A G316A Polymorphism in the Ornithine Decarboxylase Gene Promoter Modulates MYCN-Driven Childhood Neuroblastoma

Simple Summary

Neuroblastoma is a devasting childhood cancer in which multiple copies (amplification) of the cancer-causing gene MYCN strongly predict poor outcome. Neuroblastomas are reliant on high levels of cellular components called polyamines for their growth and malignant behavior, and the gene regulating polyamine synthesis is called ODC1. ODC1 is often coamplified with MYCN, and in fact is regulated by MYCN, and like MYCN is prognostic of poor outcome. Here we studied a naturally occurring genetic variant or polymorphism that occurs in the ODC1 gene, and used gene editing to demonstrate the functional importance of this variant in terms of ODC1 levels and growth of neuroblastoma cells. We showed that this variant impacts the ability of MYCN to regulate ODC1, and that it also influences outcome in neuroblastoma, with the rarer variant associated with a better survival. This study addresses the important topic of genetic polymorphisms in cancer.

Abstract

Ornithine decarboxylase (ODC1), a critical regulatory enzyme in polyamine biosynthesis, is a direct transcriptional target of MYCN, amplification of which is a powerful marker of aggressive neuroblastoma. A single nucleotide polymorphism (SNP), G316A, within the first intron of ODC1, results in genotypes wildtype GG, and variants AG/AA. CRISPR-cas9 technology was used to investigate the effects of AG clones from wildtype MYCN-amplified SK-N-BE(2)-C cells and the effect of the SNP on MYCN binding, and promoter activity was investigated using EMSA and luciferase assays. AG clones exhibited decreased ODC1 expression, growth rates, and histone acetylation and increased sensitivity to ODC1 inhibition. MYCN was a stronger transcriptional regulator of the ODC1 promoter containing the G allele, and preferentially bound the G allele over the A. Two neuroblastoma cohorts were used to investigate the clinical impact of the SNP. In the study cohort, the minor AA genotype was associated with improved survival, while poor prognosis was associated with the GG genotype and AG/GG genotypes in MYCN-amplified and non-amplified patients, respectively. These effects were lost in the GWAS cohort. We have demonstrated that the ODC1 G316A polymorphism has functional significance in neuroblastoma and is subject to allele-specific regulation by the MYCN oncoprotein.

Incident cancers and late mortality in Australian children treated by allogeneic stem cell transplantation for non-malignant diseases

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) is a life-saving procedure for children with a variety of non-malignant conditions. However, these children face an increased risk of late death and incident cancers after HSCT, which may occur many years after their initial HSCT.

PROCEDURE

We examined cancer occurrence and late mortality in a population-based cohort of 318 Australian children who underwent allogeneic HSCT for non-malignant disease. Standardized incident ratios (SIRs) and standardized mortality ratios (SMRs) were calculated and compared with population controls.

RESULTS

We identified six (1.9%) cancers at a median 9.2 years post-HSCT. Cancer occurred 15 times more frequently than in the general population (SIR 15.4, 95% CI = 6.9-34.2). Of the 198 patients who survived for at least 2 years post-HSCT, 11 (5.6%) died at a median 7.5 years post-HSCT. The mortality rate was 17 times higher than in the general population (SMR 17.5, 95% CI = 9.7-31.2).

DISCUSSION

Children transplanted for non-malignant conditions require evidence-based survivorship programs to reduce excess morbidity and mortality.

MYCN amplification confers enhanced folate dependence and methotrexate sensitivity in neuroblastoma

MYCN amplification occurs in 20% of neuroblastomas and is strongly related to poor clinical outcome. We have identified folate-mediated one-carbon metabolism as highly upregulated in neuroblastoma tumors with MYCN amplification and have validated this finding experimentally by showing that MYCN amplified neuroblastoma cell lines have a higher requirement for folate and are significantly more sensitive to the antifolate methotrexate than cell lines without MYCN amplification. We have demonstrated that methotrexate uptake in neuroblastoma cells is mediated principally by the reduced folate carrier (RFC; SLC19A1), that SLC19A1 and MYCN expression are highly correlated in both patient tumors and cell lines, and that SLC19A1 is a direct transcriptional target of N-Myc. Finally, we assessed the relationship between SLC19A1 expression and patient survival in two independent primary tumor cohorts and found that SLC19A1 expression was associated with increased risk of relapse or death, and that SLC19A1 expression retained prognostic significance independent of age, disease stage and MYCN amplification. This study adds upregulation of folate-mediated one-carbon metabolism to the known consequences of MYCN amplification, and suggests that this pathway might be targeted in poor outcome tumors with MYCN amplification and high SLC19A1 expression.

Second Cancer Risk and Late Mortality in Adult Australians Receiving Allogeneic Hematopoietic Stem Cell Transplantation: A Population-Based Cohort Study

We quantified the risk of second cancer and late mortality in a population-based Australian cohort of 3273 adult (≥15 years) allogeneic hematopoietic stem cell transplant recipients (1992 to 2007). Most recipients received nonradiation-based conditioning and a peripheral blood graft from a matched related donor. Using record linkage with death and cancer registries, 79 second cancers were identified a median of 3.5 years after transplantation. The competing-risk adjusted cumulative incidence of second cancers was 3.35% (95% CI, 2.59 to 4.24) at 10 years, and the cancer risk relative to the matched general population was 2.10 (95% CI, 1.65 to 2.56). We observed an excess risk of melanoma and lip, tongue, esophagus, and soft tissue cancers. Cancer risk relative to the general population was elevated for those transplanted for lymphoma, some leukemia subtypes, and severe aplastic anemia, recipients who developed chronic graft-versus-host disease (cGVHD) and irrespective of radiation-based conditioning or stem cell source. In those alive 2 years after transplantation (n = 1463), the cumulative incidence of late mortality was 22.2% (95% CI, 19.7 to 24.9) at 10 years, and the risk of death relative to the matched general population was 13.8 (95% CI, 12.2 to 15.6). In multivariable modeling, risk of late death was reduced for females compared with males and those transplanted for chronic myeloid leukemia compared with acute myeloid leukemia; risk was increased for recipients with discordant sex donors, cGVHD, those undergoing second transplants, and disease relapse. Adults undergoing allogeneic transplantation have unique cancer and mortality risk profiles that continue to warrant prevention and surveillance activities targeted at high-risk subgroups.

Childhood acute lymphoblastic leukemia and indicators of early immune stimulation: a Childhood Leukemia International Consortium study

The associations between childhood acute lymphoblastic leukemia (ALL) and several proxies of early stimulation of the immune system, that is, day-care center attendance, birth order, maternally reported common infections in infancy, and breastfeeding, were investigated by using data from 11 case-control studies participating in the Childhood Leukemia International Consortium (enrollment period: 1980-2010). The sample included 7,399 ALL cases and 11,181 controls aged 2-14 years. The data were collected by questionnaires administered to the parents. Pooled odds ratios and 95% confidence intervals were estimated by unconditional logistic regression adjusted for age, sex, study, maternal education, and maternal age. Day-care center attendance in the first year of life was associated with a reduced risk of ALL (odds ratio = 0.77, 95% confidence interval: 0.71, 0.84), with a marked inverse trend with earlier age at start (P < 0.0001). An inverse association was also observed with breastfeeding duration of 6 months or more (odds ratio = 0.86, 95% confidence interval: 0.79, 0.94). No significant relationship with a history of common infections in infancy was observed even though the odds ratio was less than 1 for more than 3 infections. The findings of this large pooled analysis reinforce the hypothesis that day-care center attendance in infancy and prolonged breastfeeding are associated with a decreased risk of ALL.

