Genetic testing was first discovered in the 1950s and started the long journey of research and discovery that has made a significant impact in treatment of various diseases and cancer. Since the discovery of BRCA1 in 1994 scientists and doctors have been able to find new genes and cancer treatment pathways for patients with specific gene alterations. Thankfully we can now apply this knowledge to the treatment and management of prostate cancer.
Types of Genetic Testing
Often referred to as “hereditary” cancer testing. Germline refers to, the genetic material we have as byproduct of the combination of chromosomes from our mother and father, and are present since birth. Germline testing can identify gene alterations that can be passed on to family descendants. Additionally, other family members can be tested to see if they also harbor the same gene alteration.
Somatic refers to the genetic testing of cancer tumor tissue or DNA. Cancer cells are inherently defective and most likely the cause of a normal cell becoming a cancerous cell. The defects in the DNA can lead to gene alterations. Somatic testing will help identify any gene alterations that the cancer cells have acquired and other tumor markers that can qualify the patient for specific cancer treatments.
Applications to Prostate Cancer
Human cells can replicate, repair and defend themselves thus, helping maintain a healthy body. Specific genes are responsible for replication, repair, defense and other functions needed by the cell. Gene alterations can affect this process and make the cell vulnerable to cell death. When gene alterations are identified we can attempt to capitalize on this vulnerability utilizing targeted cancer treatments, such as, PARP inhibitors and PDL-1 inhibitors.
PARPs are part of a family of proteins that are involved in DNA damage response. Cancer cells with certain gene alterations must rely only on PARPs to repair damaged DNA. PARP inhibitors block these proteins from repairing the cancer DNA therefore, leading to more DNA damage and eventually cancer cell death. These PARP inhibitors are delivered via an oral medication, such as, Lynparza and Rubraca.
PDL-1 is a type of protein that helps keep immune cells from attacking normal cells in the body. Cancer cells can have a high level of this protein and thus not be detected by immune cells as needing to be destroyed. Cancer cells typically only possess one level of immune protection, in contrast, healthy cells have two levels of immune protection. PDL-1 inhibitors are a type of immunotherapy that block these proteins and remove the protective mechanism available to the cancer cells. The immune cells are now able to identify and destroy these cancer cells. This type of immunotherapy is delivered via an IV infusion, such as, Keytruda.
Once a gene alteration is identified, treatment, management and follow up can change. Potentially allowing for a more proactive, targeted approach for patients harboring these types of mutations.