MYCN is a major driver for the childhood cancer, neuroblastoma, however, there are no inhibitors of this target. Enhanced MYCN protein stability is a key component of MYCN oncogenesis and is maintained by multiple feedforward expression loops involving MYCN transactivation target genes. Here, we reveal the oncogenic role of a novel MYCN target and binding protein, proliferationassociated 2AG4 (PA2G4). Chromatin immunoprecipitation studies demonstrated that MYCN occupies the PA2G4 gene promoter, stimulating transcription. Direct binding of PA2G4 to MYCN protein blocked proteolysis of MYCN and enhanced colony formation in a MYCNdependent manner. Using molecular modeling, surface plasmon resonance, and mutagenesis studies, we mapped the MYCN-PA2G4 interaction site to a 14 amino acid MYCN sequence and a surface crevice of PA2G4. Competitive chemical inhibition of the MYCN-PA2G4 protein-protein interface had potent inhibitory effects on neuroblastoma tumorigenesis in vivo. Treated tumors showed reduced levels of both MYCN and PA2G4. Our findings demonstrate a critical role for PA2G4 as a cofactor in MYCN-driven neuroblastoma and highlight competitive inhibition of the PA2G4-MYCN protein binding as a novel therapeutic strategy in the disease.Significance: Competitive chemical inhibition of the PA2G4-MYCN protein interface provides a basis for drug design of small molecules targeting MYC and MYCNbinding partners in malignancies driven by MYC family oncoproteins. Characterization of the PA2G4-MYCN protein-protein interface. A, GST pulldown of overexpressed GST-MYCN deletion mutant proteins and a PA2G4-3xFlag expression vector for 24 hours in HEK-293T cells, which were then immunoblotted with an anti-Flag antibody. B, Overlay of the independent representation of the docking solutions of WS6 (green carbons) and the MYCN oligopeptide DHKALST (white carbons) to PA2G4. Both were predicted to bind to the same surface pocket of PA2G4 (gray-filled space). C, A representative SPR (Biacore T200) experiment demonstrating a direct dose-response binding interaction between the bound PA2G4 exposed to increasing concentrations of the MYCN oligopeptide, DHKALST. Each experiment was run in duplicate. Overall this interaction had a calculated K d of 28.3 AE 0.73 mmol/L (n ¼ 5). D, A molecular model of the PA2G4-MYCN protein interface. The addition of two MYCN amino acids at the C-terminus and five at the N-terminus of the DHKALST MYCN oligopeptide resulted in an oligopeptide, GGDHKALSTGEDTL (cyan carbons), which interacted with PA2G4 (white carbons) in this molecular model. A visual analysis of this static dock predicted putative hydrogen bonds (yellow dashes) with residues Ser47, Arg271, and Arg272, which were subsequently targeted for mutagenesis. E, Representative SPR curves showing the concentration-response binding of DHKALST to PA2G4 (solid lines). The addition of 10 mmol/L WS6 resulted in a repression of this binding (dotted lines). This experiment was conducted in duplicate, three times. F, HEK293 cells were transiently transfecte...
Objective Gestational trophoblastic disease (GTD) is a group of pregnancy-related disorders that arise from abnormal proliferation of placental trophoblast. Some patients with GTD develop hyperthyroidism, a rare but potentially life-threatening complication requiring early detection and management. Existing literature on hyperthyroidism in GTD is scant. This review aims to analyse the epidemiology, pathophysiology and management of this phenomenon. Methods A comprehensive search of MEDLINE, EMBASE and Cochrane Library was performed to obtain articles that explored hyperthyroidism in GTD. A total of 405 articles were screened and 228 articles were considered for full-text review. We selected articles that explored epidemiology, pathophysiology and outcomes/management of hyperthyroidism in GTD. Results The pathophysiology of hyperthyroidism in GTD is well-investigated. Placental trophoblastic tissue secretes excessive hCG, which is structurally similar to thyroid stimulating hormone and also has enhanced thyrotropic activity compared to normal hCG. The incidence and prevalence of hyperthyroidism in GTD varies worldwide, with lower rates associated with high uptake of early antenatal screening and early GTD detection. No clear risk factors for hyperthyroidism in GTD were identified. While hyperthyroidism can be definitively managed with surgical evacuation of the uterus, severe complications associated with hyperthyroidism in GTD have been reported, including thyroid storm-induced multi-organ failure, ARDS, and pulmonary hypertension. Conclusion Early detection of GTD is critical to prevent development of hyperthyroidism and its associated complications. Hyperthyroidism should be recognised as an important perioperative consideration for women undergoing surgery for GTD, and requires appropriate management. Future studies should explore risk factors for hyperthyroidism in GTD, which may facilitate earlier identification of high-risk women.
<p>Supplementary Figure S6. PA2G4 increases neuroblastoma tumorigenicity. A, Representative images of athymic nude mice inoculated with neuroblastoma (SH-EP) cells stably transfected with either EV control or a PA2G4 expression vector at 10 weeks post-injection. B, Images of tumor formation after mice were culled 12 weeks post-injection. C, Real-time PCR analysis of PA2G4 mRNA expression level in tumors from mice injected with either SH-EP cells overexpressing PA2G4, or SH-EP EV control cells. β2-microglobulin was used as a reference gene for total RNA loading. D, Protein was extracted from SH-EP tumor xenografts overexpressing PA2G4 and control vectors, then analysed for PA2G4-Flag and MYCN expression by immunoblotting using anti-MYCN and anti-PA2G4 antibodies, using a Vinculin loading control. E, Immunoblots of three tumor samples from each siRNA-treated cohort showing the levels of PA2G4 and MYCN protein expression, using a Vinculin loading control. F, Real-time PCR analysis of PA2G4 and MYCN mRNA expression in tumor samples taken from tumour-bearing mice xenografted with BE(2)-C neuroblastoma cells, which had been treated with either nano-particle encapsulated siRNA control, PA2G4 siRNA or PA2G4-p48 siRNA. Data are shown as means and SD derived from 6 mice per group, P-values were calculated by t-test.</p>
<p>Supplementary Information</p>
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