Listening to the Tweets of Exosomes

With trillions of dollars having been spent on cancer research over time, it seems surprising that there still no reliable and non-invasive method of detecting cancer during routine health check-ups. Cancer is diagnosed only when some seemingly unrelated symptom – maybe abdominal pain or a persistent cough – causes a person to seek medical advice, and then often too late for a permanent cure. Surely, the day will come when a simple blood or urine test could reveal the onset of cancer anywhere in the body without the need for a costly MRI scan or an invasive biopsy of human tissue? 

Johan Skog. Photo: Johan Gunséus/Tidningen Curie

Well, that day may be getting closer thanks to a revolutionary discovery by Swedish cell biologist Johan Skog. In 2005, Dr Skog earned his PhD in Virology while doing research at Umeå University in northern Sweden. The following year he joined the Harvard Medical School in Boston to develop a gene therapy method for treating brain tumours. In the process, he became an expert on so-called exosomes, small packages released by cells into the blood stream and other body fluids such as urine. These packages contain various molecular constituents of their cell of origin, including proteins and ribonucleid acid (RNA). 

Working late one night in the laboratory, Dr. Johan Skog found that these exosomes included RNA from cancer. RNA is the “language of cells”, and the tiny exosome packages act as a means of communication between the cells, somewhat akin to Twitter messages. Eavesdropping on the tweets makes it is possible to detect a cancer and its origin early, and also to observe how it is changing over time. By taking regular blood and urine samples from people and singling out the exosomes, proper treatment can be initiated before the disease has had a chance to grow and spread. 

Johan Skog obtained a patent for his discovery and started the company Exosome Diagnostics with initial focus on detecting prostate cancer. Currently, this type of cancer is the fifth most common cause of death among men in the USA. 

Early prostate cancer is typically diagnosed almost by accident if a person’s blood test happens to include a measurement of prostate-specific antigen (PSA). However, the PSA method is unreliable to the point where it sometimes leads to MRI scans and biopsies being performed unnecessarily. 

For Exosome Diagnostics, detecting and monitoring prostate cancer is only the first step towards the goal of providing a more universal diagnostic tool. Johan Skog has handed over the day-to-day management of the enterprise to colleagues and is now working in the company’s laboratory as Chief Scientific Officer. His ambition is to expand the usefulness of his discovery to include other forms of cancer. 

By Peter Berlin