Biology subjects

Medema, R.

Publications and source records attributed to Medema, R..

6 recordsLinked to original sources

bioRxiv2025

Oncogene Silencing via ecDNA Micronucleation

Extrachromosomal DNA (ecDNA) contributes to cancer genome instability by enabling high-copy oncogene amplification, intratumoural heterogeneity and rapid genetic change. Micronuclei (MN) are frequently observed in chromosomally unstable cancers, yet their origins and relevance in ecDNA-driven tumours remain incompletely understood. Here, we investigate the relationship between ecDNA segregation errors and MN formation. We find that ecDNA frequently localizes to MN and represents a prominent source of MN content in ecDNA-positive cancer cells. Mitotic clustering of oncogene-bearing ecDNAs is associated with asymmetric inheritance and mis-segregation into MN. Transfer of oncogenes from ecDNA into MN is accompanied by reduced transcriptional output. Single-MN sequencing shows that individual MN are enriched for ecDNA to a degree that exceeds expectations from stochastic mis-segregation and that in MN oncogenes originating from multiple distinct ecDNAs coalesce. Using live-cell imaging, we observe that cells inheriting ecDNA-positive MN show limited proliferative capacity and an increased likelihood of cell death. In neuroblastoma patients with MYCN-amplified ecDNA, higher frequencies of ecDNA-positive MN at diagnosis are associated with improved event-free and overall survival. Together, these findings link ecDNA mis-segregation to MN formation and reduced cellular fitness, suggesting that ecDNA-positive MN may reflect a state of impaired oncogenic ecDNA function with potential relevance for clinical outcome.

cancer biology↗

bioRxiv2020

CIP2A interacts with TopBP1 and is selectively essential for DNA damage-induced basal-like breast cancer tumorigenesis

Despite saturated genetic profiling of breast cancers, oncogenic drivers for the clinically challenging basal-like breast cancer (BLBC) subtype are still poorly understood. Here, we demonstrate that CIP2A is selectively essential for DNA damage-induced initiation of mouse BLBC tumors, but not of other cancer types. Mechanistically, CIP2A was discovered genome-widely the closest functional homologue for DNA-damage proteins TopBP1, RHNO, POLQ, NBN and PARP1. CIP2A directly interacts with the ATR-activation domain of TopBP1, and dampens both, chromatin binding of TopBP1 and RAD51, and G2/M checkpoint in DNA-damaged cells. CIP2A also drives BLBC-associated proliferative MYC and E2F1 signaling. Consistently with high DNA-damage response activity BLBCs, and CIP2As novel role in checkpoint signaling, CIP2A was found essential for DNA-damaged, and BRCA-mutant BLBC cells. Selective role for CIP2A as BLBC driver was supported by association of high CIP2A expression with poor patient prognosis only in BLBC, but not in other breast cancer types. Therapeutically, small molecule reactivators of PP2A (SMAPs) phenocopy CIP2A-dependent DNA damage response, and inhibit in vivo growth of patient-derived BLBC xenograft. In summary, we discover sub-type selective essential role for CIP2A in BLBC initiation and maintenance that can be explained by its newly discovered association with DNA-damage response, coordinated with regulation of proliferative signaling. The results also identify therapeutic strategy for CIP2A-dependent BLBCs.

cancer biology↗

bioRxiv2019

Glucocorticoids regulate cancer cell dormancy

The glucocorticoid receptor directly regulates thousands of genes across the human genome in a cell-type specific manner, governing various aspects of homeostasis. The influence of the glucocorticoid receptor is also seen in various pathologies, including cancer, where it has been linked to tumorigenesis, metastasis, apoptosis resistance, and therapy bypass. Nonetheless, the direct genetic and molecular underpinnings of glucocorticoid action in cancer remain elusive. Here, we dissected the glucocorticoid receptor signalling axis and uncovered the mechanism of glucocorticoid-mediated cancer cell dormancy. Upon glucocorticoid receptor activation cancer cells undergo quiescence, subserved by cell cycle arrest through CDKN1C and reprogramming of signalling orchestrated via FOXO1/IRS2. Strikingly, co-expression of these three genes, directly regulated by glucocorticoid-induced chromatin looping, correlates with a benign molecular phenotype across human cancers, whereas triple loss is associated with increased expression of proliferation/aggressiveness markers. Finally, we show that the glucocorticoid receptor signalling axis is inactivated by alterations of either the chromatin remodelling complex or TP53 in vitro and in vivo. Our results indicate that the activation of the glucocorticoid receptor leads to cancer cell dormancy, which has several implications in terms of glucocorticoid use in cancer therapy.