Breastfeeding and nutrition to 2 years of age and risk of childhood acute lymphoblastic leukemia and brain tumors

Acute lymphoblastic leukemia (ALL) and childhood brain tumors (CBT) are 2 of the most common forms of childhood cancer, but little is known of their etiology. In 2 nationwide case-control studies we investigated whether breastfeeding, age of food introduction, or early diet are associated with the risk of these cancers. Cases aged 0-14 years were identified from Australian pediatric oncology units between 2003 and 2007 (ALL) and 2005 and 2010 (CBT) and population-based controls through nationwide random-digit dialing. Mothers completed questionnaires giving details of infant feeding up to the age of 2 yr. Data from 322 ALL cases, 679 ALL controls, 299 CBT cases, and 733 CBT controls were analysed using unconditional logistic regression. Breastfeeding was associated with a reduced risk of ALL [odds ratio (OR) = 0.52, 95% confidence interval (CI): 0.32, 0.84), regardless of duration. Introduction of artificial formula within 14 days of birth was positively associated with ALL (OR = 1.57, 95% CI: 1.03, 2.37), as was exclusive formula feeding to 6 mo (OR = 1.81, 95% CI: 1.07, 3.05). No associations were seen between breastfeeding or formula use and risk of CBT. Our results suggest that breastfeeding and delayed introduction of artificial formula may reduce the risk of ALL but not CBT.

Vehicle refuelling, use of domestic wood heaters and the risk of childhood brain tumours: Results from an Australian case-control study

BACKGROUND

The aetiology of childhood brain tumours (CBT) is largely unknown. Damage to germ cells after parental exposure to airborne carcinogens, such as volatile organic compounds and polycyclic aromatic hydrocarbons is one plausible pathway. This analysis aimed to investigate whether parental refuelling of vehicles or the use of domestic wood heaters in key time periods relating to the child's birth was associated with an increased risk of CBT.

PROCEDURE

Cases <15 years of age were recruited through 10 paediatric oncology centres around Australia; controls were recruited through nationwide random-digit dialling, frequency matched to cases on age, sex and State of residence. Exposure to refuelling and wood heaters was ascertained through questionnaires from both parents. Odds ratios (ORs) and confidence intervals (CIs) were estimated using unconditional logistic regression, adjusting for relevant covariates.

RESULTS

Data were available for 306 case and 950 control families. Paternal refuelling ≥4 times/month was associated with an increased risk of CBT (OR 1.59, 95% CI: 1.11, 2.29), and a dose-dependent trend was observed (P = 0.004). No association was seen for maternal refuelling. Use of closed, but not open, wood heaters before (OR 1.51, 95% CI: 1.05, 2.15) and after (OR 1.44, 95% CI: 1.03, 2.01) the child's birth was associated with increased risk of CBT, but dose-response relationships were weak or absent.

CONCLUSIONS

Paternal refuelling of vehicles ≥4 times/month and the use of closed wood heaters before the child's birth may increase the risk of CBT. Replication in larger studies is needed. Pediatr Blood Cancer 2015;62:229-234. © 2014 Wiley Periodicals, Inc.

Second cancers and late mortality in Australian children treated by allogeneic HSCT for haematological malignancy

We examined risk of second cancer and late mortality in a population-based Australian cohort of 717 pediatric allogeneic stem cell transplant (HSCT) recipients treated for a malignant disease during 1982-2007. Record linkage with population-based death and cancer registries identified 17 second cancers at a median of 7.9 years post HSCT; thyroid cancer being the most common malignancy (n=8). The cumulative incidence of second cancer was 8.7% at follow-up, and second cancers occurred 20 times more often than in the general population (standardised incidence ratio 20.3, 95% confidence interval (CI)=12.6-32.7). Transplantation using radiation-based conditioning regimens was associated with increased second cancer risk. A total of 367 patients survived for at least 2 years post HSCT and of these 44 (12%) died at a median of 3.1 years after HSCT. Relapse was the most common cause of late mortality (n=32). The cumulative incidence of late mortality was 14.7%. The observed rate of late mortality was 36 times greater than in the matched general population (standardised mortality ratio 35.9, 95% CI=26.7-48.3). Recipients who relapsed or who had radiation-based conditioning regimens were at higher risk of late mortality. Second cancers and late mortality continue to be a risk for pediatric patients undergoing HSCT, and these results highlight the need for effective screening and survivorship programs.

Exposure to household painting and floor treatments, and parental occupational paint exposure and risk of childhood brain tumors: results from an Australian case-control study

PURPOSE

Childhood brain tumors (CBT) are the leading cause of cancer death in children, yet their etiology remains largely unknown. This study investigated whether household exposure to paints and floor treatments and parental occupational painting were associated with CBT risk in a population-based case-control study conducted between 2005 and 2010.

METHODS

Cases were identified through all ten Australian pediatric oncology centers, and controls via nationwide random-digit dialing, frequency matched to cases on age, sex, and state of residence. Data were obtained from parents in mailed questionnaires and telephone interviews. Information on domestic painting and floor treatments, and parental occupational exposure to paint, in key periods relating to the index pregnancy and childhood was obtained for 306 cases and 950 controls. Data were analyzed using unconditional logistic regression, adjusting for frequency matching variables and potential confounders.

RESULTS

Overall, we found little evidence that parental, fetal, or childhood exposure to home painting or floor treatments was associated with risk of CBT. There was, though, some evidence of a positive association between childhood exposure to indoor painting and risk of high-grade glioma [odds ratio (OR) 3.31, 95 % confidence interval (CI) 1.29, 8.52] based on very small numbers. The OR for the association between CBT and paternal occupational exposure to paint any time before the pregnancy was 1.32 (95 % CI 0.90, 1.92), which is consistent with the results of other studies.

CONCLUSIONS

Overall, we found little evidence of associations between household exposure to paint and the risk of CBT in any of the time periods investigated.

Abstract 3808: MYCN coordinately regulates the entire polyamine gene pathway to drive polyamine biosynthesis in neuroblastoma, with expression of every synthetic and catabolic polyamine pathway gene being highly prognostic of clinical outcome

Background: Polyamines are highly regulated essential cations that are elevated in rapidly proliferating tissues. We have previously shown that the MYC/MYCN target ornithine decarboxylase (ODC1), rate-limiting for polyamine biosynthesis, is a therapeutic target for neuroblastoma (Hogarty et al, Cancer Res 2008; 68: 9735). We have also shown that targeting multiple steps in the polyamine pathway enhances therapeutic efficacy in complementary pre-clinical models (Haber et al, Adv Neurobl Res, 2012, OR 88). An international Phase I trial for refractory neuroblastoma, coordinated by the New Approaches to Neuroblastoma Treatment (NANT) consortium USA, will open shortly using ODC1 inhibition by high-dose difluoromethylornithine and SAT1 induction by celecoxib. We have now examined the prognostic impact of all polyamine pathway genes in a large cohort of neuroblastoma tumors.

Methods: Gene-expression profiles of 650 primary untreated neuroblastomas were analyzed for all polyamine pathway genes, and related to clinical outcome. Gene expression was evaluated by Real-Time PCR (RT-PCR) and correlated with MYCN levels in neuroblastoma cell lines. Activation and repression of polyamine genes by MYCN were analyzed by chromatin immunoprecipitation (ChIP). Polyamine gene promoters were cloned into luciferase reporter vectors and tested as a function of MYCN expression.

Results: Expression of all polyamine pathway genes was highly prognostic of neuroblastoma outcome. High levels of each synthetic gene and low levels of each catabolic gene predicted poor outcome. Multivariate analysis showed 6/11 genes retained independent prognostic significance following adjustment for MYCN, age and stage. In neuroblastoma cell lines, in the presence or absence of MYCN expression, RT-PCR analysis demonstrated a correlation of high MYCN with high biosynthetic polyamine gene expression, but an inverse correlation of high MYCN with low catabolic polyamine gene expression. ChIP assays confirmed that MYCN associates with biosynthetic gene promoters by binding to E-box sites in order to activate transcription. In contrast, MYCN binds the promoters of the catabolic genes in proximity to the transcription start sites by interacting with the Sp1 protein in order to repress transcription of these genes. Direct activation by MYCN of biosynthetic genes and down-regulation by MYCN of catabolic genes was confirmed by luciferase activity assays.

Conclusions: These results provide a remarkable demonstration of an oncogene coordinately regulating the expression of every gene in a metabolic pathway in order to drive cell proliferation. The findings highlight the importance of polyamines in neuroblastoma and identify target enzymes in addition to ODC1 for potential therapeutic intervention.

