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Cellular and Molecular Bioengineering

Cellular and Molecular Bioengineering - Poster Session E

Poster V5 - Lipid droplet impacts on cancer cell growth and chromosomal instability

Saturday, October 26, 2024

10:00 AM – 11:00 AM EST

Location: Exhibit Hall E, F & G

Presenting Author(s)

Joanna Georgiou (she/her/hers)

PhD student
University of Pennsylvania, United States

Co-Author(s)

II

Irena Ivanovska (she/her/hers)

Senior Research Scientist
University of Pennsylvania
Philadelphia, Pennsylvania, United States
MT

Michael Tobin

Postdoc
University of Pennsylvania, United States
AA

Alişya Anlaş, PhD

Postdoctoral Researcher
University of Pennsylvania
Philadelphia, Pennsylvania, United States

Primary Investigator(s)

Dennis Discher, PhD

Robert D. Bent Professor, Director Phys Sci Onc Ctr/Proj
Biophysical Eng'g Labs, University of Pennsylvania
Philadelphia, Pennsylvania, United States

Introduction: Lipid droplets accumulate in a variety of cancer cell types (Cruz et al, 2020). They are primarily composed of a hydrophobic triacylglycerol and sterol ester core, with an outer monolayer of phospholipids and proteins (Jarc et al, 2019) that stabilizes them in the aqueous cytoplasm. Lipid droplets tend to load in a perinuclear fashion, and previous work has shown that their high interfacial tension makes them sufficiently rigid to displace and deform the cytoskeleton and even cause nuclear envelope rupture (Ivanovska et al, 2023). Nuclear envelope rupture is associated with the loss of DNA repair factors and increased DNA damage, which could lead to mis-repair and genetic changes that select for cancer progression. In this work, we evaluate the loading of different types of lipids (oleic acid, cholesterol) in different cancer cell types (U2OS osteosarcoma, A549 lung adenocarcinoma, and MCF7 breast cancer cells) to assess the possible impacts on cell cycle and genomic instability.

Materials and

Methods: To evaluate the loading of lipids in different cancer cell types, U2OS osteosarcoma, A549 lung adenocarcinoma, and MCF7 breast cancer cells, oleic acid and cholesterol (separately and as a mixture) were incubated in the cell media for a set number of days with and without the general lipid stain, Bodipy. The cells were then fixed and their DNA was stained. Cells were imaged using fluorescent microscopy and analyzed in ImageJ for lipid uptake. To evaluate heritable genetic changes, we used a recently developed chromosome reporter (ChReporter) system, in which each cell line was engineered to express GFP or RFP on one allele of the constitutive Lamin-B1 gene on chromosome 5. The losses and gains of GFP/RFP signal in small colonies were quantified together with the rates of mitosis, micronucleus formation, and number of cell divisions.

Results, Conclusions, and Discussions: Lipid droplet (LD) formation increased versus time of incubation with the exogenous lipids as expected. Consistent with recently observed cell cycle delays for U2OS cells loaded with LDs (Ivanovska et al, 2023), LDs suppress the number of cell divisions. Colonies of cells that lost or gained GFP/RFP signal were clear for control and LD-loaded cultures of cancer cells as were micronuclei and mitotic events that are the likely basis for ongoing losses or gains. Consistent with slower overall growth, the median number of cells per colony exhibiting ChReporter loss was consistently lower in the LD group across time points. Nonetheless, the maximum colony sizes increased exponentially, with cell numbers of about 4, 8, 16, etc. proving consistent with expected doublings and thus indicating growth of genetically altered cells with minimal cell death. Our results support the idea that lipid droplets cause stress to cancer cells, leading to fewer divisions but just as many chromosome segregation errors per division and possibly more.

Acknowledgements (Optional):