Selection of optimal treatment
The information gathered by personalized medicine can be used to select the optimal therapy for a patient. Knowledge of the genetic or epigenetic basis of a chronic ailment (such as irritable bowel syndrome or asthma) allows to select treatments (both drugs as well as supporting lifestyle changes) based on the particular genetic setup. This increases the chance for such therapies to be beneficial for that particular patient or patient group. However, this goes well beyond the selection of the best drug. Also individualized regimes fro dosage and even time of application can be informed by genetic factors and contribute to the efficacy of the treatment. Along the same lines known side effects can be minimized or avoided by the choice of alternative drugs provided they are compatible with the patients genetic setup.
The tumor genome: a mug shot for therapy selection
Tumor growth and cancerous diseases are characterized by the presence of cells that do differ from the genetic setup of the healthy cells. One or more mutations in the cancer genome are responsible for the cancer cells to multiply unrestricted and also their potential ability to metastasize, i.e. to shed cells from the primary tumor that travel through the blood stream and colonize distant sites in other organs. Often the ability to metastasize is acquired along with additional mutations in the cancer cells. Molecular analysis of the tumor genome(s) can reveal the driver mutations and thus the mechanism how these cells escape the normal growth control. There are many specialized therapies available now, mostly based on biologicals (antibodies) that target particular signaling pathways highjacked by cancer genomes. Blocking key genes / gene products in the direct line of a cancer growth signal can efficiently block this signaling and break the vicious growth cycle of cancer cells. This way the immune system gets a chance to take care of the rouge cells before the proliferate entirely out of control.
Savior and destroyer rolled into one - the immune system
Our main line of defense against virtually all diseases including cancer is our own immune system. This system has the power to destroy not only any intruders or abnormal cells but could also destroy the healthy tissues (as is the case in autoimmune diseases). Therefore, this powerful killing machine is under the control of various internal checks an balances to ensure it does not turn into a suicide machine. Quite a number of diseases, not only cancer, pervert some of these checks and balances to evade detection by or activation of the immune system. They induce a fatal form of immune tolerance where the offending cells are treated as “own” and ignored by the immune surveillance. Personalized medicine can help to detect which parts of the immune system get compromised by a disease. Especially in case of several tumors it was possible to extract immune cells from the patient, retrain them to attack the tumor and reintroduce them into the patient where they actually did their job they were “reminded” of outside the patient. This is called immune therapy and is a great option where possible as it harnesses the patients own immune system to fight the tumor entirely avoiding effects and side effects of external chemicals. This kind of therapy is called “individualized therapy” and it will be discussed in a separate blog entry in a bit more detail later on.
Figure 12: Selection of optimal therapy
However, optional therapy in the context of personalized medicine does not necessarily mean the absolute best therapy. Some times the really optional therapy is simply not (yet?) available. Thus, all we can expect from personalized medicine today is the selection of the best available therapy for the patient. In the long run, this will also lead to the development of new therapies but the actual patients triggering such developments are not very likely to benefit themselves from it. However, without the development of the current therapies based on the past experience gathered from former patients, also patients today could not benefit from the therapies already developed. Therefore, sharing their data and tissues samples for research will help future generations of patients as our current one benefits from the same attitude of former generations of patients.
What’s coming up next?
Next week we will leave the field of predictive P4-medicine and start with the personalized part, with an introduction into the realm of all the new Omics technologies.