a pharmacologically-inactive determination of the pharmacokinetics and biodistribution of TRT candidate ligands in advance of treatment. Thus, elementally-matched 203Pb labeled radiopharmaceuticals can be used to identify patients who may benefit from 212Pb alpha-TRT and apply appropriate dosimetry and treatment planning in advance of the therapy. In this review, we provide a brief history on the use of these isotopes for cancer therapy; describe the decay and chemical characteristics of 203/212Pb for their use in cancer theranostics and methodologies applied for production and purification of these isotopes for radiopharmaceutical production. In addition, a medical physics and dosimetry perspective is provided that highlights the potential of 212Pb for alpha-TRT and the expected safety for 203Pb surrogate imaging. Recent and current preclinical and clinical studies are presented. The sum of the findings herein and observations presented provide evidence that the 203Pb/212Pb theranostic pair has a promising future for use in radiopharmaceutical theranostic therapies for cancer.

Enhancing the Efficacy of Melanocortin 1 Receptor-Targeted Radiotherapy by Pharmacologically Upregulating the Receptor in Metastatic Melanoma

Melanocortin 1 receptor (MC1R) is under investigation as a target for drug delivery for metastatic melanoma therapy and imaging. The purpose of this study was to determine the potential of using BRAF inhibitors (BRAF_i) and histone deacetylase inhibitors (HDAC_i) to enhance the delivery of MC1R-targeted radiolabeled peptide ([²¹²Pb]DOTA-MC1L) by pharmacologically upregulating the MC1R expression in metastatic melanoma cells and tumors. MC1R expression was analyzed in de-identified melanoma biopsies by immunohistochemical staining. Upregulation of MC1R expression was determined in BRAF^V600E cells (A2058) and BRAF wild-type melanoma cells (MEWO) by quantitative real-time polymerase chain reaction, flow cytometry, and receptor-ligand binding assays. The role of microphthalmia-associated transcription factor (MITF) in the upregulation of MC1R was also examined in A2058 and MEWO cells. The effectiveness of [²¹²Pb]DOTA-MC1L α-particle radiotherapy in combination with BRAF_i and/or HDAC_i was determined in athymic nu/nu mice bearing A2058 and MEWO human melanoma xenografts. High expression of MC1R was observed in situ in clinical melanoma biopsies. BRAF_i and HDAC_i significantly increased the MC1R expression (up to 10-fold in mRNA and 4-fold in protein levels) via MITF-dependent pathways, and this increase led to enhanced ligand binding on the cell surface. Inhibition of MITF expression antagonized the upregulation of MC1R in both BRAF^V600E and BRAF^WT cells. Combining [²¹²Pb]DOTA-MC1L with BRAF_i and/or HDAC_i improved the tumor response by increasing the delivery of ²¹²Pb α-particle emissions to melanoma tumors via augmented MC1R expression. These data suggest that FDA-approved HDAC_i and BRAF_i could improve the effectiveness of MC1R-targeted therapies by enhancing drug delivery via upregulated MC1R.

Abstract LB-230: Quantitative immunohistochemistry for melanocortin 1 receptor using phosphor integrated dots

Visual scoring of biomarkers by immunohistochemistry (IHC) on formalin-fixed paraffin embedded tissues constitutes a major part of histopathologic diagnosis and staging of several cancers. To improve sensitivity and linearity of IHC methods, we have developed a quantitative IHC technique using streptavidin coated phosphor integrated dot (PID) fluorescent nanoparticles (Gonda et al, Scientific Reports, 2017). In retrospective analysis of clinically established biomarkers (i.e., PD-L1, HER2, CSF-1R), IHC-PID has provided high-sensitivity quantitative detection of target proteins with a broad dynamic range. The present study examines the utility of IHC-PID in the biomarker discovery and validation process by evaluating melanocortin subtype 1 receptor (MC1R) in cell lines and clinical biopsy samples. MC1R is currently under investigation as a potential diagnostic and therapeutic target for malignant melanoma, a lethal cancer with poor long-term prognosis. MC1R is an endocytic cell-surface G-protein coupled receptor that exhibits relatively high expression in malignant melanoma tumors vs. normal tissues. Notably, current melanoma therapies, including MAPKi (e.g., vemurafenib, dabrafenib) increase MC1R expression pharmacologically on melanoma cells (unpublished results). MC1R expression was determined in cell lines by standard radio-ligand binding assay (125I-NDP-α-MSH). The SK-Mel-28 cell line showed 5-6 fold increased expression of endogenous MC1R when compared to the A375 cell line. Formalin fixed pellets of these two cell lines were used for analytical validation of PID-IHC. By utilizing dedicated image-processing algorithms, the readout of average PID score/cell was determined to be 285 and 98, for SK-Mel-28 and A375 cell lines, respectively. To confirm the increase in sensitivity with the PID technology, enabling quantitative IHC and improved detection of MC1R, de-identified melanoma samples from varying sites were collected by surgical biopsy at The University of Iowa Hospitals and Clinics and scored by a pathologist. Sister sections were stained by conventional IHC or IHC-PID. For IHC-PID, sections were counter stained by hematoxylin; tumor regions were hand annotated by a pathologist; and fluorescent images in 5 microscopic fields were captured and analyzed. Background PID threshold was determined by using no-primary antibody as controls. IHC-PID was performed on MS0759 (T1b N0 M0), MS0045 (T3a N1a M0) and MS0868 (T4b N3 M1a) samples and showed average PID score/cell of 217±38, 68±12, and 160±21, respectively. Ongoing studies are expanding on IHC-PID use to assess MC1R expression on a clinical melanoma panel (n=20) in late stage patients undergoing pharmacological interventions including MAPKi. The overall goal of this project is to develop PID-based quantitative IHC to support the development of MC1R as an imaging biomarker for patient stratification and monitoring clinical response to MC1R-targeted radionuclide therapy for malignant melanoma.

