(145a) Influence of Nucelar Stiffness On Cell Migration

Nucleus is the largest organelle in cell, and therefore considered to be the biggest obstacle for cell migration in constrained tissue. The stiffness of cell nucleus is largely determined by filamentous protein network located at inner nuclear membrane called nuclear lamina, which is mainly composed of lamin proteins. Lamins, which are type V intermediate filament proteins, can be divided into two subtypes namely A-type and B-type lamins. Unlike ubiquitously expressed B-type, A-type lamins are found in most of differentiated cells with involvement in chromatin organization, transcription, translation, cell differentiation and many other functions. The purpose of this study is to investigate a correlation between cancer cell migration in physically constrained environment and the expression of lamin A and C proteins (lamin A/C), motivated by the fact that many types of cancer cell are known to have lower expression of lamin A/C compared to their healthy conterpart. 

Lamin A/C expression was manipulated by the use of short interfering RNA (siRNA) in human lung carcinoma cell A549. The effect of lamin A/C knockdown on nuclear stiffness was investigated by micropipette aspiration. The migration capacity of the lamin A/C knockdown A549 cells were evaluated in 2- and 3-dimentional environment by wound scratch healing assay and trans-well migration assay, respectively. Furthermore, lamin A/C down-regulated A549 cells were injected in subcutaneous tissue on one side of flank site of the immuno-deficient mouse, along with scrambled siRNA-treated control cells on the other side, in order to monitor the effect of Lamin A/C knockdown on tumor propagation in vivo.

Micropipette aspiration measurement showed more than 2-fold increase in softness of the nucleus after treatment with siRNA against lamin A/C. Lamin A/C knockdown only affected 3-D migration of the cells, not 2-D, where modification in nuclear shape is not involved in the process. These in vitro results strongly supports the in vivo observation, which showed that tumors formed by lamin A/C siRNA-treated A549 cells propagated in higher rate compared with control tumors (scrambled siRNA-treated or cells without any treatment).

In conclusion, the present study showed nuclear softening caused by knockdown of nuclear protein lamin A/C increased the cell migration capacity of A549 cells in vitro and also more effectively promoted the tumor proliferation in subcutaneous xenograft model due to more rapid expansion of the tumor. This result may explain the alleged lower lamin A/C expression or softer nuclei of cancer cells and their capability to efficiently migrate in the tissue, which ultimately leads to the metastasis to other part of the body.