Yu-Fen Lin

Abstract Complex genome rearrangements can be generated by the catastrophic pulverization of missegregated chromosomes trapped within micronuclei through a process known as chromothripsis 1–5 . As each chromosome contains a single centromere, it remains unclear how acentric fragments derived from shattered chromosomes are inherited between daughter cells during mitosis 6 . Here we tracked micronucleated chromosomes with live-cell imaging and show that acentric fragments cluster in close spatial proximity throughout mitosis for asymmetric inheritance by a single daughter cell. Mechanistically, the CIP2A–TOPBP1 complex prematurely associates with DNA lesions within ruptured micronuclei during interphase, which poises pulverized chromosomes for clustering upon mitotic entry. Inactivation of CIP2A–TOPBP1 caused acentric fragments to disperse throughout the mitotic cytoplasm, stochastically partition into the nucleus of both daughter cells and aberrantly misaccumulate as cytoplasmic DNA. Mitotic clustering facilitates the reassembly of acentric fragments into rearranged chromosomes lacking the extensive DNA copy-number losses that are characteristic of canonical chromothripsis. Comprehensive analysis of pan-cancer genomes revealed clusters of DNA copy-number-neutral rearrangements—termed balanced chromothripsis—across diverse tumour types resulting in the acquisition of known cancer driver events. Thus, distinct patterns of chromothripsis can be explained by the spatial clustering of pulverized chromosomes from micronuclei.

PURPOSE: While cardiac glycosides are the mainstay of congestive heart failure treatment, early studies showed that pharmacological doses of cardiac glycosides inhibited prostate cancer cell line proliferation. We evaluated the mechanisms of cardiac glycosides, including digoxin, digitoxin and ouabain (Sigma®), on prostate specific antigen gene expression in vitro. MATERIALS AND METHODS: We cultured LNCaP cells (ATCC®) and used them to determine the effect of cardiac glycosides on prostate derived Ets factor and prostate specific antigen expression. We determined prostate derived Ets factor and prostate specific antigen expression by reverse transcription-polymerase chain reaction, immunoblot, transient gene expression assay or enzyme-linked immunosorbent assay. RESULTS: Noncytotoxic doses (100 nM) of cardiac glycosides for 24 hours inhibited prostate specific antigen secretion by LNCaP cells. Reverse transcriptase-polymerase chain reaction and immunoblot revealed that cardiac glycosides significantly down-regulated prostate specific antigen and prostate derived Ets factor expression. Transient gene expression assays showed that prostate derived Ets factor over expression enhanced prostate specific antigen promoter activity. However, prostate specific antigen and prostate derived Ets factor gene promoter activity was attenuated when LNCaP cells were treated with 100 nM cardiac glycosides. When LNCaP cells were treated with 25 nM digitoxin or digoxin for 60 hours, prostate specific antigen secretion decreased by 30%. CONCLUSIONS: Results suggest that cardiac glycoside inhibition of prostate specific antigen gene expression may be caused by the down-regulation of prostate derived Ets factor gene expression. When cells were chronically treated with digoxin or digitoxin at concentrations close to or at therapeutic plasma levels, prostate specific antigen secretion decreased. This phenomenon merits further study to determine whether it occurs in men on cardiac glycoside therapy.

Complex genome rearrangements can be generated by the catastrophic shattering of mis-segregated chromosomes trapped within micronuclei through a process known as chromothripsis. Since each chromosome harbors a single centromere, how acentric fragments derived from shattered chromosomes are inherited between daughter cells during mitosis remains unknown. Here we tracked micronucleated chromosomes by live-cell imaging and show that acentric fragments cluster in close spatial proximity throughout mitosis for biased partitioning to a single daughter cell. Mechanistically, the CIP2A-TOPB1 complex prematurely associates with DNA lesions within ruptured micronuclei during interphase, which poises chromosome fragments for clustering upon mitotic entry. Inactivation of CIP2A or TOPBP1 caused pulverized chromosomes to untether and disperse throughout the mitotic cell, consequently resulting in the mis-accumulation of DNA fragments in the cytoplasm. The inheritance of shattered chromosomes by a single daughter cell suggests that micronucleation can drive complex rearrangements that lack the DNA copy number oscillations characteristic of canonical chromothripsis. Comprehensive analysis of pan-cancer whole-genome sequencing data revealed clusters of DNA copy number-neutral rearrangements – termed balanced chromothripsis – across diverse cancer types resulting in the acquisition of known driver events. Thus, distinct patterns of chromothripsis can be explained by the spatial mitotic clustering of pulverized chromosomes from micronuclei.

9 -, plasma, urine 389 Adriamycin 440 Advanced glycation end product 260 AGXT gene 485 Albumin 131 Alpha smooth muscle actin 410 Aluminum intoxication 274 Anaemia 23 Angiofollicular lymph node hyperplasia 323 Angiotensin 73, 302 Anionic site 88 Antibodies 278 Anticardiolipin 278 Anti-CD8 monoclonal antibody 310 Anti-idiotype antibodies 464 Antioxidant(s) 207, 296 -potential 207 Anti-Thy-1 antibody 433 -monoclonal antibody 453 -nephritis 453 Antithymocyte-induced glomerulonephritis 195