Citation Format: Murray D. Norris, Laura D. Gamble, Jayne Murray, Stefania Purgato, Giorgio Milazzo, Lesley J. Ashton, Andrei Oberthuer, Wendy B. London, Mike D. Hogarty, Mattias Fischer, David Ziegler, Glenn M. Marshall, Giovanni Perini, Michelle Haber. MYCN coordinately regulates the entire polyamine gene pathway to drive polyamine biosynthesis in neuroblastoma, with expression of every synthetic and catabolic polyamine pathway gene being highly prognostic of clinical outcome. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3808. doi:10.1158/1538-7445.AM2013-3808

Parental occupational exposure to engine exhausts and childhood brain tumors

Childhood brain tumors (CBT) are the leading cause of cancer death in children; their risk factors are still largely unknown. Since most CBTs are diagnosed before five years of age, prenatal exposure and early postnatal factors may be involved in their etiology. We investigated the association between CBT and parental occupational exposure to engine exhausts in an Australian population-based case-control study. Parents of 306 cases and 950 controls completed detailed occupational histories. Odds ratios (OR) and 95% confidence intervals (CI) were estimated for both maternal and paternal exposure in key time periods. Increased risks were observed for maternal exposure to diesel exhaust any time before the child's birth (OR 2.03, 95% CI 1.09-3.81) and paternal exposure around the time of the child's conception (OR 1.62, 95% CI 1.12-2.34). No clear associations with other engine exhausts were found. Our results suggest that parental occupational exposure to diesel exhaust may increase the risk of CBT.

Abstract 68: Beyond GWAS: The prognostic significance of promoter DNA methylation in patients with neuroblastoma

Background: Neuroblastoma is a genetically heterogenic tumor diagnosed in childhood which exhibits broad clinical diversity ranging from rapid disease progression to spontaneous regression. Although amplification of the MYCN oncogene is one of the most prominent prognostic markers of this disease it is only present in around 25% of patients. Hence, additional molecular markers are needed for patients lacking MYCN amplification to enable better stratification of patient risk groups.

To date, genome wide association studies have identified few gene candidates in neuroblastoma patients that can be further developed for prognostic use in the clinic. DNA methylation is a major epigenetic mechanism for gene silencing in a wide range of human cancers and methylation sites may reveal new prognostic targets in neuroblastoma. Recent studies have suggested that the methylation status of specific gene promoters may be useful for clinically discriminating subgroups of children diagnosed with neuroblastoma. To date, these investigations have assessed DNA methylation using variable techniques; focused on small numbers of candidate genes and; examined few primary tumor samples. The aims of our study were to characterize the clinical significance of promoter methylation in a large cohort of primary neuroblastoma tumors and investigate the association between DNA methylation and clinical outcome.

Methods: A customized Illumina GoldenGate methylation assay was used to assess methylation status of 96 CpG sites within 48 candidate genes in primary neuroblastoma tumors obtained from 131 children diagnosed in Australia between 1985 and 2000. Candidate genes were selected on the basis of previous reports of altered DNA methylation in embryonal cancers. Levels of DNA methylation were quantified and confirmed in a subset of 48 patient samples using combined bisulphite restriction analysis (CoBRA). A Cox proportional hazards model was used to investigate the association between promoter hypermethylation and the risk of relapse or death within 5 years of diagnosis, while adjusting for known prognostic cofactors such as MYCN amplification, age and stage at diagnosis.

Results: The level of promoter methylation of DNAJC15, NTRK1 and TNFRSF10D were significantly higher in older patients at diagnosis (p&lt;0.01), while higher levels of promoter methylation of DNAJC15, NTRK1 and PYCARD were observed in patients with MYCN amplification (p&lt;0.001). In multivariate analysis, promoter hypermethylation of FOLH1, MYOD1 and THBS1 remained significant independent predictors of poorer clinical outcome, after adjusting for MYCN amplification, age at diagnosis and tumor stage (p≤0.017). Around a third of patients displayed promoter hypermethylation in 2 or more of these genes and were almost 3 times more likely to relapse or die than those who did not display promoter hypermethylation (HR=2.72; 95%C1=1.55-4.78; p=0.001).

Conclusion: DNA methylation of FOLH1, MYOD1 and THBS1 appears to have independent prognostic value in children diagnosed with neuroblastoma. While the functional consequences of promoter hypermethylation in individual neuroblastoma patients remains to be fully determined, these investigations show how epigenetic profiling of tumor tissue can provide additional genetic markers for predicting treatment response in the clinical setting and has the potential to reveal important new therapeutic targets for selected patient subsets.

Citation Format: Diana T. Lau, Luke B. Hesson, Murray D. Norris, Glenn Marshall, Michelle Haber, Lesley J. Ashton. Beyond GWAS: The prognostic significance of promoter DNA methylation in patients with neuroblastoma. [abstract]. In: Proceedings of the AACR Special Conference on Post-GWAS Horizons in Molecular Epidemiology: Digging Deeper into the Environment; 2012 Nov 11-14; Hollywood, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2012;21(11 Suppl):Abstract nr 68.

Prognostic significance of promoter DNA methylation in patients with childhood neuroblastoma

PURPOSE

To characterize the clinical significance of promoter methylation in a cohort of primary neuroblastoma tumors and investigate the association between DNA methylation and clinical outcome.

EXPERIMENTAL DESIGN

A customized Illumina GoldenGate methylation assay was used to assess methylation status of 96 CpG sites within 48 candidate genes in primary neuroblastoma tumors obtained from 131 children diagnosed in Australia. Genes were selected on the basis of previous reports of altered DNA methylation in embryonal cancers. Levels of DNA methylation were validated in a subset of 48 patient samples using combined bisulfite restriction analysis (CoBRA) and bisulfite sequencing. A Cox proportional hazards model was used to investigate the association between promoter hypermethylation and the risk of relapse/death within 5 years of diagnosis, while adjusting for known prognostic factors including MYCN amplification, age, and stage at diagnosis.

RESULTS

Levels of promoter methylation of DNAJC15, neurotrophic tyrosine kinase receptor 1 or TrkA (NTRK1), and tumor necrosis factor receptor superfamily, member 10D (TNFRSF10D), were higher in older patients at diagnosis (P < 0.01), whereas higher levels of methylation of DNAJC15, NTRK1, and PYCARD were observed in patients with MYCN amplification (P < 0.001). In multivariate analysis, hypermethylation of folate hydrolase (FOLH1), myogenic differentiation-1 (MYOD1), and thrombospondin-1 (THBS1) remained significant independent predictors of poorer clinical outcome after adjusting for known prognostic factors (P ≤ 0.017). Moreover, more than 30% of patients displayed hypermethylation in 2 genes or more and were at least 2 times more likely to relapse or die (HR = 2.72, 95% confidence interval = 1.55-4.78, P = 0.001), independent of MYCN status, age, and stage at diagnosis.

CONCLUSIONS

Our findings highlight the potential use of methylation profiling to identify additional prognostic markers and detect new therapeutic targets for selected patient subsets.

Abstract 789: GSTP1 expression is regulated by MycN and is a marker of poor outcome in childhood neuroblastoma

In childhood neuroblastoma, amplification of the transcription factor MycN is associated with poor outcome and a multidrug resistant phenotype. We have previously shown that MycN regulates the expression of several ATP-binding cassette (ABC) transporter genes, and that these genes represent powerful prognostic markers in neuroblastoma (1,2,3). Although these transporters are able to efflux a wide range of cytotoxic drugs, they do not confer resistance to several important cytotoxic agents used to treat neuroblastoma, including cisplatin and cyclophosphamide, hence we explored the prognostic significance and transcriptional regulation of the phase II detoxifying enzyme, glutathione S-transferase P1 (GSTP1). Using quantitative real-time PCR, GSTP1 gene expression was assessed in a retrospective cohort of 51 patients, and subsequently in a cohort of 207 prospectively accrued primary neuroblastomas. These data, and GSTP1 expression data from an independent microarray study of 251 neuroblastoma samples, were correlated with established prognostic indicators and disease outcome. High levels of GSTP1 were associated with decreased event-free and overall survival in all three cohorts. Multivariate analyses, including age at diagnosis, tumor stage and MYCN amplification status, were conducted on the two larger cohorts and demonstrated independent prognostic significance of GSTP1 expression levels. We also explored the regulation of GSTP1 by MycN using chromatin immunoprecipitation (ChIP) and luciferase reporter assays in neuroblastoma cell lines and found that GSTP1 is a direct transcriptional target of MycN. We conclude that N-Myc regulates multiple components of drug metabolism and efflux pathways, including GSTP1 and transporters of the ABC superfamily. The regulation of these key multidrug resistance mechanisms may have particular significance for malignancies with amplification of Myc family genes. 1) J Biol Chem, 285:19532-19543, 2010 2) J Natl Cancer Institute, 103:1236-51, 2011 4) Nat Rev Cancer, 10:147-156, 2010

