Survival Pathways Are Differently Affected by Microgravity in Normal and Cancerous Breast Cells

Taking the 3Rs to a higher level: replacement and reduction of animal testing in life sciences in space research

Human settlements on the Moon, crewed missions to Mars and space tourism will become a reality in the next few decades. Human presence in space, especially for extended periods of time, will therefore steeply increase. However, despite more than 60 years of spaceflight, the mechanisms underlying the effects of the space environment on human physiology are still not fully understood. Animals, ranging in complexity from flies to monkeys, have played a pioneering role in understanding the (patho)physiological outcome of critical environmental factors in space, in particular altered gravity and cosmic radiation. The use of animals in biomedical research is increasingly being criticized because of ethical reasons and limited human relevance. Driven by the 3Rs concept, calling for replacement, reduction and refinement of animal experimentation, major efforts have been focused in the past decades on the development of alternative methods that fully bypass animal testing or so-called new approach methodologies. These new approach methodologies range from simple monolayer cultures of individual primary or stem cells all up to bioprinted 3D organoids and microfluidic chips that recapitulate the complex cellular architecture of organs. Other approaches applied in life sciences in space research contribute to the reduction of animal experimentation. These include methods to mimic space conditions on Earth, such as microgravity and radiation simulators, as well as tools to support the processing, analysis or application of testing results obtained in life sciences in space research, including systems biology, live-cell, high-content and real-time analysis, high-throughput analysis, artificial intelligence and digital twins. The present paper provides an in-depth overview of such methods to replace or reduce animal testing in life sciences in space research.

Recent studies of the effects of microgravity on cancer cells and the development of 3D multicellular cancer spheroids

The still young and developing space age, characterized by lunar and Martian exploration and the vision of extraterrestrial settlements, presents a unique environment to study the impact of microgravity (µg) on human physiology and disease development. Cancer research is currently a key focus of international space science, as µg fundamentally impacts cellular processes like differentiation, adhesion, migration, proliferation, survival, cell death, or growth of cancer cells as well as the cytoskeleton and the extracellular matrix (ECM). By creating three-dimensional (3D) tumor models in a µg-environment, like multicellular spheroids (MCS), researchers can expedite drug discovery and development, reducing the need for animal testing. This concise review analyses the latest knowledge on the influence of µg on cancer cells and MCS formation. We will focus on cells from brain tumors, lung, breast, thyroid, prostate, gastrointestinal, and skin cancer exposed to real (r-) and simulated (s-) µg-conditions.

Exploring the Idea of Human Reproduction in Space: A Potential Area for Future Research

As space travel evolves from brief missions to longer expeditions, and with the rise of space tourism, there is increasing interest in understanding how space travel affects human reproductive physiology and the feasibility of procreation in space. Space travel presents various potential hazards to reproductive health such as exposure to ionizing radiation, exposure to changes in gravity, psychological stress, and disruptions to the endocrine and urogenital systems, as well as the circadian rhythm. This article explores how cosmic radiation and microgravity impact both female and male gametogenesis, embryogenesis, and reproductive physiology.

Omics Studies of Specialized Cells and Stem Cells under Microgravity Conditions

The primary objective of omics in space with focus on the human organism is to characterize and quantify biological factors that alter structure, morphology, function, and dynamics of human cells exposed to microgravity. This review discusses exciting data regarding genomics, transcriptomics, epigenomics, metabolomics, and proteomics of human cells and individuals in space, as well as cells cultured under simulated microgravity. The NASA Twins Study significantly heightened interest in applying omics technologies and bioinformatics in space and terrestrial environments. Here, we present the available publications in this field with a focus on specialized cells and stem cells exposed to real and simulated microgravity conditions. We summarize current knowledge of the following topics: (i) omics studies on stem cells, (ii) omics studies on benign specialized different cell types of the human organism, (iii) discussing the advantages of this knowledge for space commercialization and exploration, and (iv) summarizing the emerging opportunities for translational regenerative medicine for space travelers and human patients on Earth.

