Cancer genomics has revealed many genes and core molecular processes that contribute to human malignancies, but the genetic and molecular bases of many rare cancers remains unclear. Genetic ...predisposition accounts for 5 to 10% of cancer diagnoses in children
, and genetic events that cooperate with known somatic driver events are poorly understood. Pathogenic germline variants in established cancer predisposition genes have been recently identified in 5% of patients with the malignant brain tumour medulloblastoma
. Here, by analysing all protein-coding genes, we identify and replicate rare germline loss-of-function variants across ELP1 in 14% of paediatric patients with the medulloblastoma subgroup Sonic Hedgehog (MB
)
ELP1 was the most common medulloblastoma predisposition gene and increased the prevalence of genetic predisposition to 40% among paediatric patients with MB
. Parent-offspring and pedigree analyses identified two families with a history of paediatric medulloblastoma. ELP1-associated medulloblastomas were restricted to the molecular SHHα subtype
and characterized by universal biallelic inactivation of ELP1 owing to somatic loss of chromosome arm 9q. Most ELP1-associated medulloblastomas also exhibited somatic alterations in PTCH1, which suggests that germline ELP1 loss-of-function variants predispose individuals to tumour development in combination with constitutive activation of SHH signalling. ELP1 is the largest subunit of the evolutionarily conserved Elongator complex, which catalyses translational elongation through tRNA modifications at the wobble (U
) position
. Tumours from patients with ELP1-associated MB
were characterized by a destabilized Elongator complex, loss of Elongator-dependent tRNA modifications, codon-dependent translational reprogramming, and induction of the unfolded protein response, consistent with loss of protein homeostasis due to Elongator deficiency in model systems
. Thus, genetic predisposition to proteome instability may be a determinant in the pathogenesis of paediatric brain cancers. These results support investigation of the role of protein homeostasis in other cancer types and potential for therapeutic interference.
Acute kidney injury (AKI) is a potentially fatal syndrome characterized by a rapid decline in kidney function caused by ischemic or toxic injury to renal tubular cells. The widely used chemotherapy ...drug cisplatin accumulates preferentially in the renal tubular cells and is a frequent cause of drug-induced AKI. During the development of AKI the quiescent tubular cells reenter the cell cycle. Strategies that block cell-cycle progression ameliorate kidney injury, possibly by averting cell division in the presence of extensive DNA damage. However, the early signaling events that lead to cell-cycle activation during AKI are not known. In the current study, using mouse models of cisplatin nephrotoxicity, we show that the G1/S-regulating cyclin-dependent kinase 4/6 (CDK4/6) pathway is activated in parallel with renal cell-cycle entry but before the development of AKI. Targeted inhibition of CDK4/6 pathway by small-molecule inhibitors palbociclib (PD-0332991) and ribociclib (LEE011) resulted in inhibition of cell-cycle progression, amelioration of kidney injury, and improved overall survival. Of additional significance, these compounds were found to be potent inhibitors of organic cation transporter 2 (OCT2), which contributes to the cellular accumulation of cisplatin and subsequent kidney injury. The unique cell-cycle and OCT2-targeting activities of palbociclib and LEE011, combined with their potential for clinical translation, support their further exploration as therapeutic candidates for prevention of AKI.
Significance Acute kidney injury (AKI) is a common clinical condition caused by loss of kidney function. Lack of therapeutic options has contributed to high mortality rates in AKI patients. Drug-induced AKI, as observed during cisplatin-based anticancer therapy, is responsible for about 20% of renal failure cases. The initial injury triggers a proliferative response in renal tubular cells, which in the presence of cellular damage can further accelerate renal injury. Our study provides evidence that the small-molecule cell-cycle inhibitors palbociclib and LEE011 can prevent cisplatin-induced AKI by inhibiting two relevant targets: renal cell-cycle progression and organic cation transporter 2, a renal uptake transporter of cisplatin. The future development of cyclin-dependent kinase 4/6 inhibitors as renal protective agents could have significant clinical benefits.
