The Dynamics of Cancer Cells In Self-Generated Hypoxia

Hypoxia is context-dependent but, in tissue, loosely defined as oxygen concentrations below those that are physiologically normal (Ivanovic ref). In some cases, sudden hypoxia has been demonstrated to be a powerful driver of mutations in both bacteria and eukaryotic cells. The origin of the mutagenic nature of hypoxia is connected to basic cell metabolism pathways that can generate highly reactive singlet oxygen when perturbed under low oxygen conditions. Hypoxia is a common condition in a tumor \cite{tumor-hypoxia} because the rapid and uncontrolled growth of the tumor leads to a disorganized and inefficient vascular system to feed nutrients and oxygen to the tumor. We have developed a oxygen-permeable thin film containing a platinum-porphyrin phosphorescent dye whose excited state is quenched by O2. The dye phosphorescence intensity is a function of oxygen concentration over at least 3 orders of magnitude of concentration, when used in a microfabricated 3D ecology we get time and 2D space resolved hypoxia of a PC3 cancer colony. By quantifying the intensity of the image of the steady-state phosphoresence  of the sensor film using a digital CCD camera, it is possible to image the oxygen concentration in a confluent layer of cancer cells under conditions where they generate their own high levels of hypoxia.  Tracking the motion of cancer cells versus time in self-generated high hypoxia allows us to dtermine their response to high levels of hypoxia, both during the hypoxia and when it is released.