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Breast cancer treatment

Khuloud T Al-Jamal and Izzat Suffian

Download this image from Wellcome Collection.

Scanning electron micrograph of a cluster of breast cancer cells (coloured blue). The cells have been treated with nanometre-sized particles (nanocarriers) carrying the anticancer drug doxorubicin. This is causing some of the cells to die (coloured purple) through a process known as programmed cell death, or apoptosis, which is where cells effectively commit suicide in a controlled, predictable way. Being able to specifically turn on this pathway in cancer cells will reduce a tumour's size and hopefully limit its growth. Doxorubicin does not discriminate between normal, healthy cells and cancer cells and can affect both. To overcome this the nanocarrier can be chemically modified to recognise some tumour cells and deliver the drug to the intended target. The diameter of the cell cluster is approximately 250 micrometres (0.25 mm). The nanocarriers used to treat these cells are approximately 6 nanometres (0.000006 mm) in size.

How do cells die?

Cells die through one of two different processes: necrosis or apoptosis. Necrosis occurs when a cell is damaged by something unexpected, such as infection, lack of oxygen, trauma or exposure to toxins. As the cell dies it starts to swell, holes appear and its contents leak out. This is detected by neighbouring cells and triggers inflammation, which can cause further injury and damage. In contrast, apoptosis is a much cleaner, better-managed process. An apoptotic cell starts to shrink, proteases digest the cell from the inside and the cell sends out signals to initiate a clean-up operation so that no debris remains. Apoptosis is a normal part of cell turnover and development, occurring, for example, during organ formation in the embryo.

How does doxorubicin work?

Doxorubicin is a chemotherapy drug that is used to treat a variety of different cancers, including some types of lymphoma and some breast, lung, bladder, stomach and ovarian cancers. It belongs to the anthracycline class of drugs, which are a group of antibiotics. Doxorubicin works by squeezing between the base pairs in the DNA double helix. This interferes with the normal function of DNA and prevents cells from being able to divide and grow. In an unwanted cancer cell this is good news, but if healthy, non-cancerous cells are affected then this can lead to side effects. Heart tissue is particularly susceptible to anthracyclines, which places a limit on the amount of doxorubicin that can be used therapeutically.