Note: This abstract was not presented at the meeting.

Citation Format: Apollina Goel, Kenji Nishikawa, Etsuko Futaya, Ildiko Poylak, Robert Holt, Mengshi Li, Edwin Sagastum, Brenna Marks, Aaron D. Bossler, Frances L. Johnson, Michael K. Schultz, Hideki Goda, Hisatake Okada, Kelly Orcutt, George Abe, Kenneth Bloom. Quantitative immunohistochemistry for melanocortin 1 receptor using phosphor integrated dots [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-230.

Left heart decompression by atrial stenting during extracorporeal membrane oxygenation

Persistent severe left ventricular dysfunction during extracorporeal membrane oxygenation (ECMO) requires left heart decompression. We describe stenting of the atrial septum as an alternative emergency approach for left heart decompression during ECMO in addition to the already published surgical and transcatheter approaches.

Automated cassette-based production of high specific activity [203/212Pb]peptide-based theranostic radiopharmaceuticals for image-guided radionuclide therapy for cancer

A method for preparation of Pb-212 and Pb-203 labeled chelator-modified peptide-based radiopharmaceuticals for cancer imaging and radionuclide therapy has been developed and adapted for automated clinical production. Pre-concentration and isolation of radioactive Pb2+ from interfering metals in dilute hydrochloric acid was optimized using a commercially-available Pb-specific chromatography resin packed in disposable plastic columns. The pre-concentrated radioactive Pb2+ is eluted in NaOAc buffer directly to the reaction vessel containing chelator-modified peptides. Radiolabeling was found to proceed efficiently at 85°C (45min; pH 5.5). The specific activity of radiolabeled conjugates was optimized by separation of radiolabeled conjugates from unlabeled peptide via HPLC. Preservation of bioactivity was confirmed by in vivo biodistribution of Pb-203 and Pb-212 labeled peptides in melanoma-tumor-bearing mice. The approach has been found to be robustly adaptable to automation and a cassette-based fluid-handling system (Modular Lab Pharm Tracer) has been customized for clinical radiopharmaceutical production. Our findings demonstrate that the Pb-203/Pb-212 combination is a promising elementally-matched radionuclide pair for image-guided radionuclide therapy for melanoma, neuroendocrine tumors, and potentially other cancers.

INTERMACS (Interagency Registry for Mechanically Assisted Circulatory Support) Profiling Identifies Ambulatory Patients at High Risk on Medical Therapy After Hospitalizations for Heart Failure

Background—

INTERMACS (Interagency Registry for Mechanically Assisted Circulatory Support) profiles provide important prognostic information for patients with advanced heart failure (HF) receiving mechanical support. The value of INTERMACS profiling has not been shown for patients followed on medical therapy for advanced HF at centers that also offer mechanical circulatory support.

Methods and Results—

This prospective, observational study enrolled 166 patients with chronic New York Heart Association class III–IV HF, ejection fraction ≤30%, and ≥1 HF hospitalization in the previous year, excluding patients listed for transplant or receiving chronic intravenous inotropic therapy. Subjects were followed for at least 12 months or until death, mechanical support, or transplant. Baseline features, quality of life, and outcomes were compared according to INTERMACS profile. Mean age was 57 years, ejection fraction 18%, and 57% had HF >5 years, whereas 23% of subjects were INTERMACS profile 4, 32% profile 5, and 45% profile 6/7. At 1 year, only 47% of this ambulatory advanced HF cohort remained alive on medical therapy. Patients in INTERMACS profile 4 were more likely to die or require mechanical support, with only 52% of these patients alive without support after the first 6 months. Profile 6/7 patients had 1-year survival of 84%, similar to outcomes for contemporary destination left ventricular assist device recipients. Quality of life using the indexed EuroQol score was poor across profiles 4 to 7, although severe limitation was less common than for ambulatory patients enrolled in INTERMACS before ventricular assist device implantation.

Conclusions—

Ambulatory patients with systolic HF, a heavy symptom burden, and at least 1 recent HF hospitalization are at high risk for death or left ventricular assist device rescue. INTERMACS profiles help identify ambulatory patients with advanced HF who may benefit from current mechanical support devices under existing indications.

Elucidation of transcriptome-wide microRNA binding sites in human cardiac tissues by Ago2 HITS-CLIP

MicroRNAs (miRs) have emerged as key biological effectors in human health and disease. These small noncoding RNAs are incorporated into Argonaute (Ago) proteins, where they direct post-transcriptional gene silencing via base-pairing with target transcripts. Although miRs have become intriguing biological entities and attractive therapeutic targets, the translational impacts of miR research remain limited by a paucity of empirical miR targeting data, particularly in human primary tissues. Here, to improve our understanding of the diverse roles miRs play in cardiovascular function and disease, we applied high-throughput methods to globally profile miR:target interactions in human heart tissues. We deciphered Ago2:RNA interactions using crosslinking immunoprecipitation coupled with high-throughput sequencing (HITS-CLIP) to generate the first transcriptome-wide map of miR targeting events in human myocardium, detecting 4000 cardiac Ago2 binding sites across >2200 target transcripts. Our initial exploration of this interactome revealed an abundance of miR target sites in gene coding regions, including several sites pointing to new miR-29 functions in regulating cardiomyocyte calcium, growth and metabolism. Also, we uncovered several clinically-relevant interactions involving common genetic variants that alter miR targeting events in cardiomyopathy-associated genes. Overall, these data provide a critical resource for bolstering translational miR research in heart, and likely beyond.

