Nuclear envelope rupture and repair during cancer cell migration

Abstract

During cancer metastasis, tumor cells penetrate tissues through tight interstitial spaces, requiring extensive deformation of the cell and its nucleus. Here, we investigated tumor cell migration in confining microenvironments in vitro and in vivo. Nuclear deformation caused localized loss of nuclear envelope (NE) integrity, which led to the uncontrolled exchange of nucleo-cytoplasmic content, herniation of chromatin across the NE, and DNA damage. The incidence of NE rupture increased with cell confinement and with depletion of nuclear lamins, NE proteins that structurally support the nucleus. Cells restored NE integrity using components of the endosomal sorting complexes required for transport-III (ESCRT-III) machinery. Our findings indicate that cell migration incurs substantial physical stress on the NE and its content, requiring efficient NE and DNA damage repair for survival.

A Chemomechanical Model for Nuclear Morphology and Stresses during Cell Transendothelial Migration

“…Cells migrate along a chemotactic gradient, and nuclear deformation is observed by time-lapse imaging of fluorescently labeled histones. As decribed previously, NE rupture was detected by monitoring the transient escape of green fluorescent protein (GFP) fused with a nuclear localization signal (NLS-GFP) from the nucleus into the cytoplasm and fluorescently labeled cytoplasmic DNA-binding protein (cGAS-RFP) that accumulates at newly exposed genomic DNA was used to monitor the sites of NE rupture (13). Cells were generated by stable expression of fluorescent reporter proteins, i.e., NLS-GFP and cGAS-RFP, by lentiviral transduction.…”

“…Recently it has been shown that rupture of the NE during cell migration through rigid constrictions can potentially lead to herniation of chromatin across the NE and breaking of DNA double strands (12,13). The rupture and blebs are often found at defective sites in the NE where the nuclear lamina signal was weak or absent (13).…”

“…On the other hand, since the nucleus houses the genetic machinery of the cell, changes in the nuclear morphology and positioning within the cytoplasm during migration can influence the phenotypic profile of the cell (5,11). For instance, it has been recently shown that in addition to the ability of cells to dramatically squeeze their nuclei to pass through small constrictions, cells utilize components of the endosomal sorting complexes required for transport (ESCRT) machinery to repair the concomitant damage to their nuclear envelope (NE) and DNA that occur during confined migration (12,13).…”

Chromatin Is Stretched but Intact When the Nucleus Is Squeezed through Constrictions

“…Such movements also occur during cancer metastasis when tumor cells crawl through tight spaces possibly resulting in severe distortion of the cell nucleus (1). For these reasons a number of studies have focused on elucidating the mechanical properties of the nucleus, which is possibly the stiffest organelle in the cell.…”

“…A few that come to mind are: (1) What is the mechanism underlying the maintenance of integrity of stretched DNA even on timescales of minutes? (2) Can one go beyond the scaling picture to describe the consequences of crowding in a deformed nucleus?…”