Citations

Abstract Imatinib mesylate (IM) has revolutionized the treatment of gastrointestinal stromal tumor (GIST). However, most patients inevitably acquire IM resistance. Second- and third-line treatments exhibit modest clinical benefits with a median time to disease progression of 4 to 6 months, highlighting the urgency for novel therapeutic approaches. Here, we report that the expression of BCL6, a known oncogenic driver and transcriptional repressor, was significantly induced in GIST cells following IM treatment. Elevated BCL6 levels suppressed apoptosis and contributed to IM resistance. Mechanistically, BCL6 recruited SIRT1 to the TP53 promoter to modulate histone acetylation and transcriptionally repress TP53 expression. The reduction in p53 subsequently attenuated cell apoptosis and promoted tolerance of GIST cells to IM. Concordantly, treatment of GIST cells showing high BCL6 expression with a BCL6 inhibitor, BI-3802, conferred IM sensitivity. Furthermore, BI-3802 showed striking synergy with IM in IM-responsive and IM-resistant GIST cells in vitro and in vivo. Thus, these findings reveal a role for BCL6 in IM resistance and suggest that a combination of BCL6 inhibitors and IM could be a potentially effective treatment for GIST. Significance: BCL6 drives resistance to imatinib by inhibiting p53-mediated apoptosis and can be targeted in combination with imatinib to synergistically suppress tumor growth, providing a therapeutic strategy for treating gastrointestinal stromal tumor.

BACKGROUND: Heart failure remains a global health burden, and patients hospitalized are particularly at risk, but genetic associates for subsequent death or rehospitalization are still lacking. METHODS: The genetic substudy of the ASCEND-HF trial (Acute Study of Clinical Effectiveness of Nesiritide in Decompensated Heart Failure) was used to perform genome-wide association study and transethnic meta-analysis. The overall trial included the patients of self-reported European ancestry (n=2173) and African ancestry (n=507). The end point was death or heart failure rehospitalization within 180 days. Cox models adjusted for 11 a priori predictors of rehospitalization and 5 genetic principal components were used to test the association between single-nucleotide polymorphisms and outcome. Summary statistics from the 2 populations were combined via meta-analysis with the significance threshold considered P <5×10 − 8 . RESULTS: Common variants (rs2342882 and rs35850039 in complete linkage disequilibrium) located in FGD5 were significantly associated with the primary outcome in both ancestry groups (European Americans: hazard ratio [HR], 1.38; P =2.42×10 −6 ; African ancestry: HR, 1.51; P =4.43×10 − 3 ; HR in meta-analysis, 1.41; P =4.25×10 −8 ). FGD5 encodes a regulator of VEGF (vascular endothelial growth factor)-mediated angiogenesis, and in silico investigation revealed several previous genome-wide association study hits in this gene, among which rs748431 was associated with our outcome (HR, 1.20; meta P <0.01). Sensitivity analysis proved FGD5 common variants survival association did not appear to operate via coronary artery disease or nesiritide treatment ( P >0.05); and the signal was still significant when changing the censoring time from 180 to 30 days (HR, 1.39; P =1.59×10 −5 ). CONCLUSIONS: In this multiethnic genome-wide association study of ASCEND-HF, single-nucleotide polymorphisms in FGD5 were associated with increased risk of death or rehospitalization. Additional investigation is required to examine biological mechanisms and whether FGD5 could be a therapeutic target. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT00475852.

