Employing an xCELLigence Real-Time Cell Analysis instrument, Korean scientists demonstrate that within a hypoxic environment the hYSK1 protein negatively regulates p16 to promote tumorigenesis
Tracking the growth and migration of cells under hypoxic conditions in vitro can be challenging because measurements must be made in a manner that does not perturb the atmospheric composition of the closed system. A team of Korean scientists headed by Bu Young Choi at Seowon University have described an elegant solution to this challenge by placing an xCELLigence Real-Time Cell Analyzer (RTCA) directly within a hypoxia chamber. This approach, wherein the number, size, attachment strength, and migration of cells are continuously monitored using gold biosensors, enabled experiments to be run from start to finish without ever needing to manipulate samples or open the hypoxia chamber.
Owing to their rapid proliferation, the cells within a solid tumor often outpace the ability of the surrounding vasculature to provide nutrients and oxygen. This hypoxic microenvironment has distinct biochemical effects on tumor progression, but the underlying mechanisms are not completely understood. Citing that levels of the cell cycle inhibitor/tumor suppressor protein p16 are reduced within hypoxic tumors, Choi’s team sought to provide a molecular explanation for this phenomenon. Screening an extensive protein array for p16 binding proteins identified hYSK1, an oxidative stress response kinase. After detailed biochemical mapping of the p16 and hYSK1 interaction domains the authors validated the physiological relevance of this interaction using a variety of in vivo assays. hYSK1 was found to suppress p16 expression and to, under hypoxic conditions, directly bind p16 and thereby sequester it away from CDK4 binding. Hypoxic stimulation of HYSK1 expression was also found to stimulate expression of matrix metalloproteinase 2, which is known to contribute to basement membrane degradation and metastatic spread. Consistent with the above findings, in hypoxic xCELLigence live cell analysis assays hYSK1 promoted both proliferation and migration of melanoma cell lines.
Choi’s team concluded that “hYSK1 is a specific negative regulator of the tumor suppressor p16 and may represent a novel molecular target for reactivation of tumor suppressor genes in humans.”