Biology subjects

Zeineldin, M.

Publications and source records attributed to Zeineldin, M..

6 recordsLinked to original sources

bioRxiv2026

Cell Ploidy Modulates Nucleolar Size via Dosage of Nucleolar Organizing Regions

Abnormal nucleolar morphology is a pathognomonic histologic feature of cancer cells. Nucleoli are biomolecular condensates and cytogenetic entities that form around nucleolar organizing regions (NORs), located on the short arms of acrocentric chromosomes. Given that aneuploidy is pervasive in human cancers and can involve NOR-bearing chromosomes, we investigated how aneuploidy-driven changes in NOR dosage impact nucleolar morphology. We used reversine, a spindle assembly checkpoint inhibitor, to induce chromosomal instability and complex aneuploidy in DLD1 colorectal cancer cells (near-euploid) and normal human colon organoids (colonoids, euploid). High resolution 3D imaging and quantitative analyses of reversine-treated cells showed overall doubling of total nucleolar volume per nucleus. Reversine-associated nucleolar enlargement occurred independently of global protein synthesis, and thus was not solely driven by increases in biosynthetic demand. The volume of individual nucleoli showed a direct linear correlation with the number of associated NORs, as revealed by 3D co-localization with NOR-specific FISH probes. These findings establish NOR dosage as a determinant of nucleolar morphology and metric of genomic instability, providing a new paradigm by which aneuploidy can modulate spatial chromosomal constraints and nuclear architecture in cancer. Significance statementCancer cells often show enlarged and abnormal nucleoli. We show that aneuploidy, a common feature of cancer, can directly reshape nucleolar morphology by altering the copy number of acrocentric chromosomal regions around which nucleoli form, NORs. Using high-resolution 3D imaging in cell lines and patient-derived colonoids, we find that nucleolar number and volume directly correlate with NOR number, independent of overall protein synthesis. Individual nucleolar volume scales with the number of 3D NOR associations, and prominent single nucleoli arise when NORs accumulate. These results provide evidence that aneuploidy can lead to aberrant nucleolar morphologies seen in many human cancers.

cancer biology↗

bioRxiv2023

Disruption of Epithelium Integrity by Inflammation-Associated Fibroblasts through Prostaglandin Signaling

Inflammation-associated fibroblasts (IAFs) are associated with the progression and drug resistance of chronic inflammatory diseases such as inflammatory bowel disease (IBD), but their direct impact on epithelial function and architecture is unknown. In this study, we developed an in vitro model whereby human colon fibroblasts are induced to become IAFs by specific cytokines and recapitulate key features of IAFs in vivo. When co-cultured with patient-derived colon organoids (colonoids), IAFs induced rapid colonoid swelling and barrier disruption due to swelling and rupture of individual epithelial cells. Epithelial cells co-cultured with IAFs also exhibit increased DNA damage, mitotic errors, and proliferation arrest. These IAF-induced epithelial defects are mediated through a paracrine pathway involving prostaglandin E2 (PGE2) and the PGE2 receptor EP4, leading to PKA-dependent activation of the CFTR chloride channel. Importantly, EP4-specific chemical inhibitors effectively prevented colonoid swelling and restored normal proliferation and genome stability of IAF-exposed epithelial cells. These findings reveal a mechanism by which IAFs could promote and perpetuate IBD and suggest a potential treatment to mitigate inflammation-associated epithelial injury. TeaserInflammation-associated fibroblasts compromise colon epithelial barrier integrity and genome stability via PGE2-EP4 signaling.

cell biology↗

bioRxiv2023

SATB2 loss in inflammatory bowel disease-associated small intestinal metaplasia of the distal colon

Epithelial metaplasia is a common adaptation to chronic inflammatory processes and can be associated with increased risk of dysplasia and cancer. The distal colon of patients with inflammatory bowel disease (IBD) commonly shows crypt architectural distortion and Paneth cell metaplasia (PCM), and IBD patients also carry increased risk of colitis-associated dysplasia and cancer (CAC). Loss of SATB2 expression (Special AT-rich binding 2 protein, a colon-restricted chromatin remodeler) has recently been shown to distinguish colitis-associated dysplasia and CAC from sporadic disease. Here we report non-diffuse heterogeneous patterns of SATB2 loss across non-dysplastic distal colon biopsies from IBD patients (n=20). This cohort was specifically curated to include biopsies with well-developed histologic features of villiform growth and PCM. Notably, CDX2 was strongly expressed and P53 showed a wild-type immunolabeling pattern across our non-dysplastic cohort, regardless of SATB2 immunolabeling pattern. Our findings fit with recent murine studies in which colon-specific Satb2 deletion resulted in histologic conversion of colonic mucosa to small intestinal-like mucosa, including emergence of villi and Paneth cells. Taken together, we show that SATB2 loss is associated with a preneoplastic metaplastic response to chronic injury in human IBD and chronic colitis, reframing PCM more broadly as small intestinal metaplasia. We propose that inflammation-associated SATB2 loss mediates a remodeled chromatin landscape permissive for dysplasia and CAC.

