DNAJB1-PRKACA fusion protein-regulated LINC00473 promotes tumor growth and alters mitochondrial fitness in fibrolamellar carcinoma.

Fibrolamellar carcinoma (FLC) is a rare liver cancer that disproportionately affects adolescents and young adults. Currently, no standard of care is available and there remains a dire need for new therapeutics. Most patients harbor the fusion oncogene DNAJB1-PRKACA (DP fusion), but clinical inhibitors are not yet developed and it is critical to identify downstream mediators of FLC pathogenesis. Here, we identify long noncoding RNA LINC00473 among the most highly upregulated genes in FLC tumors and determine that it is strongly suppressed by RNAi-mediated inhibition of the DP fusion in FLC tumor epithelial cells. We show by loss- and gain-of-function studies that LINC00473 suppresses apoptosis, increases the expression of FLC marker genes, and promotes FLC growth in cell-based and in vivo disease models. Mechanistically, LINC00473 plays an important role in promoting glycolysis and altering mitochondrial activity. Specifically, LINC00473 knockdown leads to increased spare respiratory capacity, which indicates mitochondrial fitness. Overall, we propose that LINC00473 could be a viable target for this devastating disease.

Identification of gene fusions associated with amyotrophic lateral sclerosis.

INTRODUCTION/AIMS: Genetics is an important risk factor for amyotrophic lateral sclerosis (ALS), a neurodegenerative disease affecting motor neurons. Recent findings demonstrate that in addition to specific genetic mutations, structural variants caused by genetic instability can also play a causative role in ALS. Genomic instability can lead to deletions, duplications, insertions, inversions, and translocations in the genome, and these changes can sometimes lead to fusion of distinct genes into a single transcript. Gene fusion events have been studied extensively in cancer; however, they have not been thoroughly investigated in ALS. The aim of this study was to determine whether gene fusions are present in ALS. METHODS: Gene fusions were identified using STAR Fusion v1.10.0 software in bulk RNA-Seq data from human postmortem samples from publicly available data sets from Target ALS and the New York Genome Center ALS Consortium. RESULTS: We report the presence of gene fusion events in several brain regions as well as in spinal cord samples in ALS. Although most gene fusions were intra-chromosomal events between neighboring genes and present in both ALS and control samples, there was a significantly greater number of unique gene fusions in ALS compared to controls. Lastly, we identified specific gene fusions with a significant burden in ALS, that were absent from both control samples and known cancer gene fusion databases. DISCUSSION: Collectively, our findings reveal an enrichment of gene fusions in ALS and suggest that these events may be an additional genetic cause linked to ALS pathogenesis.

Surgical management of pediatric renovascular hypertension and midaortic syndrome at a single-center multidisciplinary program.

OBJECTIVE: To evaluate the outcomes of various surgical approaches in the treatment of renovascular hypertension and midaortic syndrome (MAS) in children. METHODS: We performed a retrospective medical record review of patients who had undergone surgery for renovascular hypertension from 2010 to 2018 at our center under the care of a multidisciplinary team. The operative interventions included mesenteric artery growth improves circulation (MAGIC), tissue expander-stimulated lengthening of arteries (TESLA), aortic bypass using polytetrafluorethylene, renal artery reimplantation, and autotransplantation. The MAGIC procedure uses the meandering mesenteric artery as a free conduit for aortic bypass. The TESLA procedure is based on lengthening the normal distal aorta and iliac arteries by gradual filling of a retroaortic tissue expander for several weeks, followed by resection of the stenotic aorta and subsequent primary reconstruction. RESULTS: A total of 39 patients were identified, 10 with isolated renal artery stenosis, 26 with MAS, and 3 with systemic inflammatory vasculitis. The median age at presentation and surgery was 6.4 years (range, 0-16.3 years) and 9.3 years (range, 0-9.2 years), respectively. The MAS-associated syndromes included neurofibromatosis type 1 (15.4%) and Williams syndrome (5.1%), although most cases were idiopathic. At surgery, 33.3% had had stage 1 hypertension (HTN), 53.8% stage 2 HTN, and 12.8% normal blood pressure with a median of three antihypertensive medications. Follow-up of 37 patients at a median of 2.5 years demonstrated normal blood pressure in 86.1%, stage 1 HTN in 8.3%, and stage 2 HTN in 5.6%, with a median of one antihypertensive medication for the entire cohort. CONCLUSIONS: The patterns of vascular involvement leading to renovascular hypertension in children are variable and complex, requiring thoughtful multidisciplinary planning and surgical decision-making. The MAGIC and TESLA procedures provide feasible approaches for aortic bypass and reconstruction using autologous tissues and will result in normalization of blood pressure in 85% of children 2.5 years after surgery.

