Sieme Hamaidia

Tumor progression is driven by cancer cell fitness, defined as the capacity of malignant cells to maintain growth, adapt to stress and withstand therapy Cellular fitness is fundamentally governed by nucleolar processes, which act as central regulators by integrating RNA processing with ribosome biogenesis to support protein synthesis and stress adaptation. The nuclear protein CYCLON, containing a large intrinsically disordered region (IDR) could be implicated in mediating biomolecular condensates and regulatory plasticity, which are key elements of nucleolar biology. CYCLON also emerged as a candidate regulator of cancer cell fitness, as it is frequently overexpressed across tumor types. Inducible silencing and cell biology approaches have shown that CYCLON maintains nucleolar integrity, controls nucleoli size and number, nucleolin and Ki-67 distribution and prevents nucleolar stress. CYCLON contributes to ribosome biogenesis by binding ribosomal RNA (rRNA) and regulating 32S and 21S pre-rRNA processing, ultimately influencing ribosomal subunit production and global protein synthesis. Its depletion impairs proliferation and clonogenic capacity by prolonging both interphase and mitosis, leading to slowed cell cycle progression. The impact of CYCLON on cellular fitness has been consistently observed across cancer models, reinforcing its essential role in the regulation of nucleolar biology.

The pharmaceutical industry has a pervasive need for chiral specific molecules with optimal affinity for their biological targets. However, the mass production of such compounds is currently limited by conventional chemical routes, that are costly and have an environmental impact. Here, we propose an easy access to obtain new tetrahydroquinolines, a motif found in many bioactive compounds, that is rapid and cost effective. Starting from simple raw materials, the procedure uses a proline‐catalyzed Mannich reaction followed by the addition of BF₃ ⋅ OEt₂, which generates a highly electrophilic aza‐ortho‐quinone methide intermediate capable of reacting with different nucleophiles to form the diversely functionalized tetrahydroquinoline. Moreover, this enantioselective one‐pot process provides access for the first time to tetrahydroquinolines with a cis‐2,3 and trans‐3,4 configuration. As proof of concept, we demonstrate that a three‐step reaction sequence, from simple and inexpensive starting compounds and catalysts, can generate a BD2‐selective BET bromodomain inhibitor with anti‐inflammatory effect.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and highly aggressive leukemia for which knowledge on disease mechanisms and effective therapies are currently lacking. Only a handful of recurring genetic mutations have been identified and none is specific to BPDCN. In this study, through molecular cloning in an index case that presented a balanced t(3;5)(q21;q31) and molecular cytogenetic analyses in a further 46 cases, we identify monoallelic deletion of NR3C1 (5q31), encoding the glucocorticoid receptor (GCR), in 13 of 47 (28%) BPDCN patients. Targeted deep sequencing in 36 BPDCN cases, including 10 with NR3C1 deletion, did not reveal NR3C1 point mutations or indels. Haploinsufficiency for NR3C1 defined a subset of BPDCN with lowered GCR expression and extremely poor overall survival (P = .0006). Consistent with a role for GCR in tumor suppression, functional analyses coupled with gene expression profiling identified corticoresistance and loss-of-EZH2 function as major downstream consequences of NR3C1 deletion in BPDCN. Subsequently, more detailed analyses of the t(3;5)(q21;q31) revealed fusion of NR3C1 to a long noncoding RNA (lncRNA) gene (lincRNA-3q) that encodes a novel, nuclear, noncoding RNA involved in the regulation of leukemia stem cell programs and G1/S transition, via E2F. Overexpression of lincRNA-3q was a consistent feature of malignant cells and could be abrogated by bromodomain and extraterminal domain (BET) protein inhibition. Taken together, this work points to NR3C1 as a haploinsufficient tumor suppressor in a subset of BPDCN and identifies BET inhibition, acting at least partially via lncRNA blockade, as a novel treatment option in BPDCN. Key Points NR3C1 haploinsufficiency is found in patients with a plasmacytoid dendritic cell neoplasm characterized by very poor clinical outcome. Overexpression of lincRNA-3q is a consistent feature of malignant cells in these patients and can be abrogated by BET protein inhibition.