cancer biology↗

bioRxiv2019

Degree and site of chromosomal instability define its oncogenic potential

Most human cancers are aneuploid, due to a chromosomal instability (CIN) phenotype. Despite being hallmarks of cancer, however, the roles of CIN and aneuploidy in tumor formation have not unequivocally emerged from animal studies and are thus still unclear. CIN can both promote and suppress tumorigenesis, but variances in mechanisms and timings of CIN induction in different oncogenic backgrounds and associated tissues limit interpretation of the contributions of CIN. Using a novel conditional mouse model for diverse degrees of CIN, we find that a particular range is sufficient to drive very early onset spontaneous adenoma formation in the intestine, showing that CIN can act as a much more potent oncogenic driver than was previously reported. In mice predisposed to intestinal cancer (ApcMin/+), moderate but not low CIN causes a remarkable increase in adenoma burden in the entire intestinal tract, especially in the distal colon, more closely modelling human disease. Strikingly, high levels of CIN promote adenoma formation in the distal colon even more than moderate CIN does, but have no effect in the small intestine. Our results thus show that CIN can be potently oncogenic, but that certain levels of CIN can have contrasting effects in distinct tissues.

cancer biology↗

bioRxiv2018

Molecular basis of mitotic decline during human aging

Aneuploidy, an abnormal chromosome number, has been linked to aging and age-associated diseases, but the underlying molecular mechanisms remain unknown. Supported by direct live-cell imaging of young, middle-aged and old-aged primary human dermal fibroblasts, we found that aneuploidy increases with aging due to general dysfunction of the mitotic machinery. Increased chromosome segregation defects in elderly mitotic cells correlated with an early senescence-associated secretory phenotype (SASP) and repression of Forkhead box M1 (FoxM1), the transcription factor that drives expression of most G2/M genes. By restoring FoxM1 levels in elderly and Hutchison-Gilford Progeria Syndrome fibroblasts we prevented aneuploidy and, importantly, ameliorated cellular phenotypes associated with aging. Moreover, senescent fibroblasts isolated from elderly donors cultures were mostly aneuploid, suggesting that aneuploidy is a key player in the progression into full senescence phenotypes. Based on this feedback loop between cellular aging and aneuploidy, we propose modulation of mitotic efficiency through FoxM1 as a potential strategy against aging and progeria syndromes.

cell biology↗

bioRxiv2017

Understanding inhibitor resistance in Mps1 kinase through novel biophysical assays and structures

Monopolar spindle 1 (Mps1/TTK) is a protein kinase essential in mitotic checkpoint signalling, preventing anaphase until all chromosomes are properly attached to spindle microtubules. Mps1 has emerged as a potential target for cancer therapy, and a variety of compounds have been developed to inhibit its kinase activity. Mutations in the catalytic domain of Mps1 that give rise to inhibitor resistance, but retain catalytic activity and do not display cross-resistance to other Mps1 inhibitors, have been described. Here we characterize the interactions of two such mutants, Mps1 C604Y and C604W, which raise resistance to two closely related compounds, NMS-P715 and its derivative Cpd-5, but not to the well-characterised Mps1 inhibitor, reversine. We show that estimates of the IC50 (employing a novel specific and efficient assay that utilizes a fluorescently labelled substrate) and of the binding affinity (KD) indicate that in both mutants, Cpd-5 should be better tolerated than the closely related NMS-P715. To gain further insight, we determined the crystal structure of the Mps1 kinase mutants bound to Cpd-5 and NMS-P715, and compare the binding modes of Cpd-5, NMS-P715 and reversine. The difference in steric hindrance between Tyr/Trp604 and the trifluoromethoxy moiety of NMS-P715, the methoxy moiety of Cpd-5, and complete absence of such a group in reversine, account for differences we observe in vitro. Our analysis enforces the notion that inhibitors targeting Mps1 drug-resistant mutations can emerge as a feasible intervention strategy based on existing scaffolds, if the clinical need arises.\n\nSummary statementThe inhibition of specific Mps1 kinase inhibitors towards the wild-type protein and inhibitor-resistant mutants is explained by a novel specific activity assay, biophysical characterisation, and X-ray structures.\n\nAbbreviations

biochemistry↗