Discovery And Mechanistic Study About Inhibition Effect Of Static Magnetic Field On Cancer Cell Proliferation

With the development and popularization of modern electric appliances and the wide application of MRI equipments in hospitals,the potential impact of magnetic field on human health has attracted more attention.Although there are preliminary studies about the effects of magnetic fields on cells,there is no systematic analysis about the relationship between the various parameters of the magnetic field and the differences of the cells.In addition,compared with time-varying magnetic field,the variable of static magnetic field is less,which is more conducive to study the cell and molecular mechanism of magnetic field on organism.Therefore,it is more advantageous to study the biological effect of static magnetic field.By means of 9 T superconducting magnet and 27 T water-cooled magnet in High Magnetic Field Laboratory,Chinese Academy of Sciences,we investigated the effects of static magnetic fields on the proliferation of tumor cells and the molecular mechanism,namely the moderate and strong static magnetic fields directly affect EGFR kinase domain orientation to inhibit cancer cell proliferation,and the ultra-high static magnetic field changes orientation and morphology of mitotic spindles in human cells.1.Moderate static magnetic fields could inhibit the cancer cells proliferation by affecting EGFR kinase activity,which is related with cell type and cell density.EGFR(Epidermal Growth Factor Receptor,170 kDa)is a kind of transmembrane glycoprotein receptor tyrosine kinase belonging to the ErbB/HER family,which is activated by EGF and affects the growth and differentiation of the cells.EGFR is widely distributed in many kinds of normal and cancer cells,and the occurrence and development of many tumors are accompanied by the over-expression and self-activation of EGFR.Therefore,it is also an important target of many anticancer drugs.Currently,some researches have shown that both the power frequency magnetic field and the pulsed magnetic field can affect the activity of EGFR and its downstream signaling pathways,but whether the static magnetic field will affect EGFR is not clear.Firstly,we took use of purified EGFR protein kinase domain to do phosphorylation experiments in vitro under different intensity magnetic fields(0,0.005 T,0.05 T,0.1 T,0.7 T,1 T)and found that the phosphorylation level would decrease with the increase of magnetic field intensity,indicating that the static magnetic field can directly inhibit EGFR kinase activity in vitro.In order to intuitively understand the changes of EGFR kinase domain molecules in the static magnetic field,we not only used advanced liquid phase scanning tunneling microscope(L-STM)to get the high resolution single molecule image,but also observed that the change of molecular orientation in static magnetic field.And this change affects the interaction between EGFR protein monomers and then affects its activity.Using the molecular dynamics simulation,we found that in the 1-9 T static magnetic field,the proportion of EGFR molecules parallel to the magnetic field direction increased with the increase of field strength.In the cell experiment,we found that the static magnetic field could inhibit the proliferation of human nasopharyngeal carcinoma cell CNE-2Z and human colon cancer cell HCT116.In addition,we constructed the CHO-EGFR-Flag cell line that expressed EGFR,and found that the static magnetic field could inhibit the proliferation of CHO-EGFR-Flag cells,but did not affect the growth of CHO cells.Our findings confirmed that the static magnetic field can inhibit the proliferation of tumor cells by affecting the activity of EGFR protein.In addition,we also found that cell type-and density-dependent effect of 1 T static magnetic field on cell proliferation,and it is also related to EGFR-Akt-mTOR signaling pathway.2.27T ultra-high static magnetic field affects the mitotic spindles in human cells.Studies have shown that the main components of an organism,such as proteins and DNA,are magnetic,and magnetic fields can alter a variety of life processes by influencing the arrangement and assembly of large biological molecules.The important cytoskeletal protein microtubules in eukaryotic cells will be affected by the static magnetic field,which is involved in many important life processes,such as cell division,cell migration and so on.In vitro experiments showed that purified tubulin due to its magnetic anisotropy will be arranged along the magnetic field direction in static magnetic fields.However,whether the mitotic spindles composed of microtubules in static magnetic field will change has not been reported yet,especially the effect of ultra high static magnetic field higher than 20 T on mammalian cells is.unknown.We set up the first cell culture device suitable for 27 T water cooled magnet in China,and used 27 T static magnetic field to treat human nasopharyngeal carcinoma cell CNE-2Z and human retinal epithelial cell RPE1.We found that the morphology and number of CNE-2Z cells did not change significantly after 4 hours in 27 T magnetic field,but the number of CNE-2Z was reduced by about 40%after the removal of magnetic field three days later.In order to understand the mechanism,we focused on the rmitotic spindle.When the magnetic field is perpendicular to the cell basement,we found that spindle long axis orientation has obvious changes after 4 hours in 27 T magnetic field.After more detailed research,we found that the magnetic torque produced by the 27 T magnetic field acts on both the spindle and the chromosome at the same time,and the final tendency of the spindle long axis depends on the both sides.Then we made the cell basement parallel to the magnetic field.It was found that the spindle long axis of the prometaphase cells tended to parallel to the magnetic field direction.However,the chromosomes of the metaphase cells tended to parallel to the direction of the magnetic field,thus making the spindle long axis perpendicular to the direction of the magnetic field.In addition,we also found that the morphology of spindle was changed by 27 T static magnetic field.To sum up,we explored the effect of the static magnetic field on the proliferation of tumor cells and studied the mechanism in two aspects.These research advances clarify our future research directions,and help to further reveal the relationship between static magnetic field and life activities,so that we can use it to serve human health.