Molecular Determinants of Calpain-dependent Cleavage of Junctophilin-2 Protein in Cardiomyocytes

Junctophilin-2 (JP2), a membrane-binding protein that provides a structural bridge between the plasmalemma and sarcoplasmic reticulum, is essential for precise Ca(2+)-induced Ca(2+) release during excitation-contraction coupling in cardiomyocytes. In animal and human failing hearts, expression of JP2 is decreased markedly, but the molecular mechanisms underlying JP2 down-regulation remain incompletely defined. In mouse hearts, ischemia/reperfusion injury resulted in acute JP2 down-regulation, which was attenuated by pretreatment with the calpain inhibitor MDL-28170 or by transgenic overexpression of calpastatin, an endogenous calpain inhibitor. Using a combination of computational analysis to predict calpain cleavage sites and in vitro calpain proteolysis reactions, we identified four putative calpain cleavage sites within JP2 with three N-terminal and one C-terminal cleavage sites. Mutagenesis defined the C-terminal region of JP2 as the predominant calpain cleavage site. Exogenous expression of putative JP2 cleavage fragments was not sufficient to rescue Ca(2+) handling in JP2-deficient cardiomyocytes, indicating that cleaved JP2 is non-functional for normal Ca(2+)-induced Ca(2+) release. These data provide new molecular insights into the posttranslational regulatory mechanisms of JP2 in cardiac diseases.

Microtubule-mediated defects in junctophilin-2 trafficking contribute to myocyte transverse-tubule remodeling and Ca2+ handling dysfunction in heart failure

BACKGROUND

Cardiac dysfunction in failing hearts of human patients and animal models is associated with both microtubule densification and transverse-tubule (T-tubule) remodeling. Our objective was to investigate whether microtubule densification contributes to T-tubule remodeling and excitation-contraction coupling dysfunction in heart disease.

METHODS AND RESULTS

In a mouse model of pressure overload-induced cardiomyopathy by transaortic banding, colchicine, a microtubule depolymerizer, significantly ameliorated T-tubule remodeling and cardiac dysfunction. In cultured cardiomyocytes, microtubule depolymerization with nocodazole or colchicine profoundly attenuated T-tubule impairment, whereas microtubule polymerization/stabilization with taxol accelerated T-tubule remodeling. In situ immunofluorescence of heart tissue sections demonstrated significant disorganization of junctophilin-2 (JP2), a protein that bridges the T-tubule and sarcoplasmic reticulum membranes, in transaortic banded hearts as well as in human failing hearts, whereas colchicine injection significantly preserved the distribution of JP2 in transaortic banded hearts. In isolated mouse cardiomyocytes, prolonged culture or treatment with taxol resulted in pronounced redistribution of JP2 from T-tubules to the peripheral plasma membrane, without changing total JP2 expression. Nocodazole treatment antagonized JP2 redistribution. Moreover, overexpression of a dominant-negative mutant of kinesin 1, a microtubule motor protein responsible for anterograde trafficking of proteins, protected against JP2 redistribution and T-tubule remodeling in culture. Finally, nocodazole treatment improved Ca(2+) handling in cultured myocytes by increasing the amplitude of Ca(2+) transients and reducing the frequency of Ca(2+) sparks.

CONCLUSION

Our data identify a mechanistic link between microtubule densification and T-tubule remodeling and reveal microtubule-mediated JP2 redistribution as a novel mechanism for T-tubule disruption, loss of excitation-contraction coupling, and heart failure.

The impact of prolonged rotary ventricular assist device support upon ventricular geometry and flow kinetics

BACKGROUND

The aim of this study was to determine the impact of prolonged left ventricular assist device (VAD) support on cardiac ventricular geometry and VAD flow kinetics.

METHODS

Nineteen patients with end-stage heart failure underwent the implantation of HeartMate II rotary flow VADs. Left and right ventricular geometry and VAD flow kinetics were assessed by transthoracic echocardiography early (7 ± 1 days) and late (113 ± 21 days) after VAD implantation.

RESULTS

Left ventricular end-diastolic internal dimension decreased by 21% and 35%, respectively, early and late after VAD implantation (n = 19; P < .001 vs before VAD implantation). Right ventricular end-diastolic internal dimension did not decrease at either time. Hemodynamic trends were similar. VAD inflow obstruction by myocardium was observed in eight patients, seven of whom demonstrated significantly increased variation of VAD inflow during the cardiac cycle ("pulsatility") detected by Doppler studies. Medical or surgical intervention returned VAD flow patterns toward baseline in seven of eight patients with VAD obstructions.

CONCLUSIONS

Prolonged rotary VAD support unloads the left ventricle, with modest effects on the right ventricle. These changes are often associated with alterations of VAD flow kinetics, requiring therapeutic intervention. These findings indicate the usefulness of echocardiographic surveillance in patients undergoing prolonged VAD support.

Clinical Outcomes Are Similar in Pulsatile and Nonpulsatile Left Ventricular Assist Device Recipients

BACKGROUND

Despite concerns about the adequacy of support provided by continuous-flow left ventricular assist devices (LVADs), direct comparisons of patient characteristics and outcomes between first-generation pulsatile and second-generation nonpulsatile LVADs are absent. We hypothesized that a nonpulsatile Jarvik 2000 LVAD (Jarvik Heart, Inc, New York, NY) would result in comparable outcomes to those of similarly ill patients implanted with a pulsatile LVAD (Novacor, WorldHeart Inc, Oakland, CA; and HeartMate XVE, Thoratec, Pleasanton, CA).