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 789. doi:1538-7445.AM2012-789

Abstract 1425: Prognostic significance of promoter DNA methylation in patients with neuroblastoma

Background: Neuroblastoma is a genetically heterogenic tumor diagnosed in childhood which exhibits broad clinical diversity ranging from rapid disease progression to spontaneous regression. One of the most prominent prognostic markers of this disease is the amplification of the MYCN oncogene, which occurs in approximately 25% of patients. However, additional molecular markers are needed for patients lacking MYCN amplification to enable better stratification of patient risk groups. DNA methylation is a major epigenetic mechanism for gene silencing in a wide range of human cancers, including neuroblastoma. Recent studies have suggested that the methylation status of specific gene promoters may be useful for clinically discriminating subgroups of children diagnosed with neuroblastoma. To date, these investigations have assessed DNA methylation using variable techniques; focused on small numbers of candidate genes and; examined few primary tumor samples. The aims of our study were to characterize the clinical significance of promoter methylation in a large cohort of primary neuroblastoma tumors and investigate the association between DNA methylation and clinical outcome. Methods: A customized Illumina GoldenGate methylation assay was used to assess methylation status of 96 CpG sites within 48 candidate genes in primary neuroblastoma tumors obtained from 131 children diagnosed in Australia between 1985 and 2000. Candidate genes were selected on the basis of previous reports of altered DNA methylation in embryonal cancers. Levels of DNA methylation were quantified and confirmed in a subset of 48 patient samples using combined bisulphite restriction analysis (CoBRA). A Cox proportional hazards model was used to investigate the association between promoter hypermethylation and the risk of relapse or death within 5 years of diagnosis, while adjusting for known prognostic cofactors such as MYCN amplification, age and stage at diagnosis. Results: The level of promoter methylation of DNAJC15, NTRK1 and TNFRSF10D were significantly higher in older patients at diagnosis (p&lt;0.01), while higher levels of promoter methylation of DNAJC15, NTRK1 and PYCARD were observed in patients with MYCN amplification (p&lt;0.001). In multivariate analysis, promoter hypermethylation of FOLH1, MTRR, MYOD1 and THBS1 remained significant independent predictors of poorer clinical outcome, after adjusting for MYCN amplification, age at diagnosis, and tumor stage (p≤0.009). Moreover, over 40% of patients displayed promoter hypermethylation in 2 or more of these genes and were 3 times more likely to relapse or die than those who did not display promoter hypermethylation (HR=3.08; 95%C1=1.71-5.54; p&lt;0.001). Conclusion: DNA methylation of FOLH1, MTRR, MYOD1 and THBS1 appears to have independent prognostic value in children diagnosed with neuroblastoma and highlights important new therapeutic targets for selected patient subsets.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1425. doi:1538-7445.AM2012-1425

HLA-G polymorphisms, genetic susceptibility, and clinical outcome in childhood neuroblastoma

Neuroblastoma is the most common solid tumor in children less than 5 years of age. The early onset of neuroblastoma suggests that genes involved in fetal development and pregnancy may have a putative role in the etiology of neuroblastoma. The human leukocyte antigen subtype G (HLA-G) molecule plays an important role in immune response regulation and appears to regulate immune tolerance during early pregnancy as well as tumor immunosurveillance. Elevated levels of soluble HLA-G (sHLA-G) have been detected in a number of malignancies including serum samples from neuroblastoma and have been reported to be predictive of tumor relapse in neuroblastoma. In light of previous investigations suggesting that single nucleotide polymorphisms in the HLA-G gene may impact on protein expression levels and isoform production, we examined the influence of HLA-G polymorphisms on the susceptibility and clinical outcome of neuroblastoma in 163 neuroblastoma patients and 404 healthy controls. The distribution of HLA-G polymorphisms, alleles, or allelic groups did not differ between children diagnosed with neuroblastoma and healthy controls. Our analyses did not detect an association between common HLA-G polymorphisms and clinical outcome in patients treated for neuroblastoma.

ABCC multidrug transporters in childhood neuroblastoma: clinical and biological effects independent of cytotoxic drug efflux

Background

Although the prognostic value of the ATP-binding cassette, subfamily C (ABCC) transporters in childhood neuroblastoma is usually attributed to their role in cytotoxic drug efflux, certain observations have suggested that these multidrug transporters might contribute to the malignant phenotype independent of cytotoxic drug efflux.

Methods

A v-myc myelocytomatosis viral related oncogene, neuroblastoma derived (MYCN)–driven transgenic mouse neuroblastoma model was crossed with an Abcc1-deficient mouse strain (658 hMYCN^1/−, 205 hMYCN^+/1 mice) or, alternatively, treated with the ABCC1 inhibitor, Reversan (n = 20). ABCC genes were suppressed using short interfering RNA or overexpressed by stable transfection in neuroblastoma cell lines BE(2)-C, SH-EP, and SH-SY5Y, which were then assessed for wound closure ability, clonogenic capacity, morphological differentiation, and cell growth. Real-time quantitative polymerase chain reaction was used to examine the clinical significance of ABCC family gene expression in a large prospectively accrued cohort of patients (n = 209) with primary neuroblastomas. Kaplan–Meier survival analysis and Cox regression were used to test for associations with event-free and overall survival. Except where noted, all statistical tests were two-sided.

Results

Inhibition of ABCC1 statistically significantly inhibited neuroblastoma development in hMYCN transgenic mice (mean age for palpable tumor: treated mice, 47.2 days; control mice, 41.9 days; hazard ratio [HR] = 9.3, 95% confidence interval [CI] = 2.65 to 32; P < .001). Suppression of ABCC1 in vitro inhibited wound closure (P < .001) and clonogenicity (P = .006); suppression of ABCC4 enhanced morphological differentiation (P < .001) and inhibited cell growth (P < .001). Analysis of 209 neuroblastoma patient tumors revealed that, in contrast with ABCC1 and ABCC4, low rather than high ABCC3 expression was associated with reduced event-free survival (HR of recurrence or death = 2.4, 95% CI = 1.4 to 4.2; P = .001), with 23 of 53 patients with low ABCC3 expression experiencing recurrence or death compared with 31 of 155 patients with high ABCC3. Moreover, overexpression of ABCC3 in vitro inhibited neuroblastoma cell migration (P < .001) and clonogenicity (P = .03). The combined expression of ABCC1, ABCC3, and ABCC4 was associated with patients having an adverse event, such that of the 12 patients with the “poor prognosis” expression pattern, 10 experienced recurrence or death (HR of recurrence or death = 12.3, 95% CI = 6 to 27; P < .001).

Conclusion

ABCC transporters can affect neuroblastoma biology independently of their role in chemotherapeutic drug efflux, enhancing their potential as targets for therapeutic intervention.

Abstract LB-367: New evidence supports the potential use of methotrexate in children with MYCN-amplified neuroblastoma

Background

Folate is essential for cell growth and differentiation. Cancer cells frequently up-regulate folate receptors to increase folate uptake to meet their elevated need for nucleotides to support DNA synthesis and growth. SLC19A1 encodes for a major folate or anti-folate transporter and has been reported to be regulated by oncogenic transcription factors. In childhood neuroblastoma, amplification of the MYCN oncogene is a strong prognostic marker for predicting unfavourable outcome. In light of previous findings showing that overexpression of SLC19A1 increases folate influx and methotrexate (MTX) sensitivity, we aimed to investigate the relationship between SLC19A1 expression, MYCN amplification and expression, to determine if this relationship modified MTX sensitivity in neuroblastoma.

Methods

Expression levels of SLC19A1 and MYCN were examined in 42 neuroblastoma patient samples and in two independent in vitro MYCN functional systems. The impact of MYCN amplification/expression and SLC19A1 expression on MTX sensitivity were evaluated on 13 neuroblastoma cell lines. SLC19A1 G80A polymorphism was also examined to determine its impact on SLC19A1 gene expression and MTX sensitivity.