Donor-to-recipient weight ratio is a risk factor for hepatic artery thrombosis after whole-liver transplantation in children under 25 kg.

Hepatic artery thrombosis (HAT) following pediatric liver transplantation increases morbidity and risk of graft failure. We performed a retrospective chart review of all patients who underwent deceased-donor liver transplantation from August 2002 to July 2016. Multi-organ transplant recipients were excluded. We examined the incidence of HAT at our institution and sought to identify associated donor or recipient risk factors. A total of 127 deceased-donor liver transplant patients with a median age of 1.7 years (IQR 0.67-6.7) were identified. Of those, 14 developed HAT, all weighing under 25 kg. Among 100 patients under 25 kg, whole-liver graft recipients had an odds ratio of 3.98 (95% confidence interval [CI]: 1.03, 15.34; P = .045) for developing HAT compared with split-liver graft recipients. Within the whole-liver recipient group under 25 kg, 11 patients developed HAT with a median donor-to-recipient ratio (DRWR) of 0.9 (IQR: 0.7-1.2) compared with a median DRWR of 1.4 (IQR: 1.1-1.9) for those who did not develop HAT. Multivariate analysis showed DRWR to be an independent risk factor for HAT in patients weighing under 25 kg who received whole organ grafts, with an odds ratio of 3.89 (95% CI: 1.43, 10.54; P = .008) for each 0.5 unit decrease in DRWR. Our results suggest that in recipients under 25 kg 1) split-liver grafts may have a lower rate of HAT and 2) selecting whole organ donors with a higher DRWR may decrease the incidence of HAT.

Transient elastography assessment of liver allograft fibrosis in pediatric transplant recipients.

TE measures liver stiffness to assess fibrosis. Its use in post-transplant patients was reported in few small pediatric studies. We evaluated TE ability to predict liver graft fibrosis in a large cohort while comparing it to the performance of APRI and FIB-4. We also investigated the effect of graft type on LSMs. Patients at Boston Children's Hospital who underwent LT and LSM ≤ 1 year from biopsy (2007-2018) were eligible. Ninety-four patients (45%M) aged 1-21 years (89% < 18 years; 13% < 2 years) were eligible. Median time between transplant/biopsy and LSM was 5.1 years and 52 days, respectively. Thirty-nine percent received whole-liver grafts, 54% TV grafts, and 6% as part of MV. At LSM, median ALT was 25 [IQR 16-33] IU/L. Twenty-one percent had METAVIR ≥ F2. LSM was statistically higher among those with significant fibrosis (METAVIR ≥ F2) compared to those with METAVIR F0/F1 (median [IQR] 7.5 [4.6, 13.6] vs 5.1 [4.0, 6.4] kPa, respectively) (P = .005 by Wilcoxon rank-sum test). APRI and FIB-4 distributions were not different across METAVIR stages. The AUROC for LSM was 0.71 (95% CI 0.56-0.85) with an optimal cut-point of 6.5 kPa. Graft type had no influence on the AUROC for LSM. TE is useful for assessing significant graft fibrosis in children and young adult LT recipients and performs better than APRI and FIB-4. TV grafts demonstrate similar correlation with histology as whole-liver grafts.