METHODS

We retrospectively compared common pre-LVAD clinical characteristics and indicators of heart failure severity between 13 pulsatile and 14 nonpulsatile LVAD recipients. The outcomes analyzed were either heart transplantation, if the LVAD was intended as a bridge to transplantation, or hospital discharge if the intention was destination therapy.

RESULTS

There was no significant difference between groups in pre-LVAD disease severity indicators. Nonpulsatile LVAD recipients had a significantly smaller body surface area (1.9 +/- 0.2 m2 versus 2.1 +/- 0.2 m2, p = 0.04) and cardiopulmonary bypass time was also significantly shorter (61 +/- 34 minutes versus 110 +/- 49 minutes, p = 0.01). Aside from duration of initial intensive care unit stay (nonpulsatile, 10 +/- 16 days; pulsatile, 14 +/- 11 days; p = 0.02), there was no difference in post-LVAD outcomes: 10 of 14 nonpulsatile and 8 of 13 pulsatile LVAD patients achieved the combined end point (p = 0.69).

CONCLUSIONS

Similarly ill congestive heart failure patients benefited equally well from either a nonpulsatile or a pulsatile LVAD. This may support an expanded role for nonpulsatile LVADs in the treatment of severe heart failure.

Robust gene expression with amplified RNA from biopsy-sized human heart tissue

The need to assess heart failure at an early stage highlights the importance of accurate microarray analysis using small tissue samples. To test our ability to obtain high quality RNA from biopsy-sized cardiac specimens, amplification was performed on RNA from biopsy-sized samples of left ventricle (LV) tissue from one explanted failing human heart and one non-failing heart. Two methods were used: one-cycle (1C) amplification of 1.6 microg of RNA, and two-cycle (2C) amplification of 50 ng of RNA. The resulting cRNA was hybridized to Affymetrix GeneChip arrays. Over 65% of all differentially expressed genes for failing vs non-failing hearts were concordant between 1C and 2C RNA amplification. Differentially expressed genes between 1C and 2C RNA amplification in our study were highly correlated (R(2) = 0.957 and changes in gene expression agreed with prior studies on genes and heart failure; e.g., decreased alpha-myosin heavy chain and alpha-tropomyosin, as well as increased expression of insulin-like growth factor). Two cycles of amplification from cardiac biopsies will permit accurate transcription profiling of heart failure at pre-symptomatic stages. Ability to measure gene expression from nanogram amounts of RNA will provide new opportunities to predict progression to symptomatic heart failure, and to identify potential targets for therapy.

Noninvasive discrimination of rejection in cardiac allograft recipients using gene expression profiling

Rejection diagnosis by endomyocardial biopsy (EMB) is invasive, expensive and variable. We investigated gene expression profiling of peripheral blood mononuclear cells (PBMC) to discriminate ISHLT grade 0 rejection (quiescence) from moderate/severe rejection (ISHLT > or = 3A). Patients were followed prospectively with blood sampling at post-transplant visits. Biopsies were graded by ISHLT criteria locally and by three independent pathologists blinded to clinical data. Known alloimmune pathways and leukocyte microarrays identified 252 candidate genes for which real-time PCR assays were developed. An 11 gene real-time PCR test was derived from a training set (n = 145 samples, 107 patients) using linear discriminant analysis (LDA), converted into a score (0-40), and validated prospectively in an independent set (n = 63 samples, 63 patients). The test distinguished biopsy-defined moderate/severe rejection from quiescence (p = 0.0018) in the validation set, and had agreement of 84% (95% CI 66% C94%) with grade ISHLT > or = 3A rejection. Patients >1 year post-transplant with scores below 30 (approximately 68% of the study population) are very unlikely to have grade > or = 3A rejection (NPV = 99.6%). Gene expression testing can detect absence of moderate/severe rejection, thus avoiding biopsy in certain clinical settings. Additional clinical experience is needed to establish the role of molecular testing for clinical event prediction and immunosuppression management.

Chronic mitral valve rejection requiring replacement in a nine-year-old allograft

A 43-year-old woman underwent mitral valve replacement for severe mitral regurgitation nine years after orthotopic heart transplant. Histopathology showed chronic rejection of the mitral valve with lymphocytic infiltrates. The patient is well at one year follow-up. This report describes an identified case of chronic mitral valve rejection requiring valve replacement.

Novel role for the potent endogenous inotrope apelin in human cardiac dysfunction

BACKGROUND

Apelin is among the most potent stimulators of cardiac contractility known. However, no physiological or pathological role for apelin-angiotensin receptor-like 1 (APJ) signaling has ever been described.

METHODS AND RESULTS

We performed transcriptional profiling using a spotted cDNA microarray with 12 814 unique clones on paired samples of left ventricle obtained before and after placement of a left ventricular assist device in 11 patients. The significance analysis of microarrays and a novel rank consistency score designed to exploit the paired structure of the data confirmed that natriuretic peptides were among the most significantly downregulated genes after offloading. The most significantly upregulated gene was the G-protein-coupled receptor APJ, the specific receptor for apelin. We demonstrate here using immunoassay and immunohistochemical techniques that apelin is localized primarily in the endothelium of the coronary arteries and is found at a higher concentration in cardiac tissue after mechanical offloading. These findings imply an important paracrine signaling pathway in the heart. We additionally extend the clinical significance of this work by reporting for the first time circulating human apelin levels and demonstrating increases in the plasma level of apelin in patients with left ventricular dysfunction.

CONCLUSIONS

The apelin-APJ signaling pathway emerges as an important novel mediator of cardiovascular control.