Results

Expression levels of SLC19A1 and MYCN were positively correlated in neuroblastoma tumour samples (p=0.0001). Induction of MYCN in vitro increased the mRNA expression levels of SLC19A1 by 12-fold (p=0.0003) while silencing of MYCN reduced the expression levels of SLC19A1 by 7-fold (p=0.0017). Neuroblastoma cell lines with MYCN overexpression or amplification were at least 2000-fold more sensitive to MTX than those without (expression: p=0.0002; amplification: p&lt;0.0001). However, SLC19A1 G80A polymorphism did not appear to impact on SLC19A1 gene expression or MTX sensitivity.

Conclusions

Our data indicate a potential functional link between MYCN and the regulation of anti-folate uptake. Our findings suggest that MYCN amplification confers MTX sensitivity through the regulation of the folate receptor; SLC19A1. Targeting SLC19A1 mediated anti-folate uptake in patients with MYCN amplification may provide a new therapeutic approach in children with neuroblastoma.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-367. doi:10.1158/1538-7445.AM2011-LB-367

Clinical significance of minimal residual disease at day 15 and at the end of therapy in childhood acute lymphoblastic leukaemia

Detection of minimal residual disease (MRD) after induction and consolidation therapy is highly predictive of outcome for childhood acute lymphoblastic leukaemia (ALL) and is used to identify patients at high risk of relapse in several current clinical trials. To evaluate the prognostic significance of MRD at other treatment phases, MRD was measured by real-time quantitative polymerase chain reaction on a selected group of 108 patients enrolled on the Australian and New Zealand Children's Cancer Study Group Study VII including 36 patients with a bone marrow or central nervous system relapse and 72 matched patients in first remission. MRD was prognostic of outcome at all five treatment phases tested: at day 15 (MRD > or = 5 x 10(-2), log rank P < 0.0001), day 35 (> or =1 x 10(-2), P = 0.0001), 4 months (> or =5 x 10(-4), P < 0.0001), 12 months (MRD > or = 1 x 10(-4), P = 0.006) and 24 months (MRD > or = 1 x 10(-4), P < 0.0001). Day 15 was the best early MRD time-point to differentiate between patients with high, intermediate and low risk of relapse. MRD testing at 12 and particularly at 24 months, detected molecular relapses in some patients up to 6 months before clinical relapse. This raised the question of whether a strategy of late monitoring and salvage therapy will improve outcome.

Tracing survivors of childhood cancer in Australia

BACKGROUND

A major challenge when establishing a retrospective cohort of childhood cancer survivors is maximizing the enrolment of individuals treated as children. In Australia, several public databases can facilitate tracing of childhood cancer survivors; these include the Births, Deaths and Marriage Registers (BDMR), the telephone white pages (EWP), and the Australian Electoral Roll (AER). The aim of this study was to evaluate the characteristics of survivors traced for a cohort study examining the late effects of childhood cancer.

PROCEDURE

Eligible participants included 1,198 individuals treated for cancer during childhood at Sydney Children's Hospital. Of these, 1,156 individuals were confirmed alive and subsequently traced by cross matching against the AER, BDMR, WP, and clinical records. Characteristics influencing the likelihood of tracing were evaluated using logistic regression analyses.

RESULTS

Current addresses were obtained for 810 (70.1%) survivors. Overall, those diagnosed within the last decade were more easily traced than those diagnosed in an earlier decade (Test for trend, P < 0.01). In addition, older age at diagnosis and diagnosis of a sympathetic nervous system or renal malignancy were associated with a decreased likelihood of tracing in survivors, aged >/=18 years (P < 0.05). In survivors aged <18 years, age at diagnosis, sex, and cancer diagnosis were not associated with the likelihood of tracing (P > 0.05).

CONCLUSIONS

Our findings show that cancer type and year of diagnosis are independent factors influencing the ability to trace survivors of childhood cancer. Linkage to public databases provides a unique opportunity to recruit a representative hospital-based cohort of childhood cancer survivors in Australia.

Buccal swabs and treated cards: methodological considerations for molecular epidemiologic studies examining pediatric populations

Self-collection of buccal cells provides a noninvasive method for obtaining biologic samples for genetic analyses in pediatric studies. Nevertheless, low yields, microbial contamination, and degradation of buccal samples present challenges for epidemiologic studies incorporating genetic investigations. The aims of this study were to compare the quality and yield of DNA extracted from buccal specimens with BuccalAmp swabs (Epicenter BioTechnologies, Madison, Wisconsin) or FTA cards (Whatman, Inc., Clifton, New Jersey) and to investigate the use of whole-genome amplification (WGA) for increasing DNA yields for single nucleotide polymorphism analyses. Buccal specimens were collected from 55 children with acute lymphoblastic leukemia and 52 control children without acute lymphoblastic leukemia in New South Wales, Australia, in 2003-2004. Real-time polymerase chain reaction was used to evaluate polymorphisms in the genes encoding the cytochrome p450 enzyme CYP3A4 (CYP3A4 A392G, also known as CYP3A4*1B) and the steroid xenobiotic receptor (SXR C25385T). Results showed that DNA could be isolated from buccal specimens collected by use of both methods and that yields could be substantially improved with WGA without introducing genotyping error. However, DNA quality was poorer in samples collected by BuccalAmp swabs, and the presence of polymerase chain reaction inhibitors in these samples reduced the sensitivity of quantitative real-time PCR analysis. These findings show that different methods for collecting buccal samples impact on the downstream success of genetic investigations and influence DNA quality after WGA.

Polymorphisms in genes encoding drug metabolizing enzymes and their influence on the outcome of children with neuroblastoma

BACKGROUND

Although several studies have shown that drug metabolizing enzyme gene polymorphisms may influence the impact of therapy in childhood leukemia, no comprehensive investigations have been carried out in children with neuroblastoma. The aim of this study was to identify polymorphisms in the genes encoding phase I and II drug metabolizing enzymes associated with the risk of relapse or death in a cohort of 209 children with neuroblastoma.

METHODS

Real-time PCR allelic discrimination was used to characterize the presence of polymorphisms in DNA from children with neuroblastoma. Three broad gene categories were examined: cytochrome P450, glutathione-S-transferase and N-acetyltransferase. Cumulative event-free survival was computed by the Kaplan-Meier method. The influence of selected factors on event-free survival was tested using the Cox proportional hazards model.

RESULTS

As previously reported, amplification of MYCN (hazards ratio=4.25, 95% confidence interval=2.76-6.56, P<0.001), unfavorable stage (hazard ratio=4.14, 95% confidence interval=2.3-7.47, P<0.001) or age more than 1 year at diagnosis (hazard ratio=1.86, 95% confidence interval=1.19-2.92, P=0.007) were all associated with an increased risk of relapse or death. Carriers of a NAT1*11 allele variant were significantly less likely to relapse or die compared with those with NAT1*10 or other NAT1 allele variants (P<0.001). In multivariate analysis, children who were GSTM1 null were more likely to relapse or die during follow-up after adjusting for MYCN amplification, stage and age at diagnosis (hazard ratio=1.6, 95% confidence interval=1.02-2.9, P=0.04).

CONCLUSIONS

These observations suggest that the NAT1*11 variant and the GSTM1 wild-type genotype contribute to a more favorable outcome in patients treated for neuroblastoma and are the first to demonstrate a relationship between NAT1 and GSTM1 genotypes in childhood neuroblastoma.

