Cell Cycle Control, Oncogenes, Tumor S…
CELL CYCLE AND CELL DIVISION | Lead Editor: Zhaohua Tang, Ivor Hickey
Cell Cycle Control by Oncogenes and Tumor Suppressors: Driving the Transformation of Normal Cells into Cancerous Cells
By: Amy Y. Chow, Ph.D. (Division of Tumor Cell Biology, Beckman Research Institute, City of Hope) © 2010 Nature Education Citation: Chow, A. Y.(2010) Cell Cycle Control by Oncogenes and Tumor Suppressors: Driving the Transformation of Normal Cells into Cancerous Cells. Nature Education 3(9):7
How is a normal cell transformed into a cancerous cell? The proteins involved in cell division events no longer appropriately drive progression from one cell cycle stage to the next.
How is a normal cell transformed into a cancerous cell? Theproteins involved in regulating cell division events no longer appropriately drive progression from one cell cycle stage to the next. Rather than lacking function, cancer cells reproduce at a rate far beyond the normally tightly regulated boundaries of the cell cycle. Cancer can be distinguished from many other human diseases because its root cause is
not a lack of, or reduction in, cell function.For example, individuals w ith diabetes may lack insulin production or the ability to respond to insulin. With coronary heart disease, poor
blood supply to the heart can cause the organ to eventually fail. In the case of acquired immune deficiency syndrome (AIDS), the immune system loses the cells it needs to fend off infection. And w ith many infectious diseases, foreign microorganisms w reakhavoc on the host they have invaded, causing a loss of function w ithin cells, tissues or entire organ systems. Cancers, how ever, occur due to an alteration of a normal biological process — cell division. Cells that progress through the cell cycle unchecked may eventually form malignant tumors, w here masses of cells grow and divide uncontrollably, then develop the ability to spread and migratethroughout the body. Fortunately, cancer prevention usually occurs through the strict regulation of the cell cycle by groups of proteins that interact w ith each other in a very specific sequence of events. It is these events that determine w hether the cell cycle w ill go forw ard or remain stalled betw een stages. Given that cancer is fundamentally a disorder at the cellular level, thetechnological achievement of cultivating cells in vitro, or outside the organism as a w hole, has allow ed investigators to determine w hat events lead to tumor formation and to identify the proteins involved in the process. Typically called cell culture or tissue culture, researchers now regularly grow cells immersed in nutrient-rich liquid also know n as media (Figure 1). Normal, non-cancerous, cells w illgrow in a single, uncrow ded layer attached to plastic dishes. These cells generally undergo a limited number division cycles, depending on space and nutrient availability, among other constraints. What, then, can go w rong w ith this orderly cell grow th system? And w hat can be learned w hen things go aw ry? The answ ers to these questions serve as the basis for fundamental discoveries made byresearchers in tumor cell biology. Abnormal or cancerous cells, grow n in Figure 1: Cells grow ing in a tissue culture petri dish, adhered to dish bottom and im mersed in liquid m edium (pink) © 2010 Nature Education All rights reserved.
vitro have been transform ed from their normal phenotype due to
genetic changes affecting proteins involved in cell cycle control. Historically, thesetransformation assays have led to the identification of the genes and proteins important for driving the cell cycle forw ard. As a class, these genes have been named oncogenes. More recently, creative scientists have used advances in methods of genetic manipulation in combination w ith the transformation assay to identify the genes and proteins important for restricting cell cycle progression. As a...