Heart transplantation. An update and review

Since the 1(st) heart transplant was performed over 30 y ago, recipients have benefited from dramatic improvements in survival and quality of life following the procedure. Approximately 3 500 people worldwide now undergo heart transplantation each year. The vast majority of patients will have no limitations in their daily activities and will remain free of re-hospitalization after the 1(st) year. The median survival following heart transplant is now 9 y, and it remains the treatment of choice for children and adults with end-stage heart disease despite emerging therapies. This article will review patient selection, perioperative management issues, medical management of recipients, and future trends in the treatment of this patient population.

The embryonic angiogenic factor Del1 accelerates tumor growth by enhancing vascular formation

Del1 is a unique alpha v beta 3 integrin ligand that is produced by endothelial cells, and thus provides an autocrine signaling pathway in this cell type. It is expressed transiently in the embryo and mediates cell attachment, migration, and activation of cytoplasmic signaling molecules in focal contacts. Del1 also activates angiogenesis in the chick chorioallantoic membrane assay. Reexpression of this embryonic signaling molecule has now been documented in naturally occurring human tumors, where it is expressed by both tumor cells and angiogenic endothelial cells, suggesting that Del1 is important in mediating angiogenesis under pathophysiological conditions in the adult. To investigate the role of Del1 in tumor growth and angiogenesis, human 143B osteosarcoma cells and murine Lewis lung carcinoma cells were engineered to express Del1 and compared to control transfectants for their ability to produce tumors in nude or syngeneic mice, respectively. Del1 expressing tumors showed a two- to fourfold increase in capillary density and an accelerated rate of growth. Expression of Del1 also correlated with a decrease in apoptosis in tumor cells in vivo. Taken together, these data suggest that Del1 acts as an angiogenic factor in the context of solid tumor formation and that this increase in vascularization accelerates tumor growth through decreased apoptosis.

Physiological migration of hematopoietic stem and progenitor cells

Hematopoietic stem cells (HSCs) reside predominantly in bone marrow, but low numbers of HSCs are also found in peripheral blood. We examined the fate of blood-borne HSCs using genetically marked parabiotic mice, which are surgically conjoined and share a common circulation. Parabionts rapidly established stable, functional cross engraftment of partner-derived HSCs and maintained partner-derived hematopoiesis after surgical separation. Determination of the residence time of injected blood-borne progenitor cells suggests that circulating HSCs/progenitors are cleared quickly from the blood. These data demonstrate that HSCs rapidly and constitutively migrate through the blood and play a physiological role in, at least, the functional reengraftment of unconditioned bone marrow.

NHLBI workshop report: endothelial cell phenotypes in heart, lung, and blood diseases

Endothelium critically regulates systemic and pulmonary vascular function, playing a central role in hemostasis, inflammation, vasoregulation, angiogenesis, and vascular growth. Indeed, the endothelium integrates signals originating in the circulation with those in the vessel wall to coordinate vascular function. This highly metabolic role differs significantly from the historic view of endothelium, in which it was considered to be merely an inert barrier. New lines of evidence may further change our understanding of endothelium, in regard to both its origin and function. Embryological studies suggest that the endothelium arises from different sites, including angiogenesis of endothelium from macrovascular segments and vasculogenesis of endothelium from microcirculatory segments. These findings suggest an inherent phenotypic distinction between endothelial populations based on their developmental origin. Similarly, diverse environmental cues influence endothelial cell phenotype, critical to not only normal function but also the function of a diseased vessel. Consequently, an improved understanding of site-specific endothelial cell function is essential, particularly with consideration to environmental stimuli present both in the healthy vessel and in development of vasculopathic disease states. The need to examine endothelial cell phenotypes in the context of vascular function served as the basis for a recent workshop sponsored by the National Heart, Lung, and Blood Institute (NHLBI). This report is a synopsis of pertinent topics that were discussed, and future goals and research opportunities identified by the participants of the workshop are presented.

Effect of aerosolized uridine 5'-triphosphate on mucociliary clearance in mild chronic bronchitis

Previous studies show that uridine 5'-triphosphate (UTP), a P2Y(2) receptor agonist, is effective at acutely enhancing mucociliary clearance in healthy, nonsmoking adults. UTP solution for inhalation is being developed by Inspire Pharmaceuticals under the compound number INS316. In a double-blind, randomized, crossover, placebo-controlled study we tested the single-dose effect of UTP in chronic smokers with mild chronic bronchitis (n = 15) by measuring the clearance of (99m)Tc-Fe(2)O(3) particles (4.0 microm mass median aerodynamic diameter [MMAD]) after inhalation of nebulized placebo (0.9% saline) and two doses of UTP (20 and 100 mg in the nebulizer). On each study day, gamma camera scanning was performed over a 2-h period. After an initial deposition scan, subjects inhaled placebo or UTP during the first 20 min of scanning. Analysis of whole lung clearance showed that the retention-time curves for each day were biphasic and that the earliest break point in the average curves occurred at 50 min. Mean particle clearance rate (Clr in %/min) through 50 min for placebo treatment was Clr = 0.65 +/- 0.27 whereas treatment with UTP showed Clr significantly increased to 0.95 +/- 0.48 and 0.93 +/- 0.44 for the 20-mg and 100-mg dose respectively, p < 0.005 for both as compared with placebo. These data show that mucociliary clearance associated with mild chronic bronchitis is acutely improved with minimal doses of aerosolized UTP, presumably because of its stimulation of ciliary beating and hydration of airway secretions.

