Preimplantation Genetic Diagnosis to Curb Cancer

Preimplantation genetic testing is a relatively newer technique that is used to find and identify an embryo’s genetic defects, through the use of in vitro fertilization (IVF). Preimplantation genetic diagnosis (PGD) is used specifically when one or both parents are know to carry an abnormal gene, so testing is used and performed on an embryo to identify and screen those specific embryo before they are implanted into the uterus. The term pre-implantation genetic screening (PGS) is used to denote procedures that do not look for a specific disease but use PGD techniques to identify embryos at risk.

PGD baby sleepingPhoto Credit: Kristin Kokkersvold

By using these techniques only unaffected embryos are implanted within the uterus. Many of the most frequently screened for abnormalities are autosomal recessive disorders like cystic fibrosis, sickle cell disease, Beta-thalassemia and spinal muscular atrophy. But inroads are being made in other areas such as that of breast cancer.

This is particularly relevant as in the news this past week Angelina Jolie recently underwent a double mastectomy so as to reduce her risks of developing breast cancer. She is a carrier of a gene mutation known as BRCA 1. Unfortunately the lifetime chance of developing breast cancer from the carriers of this gene is 80%. And the only known procedure to reduce the risk or prevent it is a double mastectomy.

Recently Dr Jain of Santa Monica fertility has written about this subject, and in particular how PGD has the potential to screen for these types of genetic defects.

He further explains:

BRCA 1 and 2 genes are normal genes found in the body. The typical role of these genes is to keep DNA stable and prevent cells from growing out of control, or mutating. Mutations of either BRCA 1 or BRCA 2 genes can lead to loss of cell control and the development of various cancers, among which breast and ovarian cancers are most prevalent.

BRCA 1 and 2 mutations can be passed on to children leading to hereditary breast and ovarian cancer in multiple generations. The chances of inheriting a BRCA 1 or 2 mutation are somewhat high. In order for an egg to be fertilized by sperm, it must discard half of its chromosomes. Since the BRCA mutation is typically found on one chromosome, there is a 50% chance that the mutation will be randomly discarded by the egg. If the gene is not discarded, it will pass to the child who will also be a BRCA mutation carrier. In other words, there is a 50% chance of passing the mutation to a child.

Dr. John Jain and his colleague, Dr. Dagan Wells of Oxford University, are currently conducting a study aimed at identifying eggs that have successfully discarded the BRCA mutation, and studying what makes those particular eggs more resilient. If experts can effectively identify the mutation-resistant eggs, then these healthy eggs can be used to create embryos, ultimately eliminating hereditary breast and ovarian cancer from future generations.

This is pretty exciting, to have the ability to screen out certain genes that have an 80% likelihood of developing breast cancer is something that can change the lives of so many people. PGD has great potential to help us further screen out other abnormalities as well that have caused a lot of suffering and needless loss of life for so many people. There are many who have begun to travel to get these techniques done at clinics who have the ability to accomplish them.