Whole-Exome Sequencing Enables a Precision Medicine Approach for Kidney Transplant Recipients.

BACKGROUND: Whole-exome sequencing (WES) finds a CKD-related mutation in approximately 20% of patients presenting with CKD before 25 years of age. Although provision of a molecular diagnosis could have important implications for clinical management, evidence is lacking on the diagnostic yield and clinical utility of WES for pediatric renal transplant recipients. METHODS: To determine the diagnostic yield of WES in pediatric kidney transplant recipients, we recruited 104 patients who had received a transplant at Boston Children's Hospital from 2007 through 2017, performed WES, and analyzed results for likely deleterious variants in approximately 400 genes known to cause CKD. RESULTS: By WES, we identified a genetic cause of CKD in 34 out of 104 (32.7%) transplant recipients. The likelihood of detecting a molecular genetic diagnosis was highest for patients with urinary stone disease (three out of three individuals), followed by renal cystic ciliopathies (seven out of nine individuals), steroid-resistant nephrotic syndrome (nine out of 21 individuals), congenital anomalies of the kidney and urinary tract (ten out of 55 individuals), and chronic glomerulonephritis (one out of seven individuals). WES also yielded a molecular diagnosis for four out of nine individuals with ESRD of unknown etiology. The WES-related molecular genetic diagnosis had implications for clinical care for five patients. CONCLUSIONS: Nearly one third of pediatric renal transplant recipients had a genetic cause of their kidney disease identified by WES. Knowledge of this genetic information can help guide management of both transplant patients and potential living related donors.

Perioperative renal transplantation management in small children using adult-sized living or deceased donor kidneys: A single-center experience.

Kidney transplantation remains the treatment of choice for children with ESRD. Optimal perioperative management is critical in small recipients of ASK to assure adequate graft perfusion. We present a single-center experience outlining management for patients weighing <20 kg who underwent primary renal transplantation with ASKs between 2007 and 2016. Sixty-three patients met study criteria and underwent 34 living-related, six living-unrelated, and 23 deceased donor kidney transplants. Median age and weight at transplant were 25 months (IQR 18-37 months; range 11 months-6 years) and 11.0 kg (IQR 9.2-14.5 kg; range 7.1-19.5 kg). Eighty-nine percent of patients required vasoactive agents intra-operatively, with twenty patients requiring prolonged vasoactive agents post-operatively. Intra-operatively, patients received 51.9 mL/kg of crystalloid, 27.3 mL/kg of 5% albumin, and 13.6 mL/kg of packed red blood cells. Most (93.7%) patients were extubated on POD#0. Weights peaked on post-operative days three through five. Over a median follow-up of 49 months (IQR 31-86 months; range 0-130 months), four grafts were lost, two due to thrombosis and two secondary to chronic rejection. There was one patient death six months post-transplant due to causes unrelated to transplantation. Graft survival at 1, 5, and 10 years was 98.4%, 96.6%, and 84.2%, respectively. Of surviving allografts, the median 1, 5, and 10 years post-transplant eGFR was 122.9, 90.0, and 59.2 mL/min/1.73 m2 as determined by the 2009 Schwartz formula. Renal transplantation in small children using ASKs requires meticulous perioperative management including adequate fluid resuscitation and judicious use of pressors to assure adequate graft perfusion. The use of ASKs from living or deceased donors results in satisfactory short and long-term outcomes.

Pediatric post-transplant hepatic kaposi sarcoma due to donor-derived human herpesvirus 8.

