Chemical Analysis of Morphological Changes in Lysophosphatidic Acid-Treated Ovarian Cancer Cells

Karen A Bailey,Zachary D Schultz,M Sharon Stack,Yuliya Klymenko,Peter E Feist,Amanda B Hummon

doi:10.1038/s41598-017-15547-7

Karen A Bailey, Zachary D Schultz + Show 4 more

Open Access

https://doi.org/10.1038/s41598-017-15547-7

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Abstract

Ovarian cancer (OvCa) cells are reported to undergo biochemical changes at the cell surface in response to treatment with lysophosphatidic acid (LPA). Here we use scanning electron microscopy (SEM) and multiplex coherent anti-Stokes Raman scattering (CARS) imaging via supercontinuum excitation to probe morphological changes that result from LPA treatment. SEM images show distinct shedding of microvilli-like features upon treatment with LPA. Analysis of multiplex CARS images can distinguish between molecular components, such as lipids and proteins. Our results indicate that OvCa429 and SKOV3ip epithelial ovarian cancer cells undergo similar morphological and chemical responses to treatment with LPA. The microvilli-like structures on the surface of multicellular aggregates (MCAs) are removed by treatment with LPA. The CARS analysis shows a distinct decrease in protein and increase in lipid composition on the surface of LPA-treated cells. Importantly, the CARS signals from cellular sheddings from MCAs with LPA treatment are consistent with cleavage of proteins originally present. Mass spectrometry on the cellular sheddings show that a large number of proteins, both membrane and intracellular, are present. An increased number of peptides are detected for the mesenchymal cell line relative to the epithelial cell indicating a differential response to LPA treatment with cancer progression.

Highlights

Coherent anti-Stokes Raman scattering (CARS) is a powerful tool for biomedical analysis that provides label-free morphological and chemical contrast with video-rate imaging comparable to fluorescence microscopy without the use of exogenous agents[14,15,16,17]
We utilize the combination of scanning electron microscopy (SEM), multiplex coherent anti-Stokes Raman scattering imaging, and mass spectrometry to investigate the biochemical signals associated with morphology changes on the surface of two distinct ovarian cancer lines resulting from treatment with lysophosphatidic acid (LPA)
For epithelial ovarian cancer cells, there is an abundance of microvilli that appear as dense microscopic protrusions on the cell surface[37,38,39]

Summary

Introduction

Coherent anti-Stokes Raman scattering (CARS) is a powerful tool for biomedical analysis that provides label-free morphological and chemical contrast with video-rate imaging comparable to fluorescence microscopy without the use of exogenous agents[14,15,16,17]. By plotting the CARS intensity as a function of coordinate, a high contrast image generally outlines the lipid membrane, fatty acids, and nucleus of the cells in a given tissue sample. This property has been helpful in diagnosing a variety of carcinomas originating from lung, breast, skin, brain, and prostate cancer[18,19,20,21,22,23,24]. The reconstructed multiplex CARS spectrum from the high spectral resolution image has the ability to distinguish between lipids and proteins for clinical diagnostics[32]. We utilize the combination of scanning electron microscopy (SEM), multiplex coherent anti-Stokes Raman scattering imaging, and mass spectrometry to investigate the biochemical signals associated with morphology changes on the surface of two distinct ovarian cancer lines resulting from treatment with LPA

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