Chemotherapy. Coloured scanning electron micrograph (SEM) of an cultured cancer cell which has become apoptotic after treatment with doxorubicin. Doxorubicin is a type of chemotherapy drug called an anthracycline. It slows or stops the growth of cancer cells in part by blocking an enzyme called topoisomerase 2. All cells need this enzyme to divide and renew. Apoptosis (also known as programmed cell death I) is one of the main ways cancer cell death is induced by chemotherapeutic drugs and is shown here with cervical cancer cells (Hela). Characteristics of apoptosis at SEM level are membrane blebs called apoptotic bodies. In culture, apoptotic cells typically undergo further degradation in a process called secondary necrosis. Magnification: x8000 when printed at 10 centimetres wide. Specimen courtesy of Greg Towers, UCL.