In areas of the world where human herpesvirus 8 (HHV-8) is endemic, Kaposi sarcoma (KS) is a common SOT-associated cancer. In the United States, where the virus is not prevalent, PTKS is rare, and there is little literature on pediatric PTKS. We present a North American female who underwent deceased donor, left lateral segment liver transplant for biliary atresia at age 11 months. The donor was a male with no known history of KS, originally from an HHV-8-endemic country. Three months after transplantation, the patient developed liver nodules and portal vein thrombosis. Analysis of needle biopsy established the diagnosis of KS and confirmed that the transformed cells were donor-derived. HHV-8 viremia was detected, and ganciclovir dosing (which had been started prophylactically) was increased. Immunosuppression was changed from tacrolimus to sirolimus. After further disease progression, 8 cycles of paclitaxel were administered. Under this treatment, her nodules regressed, HHV-8 viremia resolved, and she had marked clinic improvement. Notably, the adult recipient of the right liver lobe from the same donor also developed PTKS. This is one of few pediatric PTKS cases described in the literature. It contributes to the mechanistic understanding of PTKS development, illustrating the risk posed by donors from HHV-8-endemic countries, as well as the potential for strong PTKS correlation between multiple recipients of organs from a single shared donor.

Tissue expander-stimulated lengthening of arteries for the treatment of midaortic syndrome in children.

BACKGROUND: Midaortic syndrome (MAS) is a rare condition characterized by stenosis of the abdominal aorta. Patients with disease refractory to medical management will usually require either endovascular therapy or surgery with use of prosthetic graft material for bypass or patch angioplasty. We report our early experience with a novel approach using a tissue expander (TE) to lengthen the normal native arteries in children with MAS, allowing primary aortic repair without the need for prosthetic graft material. METHODS: We conducted a retrospective review of patients with MAS undergoing the TE-stimulated lengthening of arteries (TESLA) procedure at our institution from 2010 to 2014. Data are presented as mean (range). RESULTS: Five patients aged 4.8 years (3-8 years) underwent the TESLA procedure. Stages of this procedure include the following: stage I, insertion of retroaortic TE; stage II, serial TE injections; and stage III, final repair with excision of aortic stenosis and primary end-to-end aortic anastomosis. Stage II was completed in 4 months (1-9 months) with 12 (7-20) TE injections. Goal lengthening was achieved in all patients. Stage III could not be completed in one patient because of extreme aortic inflammation, which precluded safe excision of the aortic stenosis and required use of a prosthetic bypass graft. The other four patients completed stage III with two (one to three) additional vessels also requiring reconstruction (renal or mesenteric arteries). At 3.2 years (1-6 years) of follow-up, all patients are doing well. CONCLUSIONS: The TESLA procedure allows surgical correction of MAS without the need for prosthetic grafts in young children who are still growing.

Long-term outcomes of liver transplantation for hepatoblastoma: A single-center 14-year experience.

HB is the most common primary liver tumor in children. Complete tumor excision, either by partial resection or by total hepatectomy and liver transplantation, in combination with chemotherapy provides the best chance for cure. We performed a retrospective analysis of patients who underwent liver transplantation for HB and herein present our 14-year single-institution experience. Twenty-five patients underwent liver transplantation for HB at a median age of 26 months (IQR: 15-44). Graft survival was 96%, 87%, and 80% at 1, 3, and 5 years, respectively. There were four patient deaths, three of them due to disease recurrence within the first year post-transplant. Ten-year overall survival was 84%. Three recipients initially presented with pulmonary metastases and underwent resection of metastatic disease, of which two are alive at 3.9 years. Of three patients who underwent salvage transplants, two are alive at 1.5 years after transplant. Non-survivors were associated with lower median alpha fetoprotein value at presentation compared to survivors (21 707 vs 343 214; P = .04). In conclusion, the overall long-term outcome of primary liver transplantation for HB is excellent. Tumor recurrence was the highest contributor to mortality. Even patients with completely treated pulmonary metastases prior to transplant demonstrated a favorable survival.

Bilateral native nephrectomy to reduce oxalate stores in children at the time of combined liver-kidney transplantation for primary hyperoxaluria type 1.

