Real Microgravity Influences the Cytoskeleton and Focal Adhesions in Human Breast Cancer Cells

Abstract

With the increasing number of spaceflights, it is crucial to understand the changes occurring in human cells exposed to real microgravity (r-µg) conditions. We tested the effect of r-µg on MCF-7 breast cancer cells with the objective to investigate cytoskeletal alterations and early changes in the gene expression of factors belonging to the cytoskeleton, extracellular matrix, focal adhesion, and cytokines. In the Technische Experimente unter Schwerelosigkeit (TEXUS) 54 rocket mission, we had the opportunity to conduct our experiment during 6 min of r-µg and focused on cytoskeletal alterations of MCF-7 breast cancer cells expressing the Lifeact-GFP marker protein for the visualization of F-actin as well as the mCherry-tubulin fusion protein using the Fluorescence Microscopy Analysis System (FLUMIAS) for fast live-cell imaging under r-µg. Moreover, in a second mission we investigated changes in RNA transcription and morphology in breast cancer cells exposed to parabolic flight (PF) maneuvers (31st Deutsches Zentrum für Luft- und Raumfahrt (DLR) PF campaign). The MCF-7 cells showed a rearrangement of the F-actin and tubulin with holes, accumulations in the tubulin network, and the appearance of filopodia- and lamellipodia-like structures in the F-actin cytoskeleton shortly after the beginning of the r-µg period. PF maneuvers induced an early up-regulation of KRT8, RDX, TIMP1, CXCL8 mRNAs, and a down-regulation of VCL after the first parabola. E-cadherin protein was significantly reduced and is involved in cell adhesion processes, and plays a significant role in tumorigenesis. Changes in the E-cadherin protein synthesis can lead to tumor progression. Pathway analyses indicate that VCL protein has an activating effect on CDH1. In conclusion, live-cell imaging visualized similar changes as those occurring in thyroid cancer cells in r-µg. This result indicates the presence of a common mechanism of gravity perception and sensation.

Modeling the Impact of Microgravity at the Cellular Level: Implications for Human Disease

“…Many studies have reported that microgravity exposure had decreased expression of actin and actin-associated proteins, namely Arp2/3 and RhoA, subsequently resulting in the disorganization of the actin cytoskeleton (Carlsson et al, 2003;Higashibata et al, 2006;Corydon et al, 2016a,b;Louis et al, 2017;Tan et al, 2018). However, other studies have showed increased F-actin and stress fiber formation that accompanied the development of lamellipodia protrusions following exposure to microgravity (Gruener et al, 1994;Nassef et al, 2019). Contrary to this, Rosner et al (2006) reported no changes to actin structure or organization and further suggested that the actin cytoskeleton is only regulated in a hyper-gravity environment.…”

Changes in the Surface Expression of Intercellular Adhesion Molecule 3, the Induction of Apoptosis, and the Inhibition of Cell-Cycle Progression of Human Multidrug-Resistant Jurkat/A4 Cells Exposed to a Random Positioning Machine

“…Short-term microgravity led to an increased synthesis of ICAM-1 and VCAM-1 proteins in MDA-MB-231 breast cancer cells during a parabolic flight campaign [31]. Modulation of the expression of surface adhesion molecules such as ICAM-1 has been reported as a consequence of long-term microgravity of cultured human endothelial cells [38,39].…”

“…Some researchers have reported that microgravity exposure changes the morphological phenotype, cell cycle, and cell adhesion, and has an impact on cell survival that is highly dependent upon the cell type, as well as on the duration of exposure [30,31]. Long-term RPM exposure of human endothelial cells induced the formation of three-dimensional tubular structures and spheroids [32].…”

Alteration of calcium signalling in cardiomyocyte induced by simulated microgravity and hypergravity

“…In vitro studies have demonstrated that space flight and simulated microgravity induce significant changes in gene expression patterns, autophagy, cell migration, extracellular matrix composition and the cytoskeleton . The clinostat is widely used for space biology research, as it can simulate the effect of microgravity on cells .…”