Immunology of THymectomy And childhood CArdiac transplant (ITHACA): protocol for a UK-wide prospective observational cohort study to identify immunological risk factors of post-transplant lymphoproliferative disease (PTLD) in thymectomised children.

INTRODUCTION: Paediatric heart transplant patients are disproportionately affected by Epstein-Barr virus (EBV)-related post-transplant lymphoproliferative disease (PTLD) compared with other childhood solid organ recipients. The drivers for this disparity remain poorly understood. A potential risk factor within this cohort is the routine surgical removal of the thymus-a gland critical for the normal development of T-lymphocyte-mediated antiviral immunity-in early life, which does not occur in other solid organ transplant recipients. Our study aims to describe the key immunological differences associated with early thymectomy, its impact on the temporal immune response to EBV infection and subsequent risk of PTLD. METHODS AND ANALYSIS: Prospective and sequential immune monitoring will be performed for 34 heart transplant recipients and 6 renal transplant patients (aged 0-18 years), stratified into early (<1 year), late (>1 year) and non-thymectomy groups. Peripheral blood samples and clinical data will be taken before transplant and at 3, 6, 12 and 24 months post-transplant. Single cell analysis of circulating immune cells and enumeration of EBV-specific T-lymphocytes will be performed using high-dimensional spectral flow cytometry with peptide-Major Histocompatibilty Complex (pMHC) I/II tetramer assay, respectively. The functional status of EBV-specific T-lymphocytes, along with EBV antibodies and viral load will be monitored at each of the predefined study time points. ETHICS AND DISSEMINATION: Ethical approval for this study has been obtained from the North of Scotland Research Ethics Committee. The results will be disseminated through publications in peer-reviewed journals, presentations at scientific conferences and patient-centred forums, including social media. TRIAL REGISTRATION NUMBER: ISRCTN10096625.

Transplantation for congenital heart disease is associated with an increased risk of Epstein-Barr virus-related post-transplant lymphoproliferative disorder in children.

BACKGROUND: Children undergoing heart transplant are at higher risk of developing post-transplant lymphoproliferative disorder (PTLD) than other solid organ recipients. The factors driving that risk are unclear. This study investigated risk factors for PTLD in children transplanted at 1 of 2 United Kingdom pediatric cardiac transplantation centers. METHODS: All children (<18 years, n = 200) transplanted at our institution over a 16-year period were analyzed. Freedom from PTLD was assessed using the Kaplan-Meier method and Cox proportional regression. RESULTS: PTLD occurred in 17 of 71 children transplanted for congenital heart disease (CHD) and 18 of 129 transplanted for acquired cardiomyopathy (ACM). The cumulative incidence of all PTLD was 21.1% at 5 years after transplant. Median time from transplant to PTLD was 2.9 years (interquartile range: 0.9-4.6). Negative Epstein-Barr virus (EBV) serostatus pre-transplant (adjusted hazard ratio [HR]: 2.7, 95% CI: 1.3-5.6, p = 0.01) and underlying CHD (adjusted HR: 3.2, 95% CI: 1.4-7.4, p = 0.007) were independently associated with higher risk of PTLD. Age at thymectomy was significantly different between children with CHD and ACM (0.4 vs 5.5 years, p < 0.01). Median CD4+ and CD8+ T lymphocyte counts at 2 years after transplant were significantly lower in children transplanted for CHD vs ACM (CD4+: 391/µl vs 644/µl, p = 0.01; CD8+: 382/µl vs 500/µl, p = 0.01). At 5 years after transplant, those differences persisted among patients who developed PTLD (CD4+, 430/µl vs 963/µl, p < 0.01 and CD8+, 367/µl vs 765/µl, p < 0.01). CONCLUSION: Underlying CHD is an independent risk factor for PTLD and is associated with a younger age at thymectomy. A persistent association with altered T lymphocyte subsets may contribute to the impaired response to primary EBV infection and increase the risk of PTLD.

Sporadic and endemic Burkitt lymphoma have frequent FOXO1 mutations but distinct hotspots in the AKT recognition motif.