pathology↗

bioRxiv2022

The TERT promoter is polycomb-repressed in neuroblastoma cells with long telomeres

Acquiring a telomere maintenance mechanism is one of the hallmarks of high-risk neuroblastoma and commonly occurs by expressing telomerase (TERT). Telomerase-negative neuroblastoma has, characteristically, long telomeres and most utilize the telomerase-independent alternative lengthening of telomeres (ALT) mechanism. Conversely, no discernable telomere maintenance mechanism is detected in a fraction of neuroblastoma with long telomeres, representing a phenomenon referred to as ever-shorter telomeres. Here, we show that, unlike most cancers, DNA of the TERT promoter is broadly hypomethylated in neuroblastoma. In telomerase-positive neuroblastoma cells, the hypomethylated DNA promoter is approximately 1.5-kb in length and is bound by hypermethylated TERT gene body and upstream intergenic sequences. The TERT locus shows active chromatin marks including H3K4me3, H3K27Ac, H3K14Ac, RNA PolII and BRD4 with low enrichment for the repressive mark, H3K27me3. Strikingly, in neuroblastoma with long telomeres, the hypomethylated region spans the entire TERT locus, including multiple nearby genes with enrichment for the repressive H3K27me3 chromatin mark. Furthermore, subtelomeric regions showed enrichment of repressive chromatin marks in neuroblastomas with long telomeres relative to those with short telomeres. These repressive marks were even more evident at the genic loci, suggesting a telomere position effect. Inhibiting H3K27 methylation by the EZH2 inhibitor, Tazemetostat, induced the expression of TERT, particularly in cell lines with long telomeres and H3K27me3 marks in the promoter region. Taken together, these data suggest that epigenetic regulation of TERT expression differs in neuroblastoma depending on the telomere maintenance status, and H3K27 methylation is important in repressing TERT expression in neuroblastoma with long telomeres.

cancer biology↗

bioRxiv2021

Colonic epithelial adaptation to EGFR-independent growth induces induces chromosomal instability and is accelerated by prior injury

Although much is known about the gene mutations required to drive colorectal cancer (CRC) initiation, the tissue-specific selective microenvironments in which neoplasia arises remains less characterized. Here, we determined whether modulation of intestinal stem cell niche morphogens alone can exert a neoplasia-relevant selective pressure on normal colonic epithelium. Using adult stem cell-derived murine colonic epithelial organoids (colonoids), we employed a strategy of sustained withdrawal of EGF and EGFR inhibition to select for and expand survivors. EGFR-signaling-independent (iEGFR) colonoids emerged over rounds of selection and expansion. Colonoids derived from a mouse model of chronic mucosal injury showed an enhanced ability to adapt to EGFR inhibition. Whole-exome and transcriptomic analyses of iEGFR colonoids demonstrated acquisition of deleterious mutations and altered expression of genes implicated in EGF signaling, pyroptosis, and CRC. iEGFR colonoids acquired dysplasia-associated cytomorphologic changes, an increased proliferative rate, and the ability to survive independently of other required niche factors. These changes were accompanied by emergence of aneuploidy and chromosomal instability; further, the observed mitotic segregation errors were significantly associated with loss of interkinetic nuclear migration, a fundamental and dynamic process underlying intestinal epithelial homeostasis. This study provides key evidence that chromosomal instability and other phenotypes associated with neoplasia can be induced ex vivo via adaptation to EGF withdrawal in normal and stably euploid colonic epithelium, without introducing cancer-associated driver mutations. In addition, prior mucosal injury accelerates this evolutionary process. Key definitionsColonoids: adult stem cell-derived colonic epithelial organoids iEGFR: in vitro selective conditions devoid of EGF (epidermal growth factor) and including an EGFR (EGF receptor) inhibitor 1 iEGFR colonoids: colonoids tolerant to iEGFR culture conditions with growth and survival similar to unselected passage-matched controls INM: Interkinetic nuclear migration

cancer biology↗

bioRxiv2018

MYCN Amplification and ATRX Mutations are Incompatible in Neuroblastoma

Aggressive cancers often have activating mutations in growth-controlling oncogenes and inactivating mutations in tumor-suppressor genes. In neuroblastoma, amplification of the MYCN oncogene and inactivation of the ATRX tumor-suppressor gene correlate with high-risk disease and poor prognosis. Here we show that ATRX mutations and MYCN amplification are mutually exclusive across all ages and stages in neuroblastoma. Using human cell lines and mouse models, we found that elevated MYCN expression and ATRX mutations are incompatible. Elevated MYCN levels promote metabolic reprogramming, mitochondrial dysfunction, reactive-oxygen species generation, and DNA-replicative stress. The combination of replicative stress caused by defects in the ATRX-histone chaperone complex and that induced by MYCN-mediated metabolic reprogramming leads to synthetic lethality. Therefore, ATRX and MYCN represent an unusual example, where inactivation of a tumor-suppressor gene and activation of an oncogene are incompatible. This synthetic lethality may eventually be exploited to improve outcomes for patients with high-risk neuroblastoma.

cancer biology↗