Cytokine-induced immune cell migration towards tumour cells in a microchip environment
Abstract: The purpose of this project was to study the migration patterns of human immune cells in response to human renal cancer cells. This is useful in the study of different cancer treatments and the body’s own response to cancer. Cancer cells can release cytokines which can be detected by immune cells with the correct receptors. The specific type of immune cell that was studied, was the type of lymphocyte called Natural killer cell, abbreviated to NK cell. These lymphocytes have the characteristics that they can differentiate between a cancer cell and a healthy cell, and then have the capability to kill the cancer cell by different means. On the surface of cells there exist receptors. These receptors can interact with signal molecules in the environment near the cell. In this study the effect on the migration caused by the interaction between the receptor CXCR2 and the chemokine CXCL2 have been studied. This was done by transfecting some NK-92 cells with the receptor CXCR2 and the rest with the receptor NGFR then subjecting them to a CXCL2 chemokine gradient. This gradient originated from human renal cancer cells known to produce this chemokine. The specific cancer cells used was the human renal cancer cell line 786-0 which NK-92 cells are known to have the ability to kill when coming in contact with them. It is because of this trait it is of interest to study if the average movement is altered significantly by this receptor induced movement compared to the control NK-92 NGFR. To determine if a significant difference in preferred direction of migration could be discerned between the NK cells expressing either the receptor CXCR2 or NGFR, two analytic methods were devised and applied. The first method was a visualization of the cell migration in the direction of the chemokine gradient, this analyze had no quantitative properties but served as way to determine a general migration. The second, and more precise method involved 3D cell identification, cell tracing, and quantifying the migration. This method yielded quantifiable results that could be analyzed further. A biocompatible microchip with a small passage was utilized to study the migration of the NK cells subjected to this chemokine gradient. Two different approaches to this problem were made. The first approach was to seed the cells onto the chip in a fluid and observe the migration of the sedimented cells the two dimensional surface the glass bottom of the chip constituted. After several attempts with the fluid approach the conclusion was made that because the NK-92 cells aren’t adherent, fluid flows were found to be the main cause for the most of the NK-92 cells movement. A few attempts were made to stop the fluid from flowing over the passage by utilizing a plug placed in the center of the passage during the seeding of the cells and removed before the experiment, but this was without success. Since this flow made all unassisted migration by the cells impossible, no useful data could be obtained from this method. This introduces the second approach which was to suspended the cells in collagen. In these experiment no apparent movement by the NK-92 cells was observed that could originate from fluid movement but did instead seem to be unassisted cell migration. It was found that in an open fluidic environment, fluidic phenomena preponderated the cells own migration, and in the collagen environment the cell migration was to small to yield any obvious results. The analytic methods devised to trace cells and measure the cell migration worked well and gave quantifiable results. In the 3D experiments these methods were able to trace the NK cells and study the migration of the cells with different receptors.
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