Recently, an efficient liver detoxification process dubbed "hepatocyte hopping" was proposed on the basis of findings with the endogenous compound, bilirubin glucuronide. According to this model, ...hepatocytic bilirubin glucuronide can follow a liver-to-blood shuttling loop via Abcc3 transporter-mediated efflux and subsequent Oatp1a/1b-mediated liver uptake. We hypothesized that glucuronide conjugates of xenobiotics, such as the anticancer drug sorafenib, can also undergo hepatocyte hopping. Using transporter-deficient mouse models, we show here that sorafenib-glucuronide can be extruded from hepatocytes into the bile by Abcc2 or back into the systemic circulation by Abcc3, and that it can be taken up efficiently again into neighboring hepatocytes by Oatp1a/1b. We further demonstrate that sorafenib-glucuronide excreted into the gut lumen can be cleaved by microbial enzymes to sorafenib, which is then reabsorbed, supporting its persistence in the systemic circulation. Our results suggest broad relevance of a hepatocyte shuttling process known as "hepatocyte hopping"-a novel concept in clinical pharmacology-for detoxification of targeted cancer drugs that undergo hepatic glucuronidation, such as sorafenib.
The use of multikinase inhibitors (MKI) in oncology, such as sorafenib, is associated with a cutaneous adverse event called hand-foot skin reaction (HFSR), in which sites of pressure or friction ...become inflamed and painful, thus significantly impacting quality of life. The pathogenesis of MKI-induced HFSR is unknown, and the only available treatment options involve dose reduction or discontinuation of therapy, which have negative effects on primary disease management. To investigate the underlying mechanisms by which sorafenib promotes keratinocyte cytotoxicity and subsequent HFSR induction, we performed a transporter-directed RNAi screen in human epidermal keratinocytes and identified SLC22A20 (OAT6) as an uptake carrier of sorafenib. Further investigations into the intracellular mechanism of sorafenib activity through in situ kinome profiling identified the mitogen-activated protein kinase MAP3K7 (TAK1) as a target of sorafenib that induces cell death. Finally, we demonstrate that sorafenib induced keratinocyte injury in vivo and that this effect could be reversed by cotreatment with the OAT6 inhibitor probenecid. Collectively, our findings reveal a novel pathway that regulates the entry of some MKIs into keratinocytes and explains the basis underlying sorafenib-induced skin toxicity, with important implications for the therapeutic management of HFSR.
Historically, qualitative research has complemented quantitative biologic and epidemiologic studies to provide a more complete understanding of pandemics. The COVID-19 pandemic has generated unique ...and novel challenges for qualitative researchers, who have embraced creative solutions including virtual focus groups and rapid analyses to continue their work. We present our experience conducting a multilingual global qualitative study of healthcare resilience among teams of pediatric oncology professionals during the COVID-19 pandemic. We provide an in-depth description of our methodology and an analysis of factors we believe contributed to our study’s success including our use of technology, engagement of a large multilingual team, global partnerships, and framework-based rapid analysis. We hope these techniques may be useful to qualitative researchers conducting studies during the current pandemic, as well as for all pediatric oncology studies including multiple languages or geographically disparate subjects.
A child near death with an ALK-fusion–positive high-grade glioma refractory to standard treatment had a dramatic response when treatment with lorlatinib was begun. The drug was stopped once the child ...had an apparent complete remission, but treatment with lorlatinib resumed when relapse occurred 6 months later. At this time, the child is attending preschool and has normal neurologic function.
Background
Coronavirus disease 2019 (COVID‐19) disrupted pediatric oncology care globally, increasing demands on health care providers (HCPs) who adapted to continue care. This study sought to ...characterize the pandemic's impact on pediatric oncology HCPs worldwide.
Methods
A 60‐item survey focused on changes to clinical care, resources, and effects on clinicians. A diverse subgroup of institutions was purposefully selected for focus groups that explored teamwork, communication, and changes to care delivery.
Results
The survey included 311 responses from 213 institutions representing 79 countries. Sixteen institutions participated in 19 multidisciplinary focus groups in 8 languages. Decreased clinical staff availability was cited by 51% of institutions as a major impact. Staffing modifications included decreased provider availability (66% of institutions), roles or responsibility changes, and transfer outside the specialty. Physical effects included frequent COVID‐19 illness; 8% of respondents reported HCP deaths. Fifty percent of providers did not have the necessary personal protective equipment. HCPs also experienced psychological distress and financial concerns. Findings indicated more frequent impact on nurses than other providers. Impacts were described across all hospital resource levels, with staffing modifications more frequent in countries with higher COVID‐19 incidence (P < .001) and mortality rate (P = .004). Focus groups revealed negative impacts were stabilized by increased teamwork, communication, contributions outside usual roles, policies aimed at optimizing safety, and feeling that they were contributing.
Conclusions
COVID‐19 had a profound impact on the pediatric oncology workforce, creating challenging modifications to staffing and resulting in physical, psychological, and financial distress. Despite these challenges, HCPs caring for children with cancer came together to continue to provide high‐quality care.