AbstractObjectivesAlthough hemispheric surgeries are among the most effective procedures for drug‐resistant epilepsy (DRE) in the pediatric population, there is a large variability in seizure outcomes at the group level. A recently developed HOPS score provides individualized estimation of likelihood of seizure freedom to complement clinical judgement. The objective of this study was to develop a freely accessible online calculator that accurately predicts the probability of seizure freedom for any patient at 1‐, 2‐, and 5‐years post‐hemispherectomy.MethodsRetrospective data of all pediatric patients with DRE and seizure outcome data from the original Hemispherectomy Outcome Prediction Scale (HOPS) study were included. The primary outcome of interest was time‐to‐seizure recurrence. A multivariate Cox proportional‐hazards regression model was developed to predict the likelihood of post‐hemispheric surgery seizure freedom at three time points (1‐, 2‐ and 5‐ years) based on a combination of variables identified by clinical judgment and inferential statistics predictive of the primary outcome. The final model from this study was encoded in a publicly accessible online calculator on the International Network for Epilepsy Surgery and Treatment (iNEST) website (https://hops‐calculator.com/).ResultsThe selected variables for inclusion in the final model included the five original HOPS variables (age at seizure onset, etiologic substrate, seizure semiology, prior non‐hemispheric resective surgery, and contralateral fluorodeoxyglucose–positron emission tomography [FDG‐PET] hypometabolism) and three additional variables (age at surgery, history of infantile spasms, and magnetic resonance imaging [MRI] lesion). Predictors of shorter time‐to‐seizure recurrence included younger age at seizure onset, prior resective surgery, generalized seizure semiology, FDG‐PET hypometabolism contralateral to the side of surgery, contralateral MRI lesion, non‐lesional MRI, non‐stroke etiologies, and a history of infantile spasms. The area under the curve (AUC) of the final model was 73.0%.SignificanceOnline calculators are useful, cost‐free tools that can assist physicians in risk estimation and inform joint decision‐making processes with patients and families, potentially leading to greater satisfaction. Although the HOPS data was validated in the original analysis, the authors encourage external validation of this new calculator.

Abstract Enhanced DNA repair is an important mechanism of inherent and acquired resistance to DNA targeted therapies, including poly ADP ribose polymerase inhibition. Spleen associated tyrosine kinase (Syk) is a non-receptor tyrosine kinase known to regulate immune cell function, cell adhesion, and vascular development. Here, we report that Syk can be expressed in high grade serous ovarian cancer and triple negative breast cancers and promotes DNA double strand break resection, homologous recombination (HR) and therapeutic resistance. We found that Syk is activated by ATM following DNA damage and is recruited to DNA double strand breaks by NBS1. Once at the break site, Syk phosphorylates CtIP, a key mediator of resection and HR, at Thr-847 to promote repair activity, specifically in Syk expressing cancer cells. Syk inhibition or genetic deletion abolished CtIP Thr-847 phosphorylation and overcame the resistant phenotype. Collectively, our findings suggest that Syk drives therapeutic resistance by promoting DNA resection and HR through a novel ATM-Syk-CtIP pathway, and that Syk is a new tumor-specific target to sensitize Syk-expressing tumors to PARPi and other DNA targeted therapy.

