You may be aware that there are different types of breast cancer, but do you know why they need to be treated in different ways?
A breast is comprised of many types of cells, some of which are programmed to respond to different growth stimuli in order to function as part of the healthy reproductive system.
For example, hormones like oestrogen and progesterone play a big role in the natural regulation of breast cell growth and development between puberty and menopause. Therefore, some cells in the breast have detectors on the cell surface (receptors) which allows the cell to respond to growth signals such as oestrogen, as part of the monthly menstrual cycle and to develop during pregnancy or breast feeding. When this type of cell becomes cancerous, it receives or grows excessively in response to hormone growth signals, which can be targeted by hormone treatments.
Breast cancers with oestrogen receptors are classed as ER+ and can be treated by blocking the receptor to stop oestrogen telling the cancerous cells to grow with Tamoxifen tablets or by stopping oestrogen production.
In pre-menopausal women, ovaries are the main source of oestrogen; ovaries can be surgically removed or luteinizing hormone blocker tablets can be taken to stop hormone production. In post-menopausal women, the main source of oestrogen in the body is from body fat, and there are several types of aromatase inhibitors that prevent this production.
Another growth signal receiver involved in breast cancer is HER2 (Human Epidermal Growth Factor 2). Some cancer cells make more of the HER2 protein than is found on healthy cells. HER2 proteins relay growth signals from the cell surface into the cell telling it when to divide.
In healthy cells, these signals go through checkpoints to prevent uncontrolled cell division but in a HER2+ cancerous cell these checks can be bypassed because there are so many HER2 signals, causing uncontrolled cell division and tumours to develop.
Trastuzumab (trade name is Herceptin) and lapatinib (trade name is Tyverb) are treatments used against breast cancers that are classed by doctors as HER2 positive. These antibody treatments stick to the HER2 protein and block the extra growth signals to prevent tumour growth and may also flag up the presence of the cancerous cell to the body’s natural immune system, allowing it to kill off the breast cancer cells.
Triple negative (basal-like) cells are at an earlier stage of cell development, so these cancerous cells have no hormone or other type of growth signal receptor identified, and more research is required to design treatments beyond chemotherapy, that are specific for this cancer type.