Exploring the influence of microgravity on chemotherapeutic drug response in cancer: Unveiling new perspectives

Microgravity, an altered gravity condition prevailing in space, has been reported to have a profound impact on human health. Researchers are very keen to comprehensively investigate the impact of microgravity and its intricate involvement in inducing physiological changes. Evidenced transformations were observed in the internal architecture including cytoskeletal organization and cell membrane morphology. These alterations can significantly influence cellular function, signalling pathways and overall cellular behaviour. Further, microgravity has been reported to alter in the expression profile of genes and metabolic pathways related to cellular processes, signalling cascades and structural proteins in cancer cells contributing to the overall changes in the cellular architecture. To investigate the effect of microgravity on cellular and molecular levels numerous ground-based simulation systems employing both in vitro and in vivo models are used. Recently, researchers have explored the possibility of leveraging microgravity to potentially modulate cancer cells against chemotherapy. These findings hold promise for both understanding fundamental processes and could potentially lead to the development of more effective, personalized and innovative approaches in therapeutic advancements against cancer.

Omics Studies of Tumor Cells under Microgravity Conditions

Cancer is defined as a group of diseases characterized by abnormal cell growth, expansion, and progression with metastasis. Various signaling pathways are involved in its development. Malignant tumors exhibit a high morbidity and mortality. Cancer research increased our knowledge about some of the underlying mechanisms, but to this day, our understanding of this disease is unclear. High throughput omics technology and bioinformatics were successful in detecting some of the unknown cancer mechanisms. However, novel groundbreaking research and ideas are necessary. A stay in orbit causes biochemical and molecular biological changes in human cancer cells which are first, and above all, due to microgravity (µg). The µg-environment provides conditions that are not reachable on Earth, which allow researchers to focus on signaling pathways controlling cell growth and metastasis. Cancer research in space already demonstrated how cancer cell-exposure to µg influenced several biological processes being involved in cancer. This novel approach has the potential to fight cancer and to develop future cancer strategies. Space research has been shown to impact biological processes in cancer cells like proliferation, apoptosis, cell survival, adhesion, migration, the cytoskeleton, the extracellular matrix, focal adhesion, and growth factors, among others. This concise review focuses on publications related to genetic, transcriptional, epigenetic, proteomic, and metabolomic studies on tumor cells exposed to real space conditions or to simulated µg using simulation devices. We discuss all omics studies investigating different tumor cell types from the brain and hematological system, sarcomas, as well as thyroid, prostate, breast, gynecologic, gastrointestinal, and lung cancers, in order to gain new and innovative ideas for understanding the basic biology of cancer.

Heterotypic Cell Culture from Mouse Bone Marrow under Simulated Microgravity: Lessons for Stromal Lineage Functions

Muscle and skeleton structures are considered most susceptible to negative factors of spaceflights, namely microgravity. Three-dimensional clinorotation is a ground-based simulation of microgravity. It provides an opportunity to elucidate the effects of microgravity at the cellular level. The extracellular matrix (ECM) content, transcriptional profiles of genes encoding ECM and remodelling molecules, and secretory profiles were investigated in a heterotypic primary culture of bone marrow cells after 14 days of 3D clinorotation. Simulated microgravity negatively affected stromal lineage cells, responsible for bone tissue formation. This was evidenced by the reduced ECM volume and stromal cell numbers, including multipotent mesenchymal stromal cells (MSCs). ECM genes encoding proteins responsible for matrix stiffness and cell-ECM contacts were downregulated. In a heterotypic population of bone marrow cells, the upregulation of genes encoding ECM degrading molecules and the formation of a paracrine profile that can stimulate ECM degradation, may be mechanisms of osteodegenerative events that develop in real spaceflight.