This mixed‐methods study reveals the impact that the coronavirus disease 2019 (COVID‐19) pandemic has had on pediatric oncology providers globally, and it highlights the importance of implementing strategies to protect the health care workforce during challenging situations.
The critical importance of membrane‐bound transporters in pharmacotherapy is widely recognized, but little is known about drug transporter activity in children. In this white paper, the Pediatric ...Transporter Working Group presents a systematic review of the ontogeny of clinically relevant membrane transporters (e.g., SLC, ABC superfamilies) in intestine, liver, and kidney. Different developmental patterns for individual transporters emerge, but much remains unknown. Recommendations to increase our understanding of membrane transporters in pediatric pharmacotherapy are presented.
Purpose
This study used uncertainty and sensitivity analysis to evaluate a physiologically based pharmacokinetic (PBPK) model of the complex mechanisms of sorafenib and its two main metabolites, ...sorafenib glucuronide and sorafenib N-oxide in mice.
Methods
A PBPK model for sorafenib and its two main metabolites was developed to explain disposition in mice. It included relevant influx (Oatp) and efflux (Abcc2 and Abcc3) transporters, hepatic metabolic enzymes (CYP3A4 and UGT1A9), and intestinal β-glucuronidase. Parameterization of drug-specific processes was based on in vitro, ex vivo, and in silico data along with plasma and liver pharmacokinetic data from single and multiple transporter knockout mice.
Results
Uncertainty analysis demonstrated that the model structure and parameter values could explain the observed variability in the pharmacokinetic data. Global sensitivity analysis demonstrated the global effects of metabolizing enzymes on sorafenib and metabolite disposition and the local effects of transporters on their respective substrate exposures. In addition, through hypothesis testing, the model supported that the influx transporter Oatp is a weak substrate for sorafenib and a strong substrate for sorafenib glucuronide and that the efflux transporter Abcc2 is not the only transporter affected in the Abcc2 knockout mouse.
Conclusions
Translation of the mouse model to humans for the purpose of explaining exceptionally high human pharmacokinetic variability and its relationship with exposure-dependent dose-limiting toxicities will require delineation of the importance of these processes on disposition.
Abstract
BACKGROUND: Given the vast molecular heterogeneity present within medulloblastoma (MB) and considerable differences in therapy, we performed a meta-analysis of three large, recently ...published, prospective clinical trials (ACNS0331, SJMB03, ACNS0332) comprising 898 children with newly-diagnosed MB to shape future therapy.
METHODS: Molecular subgroups, subtypes, and copy number variations were uniformly procured from DNA methylation profiles and mutations from next-generation sequencing. Patients were stratified into six clinically homogeneous groups for cross-trial comparisons: (1) ACNS0331_LDCSI - patients with non-metastatic (M0), non-residual (R0), non-anaplastic MB treated with low-dose (LD) craniospinal irradiation(CSI); (2) ACNS0331_SDCSI - patients with M0R0 non-anaplastic MB treated with standard-dose(SD) CSI; (3) SJMB03_SDCSI - patients with M0R0 non-anaplastic MB treated with SDCSI; (4) SJMB03_HDCSI - patients with metastatic (M+) MB treated with high-dose (HD) CSI; (5) ACNS0332_HDCSI - patients with M+ MB treated with HDCSI; (6) ACNS0332_HDCSI_Carbo - patients with M+ MB treated with HDCSI and carboplatin.
RESULTS: 803 (WNT=125, SHH=122, G3=189, G4=367) of 898 patients formed the cohort. No significant difference was observed between the event-free survival (EFS) from ACNS0331_SDCSI and SJMB03_SDCSI or from SJMB03_HDCSI and ACNS0332_HDCSI when analyzed as a whole or by subgroup. ACNS0331_LDCSI outcome was inferior to the combined ACNS0331_SDCSI + SJMB03_SDCSI cohorts (p<0.001) and in G3 (p=0.030). ACNS0332_HDCSI_Carbo EFS was superior to ACNS0332_HDCSI + SJMB03_HDCSI only in G3/G4_subtype III (p=0.045). Additional molecular risk factor analysis identified M0R0 G3/G4_subtype VII and SHH without high-risk features as very low risk (>90% EFS) and M0R0 G3/G4_subtype III as high risk (<40% EFS).
CONCLUSION: The comparable results observed across trials presents a welcome opportunity to reduce toxicity by eliminating excessive doses of chemotherapy (i.e. vincristine, cisplatin, and cyclophosphamide) from therapy. Furthermore, these results support molecularly driven risk classification as the means for a better, more-refined, treatment stratification.
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