Buccal DNA Collection: Comparison of Buccal Swabs with FTA Cards

Collection and analysis of DNA, most commonly from blood or buccal cells, is becoming more common in epidemiologic studies. Buccal samples, which are painless to take and relatively easily collected, are often the preferred source. There are several buccal cell collection methods: swabs, brushes, mouthwash, and treated cards, such as FTA or IsoCode cards. Few studies have systematically compared methods of buccal cell collection with respect to DNA yield and amplification success under similar conditions. We compared buccal DNA collection and amplification using buccal swabs and FTA cards in 122 control subjects from our Australian case-control study of childhood acute lymphoblastic leukaemia. Buccal DNA was quantified using a real-time PCR for beta-actin and genotyped at the loci of three polymorphisms (MTHFR 677C>T, ACE I/D, and XPD 1012G>A). PCR was successful with DNA from buccal swabs for 62% to 89% of subjects and from FTA cards for 83% to 100% of subjects, depending on the locus. The matched pair odds ratios (95% confidence interval) comparing success of FTA cards with buccal swabs are as follows: MTHFR 677C>T using PCR-RFLP, 12.5 (11.6-13.5) and using real-time PCR, 130.0 (113.1-152.8); ACE I/D using PCR-amplified fragment length polymorphism, 3.36 (3.2-3.5); XPD 1012G>A using real-time PCR, 150.0 (132.7-172.3). FTA cards are a robust DNA collection method and generally produce DNA suitable for PCR more reliably than buccal swabs. There are, however, technical challenges in handling discs punched from FTA cards that intending users should be aware of.

Early Responses to Chemotherapy of Normal and Malignant Hematologic Cells Are Prognostic in Children With Acute Lymphoblastic Leukemia

Purpose

Improved cure rates for children with acute lymphoblastic leukemia (ALL) have resulted from better relapse prediction, using clinical and laboratory features at diagnosis, and more intensive therapy in high-risk patients. More recently, measurements of the variation in the response of malignant lymphoblasts to chemotherapy in vivo have further improved relapse prediction. It is unknown whether the variation in the response of nonmalignant hematologic cells after chemotherapy correlates with the response of lymphoblasts or risk of relapse.

Patients and Methods

We retrospectively evaluated myelosuppression during induction and consolidation chemotherapy in 227 children uniformly treated for ALL on consecutive Australian and New Zealand Children's Cancer Study Group protocols. The early response to treatment was assessed in a representative subset (n = 62) by determining minimal residual disease (MRD) level by molecular techniques on the end-of-induction bone marrow sample.

Results

We found that a slow rate of myeloid recovery at the end of induction chemotherapy, reflected in a low absolute neutrophil count (ANC), was highly predictive of relapse (P < .0001). Additionally, patients with a high end-of-induction MRD level had a high risk of relapse (P = .001). Multivariate analysis confirmed the independent prognostic significance of MRD and ANC at the end of induction chemotherapy (P < .05). There was no significant association between other measures of myelotoxicity and MRD or relapse.

Conclusion

We conclude that the responses of normal myeloid cells and malignant lymphoblasts to chemotherapy predict outcome by distinct mechanisms. While these results are promising, their use in the clinical setting needs to be examined in a future randomized controlled trial.

Effector HIV-specific cytotoxic T-lymphocyte activity in long-term nonprogressors: associations with viral replication and progression

Ex vivo effector cytotoxic T-lymphocyte (CTL) activity was assessed in 27 members of the Australian Long-Term Nonprogressor cohort and correlated with genetic, virological, and immunological markers. The 27 individuals were antiretroviral naive with CD4(+) T-cell counts of >500 cells/ microl for more than 8 years after human immunodeficiency virus type 1 (HIV-1) infection. Effector CTL activity was determined using a standard ex vivo chromium release assay. Individuals with CTL activity (HIV-1 env(IIIB) or pol or gag) were then compared to those without CTL activity in relation to plasma HIV-1 RNA, ICD p24 antigen, beta(2)-microglobulin, CD4 and CD8 T-cell counts, CCR5 and CCR2b genotypes, and progression to CD4 <500 cells/microl or commencement of antiretroviral treatment. Of the 27 individuals examined, 19 had no detectable effector CTL activity. The eight individuals with detectable CTL activity had significantly higher plasma levels of HIV-1 RNA (P = 0.014), immune complex dissociated p24 antigen (P = 0.006), and beta(2)-microglobulin (P = 0.009). There was increased risk of progression within 4 years of study entry in individuals with detectable effector CTL activity, higher plasma levels of HIV-1 RNA, higher beta(2)-microglobulin levels, and higher immune complex dissociated p24 antigen levels at enrollment (P = 0.017, P = 0.004, P = 0.027, P = 0.008 respectively). Multivariate analysis demonstrated viral load remained the strongest predictor of disease progression within this group (P = 0.017). There were no significant associations between CTL response and chemokine receptor genotype. These findings demonstrate the importance of HIV replication in generating an effector CTL response and show that effector CTL activity may be an early predictor of progression in people with long-term asymptomatic HIV infection.

Heterozygosity for CCR5-Delta32 but not CCR2b-64I protects against certain intracellular pathogens

OBJECTIVE

To determine the association between CCR5 and CCR2b genotype and the clinical manifestation of first and subsequent AIDS-defining illnesses (ADIs).

METHODS

The distribution of ADIs was examined by CCR5 and CCR2b genotype in a subset of homosexual men enrolled in the Sydney AIDS Prospective Study. The expected number of ADIs was calculated from rates observed in the same tertiary hospital over the same period.

RESULTS

Information on initial ADI was collected for 117 homosexual men diagnosed with AIDS before January 1998. Of these individuals, 17 were heterozygous for the CCR5-Delta32 mutation and 11 were heterozygous for CCR2b-64I. The number of observed cases of Pneumocystis carinii pneumonia (PCP), toxoplasmosis, Mycobacterium avium complex (MAC) and cryptosporidiosis reported as a first ADI was substantially fewer in people heterozygous for the CCR5-Delta32 mutation than for those without the mutation, despite similar age, CD4 T-cell count at AIDS diagnosis, year of AIDS diagnosis and receipt of antiretroviral treatment. In addition, among individuals heterozygous for CCR5-Delta32 there were fewer cases of PCP, toxoplasmosis, MAC, and cryptosporidiosis observed as subsequent ADIs compared to the number expected, based on rates measured in the same hospital during the same period (seven observed vs. 24 expected, RR = 0.3, 95% CI = 0.01-0.6). The distribution of first and subsequent ADIs did not differ from the number expected in individuals heterozygous for the CCR2b-64I mutation.

CONCLUSION

Results from this study show that heterozygosity for CCR5-Delta32 but not CCR2b-64I appears to protect against opportunistic infections.

Effects of CCR5-Delta32, CCR2-64I, and SDF-1 3'A alleles on HIV-1 disease progression: An international meta-analysis of individual-patient data

BACKGROUND

Studies relating certain chemokine and chemokine receptor gene alleles with the outcome of HIV-1 infection have yielded inconsistent results.

OBJECTIVE

To examine postulated associations of genetic alleles with HIV-1 disease progression.

DESIGN

Meta-analysis of individual-patient data.

SETTING

19 prospective cohort studies and case-control studies from the United States, Europe, and Australia.

PATIENTS

Patients with HIV-1 infection who were of European or African descent.

MEASUREMENTS

Time to AIDS, death, and death after AIDS and HIV-1 RNA level at study entry or soon after seroconversion. Data were combined with fixed-effects and random-effects models.

RESULTS

Both the CCR5-Delta32 and CCR2-64I alleles were associated with a decreased risk for progression to AIDS (relative hazard among seroconverters, 0.74 and 0.76, respectively; P = 0.01 for both), a decreased risk for death (relative hazard among seroconverters, 0.64 and 0.74; P < 0.05 for both), and lower HIV-1 RNA levels after seroconversion (difference, -0.18 log(10) copies/mL and -0.14 log(10) copies/mL; P < 0.05 for both). Having the CCR5-Delta32 or CCR2-64I allele had no clear protective effect on the risk for death after development of AIDS. The results were consistent between seroconverters and seroprevalent patients. In contrast, SDF-1 3'A homozygotes showed no decreased risk for AIDS (relative hazard for seroconverters and seroprevalent patients, 0.99 and 1.03, respectively), death (relative hazard, 0.97 and 1.00), or death after development of AIDS (relative hazard, 0.81 and 0.97; P > 0.5 for all).

CONCLUSIONS

The CCR5-Delta32 and CCR2-64I alleles had a strong protective effect on progression of HIV-1 infection, but SDF-1 3'A homozygosity carried no such protection.