Current Knowledge about the Impact of Microgravity on Gene Regulation

Microgravity (µg) has a massive impact on the health of space explorers. Microgravity changes the proliferation, differentiation, and growth of cells. As crewed spaceflights into deep space are being planned along with the commercialization of space travelling, researchers have focused on gene regulation in cells and organisms exposed to real (r-) and simulated (s-) µg. In particular, cancer and metastasis research benefits from the findings obtained under µg conditions. Gene regulation is a key factor in a cell or an organism’s ability to sustain life and respond to environmental changes. It is a universal process to control the amount, location, and timing in which genes are expressed. In this review, we provide an overview of µg-induced changes in the numerous mechanisms involved in gene regulation, including regulatory proteins, microRNAs, and the chemical modification of DNA. In particular, we discuss the current knowledge about the impact of microgravity on gene regulation in different types of bacteria, protists, fungi, animals, humans, and cells with a focus on the brain, eye, endothelium, immune system, cartilage, muscle, bone, and various cancers as well as recent findings in plants. Importantly, the obtained data clearly imply that µg experiments can support translational medicine on Earth.

Dexamethasone Selectively Inhibits Detachment of Metastatic Thyroid Cancer Cells during Random Positioning

We recently reported that synthetic glucocorticoid dexamethasone (DEX) is able to suppress metastasis-like spheroid formation in a culture of follicular thyroid cancer (FTC)-133 cells cultured under random positioning. We now show that this inhibition was selective for two metastatic thyroid carcinoma cells, FTC-133 and WRO, whereas benign Nthy-ori 3-1 thyrocytes and recurrent ML-1 follicular thyroid cancer cells were not affected by DEX. We then compare Nthy-ori 3-1 and FTC-133 cells concerning their adhesion and mechanosignaling. We demonstrate that DEX disrupts random positioning-triggered p38 stress signaling in FTC-133 cells, thereby antagonizing a variety of biological functions. Thus, DEX treatment of FTC-133 cells is associated with increased adhesiveness, which is mainly caused by the restored, pronounced formation of a normal number of tight junctions. Moreover, we show that Nthy-ori 3-1 and ML-1 cells upregulate the anti-adhesion protein mucin-1 during random positioning, presumably as a protection against mechanical stress. In summary, mechanical stress seems to be an important component in this metastasis model system that is processed differently by metastatic and healthy cells. The balance between adhesion, anti-adhesion and cell–cell connections enables detachment of adherent human cells on the random positioning machine—or not, allowing selective inhibition of thyroid in vitro metastasis by DEX.

Long-Term Simulation of Microgravity Induces Changes in Gene Expression in Breast Cancer Cells

Microgravity changes the gene expression pattern in various cell types. This study focuses on the breast cancer cell lines MCF-7 (less invasive) and MDA-MB-231 (triple-negative, highly invasive). The cells were cultured for 14 days under simulated microgravity (s-µg) conditions using a random positioning machine (RPM). We investigated cytoskeletal and extracellular matrix (ECM) factors as well as focal adhesion (FA) and the transmembrane proteins involved in different cellular signaling pathways (MAPK, PAM and VEGF). The mRNA expressions of 24 genes of interest (TUBB, ACTB, COL1A1, COL4A5, LAMA3, ITGB1, CD44, VEGF, FLK1, EGFR, SRC, FAK1, RAF1, AKT1, ERK1, MAPK14, MAP2K1, MTOR, RICTOR, VCL, PXN, CDKN1, CTNNA1 and CTNNB1) were determined by quantitative real-time PCR (qPCR) and studied using STRING interaction analysis. Histochemical staining was carried out to investigate the morphology of the adherent cells (ADs) and the multicellular spheroids (MCSs) after RPM exposure. To better understand this experimental model in the context of breast cancer patients, a weighted gene co-expression network analysis (WGCNA) was conducted to obtain the expression profiles of 35 breast cell lines from the HMS LINCS Database. The qPCR-verified genes were searched in the mammalian phenotype database and the human genome-wide association studies (GWAS) Catalog. The results demonstrated the positive association between the real metastatic microtumor environment and MCSs with respect to the extracellular matrix, cytoskeleton, morphology, different cellular signaling pathway key proteins and several other components. In summary, the microgravity-engineered three-dimensional MCS model can be utilized to study breast cancer cell behavior and to assess the therapeutic efficacies of drugs against breast cancer in the future.