OBJECTIVE: Primary hyperoxaluria type-1 (PH-1) is a rare genetic disorder in which normal hepatic metabolism of glyoxylate is disrupted resulting in diffuse oxalate deposition and end-stage renal disease (ESRD). While most centers agree that combined liver-kidney transplant (CLKT) is the appropriate treatment for PH-1, perioperative strategies for minimizing recurrent oxalate-related injury to the transplanted kidney remain unclear. We present our management of children with PH-1 and ESRD on hemodialysis (HD) who underwent CLKT at our institution from 2005 to 2015. METHODS: On chart review, three patients (2 girls, 1 boy) met study criteria. Two patients received deceased-donor split-liver grafts, while one patient received a whole liver graft. All patients underwent bilateral native nephrectomy at transplant to minimize the total body oxalate load. Median preoperative serum oxalate was 72 µmol/L (range 17.8-100). All patients received HD postoperatively until predialysis serum oxalate levels fell <20 µmol/L. All patients, at a median of 7.5 years of follow-up (range 6.5-8.9), demonstrated stable liver and kidney function. CONCLUSIONS: While CLKT remains the definitive treatment for PH-1, bilateral native nephrectomy at the time of transplant reduces postoperative oxalate stores and may mitigate damage to the renal allograft.

Multivisceral transplantation for abdominal tumors in children: A single center experience and review of the literature.

Standard management of intra-abdominal pediatric solid tumors requires complete resection. However, tumors with multiple organ and vascular involvement present a unique surgical challenge. We conducted a retrospective chart review of four patients, aged 2-14 years, undergoing MVT for intra-abdominal tumors with significant involvement of the visceral arteries and/or portomesenteric venous system at our institution. Indications for MVT included hepatocellular carcinoma, inflammatory myofibroblastic tumor, and two cases of hepatoblastoma. Grafts included liver, stomach, small bowel, and pancreas in all patients, with two patients also receiving spleens, and one, a partial esophageal transplant. Median hospital stay was 80 days. Postoperative complications included reoperation for abdominal hematoma and bowel obstruction, steroid responsive intestinal rejection, wound dehiscence, fungemia, seizures, and chyle leak with pleural effusion. One patient developed Epstein-Barr virus-associated complications which responded well to treatment. On follow-up (range 2.8-7.8 years), all patients have satisfactory graft function and no evidence of recurrent disease. MVT is an effective means of achieving complete gross resection of intra-abdominal malignancies in patients with multiple organ and vascular involvement.

Incidence and predictors of massive bleeding in children undergoing liver transplantation: A single-center retrospective analysis.

BACKGROUND: Liver transplantation represents a major surgery involving a highly vascular organ. Reports defining the scope of bleeding in pediatric liver transplants are few. AIMS: We conducted a retrospective analysis of liver transplants performed at our pediatric tertiary care center to quantify blood loss, blood product utilization, and to determine predictors for massive intraoperative bleeding. METHODS: Pediatric patients who underwent isolated liver transplantation at Boston Children's Hospital between 2011 and 2016 were included. The amount of blood product transfused in the perioperative period and the incidence of postoperative complications were reported. Univariable and multivariable logistic regressions were used to determine predictors for massive bleeding, defined as estimated blood loss exceeding one circulating blood volume within 24 hours. RESULTS: Sixty-eight children underwent liver transplantation during the study period and were included in the analysis. Multivariable logistic regression analysis identified the following independent predictors of massive bleeding: preoperative hemoglobin level <8.5 g/dL (OR 11.09, 95% CI 1.87-65.76), INR >1.5 (OR 11.62, 95% CI 2.36-57.26), platelet count <100 109 /L (OR 7.92, 95% CI 1.46-43.05), and surgery duration >600 minutes (OR 6.97, 95% CI 0.99-48.92). CONCLUSIONS: Pediatric liver transplantation is associated with substantial blood loss and a significant blood product transfusion burden. A 43% incidence of massive bleeding is reported. Further efforts are needed to improve bleeding management in this high-risk population.