HLA and other host factors in transfusion-acquired HIV-1 infection

The host and viral factors that underlie infection with HIV-1 vary considerably with some individuals progressing to AIDS within 3 to 5 years after infection, whereas others remain clinically asymptomatic for over 10 years. Host factors that may contribute to disease progression include HLA and allelic variants of the chemokine receptors CCR5 and CCR2, which have been shown to influence both long-term survival and rapid progression. In this study, we have examined the contribution of HLA and polymorphisms in CCR5 and CCR2 to long-term survival in transfusion-acquired HIV-1-infected individuals. We have found a higher number of HLA-A32 and -A25 alleles but a lower number of the HLA-B8 allele in the study group compared with the frequencies seen in the HIV-1-negative Australian caucasian population. However, there was no apparent contribution by allelic variants of CCR5 and CCR2 to long-term survival and the combined influence of HLA and CCR polymorphisms could not be evaluated in this relatively small (n = 20) group of study subjects. The results of this work support a role for HLA in long-term nonprogression though the presence in the Sydney Blood bank Cohort of nef-defective HIV-1 may confound associations between certain HLA alleles and long-term survival in the face of infection with HIV-1.

CCR5 promoter polymorphisms, CCR5 59029A and CCR5 59353C, are under represented in HIV-1-infected long-term non-progressors. The Australian Long-Term Non-Progressor Study Group

OBJECTIVE

To determine the influence of CCR5 promoter polymorphisms on HIV-1 progression to AIDS and to evaluate the interaction between CCR5 structural polymorphisms and those occurring in the regulatory region of the same gene.

PARTICIPANTS

Seventy-one HIV-1-infected long-term non-progressors with a CD4+ T cell count of > 500 x 10(6)/I more than 8 years after infection were compared with 75 HIV-1-infected individuals who had progressed to AIDS and/or death within 8 years and with a further 119 HIV-1-positive patients who had CD4+ T cell counts of 200-500 x 10(6)/l. An additional 92 HIV-negative individuals were also studied.

METHODS

CCR5 delta32 genotype was determined by PCR with primers spanning the 32 base pair deletion. CCR2-64I, CCR5 59029A/G and CCR5 59353C/T genotypes were determined by PCR followed by restriction fragment length polymorphism analysis.

RESULTS

Strong linkage disequilibrium between the CCR5 59029A and CCR5 59353C polymorphic variants was identified. CCR5 59029A and CCR5 59353C homozygotes were found to be significantly under-represented in the long-term non-progressor group as compared with the other HIV-1-positive groups, with the effect being more marked in the absence of the CCR5 delta32 and CCR2 64I mutations.

CONCLUSIONS

This study provides the first evidence for an association between CCR5 promoter polymorphisms and long-term asymptomatic HIV-1 infection, with individuals lacking the CCR5 59029A/CCR5 59353C homozygous genotype likely to progress more slowly towards AIDS and/or death.

Effect of long-term infection with nef-defective attenuated HIV type 1 on CD4+ and CD8+ T lymphocytes: increased CD45RO+CD4+ T lymphocytes and limited activation of CD8+ T lymphocytes

Members of the Sydney Blood Bank Cohort (SBBC) have been infected with an attenuated strain of HIV-1 with a natural nef/LTR mutation and have maintained relatively stable CD4+ T lymphocyte counts for 14-18 years. Flow cytometric analysis was used to examine the phenotype of CD4+ and CD8+ T lymphocytes in these subjects, including the immunologically important naive (CD45RA+CD62L+), primed (CD45RO+), and activated (CD38+HLA-DR+ and CD28-) subsets. The median values were compared between the SBBC and control groups, comprising age-, sex-, and transfusion-matched HIV-1-uninfected subjects; transfusion-acquired HIV-1-positive LTNPs; and sexually acquired HIV-1-positive LTNPs. Members of the SBBC not only had normal levels of naive CD4+ and CD8+ T lymphocytes, but had primed CD45RO+ CD4+ T lymphocytes at or above normal levels. Furthermore, these primed cells expressed markers suggesting recent exposure to specific antigen. SBBC members exhibited variable activation of CD8+ T lymphocytes. In particular, SBBC members with undetectable plasma HIV-1 RNA had normal levels of activated CD8+ T lymphocytes. Therefore, the result of long-term infection with natural nef/LTR mutant HIV-1 in these subjects suggests a decreased cytopathic effect of attenuated HIV-1 on susceptible activated CD4+ T lymphocyte subsets in vivo, and minimal activation of CD8+ T lymphocytes.

Immunologic and virologic status after 14 to 18 years of infection with an attenuated strain of HIV-1. A report from the Sydney Blood Bank Cohort

BACKGROUND AND METHODS

The Sydney Blood Bank Cohort consists of a blood donor and eight transfusion recipients who were infected before 1985 with a strain of human immunodeficiency virus type 1 (HIV-1) with a deletion in the region in which the nef gene and the long terminal repeat overlap. Two recipients have died since 1994, at 77 and 83 years of age, of causes unrelated to HIV infection; one other recipient, who had systemic lupus erythematosus, died in 1987 at 22 years of age of causes possibly related to HIV. We present longitudinal immunologic and virologic data on the six surviving members and one deceased member of this cohort through September 30, 1998.

RESULTS

The five surviving recipients remain asymptomatic 14 to 18 years after HIV-1 infection without any antiretroviral therapy; however, the donor commenced therapy in February 1999. In three recipients plasma concentrations of HIV-1 RNA are undetectable (<200 copies per milliliter), and in two of these three the CD4 lymphocyte counts have declined by 9 and 30 cells per cubic millimeter per year (P=0.3 and P=0.5, respectively). The donor and two other recipients have median plasma concentrations of HIV-1 RNA of 645 to 2850 copies per milliliter; the concentration has increased in the donor (P<0.001). The CD4 lymphocyte counts in these three cohort members have declined by 16 to 73 cells per cubic millimeter per year (P<0.001). In the recipient who died after 12 years of infection, the median plasma concentration of HIV-1 RNA was 1400 copies per milliliter, with a decline in CD4 lymphocyte counts of 17 cells per cubic millimeter per year (P=0.2).

CONCLUSIONS

After prolonged infection with this attenuated strain of HIV-1, there is evidence of immunologic damage in three of the four subjects with detectable plasma HIV-1 RNA. The CD4 lymphocyte counts appear to be stable in the three subjects in whom plasma HIV-1 RNA remains undetectable.

Predictors of progression in long-term nonprogressors. Australian Long-Term Nonprogressor Study Group

It is now apparent that a proportion of individuals (5-8%) remains clinically free of HIV-1 disease with normal levels of CD4+ lymphocytes (> or =500/microl) for more than 8 years following infection. However, the proportion of these individuals who ultimately progress to AIDS remains to be established. We determined the virological and immunological characteristics of a cohort of long-term nonprogressors in Australia and examined the role of these factors in predicting disease progression. Individuals with documented asymptomatic HIV-1 infection for at least 8 years with CD4+ lymphocyte counts >500 cells/microl were recruited from hospital clinics and general practices serving the eastern area of Australia. CD4+ lymphocyte count, rate of CD4+ lymphocyte change, CD8+ lymphocyte count, beta2-microglobulin, immune complex dissociated (ICD) HIV-1 p24 antigen, and plasma HIV-1 RNA were measured at baseline and multiple visits at 6-month intervals over an average period of 2 years. Up to November 1996, 67 study participants were recruited, of whom 72% had been infected with HIV-1 for at least 10 years. HIV-1 RNA correlated with beta2-microglobulin, ICD p24 antigen, and the ability to isolate virus in culture but not with levels of CD4+ or CD8+ lymphocytes. Serum beta2-microglobulin was a stronger predictor of CD4+ lymphocyte decline than HIV-1 RNA and the only factor significantly associated with CD4+ lymphocyte decline. These findings show that the serum concentration of beta2-microglobulin is a strong predictor of immunological progression in people with long-term asymptomatic HIV-1 infection and provides additional prognostic information to HIV-1 RNA in determining the risk of disease progression.

Increased frequency of CCR-5 delta 32 heterozygotes among long-term non-progressors with HIV-1 infection. The Australian Long-Term Non-Progressor Study Group

BACKGROUND

The beta-chemokine receptor CCR-5 is used as a coreceptor by macrophage-tropic strains of HIV-1 to gain entry into CD4+ cells.

OBJECTIVE

To determine the effect of a common 32 base-pair deletion mutation in the CCR-5 gene (CCR-5 delta 32) on progression of HIV infection to AIDS, and to assess the level of heterozygosity for this mutation in a well-defined group of long-term non-progressors (LTNP).

