COMPARING THE MECHANICAL PROPERTIES OF CLL B-CELLS WITH HEALTHY B-CELLS USING ATOMIC FORCE MICROSCOPY

Oren Pinshow ^1,4 Daniel Rosenblum ¹ Artium Khatchtouriants ¹ Osnat Bairey ² Pia Raanani ² Ohad Binyamini ³ Arnon Nagler ³ Inbal Hazan-Halevy ¹ Dan Peer ^1,4

¹Cell Research and Immunology Department, Nanocenter for Nanoscience and Nanotechnology, Tel Aviv University, Tel Aviv
²Institute of Hematology, Rabin Medical Center, Beilinson Hospital, Petah Tikva
³Division of Hematology, Chaim Sheba Medical Center, Tel Hashomer
⁴The Department of Materials Science and Engineering, The Faculty of Engineering, Tel Aviv University, Tel Aviv

Chronic lymphocytic leukemia (CLL), the most common leukemia in Western countries, is characterized by the clonal proliferation and accumulation of B-cells lymphocytes in the blood, bone marrow, lymph nodes, and spleen. CLL cells resemble normal lymphocytes under the microscope; however some cells are fragile when smeared onto a glass slide, giving rise to many broken cells, which are called "smudge" cells. The appearance of smudge cells suggests that the mechanical properties of malignant B-CLL cells are altered. Investigation of changes in cell membrane mechanical properties can provide better understanding of biophysical changes in leukemia cells, such as deformability, spreading of the cells, and interaction with microenvironment.

Atomic force microscopy (AFM) has become an important tool for quantifying mechanical properties of various biological materials. The aim of this research is to characterize the mechanical properties of malignant B-CLL cells in comparison with healthy B-cells using the AFM instrument.

A ficoll gradient and negative selection of B-cells were used to isolate B-cells from blood samples. AFM was used to measure the Young modulus of a single cell trapped in micro wells made by lithography.

For the healthy B-cells, we measured 50±16 Pa for the cell surface and 188±60 Pa for internal cell components (n = 40). The Young modulus for the B-CLL was 85±39 Pa for the cell surface, and 329±159 for the internal cell components (n=31).

Our results demonstrate that malignant B-CLL cells have lower Young modulus than healthy B-cells for both the cell surface and internal components. This may indicate a lower elasticity of malignant cells, and provide insight on the dynamics of B-CLL smearing.