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Pediatric adrenal tumors are unique entities with specific diagnostic, prognostic, and therapeutic challenges. The adrenal medulla gives rise to peripheral neuroblastic tumors (pNTs), pathologically defined by their architecture, stromal content, degree of differentiation, and mitotic-karyorrhectic index. Successful risk stratification of pNTs uses patient age, stage, tumor histology, and molecular/genetic aberrations. The adrenal cortex gives rise to adrenocortical tumors (ACTs), which present diagnostic and prognostic challenges. Histologic features that signify poor prognosis in adults can be meaningless in children, who have superior outcomes. The key clinical, pathologic, and molecular findings of pediatric ACTs have yet to be completely identified., Competing Interests: Disclosure None., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Introduction: The utility of cytologic evaluation of effusion fluids in adults is well established but has been less well documented in the pediatric population. We examined the clinicopathologic characteristics of children with malignant effusions to establish the value of cytologic examination of these specimens., Materials and Methods: Pleural, pericardial, peritoneal, and intraoperative washing specimens obtained between January 2000 and October 2015 were identified via surgical pathology database search. Relevant clinical and pathologic data was recorded. Statistical analysis of patient groups was performed via two-sided heteroscedastic Student t tests, and Kaplan-Meier analysis was used to compare overall survival between patient groups., Results: 474 effusion/washing specimens obtained from 342 patients were identified: 179 pleural effusions, 220 peritoneal fluids, 28 pericardial effusions, and 47 intraoperative washing specimens. Of these, 13.7% (56 of 474) effusion specimens were positive for malignancy. Among cancer patients with effusions, malignant effusions were seen in 54.5% of patients with rhabdomyosarcoma and 28.8% of patients with hematolymphoid malignancies. Regarding patient outcomes, malignant effusions were associated with statistically significantly shorter overall survival (P = 0.019). When compared with stage IV patients with benign effusions, those with malignant effusions had a shorter 5-year overall survival (P = 0.042); multiple malignant effusions were associated with a dramatically shorter survival than a single malignant effusion., Conclusions: The overall rate of malignant effusions in our patient population was 13.7%. Malignant effusions in children, particularly multiple, portend a poor prognosis. Our observations emphasize the importance of accurate cytologic diagnosis of effusion fluids, and reinforce the value of their cytologic evaluation., (Copyright © 2016 American Society of Cytopathology. Published by Elsevier Inc. All rights reserved.)

Ku70 was first characterized as a nuclear factor that binds DNA double-strand breaks in nonhomolog end-joining DNA repair. However, recent studies have shown that Ku70 is also found in the cytoplasm and binds Bax, preventing Bax-induced cell death. We have shown that, in neuroblastoma cells, the binding between Ku70 and Bax depends on the acetylation status of Ku70, such that, when Ku70 is acetylated, Bax is released from Ku70, triggering cell death. Thus, to survive, in neuroblastoma cells, cytoplasmic Ku70 acetylation status is carefully regulated such that Ku70 is maintained in a deacetylated state, keeping Bax complexed with Ku70. We have shown that overexpression of CREB-binding protein (CBP), a known acetyltransferase that acetylates Ku70, releases Bax from Ku70, triggering apoptosis. Although we have shown that blocking deacetylase activity using non-type-specific inhibitors also triggers Ku70 acetylation and Bax-dependent cell death, the targets of these deacetylase inhibitors in neuroblastoma cells remain unknown. Here, we demonstrate that, in neuroblastoma cells, histone deacetylase 6 (HDAC6) binds Ku70 and Bax in the cytoplasm and that knocking down HDAC6 or using an HDAC6-specific inhibitor triggers Bax-dependent cell death. Our results show that HDAC6 regulates the interaction between Ku70 and Bax in neuroblastoma cells and may be a therapeutic target in this pediatric solid tumor.

The cytotoxic mechanism of the histone deacetylase inhibitor (HDACI) Trichostatin A (TSA) was explored in a neuroblastoma (NB) model. TSA induces cell death in neuroblastic-type NB cells by increasing the acetylation of Ku70, a Bax-binding protein. Ku70 acetylation causes Bax release and activation, triggering cell death. This response to TSA depends on the CREB-binding protein (CBP) acetylating Ku70. TSA-induced cell death response correlates with CBP expression. In stromaltype NB cell lines with low levels of CBP and relative resistance to TSA, increasing CBP expression disrupts Bax-Ku70 binding and sensitizes them to TSA. Reducing CBP expression in neuroblastic cell types causes resistance. Cytotoxic response to TSA is Bax-dependent. Interestingly, depleting NB cells of Ku70 also triggers Bax-dependent cell death, suggesting that conditions that leave Bax unbound to Ku70 result in cell death. We also show that CBP, Ku70, and Bax are expressed in human NB tumors and that CBP expression varies across cell types comprising these tumors, with the highest expression observed in neuroblastic elements. Together, these results demonstrate that CBP, Bax, and Ku70 contribute to a therapeutic response to TSA against NB and identify the possibility of using these proteins to predict clinical responsiveness to HDACI treatment.