The Effect Of Nano-Graphene Oxide On The Migration Of Tumor Cells And The Underlying Mechanism

Cancer is one of the severe health problems in the world. China’s annual cancer mortality accounted for about 25% of all the death cases. Metastasis is the main characteristic of malignant tumor, and the main reason why malignant tumor is difficult to cure.Metastasis is a complicate, multi-step and cascaded process. At the beginning of the metastasis, tumor cells form new micro-vascular network, which allows them to escape from the primary tumor. Tumor cells invade into the extracellular matrix and endothelia cells, and then move into the vascular or lumphatic. With the help of circulatory system, tumor cells arrive at the target organ and then invade into the target organ. After they settle down, they begin to form the secondary tumor. Many types of cell factors take part in the progress of metastasis to induce morphological and structural changes of tumor cell, such as ICAM、VCAM、MMPs、collagen. EMT refers to the progress that the epithelia cells lose epithelial features, and acquire mesenchymal cell properties. EMT exits in the normal human physiological process such as the formantion of the embryo. Many studies have shown that EMT affects the migration of tumor cell.Tumor cell can transfer to tumor stem cell through EMT. Tumor stem cell is able to promote tumor metastasis. Tumor epithelial cells can also acquire mesenchymal properties through EMT, with the gain of ability to invade and move. These findings prove the EMT is an important part of tumor metastasis. Pseudopodium is a structure that is important in cell motility, and is essential in invasion and migration as well.Graphene is the thinnist nano material, with the thickness of one atom, and is the basic unit of many nano materials. With the study of graphene, it has become the super star in the field of material science. Functionlized graphene is the hotpot of research at present, and a variety of functionlized grapheme has been developed in many fields such as sensors and detectors, etc. In biomedicine, graphene oxide is mainly used in new drug carrior system and in gene therapy. Although graphene oxide has been widely used, its biological effects and safety remains little-known, and the research about its effects on cancel cell is limited.To study the effects of graphene oxide on tumor, we designed and carried out a series of experiments.1) The cytotocity experiments.4T1 and B16 cells were treated with different concentrations of grapheme oxide. The results show that 10μg/mL is a safe concentration.2) Wound healing experiment. The number of cells that migrate to the scratch area is significantly reduced after treated with graphene,. This result indicates that metastastic ability of these two types of cells can be inhibited by graphene oxide.3) The main genes and proteins regulated by graphene oxide. We detected the expression level of different genes’or proteins’expression in the two types of cells. Results show that ICAM and MMPs are the main proteins influenced by graphene oxide in 4T1 cells, while ICAM is the only protein influenced by graphene oxide in B16 cells.4) The molecular mechanism. RT-PCR experiments and Western Blot assays, we found that graphene oxide mainly inhibits the ErK and NF-κB signaling pathway in 4T1 and B16 cells.5) The EMT progress. EMT was induced by TGF-beta. The cells were treated with or without graphene oxide. Through RT-PCR experiments, we found that the expression of mmp9 and fibronectin were unregulated by TGF-beta in 4T1 cells. This upregulation was inhibited by graphene oxide. The regulation of fibronectin was similar in B16 cells,.6) Cytoskeleton staining. After the treatment of TGF-beta and graphene oxide, the cells were stained by Rhodamine-phalloidin. Using confocal laser scanning microscope, we observed the change of cell skeleton. The results show that TGF-beta can induce the assemble of cytoskeleton and the formation of pseudopodia. After treated with graphene oxide, the number of pseudopodia in 4T1 cells was reduced. Graphene oxide also can also inhibit TGF-beta-induced upregulation on pseudopodia number in B16 cells.Taken together, graphene oxide can cause a significantly influence on the metastasis of tumor cells. This work studied biological safety and cellular effects of the graphene oxide, and explored the molecular mechanisms of graphene oxide inhibiting tumor cell migration. All these work findings revealed the potential application of nano-graphene oxide in cancer therapy.