Nicotine stimulates angiogenesis and promotes tumor growth and atherosclerosis

We provide anatomic and functional evidence that nicotine induces angiogenesis. We also show that nicotine accelerates the growth of tumor and atheroma in association with increased neovascularization. Nicotine increased endothelial-cell growth and tube formation in vitro, and accelerated fibrovascular growth in vivo. In a mouse model of hind-limb ischemia, nicotine increased capillary and collateral growth, and enhanced tissue perfusion. In mouse models of lung cancer and atherosclerosis, we found that nicotine enhanced lesion growth in association with an increase in lesion vascularity. These effects of nicotine were mediated through nicotinic acetylcholine receptors at nicotine concentrations that are pathophysiologically relevant. The endothelial production of nitric oxide, prostacyclin and vascular endothelial growth factor might have a role in these effects.

A randomized comparison between rasburicase and allopurinol in children with lymphoma or leukemia at high risk for tumor lysis

Standard therapy in the United States for malignancy-associated hyperuricemia consists of hydration, alkalinization, and allopurinol. Urate oxidase catalyzes the enzymatic oxidation of uric acid to a 5 times increased urine soluble product, allantoin. Rasburicase is a new recombinant form of urate oxidase available for clinical evaluation. This multicenter randomized trial compared allopurinol to rasburicase in pediatric patients with leukemia or lymphoma at high risk for tumor lysis. Patients received the assigned uric acid-lowering agent for 5 to 7 days during induction chemotherapy. The primary efficacy end point was to compare the area under the serial plasma uric acid concentration curves during the first 96 hours of therapy (AUC(0-96)). Fifty-two patients were randomized at 6 sites. In an intent-to-treat analysis, the mean uric acid AUC(0-96) was 128 +/- 70 mg/dL.hour for the rasburicase group and 329 +/- 129 mg/dL.hour for the allopurinol group (P <.0001). The rasburicase versus allopurinol group experienced a 2.6-fold (95% CI: 2.0-3.4) less exposure to uric acid. Four hours after the first dose, patients randomized to rasburicase compared to allopurinol achieved an 86% versus 12% reduction (P <.0001) of initial plasma uric acid levels. No antirasburicase antibodies were detected at day 14. This randomized study demonstrated more rapid control and lower levels of plasma uric acid in patients at high risk for tumor lysis who received rasburicase compared to allopurinol. For pediatric patients with advanced stage lymphoma or high tumor burden leukemia, rasburicase is a safe and effective alternative to allopurinol during initial chemotherapy.

Allogeneic bone marrow transplantation for Alexander's disease

In this case report, we evaluate the efficacy of allogeneic bone marrow transplantation (BMT) in a 7-month-old female with the infantile form of Alexander's disease. Based on research that describes Alexander's disease as a leukodystrophy which may result from an unidentified enzyme deficiency, we attempted marrow transplantation to reverse or arrest the patient's neurological deterioration. Despite an initial return to her pretransplant neurological state, the patient's neurological status deteriorated. Marrow transplantation was not effective in changing her prognosis with Alexander's disease.

What is the most effective treatment of children with severe aplastic anemia who lack a matched sibling donor?

The most effective treatment currently available for children with severe aplastic anemia is bone marrow transplantation using a sibling donor who is completely matched with the patient at the major histocompatibility complex. Only a minority of patients, however, will have such a donor and other treatments which have been used include the use of single agent immunosuppression, multi-agent immunosuppression, multi-agent immunosuppression with hemopoietic growth factors, and the use of allogeneic stem cell transplantation using mismatched family members, unrelated individuals or placental blood. Of these approaches the most promising appears to be the use of combination immunosuppressive therapy plus hemopoietic growth factors. This paper reviews the current results obtained in using these various methods of treating children with severe aplastic anemia who lack a matched sibling donor.

Bone marrow transplantation for the treatment of haematological disorders in Down's syndrome: toxicity and outcome

We report 18 patients with Down's syndrome who underwent bone marrow transplantation, and review nine previously published patients. The indications for transplant in the combined group of 27 patients were acute lymphoblastic leukaemia in 14 cases (52%), acute myeloid leukaemia in 11 cases (41%) and aplastic anemia in two cases (7%). Transplants were autologous in five cases (19%) and allogeneic in 22 cases (81%); of the 22 allogeneic transplants, 16 donors were HLA-matched siblings. In all patients the conditioning regimen included total body irradiation of 7.5 Gy or more, and/or contained cyclophosphamide of 120 mg/kg or more. Seven patients (26%) had fatal pulmonary disease including pneumonitis and pulmonary hemorrhage. Five patients (19%) had significant airway problems including three with severe mucositis who required intubation for airway protection, one with severe mucositis with partial airway obstruction that required observation in the intensive care unit but did not require intubation, and one with Candida albicans laryngitis with development of a glottic web. Nineteen patients (70%) survived beyond 100 days post-transplant. There was no clear association between 100-day survival and the use of any particular agent or regimen used for conditioning or graft-versus-host disease prophylaxis, and the majority of patients tolerated high-dose cyclophosphamide, high-dose cytosine arabinoside, high-dose busulfan, total body irradiation, cyclosporin A, and methotrexate. There appeared to be more early deaths in patients who received the combination of cyclophosphamide and total body irradiation, compared with those receiving the combination of busulfan and cyclophosphamide or those receiving the combination of cytosine arabinoside and total body irradiation. Also, the use of methotrexate was associated with a greater number of early deaths, compared with cyclosporin A. At 3 years, life table estimates of freedom from relapse, relapse-free survival and survival were 75%, 44% and 48%, respectively. The estimated cumulative risk of death due to a non-leukaemic cause at 3 years was 39%. The data show that Down syndrome patients can tolerate the commonly used transplant conditioning regimens with acceptable toxicity; however, there is a strong suggestion in the data that the rates of life-threatening and fatal toxicity are higher than would be expected to occur in patients without Down's syndrome. Patients with Down's syndrome may have a predisposition to fatal pulmonary complications and reversible airway problems during the immediate post-transplant period.

