Table of Contents
Although most cancers are sporadic, some run in the same family from generation to generation. Some types of breast cancer have often been associated with family history. With our constantly improving knowledge of human genetics, now we have a much better understanding of reasons behind this inherited pattern. Moreover, we can calculate the risk and take preventive measure to avoid the disease.
Hereditary aspect of breast cancer
This is a clear indication that some common genes are at play here. Some of the most well-known and best studied heritable genes linked to breast cancer are the mutant forms of BRCA genes (BRCA1 and BRCA2). They are often referred to as high susceptibility genes. The mutations in these genes are inherited in an autosomal dominant pattern. This means that the presence of a single mutant gene copy is sufficient to cause the diseased condition.
The effect of BRCA mutations can be clearly seen in a small northern European nation of Iceland. Country has the largest rate of breast cancer in the world. It is almost twice higher than the world’s average. Researchers believe that this is a consequence of so-called “founder’s effect”. The whole nation was established by just few families who migrated to the island from Norway. Apparently, one of the women brought to the island was a carrier of defective BRCA gene.
Recent scientific studies show that many other genes can influence the breast cancer risk. For instance, a specific mutation in CHEK2 gene (a cell cycle check point kinase) increases the chance of breast cancer risk among women by 2-fold while that in men by a factor of 10. Mutations in the gene PALB2 has been linked to increased breast cancer risks and its pattern of mutation is quite similar to those of BRCA2. Rare mutations in BRIP1, ATM, NBS1 and Rad51 also contribute to nearly 2-fold increment in breast cancer chances.
Now researchers discuss the ‘multiple rare alleles - common disease’ model that involves the formation of a complex of eight genes that might regulate breast cancer. However, the origin of the half of all hereditary breast cancer cases still remains unknown. Involvement of many more genes and their mutants are yet to be unraveled to understand the hereditary aspect of breast cancer. Genome wide association studies (GWAS) are increasingly used to identify common genetic variants that might be involved in the development of this disease.