PARTICIPANTS

Sixty-four HIV-1-infected LTNP (CD4+ T lymphocyte count > 500 x 10(6)/l after 8 years) were compared with 95 individuals infected within a similar period (1983-1986) but who had rapidly progressed to AIDS and death, and with a further 120 HIV-positive individuals with CD4+ counts < 500 x 10(6)/l.

METHODS

The presence of the CCR-5 delta 32 mutation was assessed using polymerase chain reaction with primers spanning the 32 base-pair deletion. CD4+ and CD8+ counts, plasma HIV-1 RNA, p24 antigen and beta 2-microglobulin levels in LTNP carrying the CCR-5 delta 32 mutation were compared with LTNP lacking the mutation.

RESULTS

A marked increase in the frequency of CCR-5 delta 32 heterozygosity was found among LTNP (35.9%) compared with rapid progressors (12.6%; P = 0.0005) and patients selected on the basis of a CD4+ T-cell count < 500 x 10(6)/l (12.5%; P = 0.0004). LTNP heterozygous for CCR-5 delta 32 had a significantly higher CD8+ T-cell count than those without the mutation (1218 versus 972 x 10(6)/l; P = 0.044). No significant correlation was observed between heterozygosity and CD4 count, viral load, p24 antigen or beta 2-microglobulin within the LTNP group.

CONCLUSIONS

This study provides the strongest evidence to date for the importance of a single copy of the CCR-5 delta 32 mutation in long-term non-progression of HIV infection, which may involve, in part, CD8+ T lymphocytes.

HIV infection in recipients of blood products from donors with known duration of infection

From a registry of people with transfusion-acquired HIV infection, 25 recipients were identified for whom the dates of HIV infection in the 8 corresponding donors could be established. Longer times to AIDS and to death in recipients were independently associated (p < 0.01) with the receipt of blood from donors who developed AIDS more than 10 years after HIV infection, as well as with older age and fewer transfusions. Sex, zidovudine treatment, and severity of illness at transfusion were not significantly associated with survival.

Hurler syndrome: a patient with abnormally high levels of alpha-L-iduronidase protein

Mucopolysaccharidosis type I (MPS I: McKusick 25280) is a clinically heterogenous lysosomal storage disorder which is caused by a variable deficiency in alpha-L-iduronidase activity (alpha-L-iduronide iduronohydrolase, EC 3.2.1.76). Cultured fibroblasts from an MPS I patient (cell line 2827) with a severe clinical phenotype (Hurler syndrome) have been characterized using immunochemical and biochemical techniques. Using a specific immunoquantification assay, we have demonstrated that cell line 2827 had an alpha-L-iduronidase protein content (189 ng/mg of extracted cell protein) at least six times greater than the mean level found in normal control fibroblasts (30 ng/mg of extracted cell protein). This was the only MPS I cell line, from a group of 23 MPS I patients, that contained greater than 7% of the mean level of alpha-L-iduronidase protein detected in normal controls. Cell line 2827 had very low alpha-L-iduronidase activity toward the fluorogenic substrate 4-methylumbelliferyl-alpha-L-iduronide, and a radiolabeled disaccharide substrate derived from heparin. Maturation studies of alpha-L-iduronidase in cell line 2827 showed apparently normal levels of alpha-L-iduronidase synthesis with delayed processing to the mature form. Subcellular fractionation experiments demonstrated alpha-L-iduronidase protein in lysosomal-enriched fractions isolated from cell line 2827, suggesting a normal cell distribution and supporting the proposed delayed processing. It is proposed that the MPS I patient described has an alpha-L-iduronidase gene mutation which affects both the active site and post-translational processing of the enzyme. This mutation must be structurally conservative because it does not result in instability either during maturation or in the lysosome.

Immunoquantification and enzyme kinetics of alpha-L-iduronidase in cultured fibroblasts from normal controls and mucopolysaccharidosis type I patients

alpha-L-Iduronidase activity is deficient in mucopolysaccharidosis type I (MPS I; Hurler syndrome, Scheie syndrome) patients and results in the disruption of the sequential degradation of the glycosaminoglycans dermatan sulfate and heparan sulfate. A monoclonal antibody-based immunoquantification assay has been developed for alpha-L-iduronidase, which enables the detection of at least 16 pg alpha-L-iduronidase protein. Cultured human skin fibroblasts from 12 normal controls contained 17-54 ng alpha-L-iduronidase protein/mg extracted cell protein. Fibroblasts from 23 MPS I patients were assayed for alpha-L-iduronidase protein content. Fibroblast extracts from one MPS I patient contained at least six times the level of alpha-L-iduronidase protein for normal controls--but contained no associated enzyme activity--and is proposed to represent a mutation affecting the active site of the enzyme. Fibroblast extracts from 11 MPS I patients contained 0.05-2.03 ng alpha-L-iduronidase protein/mg extracted cell protein, whereas immunodetectable protein could not be detected in the other 11 patients. Four fibroblast extracts with no immunodetectable alpha-L-iduronidase protein had residual alpha-L-iduronidase activity, suggesting that the mutant alpha-L-iduronidase in cultured cells from these MPS I patients has been modified to mask or remove the epitopes detected by two monoclonal antibodies used in the quantification assay. Both the absence of immunoreactivity in a mild MPS I patient and high protein level in a severe MPS I patient present limitations to the use of immunoquantification analysis as a sole measure of patient phenotype. Enzyme kinetic analysis of alpha-L-iduronidase from MPS I fibroblasts revealed a number of patients with either abnormal substrate binding or catalytic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of N-acetylgalactosamine-4-sulfatase protein and kinetics in mucopolysaccharidosis type VI patients

A sensitive and specific, monoclonal antibody-based immunoquantification assay has facilitated determination of the N-acetylgalactosamine-4-sulfatase (4-sulfatase) protein content in cultured fibroblasts from normal controls and mucopolysaccharidosis type VI (MPS VI) patients. The assay enabled the quantification of 4-sulfatase protein by using a panel of seven monoclonal antibodies and has shown that fibroblasts from 16 MPS VI patients contained less than or equal to 5% of the level determined for normal controls. Fibroblasts from the most severely affected patients contained the lowest levels of 4-sulfatase protein, usually with few epitopes detected, while fibroblasts from mildly affected patients had higher levels of 4-sulfatase protein, with all seven epitopes detected. The pattern of epitope expression is proposed to reflect the conformational changes in the 4-sulfatase protein that arise from different mutations in the 4-sulfatase gene. Immunoquantification in combination with a specific and highly sensitive 4-sulfated trisaccharide-based assay of enzyme activity in these MPS VI patient fibroblasts enabled the determination of residual 4-sulfatase catalytic efficiency (kcat/Km). The capacity of fibroblasts to degrade substrate (catalytic capacity) was calculated as the product of 4-sulfatase catalytic efficiency and the content of 4-sulfatase in fibroblasts. One patient, 2357, with no clinical signs of MPS VI but with reduced 4-sulfatase activity and protein (both 5% of normal) and dermatansulfaturia, had 5% of normal catalytic capacity. The other 15 MPS VI patient fibroblasts had 0%-1.4% of the catalytic capacity of fibroblasts from normal controls and were representative of the spectrum of MPS VI clinical phenotypes, from severe to mild.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromosomal localization of the human alpha-L-iduronidase gene (IDUA) to 4p16.3

The lysosomal hydrolase alpha-L-iduronidase (IDUA) is one of the enzymes in the metabolic pathway responsible for the degradation of the glycosaminoglycans heparan sulfate and dermatan sulfate. In humans a deficiency of IDUA leads to the accumulation of glycosaminoglycans, resulting in the lysosomal storage disorder mucopolysaccharidosis type I. A genomic subclone and a cDNA clone encoding human IDUA were used to localize IDUA to chromosome 4p16.3 by in situ hybridization and this was confirmed by Southern blot analysis. This localization is different from that of a previous report mapping IDUA to chromosome 22 and places the gene for IDUA in the same region of chromosome 4 as the Huntington disease gene. Measurement of expressed human IDUA activity in human-mouse hybrid cell lines confirmed that IDUA is on chromosome 4.