Small tissue chips with big opportunities for space medicine

The spaceflight environment, including microgravity and radiation, may have considerable effects on the health and performance of astronauts, especially for long-duration and Martian missions. Conventional on-ground and in-space experimental approaches have been employed to investigate the comprehensive biological effects of the spaceflight environment. As a class of recently emerging bioengineered in vitro models, tissue chips are characterized by a small footprint, potential automation, and the recapitulation of tissue-level physiology, thus promising to help provide molecular and cellular insights into space medicine. Here, we briefly review the technical advantages of tissue chips and discuss specific on-chip physiological recapitulations. Several tissue chips have been launched into space, and more are poised to come through multi-agency collaborations, implying an increasingly important role of tissue chips in space medicine.

Extraterrestrial Gynecology: Could Spaceflight Increase the Risk of Developing Cancer in Female Astronauts? An Updated Review

Outer space is an extremely hostile environment for human life, with ionizing radiation from galactic cosmic rays and microgravity posing the most significant hazards to the health of astronauts. Spaceflight has also been shown to have an impact on established cancer hallmarks, possibly increasing carcinogenic risk. Terrestrially, women have a higher incidence of radiation-induced cancers, largely driven by lung, thyroid, breast, and ovarian cancers, and therefore, historically, they have been permitted to spend significantly less time in space than men. In the present review, we focus on the effects of microgravity and radiation on the female reproductive system, particularly gynecological cancer. The aim is to provide a summary of the research that has been carried out related to the risk of gynecological cancer, highlighting what further studies are needed to pave the way for safer exploration class missions, as well as postflight screening and management of women astronauts following long-duration spaceflight.

The Fight against Cancer by Microgravity: The Multicellular Spheroid as a Metastasis Model

Cancer is a disease exhibiting uncontrollable cell growth and spreading to other parts of the organism. It is a heavy, worldwide burden for mankind with high morbidity and mortality. Therefore, groundbreaking research and innovations are necessary. Research in space under microgravity (µg) conditions is a novel approach with the potential to fight cancer and develop future cancer therapies. Space travel is accompanied by adverse effects on our health, and there is a need to counteract these health problems. On the cellular level, studies have shown that real (r-) and simulated (s-) µg impact survival, apoptosis, proliferation, migration, and adhesion as well as the cytoskeleton, the extracellular matrix, focal adhesion, and growth factors in cancer cells. Moreover, the µg-environment induces in vitro 3D tumor models (multicellular spheroids and organoids) with a high potential for preclinical drug targeting, cancer drug development, and studying the processes of cancer progression and metastasis on a molecular level. This review focuses on the effects of r- and s-µg on different types of cells deriving from thyroid, breast, lung, skin, and prostate cancer, as well as tumors of the gastrointestinal tract. In addition, we summarize the current knowledge of the impact of µg on cancerous stem cells. The information demonstrates that µg has become an important new technology for increasing current knowledge of cancer biology.

Proteomic analysis of the effects of simulated microgravity in human gastric mucosal cells

Microgravity is an ecological factor that affects the environment of the body. In this study, quantitative isobaric labeling (tandem mass tag) method was used to study the changes in human gastric mucosal cells under simulated microgravity for the first time. Comparative proteomic analysis identified 394 (202 upregulated and 192 downregulated) and 542 (286 upregulated and 256 downregulated) proteins differentially regulated by simulated microgravity after 3 and 7 days, respectively. Then the identified proteins were subjected to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses for further exploration. The results of the analysis showed that the ribosomes of gastric mucosal cells were significantly impacted after exposure to simulated microgravity for 3 days, and the cells appeared to be in a state of stress and inflammation. Exposure to simulated microgravity for 7 days significantly affected the mitochondria of the cells, oxidative stress became more evident, while inflammation and weakened connections were observed in the cells. The results of this study highlighted the temporal response trend of gastric mucosal cells to the stressor of microgravity at the two time points of 3 and 7 days. These findings will provide insights into the development of methods to protect the gastric mucosa during space flight.

Latest knowledge about changes in the proteome in microgravity

INTRODUCTION

: A long-term stay of humans in space causes a large number of well-known health problems and changes in protists and plants. Deep space exploration will increase the time humans or rodents will spend in microgravity (µg). Moreover, they are exposed to cosmic radiation, hypodynamia, and isolation. OMICS investigations will increase our knowledge of the underlying mechanisms of µg-induced alterations in vivo and in vitro.