Variation in resource utilization in liver transplantation at freestanding children's hospitals.

We sought to examine the relationship between liver transplant-related total cost, patient outcome, and hospital resource utilization at freestanding children's hospitals. Using the PHIS database, a retrospective study of 374 patients that underwent liver transplantation at 15 freestanding children's hospitals from July 2010 to December 2012 was performed. One-year graft failure and patient mortality rates from July 2010 to December 2012 for each center were also obtained from the SRTR. There was a 5.1-fold difference in median cost (median $146 444, range $59 487-302 058, P<.001) between all centers. A 2.4-fold difference existed in median LOS (median 15 days, range 9-22 days, P<.001) across centers. Median postoperative ICU stay varied from 0 to 7 days (median 4 days, P<.001). Overall, 30-day readmission rate was 55% (31.3%-100%, P<.001). One-year graft failure varied from 0% to 19.1%, with an overall rate of 5.5% (P=.279). One-year patient mortality for all centers was 2.3% (range 0%-11.1%, P=.016). Higher total cost did not correlate with lower readmission rates, patient mortality, graft failure, or any other variable. These data suggest that identifying practice patterns at low-cost centers and implementing them at higher-cost centers may decrease the cost of pediatric liver transplantation without compromising outcomes.

Outcomes after discontinuation of routine use of transanastomotic biliary stents in pediatric liver transplantation at a single site.

Routine use of transanastomotic biliary stents (RTBS) for biliary reconstruction in liver transplantation (LT) is controversial, with conflicting outcomes in adult randomized trials. Pediatric literature contains limited data. This study is a retrospective review of 99 patients who underwent first LT (2005-2014). In 2011, RTBS was discontinued at our center. This study describes biliary complications following LT with and without RTBS. 56 (56%) patients had RTBS. Median age at LT was 1.9 yr (IQR 0.7, 8.6); 55% were female. Most common indication for LT was biliary atresia (36%). Most common biliary reconstruction was Roux-en-Y choledochojejunostomy (75% with RTBS, 58% without RTBS, p = 0.09). Biliary complications (strictures, bile leaks, surgical revision) occurred in 23% without significant difference between groups (20% with RTBS, 28% without RTBS, p = 0.33). Patients with RTBS had routine cholangiography via the tube at 6-8 wk; thus, significantly more patients with RTBS had cholangiograms (91% vs. 19%, p < 0.0001). There was no difference in the number of patients who required therapeutic intervention via endoscopic or percutaneous transhepatic cholangiography (11% with RTBS, 19% no RTBS, p = 0.26). Routine use of RTBS for biliary reconstruction in pediatric LT may not be necessary, and possibly associated with need for costlier, invasive imaging without improvement in outcomes.

Immediate extubation after pediatric liver transplantation: a single-center experience.

The care of pediatric liver transplant recipients has traditionally included postoperative mechanical ventilation. In 2005, we started extubating children undergoing liver transplantation in the operating room according to standard criteria for extubation used for general surgery cases. We reviewed our single-center experience to determine our rates of immediate extubation and practice since that time. The records of 84 children who underwent liver transplantation from 2005 to 2011 were retrospectively reviewed. The immediate extubation rate increased from 33% during 2005-2008 to 67% during 2009-2011. Immediate extubation did not result in an increased reintubation rate in comparison with delayed extubation in the intensive care unit (ICU). Patients undergoing immediate extubation had a trend toward a shorter mean ICU stay as well as a significantly decreased overall hospital length of stay. Our findings suggest that there is a learning curve for instituting immediate extubation in the operating room after liver transplantation and that the majority of pediatric liver recipients can safely undergo immediate extubation.

Dynamic alterations in Hippo signaling pathway and YAP activation during liver regeneration.