FOXO1 has an oncogenic role in adult germinal center-derived lymphomas, in which mutations, predominately within the AKT recognition motif, cause nuclear retention of FOXO1, resulting in increased cell proliferation. To determine the prevalence and distribution of FOXO1 mutations in pediatric Burkitt lymphoma (BL), we sequenced a large number of sporadic and endemic BL patient samples. We report a high frequency of FOXO1 mutations in both sporadic and endemic BL at diagnosis, occurring in 23/78 (29%) and 48/89 (54%) samples, respectively, as well as 8/16 (50%) cases at relapse. Mutations of T24 were the most common in sporadic BL but were rare in endemic cases, in which mutations of residue S22, also within the AKT recognition motif, were the most frequent. FOXO1 mutations were almost always present in the major tumor cell clone but were not associated with outcome. Analysis of other recurrent mutations reported in BL revealed that FOXO1 mutations were associated with mutations of DDX3X and ARID1A, but not MYC, TCF3/ID3, or members of the phosphatidylinositol 3-kinase signaling pathway. We further show common nuclear retention of the FOXO1 protein, irrespective of mutation status, suggesting alternative unknown mechanisms for maintaining FOXO1 transcriptional activity in BL. CRISPR/Cas9 knockout of FOXO1 in an endemic cell line produced a significant decrease in cell proliferation, supporting an oncogenic role for FOXO1 in endemic BL. Thus, FOXO1 is frequently mutated in both sporadic and endemic BL and may offer a potential therapeutic target for pediatric BL patients worldwide.

The changing clinical pattern of endemic Burkitt lymphoma in Western Africa: Experience from a tertiary center in Ghana.

BACKGROUND: Burkitt lymphoma (BL) is the most common childhood cancer in Ghana, where the endemic variant is the predominant subtype and historically presents as a highly chemo-sensitive jaw tumor. This study aimed to update the current epidemiological characteristics of childhood BL in our institution. PROCEDURE: Patient data for all children diagnosed with BL and seen at Korle Bu Teaching Hospital between January 2007 and December 2012 were retrospectively analyzed. RESULTS: BL was diagnosed in 173 children (<13 years) during the study period, with the abdomen as the most common tumor site (46%) followed by the jaw (31%). Abdominal tumors were associated with advanced/disseminated disease (P = 0.002), and were more likely to occur in females irrespective of tumor stage (relative risk = 1.56 [95% CI; 1.1-12.3]). Twenty-five percent (43/173) of the study cohort died and mortality was influenced by increasing age (P = 0.02) and advanced disease (P = 0.03). Treatment delay was experienced by nine in ten patients primarily due to familial financial constraint (75%). Treatment abandonment was observed as a first event in 94% of patients and two thirds of children in the study were eventually lost to follow-up. CONCLUSION: The predominance of primary abdominal tumors in our study cohort may indicate a changing epidemiological pattern of BL in Ghana. High rates of treatment delay and abandonment were evident and are likely to be contributing factors to the poor childhood cancer survival outcomes seen in resource-limited countries in Africa.

Is there a socioeconomic variation in survival from renal tumours in children and young people resident in northern England (1968-2012)?

BACKGROUND: Despite strong evidence of a social gradient in cancer survival among UK adults, studies in children and young people remain inconclusive and have not included renal tumours. This study investigated the relationship between socioeconomic status and survival from renal tumours among children and young people. PROCEDURE: Kaplan-Meier estimation and Cox regression were used to analyse survival for all 209 renal tumours in children and young people (0-24 years) diagnosed 1968-2012 and registered by a specialist population-based registry. Sociodemographic and clinicopathologic variables, including paternal occupation at birth, were also analysed. RESULTS: No significant disparity in overall renal tumour and Wilms tumour (WT) survival was observed according to paternal social class [p=0.988 and 0.808, respectively]. The strongest predictor of survival was stage, with late stage (III-IV) disease having a 4-fold higher risk of death compared to early stage (I-II) disease [p<0.001]. Similarly, high mortality-risk was seen for late stage WT in children aged 0-14 years (Hazard Ratio=6.37; 95% CI=2.60-15.59). CONCLUSIONS: This study did not detect a significant social gradient in renal tumour survival. The identification of tumour stage as a strong predictor of survival irrespective of age, necessitates the development of appropriate public health interventions that target early diagnosis and treatment.