AREAS COVERED

: We summarize the findings over the recent 3 years on µg-induced changes in the proteome of protists, plants, rodent and human cells. Considering the thematic orientation of microgravity-related publications in that time frame, we focus on medicine-associated findings such as the µg-induced antibiotic resistance of bacteria, the myocardial consequences of µg-induced calpain activation and the role of MMP13 in osteoarthritis. All these point to the fact that µg is an extreme stressor that could not be evolutionarily addressed on Earth.

EXPERT COMMENTARY

: In conclusion, when interpreting µg-experiments, the direct, mostly unspecific stress response, must be distinguished from specific µg-effects. For this reason, recent studies often do not consider single protein findings but place them in the context of protein-protein interactions. This enables an estimation of functional relationships, especially if these are supported by epigenetic and transcriptional data (multi-omics).

Cancer Studies under Space Conditions: Finding Answers Abroad

In this review article, we discuss the current state of knowledge in cancer research under real and simulated microgravity conditions and point out further research directions in this field. Outer space is an extremely hostile environment for human life, with radiation, microgravity, and vacuum posing significant hazards. Although the risk for cancer in astronauts is not clear, microgravity plays a thought-provoking role in the carcinogenesis of normal and cancer cells, causing such effects as multicellular spheroid formation, cytoskeleton rearrangement, alteration of gene expression and protein synthesis, and apoptosis. Furthermore, deleterious effects of radiation on cells seem to be accentuated under microgravity. Ground-based facilities have been used to study microgravity effects in addition to laborious experiments during parabolic flights or on space stations. Some potential 'gravisensors' have already been detected, and further identification of these mechanisms of mechanosensitivity could open up ways for therapeutic influence on cancer growth and apoptosis. These novel findings may help to find new effective cancer treatments and to provide health protection for humans on future long-term spaceflights and exploration of outer space.

Microgravity Effects on the Matrisome

Gravity is fundamental factor determining all processes of development and vital activity on Earth. During evolution, a complex mechanism of response to gravity alterations was formed in multicellular organisms. It includes the "gravisensors" in extracellular and intracellular spaces. Inside the cells, the cytoskeleton molecules are the principal gravity-sensitive structures, and outside the cells these are extracellular matrix (ECM) components. The cooperation between the intracellular and extracellular compartments is implemented through specialized protein structures, integrins. The gravity-sensitive complex is a kind of molecular hub that coordinates the functions of various tissues and organs in the gravitational environment. The functioning of this system is of particular importance under extremal conditions, such as spaceflight microgravity. This review covers the current understanding of ECM and associated molecules as the matrisome, the features of the above components in connective tissues, and the role of the latter in the cell and tissue responses to the gravity alterations. Special attention is paid to contemporary methodological approaches to the matrisome composition analysis under real space flights and ground-based simulation of its effects on Earth.

The CellBox-2 Mission to the International Space Station: Thyroid Cancer Cells in Space

A spaceflight to the International Space Station (ISS) is a dream of many researchers. We had the chance to investigate the effect of real microgravity (CellBox-2 Space mission) on the transcriptome and proteome of FTC-133 human follicular thyroid cancer cells (TCC). The cells had been sent to the ISS by a Falcon 9 rocket of SpaceX CRS-13 from Cape Canaveral (United States) and cultured in six automated hardware units on the ISS before they were fixed and returned to Earth. Multicellular spheroids (MCS) were detectable in all spaceflight hardware units. The VCL, PXN, ITGB1, RELA, ERK1 and ERK2 mRNA levels were significantly downregulated after 5 days in space in adherently growing cells (AD) and MCS compared with ground controls (1g), whereas the MIK67 and SRC mRNA levels were both suppressed in MCS. By contrast, the ICAM1, COL1A1 and IL6 mRNA levels were significantly upregulated in AD cells compared with 1g and MCS. The protein secretion measured by multianalyte profiling technology and enzyme-linked immunosorbent assay (AngiogenesisMAP^®, extracellular matrix proteins) was not significantly altered, with the exception of elevated angiopoietin 2. TCC in space formed MCS, and the response to microgravity was mainly anti-proliferative. We identified ERK/RELA as a major microgravity regulatory pathway.