High-dose cytosine arabinoside and fractionated total body irradiation as a preparative regimen for the treatment of children with acute lymphoblastic leukemia and Down syndrome by allogeneic bone marrow transplantation

The early toxicity, incidence of graft-versus-host disease (GVHD) and long-term follow-up were evaluated in two children with Down syndrome (DS) treated for acute lymphoblastic leukemia (ALL) in second complete remission by HLA-matched sibling allogeneic bone marrow transplantation (BMT). Preparative conditioning therapy consisted of cytosine arabinoside (Ara-C) and fractionated total body irradiation (F-TBI) and GVHD prophylaxis of cyclosporin A. The conditioning regimen was well tolerated, the only acute complication being mild mucositis. Engraftment (polymorphonuclear cells >500/microliter) was documented by day +17 in both patients. One child remains in continuous complete remission, without medical problems, 60 months after BMT. The second patient died from complications associated with chronic GVHD 21 months following BMT. Ara-C and F-TBI is a well-tolerated preparative regimen for children with DS undergoing allogeneic BMT.

Dietary polyunsaturated fat modifies low-density lipoproteins and reduces atherosclerosis of nonhuman primates with high and low diet responsiveness

We tested the hypothesis that an increased content of n-6 polyunsaturated fatty acids (principally linoleic acid) in an atherogenic diet of nonhuman primates would decrease atherosclerosis by modifying the composition and decreasing the concentration of plasma low-density lipoprotein (LDL). A species readily susceptible to diet-induced atherosclerosis (cynomolgus monkey) was compared with a less-susceptible species (African green monkey) with dietary cholesterol concentration and saturated or polyunsaturated fat (40% of energy) as variables. In both species, cholesterol concentrations in whole plasma, LDL, and high-density lipoprotein (HDL) were 20-30% lower when polyunsaturated fat was fed, whereas dietary cholesterol increased LDL cholesterol three- to fourfold. LDL was enriched in cholesteryl oleate when saturated fat and cholesterol were fed. Dietary linoleic acid prevented cholesteryl oleate enrichment and promoted cholesteryl linoleate accumulation in LDL. At the same plasma cholesterol concentration, cynomolgus monkeys had higher LDL cholesterol and lower HDL-cholesterol concentrations than did African green monkeys. LDL particle size was significantly (P < 0.001) larger in the group of cynomolgus monkeys fed polyunsaturated fat but tended to be smaller in African green monkeys fed polyunsaturated fat. Dietary polyunsaturated fat protected against coronary artery atherosclerosis in both species. Thus, LDL particle size, per se, was not atherogenic; instead, coronary artery atherosclerosis and cholesteryl oleate enrichment of LDL were more highly correlated. This outcome suggests that information about LDL composition may be more important for understanding the pathogenesis of atherosclerosis than previously suspected.

Neurologic complications after allogeneic marrow transplantation for sickle cell anemia

Seven of 21 patients with sickle cell anemia developed neurologic complications 5 to 243 days (median, 33 days) after allogeneic marrow transplantation. Among these 7 patients, indications for transplantation included either a past history of stroke (4 patients) or recurrent severe vaso-occlusive events (3 patients). All received marrow from an HLA-identical sibling after preparation with busulfan and cyclophosphamide, and in 4 patients with antithymocyte globulin. Five of 6 patients developing seizures received anticonvulsant and supportive treatment with resolution of neurologic abnormalities. Three patients experienced intracranial bleeding, which was fatal in two. Of the 14 patients free of neurologic complications, 4 patients had experienced stroke before transplantation. However, among all patients with prior stroke, the incidence of intracranial hemorrhage was 38% (3/8), whereas none of the 13 patients without prior stroke developed posttransplant intracranial bleeding (P = .026). We conclude that patients with sickle cell anemia are at increased risk for neurologic complications after marrow ablative therapy and that patients with prior stroke are at increased risk for intracranial hemorrhage. Transplantation of patients before the onset of overt stroke may reduce this risk.

Bone marrow transplantation for sickle cell disease. The United States experience

PURPOSE

As of June 1992, five patients with sickle cell disease had been treated by matched sibling bone marrow transplantation in the United States.

PATIENTS AND METHODS

Three patients underwent transplantations for complications related to sickle cell disease, two with previous cerebrovascular accidents (CVAs) and one who had had multiple severe vasoocclusive crises. Two patients had other indications for allogeneic bone marrow transplantation: one had acute myeloid leukemia and the other had Morquio's disease. The patients' ages ranged from 3 to 10 years, and four were girls. Ages of the donors ranged from 4 to 13 years; four of the donors were boys and three carried the sickle cell trait. For four patients, the preparative regimen consisted of busulfan and cyclophosphamide given either alone or combined with antithymocyte globulin (ATG). The patient with leukemia was prepared with cyclophosphamide and total body irradiation (TBI). The regimens for prophylaxis of graft-versus-host disease (GVHD) included various combinations of cyclosporine A, methotrexate, and prednisone.

RESULTS

The patient with Morquio's disease failed to engraft but underwent a successful retransplantation from the same donor. All patients eventually demonstrated donor engraftment and the donor's hemoglobin electrophoretic pattern posttransplant. Two patients had moderately severe GVHD of the skin and gastrointestinal tract, which resolved with prednisone therapy. One of these patients developed transient chronic GVHD involving the skin. Other acute complications included mild venoocclusive disease of the liver, central line infection with bacteremias, uterine hemorrhage in one patient, and pseudomonas sepsis in another.