The Hippo signaling pathway has been implicated in mammalian organ size regulation and tumor suppression. Specifically, the Hippo pathway plays a critical role regulating the activity of transcriptional coactivator Yes-associated protein (YAP), which modulates a proliferative transcriptional program. Recent investigations have demonstrated that while this pathway is activated in quiescent livers, its inhibition leads to liver overgrowth and tumorigenesis. However, the role of the Hippo pathway during the natural process of liver regeneration remains unknown. Here we investigated alterations in the Hippo signaling pathway and YAP activation during liver regeneration using a 70% partial hepatectomy (PH) rat model. Our results indicate an increase in YAP activation by 1 day following PH as demonstrated by increased YAP nuclear localization and increased YAP target gene expression. Investigation of the Hippo pathway revealed a decrease in the activation of core kinases Mst1/2 by 1 day as well as Lats1/2 and its adapter protein Mob1 by 3 days following PH. Evaluation of liver-to-body weight ratios indicated that the liver reaches its near normal size by 7 days following PH, which correlated with a return to baseline YAP nuclear levels and target gene expression. Additionally, when liver size was restored, Mst1/2 kinase activation returned to levels observed in quiescent livers indicating reactivation of the Hippo signaling pathway. These findings illustrate the dynamic changes in the Hippo signaling pathway and YAP activation during liver regeneration, which stabilize when the liver-to-body weight ratio reaches homeostatic levels.

Autologous and synthetic pediatric iliofemoral reconstruction: a novel technique for pediatric iliofemoral artery reconstruction.

Pediatric lower extremity arterial catheterization-related injuries can result in significant long-term morbidity. Revascularization is challenging due to concerns for long-term patency and growth accommodation with synthetic grafts. We describe a novel technique for iliofemoral revascularization using common iliac artery transposition and bridging polytetrafluoroethylene grafts. We treated two children who underwent femoral catheterization resulting in lifestyle-limiting claudication. Both patients experienced immediate resolution of symptoms. Postoperative imaging demonstrated widely patent vasculature. ASPIRE (autologous and synthetic pediatric iliofemoral reconstruction) is a method of pediatric iliofemoral artery revascularization that allows for an autologous artery to span the hip joint, reducing graft thrombosis risk and accommodating patient growth.

Clinical and immunophenotype correlating with response to immunotherapy in paediatric patients with primary liver carcinoma. A case series.

BACKGROUND: Paediatric hepatocellular carcinomas (HCC) traditionally arise in the context of a normal structural and functional liver and carry a dismal prognosis. While chemotherapy is the frontline standard, there is emerging interest in the study of immunotherapies for paediatric patients with relapsed/refractory disease. There is limited data to support whether immunotherapies will be of utility in this patient population. METHODS: Six paediatric patients (median age:16 years, range: 12-17 at the time of treatment) with advanced hepatocellular neosplams, either conventional hepatocellular or fibrolamellar carcinoma, were treated with immunotherapy. Patients were consented to institutional genomic profiling and biobanking protocols. Baseline samples and serial tissue samples, when available, were evaluated for somatic mutation rate, actionable gene mutations, and pan-immune bulk RNA expression profiling. Results were correlated with clinical course. FINDINGS: Three patients responded to checkpoint inhibition: one achieved a complete, durable response and the other two, prolonged stable disease. Three additional patients progressed. Diagnostic tissue from the complete responder demonstrated a higher relative mutational burden and robust immune infiltrate. Pre-treatment samples from the three responders demonstrated decreased expression of genes associated with T-cell dysfunction. INTERPRETATION: A subset of patients with primary paediatric hepatocellular tumours will respond to immunotherapy. Immunotherapies are currently under prospective study for relapsed/refractory liver tumours in paediatric patients. Results from this report support the prospective collection of serial serum and tissue samples which may further identify genomic and immunophenotypic patterns predictive of response. FUNDING: This work was supported by Philanthropic funds (Pan Mass Challenge, Team Angus and Team Perspective).