Alterations of Growth and Focal Adhesion Molecules in Human Breast Cancer Cells Exposed to the Random Positioning Machine

In this study, we evaluated changes in focal adhesions (FAs) in two types of breast cancer cell (BCC) lines (differentiated MCF-7 and the triple-negative MDA-MB-231 cell line) exposed to simulated microgravity (s-μg) created by a random positioning machine (RPM) for 24 h. After exposure, the BCC changed their growth behavior and exhibited two phenotypes in RPM samples: one portion of the cells grew as a normal two-dimensional monolayer [adherent (AD) BCC], while the other portion formed three-dimensional (3D) multicellular spheroids (MCS). After 1 h and 30 min (MDA-MB-231) and 1 h 40 min (MCF-7), the MCS adhered completely to the slide flask bottom. After 2 h, MDA-MB-231 MCS cells started to migrate, and after 6 h, a large number of the cells had left the MCS and continued to grow in a scattered pattern, whereas MCF-7 cells were growing as a confluent monolayer after 6 h and 24 h. We investigated the genes associated with the cytoskeleton, the extracellular matrix and FAs. ACTB, TUBB, FN1, FAK1, and PXN gene expression patterns were not significantly changed in MDA-MB-231 cells, but we observed a down-regulation of LAMA3, ITGB1 mRNAs in AD cells and of ITGB1, TLN1 and VCL mRNAs in MDA-MB-231 MCS. RPM-exposed MCF-7 cells revealed a down-regulation in the gene expression of FAK1, PXN, TLN1, VCL and CDH1 in AD cells and PXN, TLN and CDH1 in MCS. An interaction analysis of the examined genes involved in 3D growth and adhesion indicated a central role of fibronectin, vinculin, and E-cadherin. Live cell imaging of eGFP-vinculin in MCF-7 cells confirmed these findings. β-catenin-transfected MCF-7 cells revealed a nuclear expression in 1g and RPM-AD cells. The target genes BCL9, MYC and JUN of the Wnt/β-catenin signaling pathway were differentially expressed in RPM-exposed MCF-7 cells. These findings suggest that vinculin and β-catenin are key mediators of BCC to form MCS during 24 h of RPM-exposure.

Simulated Microgravity Effects on Human Adenocarcinoma Alveolar Epithelial Cells: Characterization of Morphological, Functional, and Epigenetic Parameters

Background: In space, the reduction or loss of the gravity vector greatly affects the interaction between cells. Since the beginning of the space age, microgravity has been identified as an informative tool in biomedicine, including cancer research. The A549 cell line is a hypotriploid human alveolar basal epithelial cell line widely used as a model for lung adenocarcinoma. Microgravity has been reported to interfere with mitochondrial activity, energy metabolism, cell vitality and proliferation, chemosensitivity, invasion and morphology of cells and organelles in various biological systems. Concerning lung cancer, several studies have reported the ability of microgravity to modulate the carcinogenic and metastatic process. To investigate these processes, A549 cells were exposed to simulated microgravity (µG) for different time points. Methods: We performed cell cycle and proliferation assays, ultrastructural analysis of mitochondria architecture, as well as a global analysis of miRNA modulated under µG conditions. Results: The exposure of A549 cells to microgravity is accompanied by the generation of polynucleated cells, cell cycle imbalance, growth inhibition, and gross morphological abnormalities, the most evident are highly damaged mitochondria. Global miRNA analysis defined a pool of miRNAs associated with µG solicitation mainly involved in cell cycle regulation, apoptosis, and stress response. To our knowledge, this is the first global miRNA analysis of A549 exposed to microgravity reported. Despite these results, it is not possible to draw any conclusion concerning the ability of µG to interfere with the cancerogenic or the metastatic processes in A549 cells. Conclusions: Our results provide evidence that mitochondria are strongly sensitive to µG. We suggest that mitochondria damage might in turn trigger miRNA modulation related to cell cycle imbalance.