Immuno‐chemotherapy elicit high response rates in B‐cell non‐Hodgkin lymphoma but heterogeneity in response duration is observed, with some patients achieving cure and others showing refractory disease or relapse. Using a transcriptome‐powered targeted proteomics screen, we discovered a gene regulatory circuit involving the nuclear factor CYCLON which characterizes aggressive disease and resistance to the anti‐CD20 monoclonal antibody, Rituximab, in high‐risk B‐cell lymphoma. CYCLON knockdown was found to inhibit the aggressivity of MYC‐overexpressing tumours in mice and to modulate gene expression programs of biological relevance to lymphoma. Furthermore, CYCLON knockdown increased the sensitivity of human lymphoma B cells to Rituximab in vitro and in vivo . Strikingly, this effect could be mimicked by in vitro treatment of lymphoma B cells with a small molecule inhibitor for BET bromodomain proteins (JQ1). In summary, this work has identified CYCLON as a new MYC cooperating factor that autonomously drives aggressive tumour growth and Rituximab resistance in lymphoma. This resistance mechanism is amenable to next‐generation epigenetic therapy by BET bromodomain inhibition, thereby providing a new combination therapy rationale for high‐risk lymphoma.

Summary: Molecular minimal residual disease (MRD) analysis is fast emerging as an essential clinical decision‐making tool for the treatment and follow‐up of mature B cell malignancies. Current EuroMRD consensus IGH real‐time quantitative polymerase chain reaction RQ‐PCR assays rely on flow cytometric assessment of diagnostic tumour burdens to construct ‘normalized’, patient‐specific, diagnostic DNA‐based MRD quantification standards. Here, we propose a new ‘hybrid’ assay that relies on plasmid‐based quantification of patient‐specific IGH VDJ targets by consensus IGH real time (RQ)‐PCR, combined with EuroMRD guidelines, for MRD monitoring in lymphoid malignancies. This assay was evaluated for MRD assessment in a total of 273 samples from 29 mantle cell lymphoma (MCL) patients treated within a Groupe Ouest Est d'Etude des Leucémies et Autres Maladies du Sang (GOELAMS) Phase II trial and was feasible, reliable and consistently comparable to gold‐standard MRD techniques (99% concordance across all samples including 32 samples within the quantitative range) when analysed in parallel (117 samples). Integrating clinical prognostic parameters and MRD status in peripheral blood at the post‐induction stage was predictive of progression‐free survival (P = 0·034) thus demonstrating the clinical utility of the approach. Plasmid‐based standards for the quantification of IGH VDJ targets are therefore confirmed to offer new opportunities for further standardization and clinical evaluation of MRD‐guided management of patients with mature B cell malignancies.

Epigenetic perturbations are increasingly described in cancer cells where they are thought to contribute to deregulated gene expression and genome instability. Here, we report the first evidence that a distinct category of chromosomal translocations observed in human tumours—those targeting 1q12 satellite DNA—can directly mediate such perturbations by promoting the formation of aberrant heterochromatic foci (aHCF). By detailed investigations of a 1q12 translocation to chromosome 2p, in a case of human B cell lymphoma, aberrant aHCF were shown to be localized to the nuclear periphery and to arise as a consequence of long range ‘pairing’ between the translocated 1q12 and chromosome 2 centromeric regions. Remarkably, adjacent 2p sequences showed increased levels of repressive histone modifications, including H4K20me3 and H3K9me3, and were bound by HP1. aHCF were associated to aberrant spatial localization and deregulated expression of a novel 2p gene (GMCL1) that was found to have prognostic impact in diffuse large B cell lymphoma. Thus constitutive heterochromatin rearrangements can contribute to tumourigenesis by perturbing gene expression via long range epigenetic mechanisms.