Breast Cancer - Introduction

Breast cancer is only one of more than 200 different kinds of cancer. Yet in women it accounts for almost one third of all cases, with a lifetime risk of one in nine.

If detected early, breast cancer can often be well treated [Wellcome].

In the UK alone, there are over 40,000 new diagnoses of breast cancer each year - around 1% of which are men. The key to successful treatment is early detection. If left untreated, cancerous cells may break away from the primary lump and spread via the bloodstream or lymphatic system to other parts of the body. If diagnosis is made early enough, survival chances are high.

What is cancer?
Tissue mass is normally controlled by a precise and strongly regulated balance between cell proliferation and cell death. Following tissue damage proliferation is often increased to effect repair. So, to prevent unwanted proliferation, cells have a suicide or death programme. Cancer occurs when a cell loses the ability to control its growth and the balance between proliferation and cell death is lost. This cancer cell either proliferates more rapidly than normal cells or fails to respond to commands to initiate the death or suicide pathway. Cancerous cells keep on dividing and eventually form a lump or tumour.

Most cancers occur sporadically. Accumulation of damage to the DNA in our cells turns a normal cell into a cancerous one. Harmful chemicals in our environment, spontaneous errors in DNA replication, or a genetic mutation are possible causes.

Amazingly, much of the fundamental research into cancer-associated genes has been done using organisms such as yeast, sea urchin and frog eggs, tiny worms (called nematodes) and fruit flies. One of the advantages of using a ‘model’ organism, such as yeast, is that individual genes can be manipulated and the effects studied in successive generations relatively quickly and easily.

But to get a better understanding of the biology of breast cancer, and of how breast cancer cells differ from normal cells, it is necessary to use rodents as they, like us, have milk-producing mammary glands (breasts). In addition, some studies can and are conducted on human breast cancer cells grown in a laboratory.

What are the risk factors for breast cancer?
Most of the risk factors for breast cancer such as aging, late-onset menstruation, having dense breast tissue or a family history of the disease cannot be controlled. But, by studying different families who have a high incidence of breast cancer, scientists were able to track down mutations in two particular genes (BRCA1 and BRCA2) that are associated with an increased risk of developing breast cancer. It is now possible to test an individual to see if they have one of the identified mutations - although this does not make breast cancer inevitable. Environment and lifestyle also affect the outcome. Indeed, these known genetic mutations account for less than 1 in 20 cases of breast cancer.

Thanks are due to David Miles and Elaine Vickers (Cancer Research UK), Barry Furr (AstraZeneca), and Nick Wright (Barts and The London, Queen Mary's School of Medicine and Dentistry).

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