A team of University of Toronto researchers has worked through the human genome, switching off genes in an effort to map out those essential in keeping our cells alive. The scientists were able to identify sets of genes associated with specific cancers, paving the way for highly targeted treatments.

While mapping the human genome was a huge step forward, actually understanding – and therefore being able to manipulate – the function of each individual gene is extremely difficult. In order to work out the individual functions of each of the thousands of genes, scientists switch off genes one-by-one, gauging what happens to the cell as a result.

Early attempts to do this were very slow or too inaccurate to be practical, but a more effective gene editing tool was introduced in 2012, known as CRISPR, which has made the process much quicker and more accurate.

The University of Toronto team decided to look at the big picture, switching off close to 18,000 genes – a number that represents 90 percent of the entire human genome. In doing so, they eventually isolated just 1,500 genes that are essential to keeping our cells alive.

Digging deeper, the researchers turned off genes associated with five different cancer cell lines – brain, ovarian, retinal and two forms of colorectal cancer – establishing that the different tumors rely on specific and unique sets of genes. This information could be used to create new treatments that attack only the identified cells, not harming surrounding tissue.

The research is a big step forward in humanity's overall understanding of how our genome works, and puts us closer than ever to achieving the ultimate goal of identifying the function of every single gene.

"We can now interrogate our genome at unprecedented resolution in human cells that we grow in the lab with incredible speed and accuracy," says the University of Toronto's Prof. Jason Moffat. "In short order, this will lead to a functional map of cancer that will link drug targets to DNA sequence variation."

The findings of the study were published in the journal Cell.