Abstract 226: Parallel microfiltration (PMF): A novel method to screen cell mechanotype
Authors: Wiedemeyer Wolf-Ruprecht , Qi Dongping , Gill Navjot Kaur , Santiskulvong Chintda , Dorigo Oliver , Rao JianYu , Taylor-Harding Barbie , Rowat Amy C. 
Published: August 2015

The mechanical phenotype of cells (mechanotype) is emerging as a valuable label-free biomarker. Cells are visco-elastic materials whose mechanotype is altered in diseases from malaria to cancer. For example, marked changes in the viscoelastic characteristics of cells occur during malignant transformation and in response to chemotherapy treatment. Malignant cells across different types of cancers are consistently softer than benign cells, exhibiting a Young's modulus that is ∼60-70% lower both in vitro and in situ. Cell mechanotype also grades metastatic potential: highly invasive human ovarian carcinoma cells are five-fold more deformable (softer) than less invasive cells. Further, chemotherapeutic drugs can alter mechanotype: human leukemia cells exhibit a nearly two orders of magnitude increase in cell elastic modulus after being treated with dexamethasone and daunorubicin. These published studies suggest the potential of cell mechanotype as a biomarker in cancer prognosis and for identifying effective drug treatments. However, in order to exploit cell mechanical properties for fundamental research and clinical applications a simple and scalable method to measure cell mechanotype is required.

Here we describe a parallel microfiltration (PMF) assay, which enables the mechanotype of multiple samples to be simultaneously measured by driving cell suspensions through porous membranes using uniform air pressure. The relative deformability of a cell sample is quantified by the fraction of sample retained above the porous membrane. Based on experimental results and theoretical considerations, we have developed a model that provides a physical explanation of PMF and allows us to relate our experimental data to cell deformability.

We employed PMF to study changes in mechanotype in ovarian carcinoma cells. We show that epithelial-to-mesenchymal transition (EMT), a process associated with cancer progression and drug resistance, yields softer cells: OVCA433 cells engineered to overexpress key EMT inducers (Snail, Slug, or Zeb) had much lower retention rates than their epithelial precursors. Similarly, cisplatin-resistant ovarian cancer cell lines (OVCAR5-cisR, SKOV3-cisR) exhibiting features of EMT, such as loss of E-cadherin expression and induction of vimentin, were more deformable than cisplatin-sensitive controls. We also compared normal p53-/- murine ovarian surface epithelial (MOSE) cells with HRasV12-transformed MOSE cells, which lose E-cadherin. PMF confirmed dramatically lower retention rates for the transformed cells relative to normal precursors. We conclude that EMT results in increased cell deformability and that PMF is a robust tool to identify changes in deformability.

In summary, we have developed a novel method to assess cell mechanotype that is compatible with high-throughput screening approaches and can complement and enhance existing technology for evaluating cancer cell phenotype and response to drugs.

Citation Format: Wolf-Ruprecht Wiedemeyer, Dongping Qi, Navjot Kaur Gill, Chintda Santiskulvong, Oliver Dorigo, JianYu Rao, Barbie Taylor-Harding, Amy C. Rowat. Parallel microfiltration (PMF): A novel method to screen cell mechanotype. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 226. doi:10.1158/1538-7445.AM2015-226