“Ten years ago, James Watson testified to Congress that once we had the genome sequenced, we would have the language of life. But it turns out that it’s a language we don’t understand.” Robert Best, 2013
In April 2003, at a cost of $2.7bn, the human genome was announced to great pomp and ceremony. This would reveal the deepest secrets of biology, give us the blueprint to create a human and disclose how diseases develop. But 10 years on, has the Human Genome Project been a true medical breakthrough and what role does it play in medical treatment today?
The Human Genome Project was headline busting. This was an international collaboration like no other, which would be the shining peak of human endeavour. Being able to look into an individual’s DNA would give us new knowledge about what caused diseases. What’s more, this would herald a new era in medicine whereby we could use this to diagnose diseases years before a patient felt any symptoms and tailor their treatment to their own personal needs.
Unfortunately, passionate headline-filling coverage has waned recently. The human genome is sadly a lot more complex than we had hoped. The quote above, from geneticist Bob Best, sums up the current state of genome sequencing. Speaking to the Guardian’s Carole Cadwalladr in her excellent first-hand account of how it feels to get your own genome sequenced, Dr. Best hits the nail on the head. We can now sequence a whole human genome for $5,000. That part of the technology has accelerated forward. What remains however, is the pining question of what it all means.
The first problem is that the most common diseases seem more complicated than we had hoped. Instead of being one disease caused by one gene, these diseases seem to be lots of smaller diseases caused by many different genes, conspiring to produce similar results. This is the most evident in cancer. People like to group cancers together into one disease but in reality, there are many, varied faulty processes that can cause a cancer to develop.
One can now do an experiment whereby you measure the genomes of a group of cancer patients and compare them to the genomes of a group of healthy volunteers. Unfortunately, this gives you many, subtle deviations and not one Holy Grail ‘cancer gene’.
Despite this disappointment, there are great success stories emerging from this area. Angelina Jolie nobly led the way earlier in the year with the announcement that she had had a preventative double mastectomy. Jolie had a genetic test which revealed she carried a faulty copy of a gene known to increase women’s chances of breast cancer to 87%. Having a complete code of the cells in your body can only increase the likelihood of finding similar preventable risks of your own. Whether you would want to is another matter entirely.
Genome sequencing has given rise to the potential for personalised treatments. We know that the best treatments we currently have do not work for all patients. This fits with the knowledge that these diseases are actually different diseases all showing similar symptoms. By understanding which small subset of disease a patient is showing and how a patient might deal with a drug, we can tailor the treatment accordingly. The way this technology can be used is explained excellently in this animation. At this stage, we have increasing numbers of great success stories from rare genetic diseases, but limited success in the most common diseases.
This could be because the genome only tells us what may be happening in a living organism. Genes contain the instructions to make life; on their own they do nothing. It is the proteins that are made from these instructions that are the true machines of the living world. Proteins are made from genes via processes known as transcription and translation (see picture below). How a protein is made from the instructions in a gene can be impacted by many lifestyle and environmental factors. This is exactly why lifestyle and environmental factors play such a huge part in disease.
There are leaps and bounds being made in the field of proteomics. This is the process in which proteins, as opposed to genes, are measured. By measuring the proteome (all the proteins in a cell) we can now see what the genes are doing. We can see which genes are more active than others by seeing how much of the respective protein is being made. The vast complexity of this comes when people can have very similar genes, but widely different combinations of proteins they make from them. The human genome contains roughly 21,000 protein-encoding genes. These are responsible for the production of an estimated 250,000 – 1 million proteins. Measuring someone’s genome alone will not tell you exactly what is going on within their bodies.
Albeit technically difficult, analysing the proteome of patients has the potential to tell you which subset of disease patients may have, it can tell you which faulty genes are the most harmful, and can give you possibilities for new treatments. We hope that what goes on beyond a person’s genes will unlock further understanding of disease and truly bring in the era of personalised medicine.
The Human Genome Project has and will continue to open up new realms of possibility for understanding more about life. It has given us the basis to build on our knowledge of how we are made and the beginning to personalised medicine. However, there is still a very long way to go. It is the proteins inside you that truly define health and disease. Until we understand more about how specific genes make specific proteins and how this is impacted in common diseases, we will only be scratching the surface of the potential personalised medicine has to revolutionise treatment.
Post by Oliver Freeman