Abstract Defects in the homologous recombination (HR) pathway, particularly in BRCA2, are of particular therapeutic relevance in mCRPC as they confer sensitivity to PARP inhibitors (PARPi). Nevertheless, durable responses to PARPi remain elusive and primary resistance is an additional major challenge. As a result, dissecting therapeutic vulnerabilities in HR-aberrant patients is crucial and may reveal novel PARPi-based combinations for evaluation in future clinical trials.In this multi-institutional study, we used the CLIA-certified PredicineCARE™ cell-free DNA (cfDNA) assay that assesses 152 genes to profile plasma from 375 mCRPC patients from Australia and the USA. Reportable alterations included pathogenic single-nucleotide (somatic and germline) and copy number variants. Association between alterations and clinical outcomes were assessed using log rank, cox proportional, and chi-squared analyses.Overall, 65 patients (17%) had evidence of a pathogenic BRCA2 aberration, which were commonly hemizygous (78% vs 22% homozygous deletions), monoallelic (70% vs 30% bi-allelic), somatic (87% vs 13% germline), and clonal (83% vs 17% subclonal) in nature. There was no significant difference in plasma tumour fraction in patients with single vs two-copy loss of BRCA2, and BRCA2 zygosity did not have differing effects on outcomes, with both being similarly associated with shorter overall survival (HR 0.48, p&lt;0.002, and HR 0.45, p=0.003, respectively). Pathogenic BRCA1 aberrations were present in 10 patients (3%). PSA response rates to androgen-receptor pathway inhibitors (ARPI) were significantly lower in patients with a BRCA1 and/or a BRCA2 aberration (32% vs 60%, p=0.02), and we observed this BRCA-defective subgroup to be enriched for AR aberrations (71% had &gt;1 AR aberration vs 38% in BRCA-intact patients, p=0.001). BRCA-defective cancers were also significantly enriched for aberrations in key neuroendocrine markers TP53 (62% vs 28%), RB1 (60% vs 17%), and MYC (27% vs 9%), as well as for PI3K pathway aberrations (PTEN 63% vs 25% and PIK3CA 37% vs 14%). In summary, we show that BRCA alterations are associated with worse prognosis in mCRPC and reduced benefit from ARPI, and that the prognostic and predictive utility of cfDNA-detected BRCA2 may be independent of zygosity state, potentially due to constraints with copy number loss identification in samples with low tumour DNA. Additionally, on top of a high proportion of AR alterations, BRCA-defective cancers were also enriched in a number of potentially actionable targets and neuroendocrine markers. Clinical trials that leverage rational co-targeting strategies will provide an opportunity to enhance the efficacy of PARPi in mCRPC. Citation Format: Heidi Fettke, Chao Dai, Edmond M. Kwan, Tiantian Zheng, Winston Tan, P Du, Nicole Ng, Patricia Bukszynska, Maria Docanto, L K. Graham, Kate Mahon, Lisa G. Horvath, Shidong Jia, Manish Kohli, Arun A. Azad. Adverse clinical outcomes and distinct genomic phenotype of BRCA-deficient metastatic castration-resistant prostate cancer (mCRPC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2303.

Understanding of the evolution of metazoans from their unicellular ancestors is a fundamental question in biology. In contrast to fungi which utilize the Mon1–Ccz1 dimeric complex to activate the small GTPase RAB7A, metazoans rely on the Mon1–Ccz1–RMC1 trimeric complex. Here, we report a near-atomic resolution cryogenic-electron microscopy structure of the Drosophila Mon1–Ccz1–RMC1 complex. RMC1 acts as a scaffolding subunit and binds to both Mon1 and Ccz1 on the surface opposite to the RAB7A-binding site, with many of the RMC1-contacting residues from Mon1 and Ccz1 unique to metazoans, explaining the binding specificity. Significantly, the assembly of RMC1 with Mon1–Ccz1 is required for cellular RAB7A activation, autophagic functions and organismal development in zebrafish. Our studies offer a molecular explanation for the different degree of subunit conservation across species, and provide an excellent example of how metazoan-specific proteins take over existing functions in unicellular organisms.

Chronic hepatitis B (CHB) is the most common cause of hepatocellular carcinoma (HCC) worldwide. Antiviral treatment reduces the risk of HCC and mortality; nonetheless, globally in 2019, only 2.2% of CHB patients received treatment. Current international CHB guidelines recommend antiviral treatment only in subsets of patients with clear evidence of liver damage. This contrasts with hepatitis C or HIV where early treatment is recommended in all infected patients, regardless of end-organ damage. This narrative review aims to provide an overview of data on the early initiation of antiviral treatment and its related potential economic impact. Literature searches were performed using PubMed and abstracts from international liver congresses (2019–2021). Data on risk of disease progression and HCC and the impact of antiviral treatment in currently ineligible patients were summarized. Cost-effectiveness data on early antiviral treatment initiation were also collated. Accumulating molecular, clinical, and economic data suggest that early initiation of antiviral treatment could save many lives through HCC prevention in a highly cost-effective manner. In light of these data, we consider several alternative expanded treatment strategies that might further a simplified ‘treatment as prevention’ approach.