CONCLUSIONS

Both patients who underwent transplantation after CVAs have experienced subsequent neurological events. However, with a median follow-up of 16 months (range 8 months to 9.3 years), all patients are surviving in good to excellent clinical condition and appear to have benefitted from treatment by bone marrow transplantation.

Bone marrow transplantation for thalassemia. The USA experience

PURPOSE

We have reviewed the results of bone marrow transplantation in 30 patients with thalassemia major who were treated in the United States.

PATIENTS AND METHODS

Ten patients who underwent transplantation in Seattle and 20 patients from five other U.S. centers were identified through a survey of the International Bone Marrow Transplant Registry. These transplants were performed between November 1981 and April 1992 in patients with diverse ethnic backgrounds and ranged in age from 6 months to 14 years (median 4.0 years). Twenty-seven of the 30 patients received marrow from a human leukocyte antigen (HLA)-identical sibling or other family member, one patient received HLA-matched marrow from an unrelated donor, and two patients were given haploidentical but HLA-mismatched marrow from a related donor. Cytoreductive (preparative) therapy varied among institutions and pretransplant risk categories. In general, patients were given busulfan (12-24 mg/kg) or dimethylmyleran (5 mg/kg) in combination with cyclophosphamide (120-240 mg/kg). A subset of patients were given total body irradiation (TBI) at a dose of 720 cGy followed by cyclophosphamide (120 mg/kg).

RESULTS

Sixteen of 27 patients (59%) who received marrow from an HLA-identical family member are event-free survivors, with a duration of follow-up ranging from 2 months to > 10 years after transplantation. Six of these 27 patients (22%) had recurrence of thalassemia and five (19%) died. The estimated actuarial rate of thalassemia recurrence was 24% and the rate of event-free survival was 57%. Only one of the three patients who received marrow from HLA-nonidentical or unrelated donors survives event-free. Liver biopsies were not routinely performed before transplant. Thus, classification of patients into Lucarelli risk groups was not possible. A modified risk classification was devised by using liver size and iron status assessed by the regularity of chelation and the serum ferritin level. With use of this classification, there was no significant difference in event-free survival between transplant risk groups.

CONCLUSIONS

The findings observed in this small series of patients confirms that thalassemia can be cured with bone marrow transplantation. Although most patients are event-free survivors, a significant number experienced recurrence of their disease. A cooperative multicenter trial of U.S. transplant centers may be necessary to evaluate the use of marrow transplantation for thalassemia and to determine optimal treatment.

Penetrating craniocerebral injury resultant from gunshot wounds: gang-related injury in children and adolescents

We prospectively and retrospectively reviewed a series of 780 patients who presented to the University of Southern California/Los Angeles County Medical Center with a diagnosis of gunshot wound to the brain during an 8-year period. Of these, 105 were children ranging in age from 6 months to 17 years. Injuries were gang related in 76 (72%) children and adolescents. Stepwise linear regression analysis was used to formulate a predictive model of outcome in this population. Patient age (F = 10.92), sex (F = 9.32), occipital entry site (F = 8.17), bihemispheric injury (F = 8.50), and admission Glasgow Coma Scale (F = 69.91) were all found to correlate with outcome (P < 0.05). Significant differences between pediatric and adult populations were noted in transit time, entrance site, and age-related outcome. Occipital or assassination-type wounds were most common in children. In addition, a younger age was associated with poor outcome (P < 0.0001). We describe both the economic and racial trends in our population of patients in addition to weapon type and toxicological evaluation. The Department of Neurological Surgery is becoming directly involved in providing information to children at the junior high school level regarding gang activity and brain and spinal cord injury. In conjunction with the Community Youth Gang Services Organization and Think First Organization, we are attempting to integrate prevention through education and community mobilization. This is a plan aimed at informing and recovering the youth affected by gangs.

Effects of chemotherapy and irradiation on the gonads

As the survival of children with cancer improves, attention must now be focused on understanding and preventing long-term toxicities of treatment and improving the quality of survival. Gonadal toxicity is relatively common, particularly with radiation therapy and alkylating agents. Continued research into the pathogenesis and prevention of gonadal toxicities needs to be included in future treatment strategies for childhood cancer. This will require a multidisciplinary approach with input from pediatric hematologist/oncologists, radiation oncologists, and pediatric endocrinologists.

Role of autotransplantation in neuroblastoma

Neuroblastoma is the most enigmatic disease treated by pediatric oncologists. The same pattern of apparent metastatic spread is associated with a high rate of spontaneous regression in children under 1 year of age (stage IVS) but an invariably fatal course in older children. For these children with truly advanced neuroblastoma, recent studies have demonstrated that the possibility of complete remission and disease-free survival is increased with more intensive conventional combination chemotherapy. Supportive care with autologous marrow has enabled further significant dose escalation of cytotoxic therapy active against neuroblastoma, resulting in disease-free survival in between 25% and 50% of patients at 2 years, an improvement over historical experience with conventional chemotherapy. The development of more effective cytotoxic combinations active against neuroblastoma, improvements in ex vivo techniques to purge marrow of neuroblastoma cells, and the application of cytokines to hasten marrow recovery should further enhance the effectiveness of autotransplantation in the treatment of advanced neuroblastoma and further improve the chances for complete remission and longer remission duration. Whether this improved remission induction and duration will translate into an increased cure rate remains to be determined. Parallel advances in therapies not involving autologous marrow support will undoubtedly modify the role of autotransplantation in neuroblastoma. Currently, however, autotransplantation offers one potential solution to a major challenge in the treatment of advanced neuroblastoma--obtaining and maintaining complete remissions--and a promising basis for future therapeutic studies.