Biology subjects

Fletcher, J. I.

Publications and source records attributed to Fletcher, J. I..

3 recordsLinked to original sources

bioRxiv2026

Preclinical trial supports dual inhibition of BCL2 and Aurora kinase A for MYCN-amplified high-risk neuroblastoma

Purpose: Treatment for children with high-risk neuroblastoma relies on conventional chemotherapy and anti-GD2 immunotherapy. However, 5-year survival is only 50%, with high rates of late effects. Targeted therapy combinations are a major priority for these patients. The BCL2 inhibitor venetoclax, in combination with cyclophosphamide/topotecan, has clinical activity in relapsed and refractory neuroblastoma. We sought more effective and safer venetoclax combinations through systematic preclinical testing. Experimental design: Synergistic combinations were identified by high-throughput screening using patient-derived xenograft (PDX) models and confirmed in vivo. The leading combination (venetoclax-alisertib) was compared to combination chemotherapy in a clinical trial-like study using 22 PDX models, in scheduling experiments designed to reduce short-term toxicity, and in combination with anti-GD2 immunotherapy. BCL2 and Bim-BCL2 complex protein levels were assessed as predictors of sensitivity. Results: In vitro synergy with venetoclax was observed for standard-of-care chemotherapies and targeted agents, including DNA topoisomerase, microtubule, HDAC and Aurora kinase A (AURKA) inhibitors. Venetoclax-alisertib was particularly effective in vivo. In an n=1 study, venetoclax-alisertib induced objective response in all models. Activity was most striking in models of MYCN-amplified disease (n=12), doubling median survival time compared to cyclophosphamide/topotecan, and outperforming venetoclax-cyclophosphamide-topotecan. Efficacy was maintained with discontinuous schedules, minimizing hematological toxicity without substantially compromising activity. PDX-engrafted animals treated with venetoclax-alisertib and anti-GD2 immunotherapy survived tumor-free long-term. BCL2 expression and BCL2-Bim complex levels were of limited value for predicting response. Conclusion: Our findings support advancement of BCL2-AURKA inhibition to clinical trial for neuroblastoma with or without anti-GD2 immunotherapy, particularly in patients with MYCN amplified disease.

cancer biology↗

bioRxiv2025

Inclusion of JNK-independent drugs within multi-agent chemotherapy improves response in relapsed high-risk neuroblastoma

The acquisition of a chemoresistant state underlies poor prognosis in many cancers, including neuroblastoma. We previously demonstrated that heterogeneity in apoptosis induction through c-Jun N-Terminal Kinase (JNK) promotes a form of non-genetic chemoresistance in neuroblastoma observable at both patient and single-cell levels. As the maintenance of this JNK-impaired state in the relapse setting is a significant barrier to the efficacy of many standard-of-care chemotherapy drugs, we combined a mechanistic, mathematical model of JNK activation with a paediatric focused drug screen and identified approved oncology drugs capable of inducing apoptosis in a JNK-independent manner. Functional genomics further revealed that synergy between these JNK-independent drugs and standard-of-care chemotherapies emerged from differential utilisation of apoptotic network components, rather than from their direct mechanistic targets. Efficacy studies with PDX models also confirmed that including a JNK-independent drug within existing chemotherapy backbones significantly improved response in the relapse setting, where new approaches are urgently needed. One Sentence SummaryDrug combinations utilising differential sets of network components can overcome the apoptotic impaired state of relapsed high-risk neuroblastoma.

cancer biology↗

bioRxiv2022

The Eyes Absent family members EYA4 and EYA1 promote PLK1 activation and successful mitosis through tyrosine dephosphorylation.

The Eyes Absent family of proteins (EYA1-4) are a biochemically unique group of tyrosine phosphatases known to be tumour promoting across a range of cancer types. To date, the molecular targets of EYA phosphatase activity remain largely uncharacterised. Here, we identify Polo-like kinase 1 (PLK1) as a direct interactor and phosphatase substrate of both EYA4 and EYA1, with pY445 on PLK1 being the primary target site. EYA-mediated dephosphorylation of PLK1 in the G2 phase of the cell cycle is required for centrosome maturation, PLK1 localization to centrosomes, and polo-box domain (PBD) dependent interactions between PLK1 and the PLK1-activating proteins BORA and CEP192. Molecular dynamics simulations support the rationale that pY445 confers a structural impairment to PBD-substrate interactions that is relieved by EYA-mediated dephosphorylation. Depletion of EYA4 or EYA1, or chemical inhibition of EYA phosphatase activity, dramatically reduces PLK1 activation, causing mitotic defects and cell death. Overall, we have characterized a novel phosphotyrosine signalling network governing PLK1 and mitosis. This work provides a mechanism of cell killing for EYA phosphatase inhibitors with important therapeutic implications.

cell biology↗