MODEL RELEASED. Cancer drug research. Female researcher holding a sample tube in front of a computer monitor during anticancer (chemotherapy) drug research. This work is on cyclin-dependent kinases (CDK) which are involved in cell division. They ensure that cells duplicate their DNA (deoxyribonucleic acid) before they divide, and always divide after their DNA is copied. However this mechanism is often defective in cancers. After treatment with a CDK-inhibiting drug, a flow cytometer can be used to count the cells at each stage of cell division, to assess whether the drug has caused the cells to accumulate at one phase. Results are displayed on the computer monitor.