A powerful new tool to diagnose salivary gland tumours

Researchers at OICR, University Health Network and Memorial Sloan Kettering Cancer Center have made an important discovery in the treatment of salivary gland cancer. Their findings, published last month in Nature Genetics, describe the discovery of a specific gene called PRKD1 that is mutated in the vast majority of patients with this disease. This new cancer gene will allow doctors to accurately diagnose this type of cancer and distinguish it from other, similar cancers that should be treated differently. The gene is also potentially the target for the development of new therapeutics.

We spoke with Dr. Paul Boutros, one of the lead researchers at OICR on the project, about the findings and what they mean for patients.

Q: Why did you focus on salivary gland cancer?

A: There are several different tumours of the salivary gland and they are “diagnostic dilemmas” – they are frequently misdiagnosed as one another. And they have very different treatments. Some are very aggressive and some are quite benign and don’t need much treatment. Having a molecular way to accurately diagnose them avoids that problem and helps ensure each patient gets the treatment options that are best for them.

Q: This is described as a new cancer gene. What does that mean exactly?

A: There are probably about 1,000 known cancer genes, which are genes that previously have been implicated in cancer growth and development or that are found to be mutated in cancer at elevated rates. There is a lot of debate about the exact definition of the term cancer gene, but I think a good one is that it either promotes the growth or survival of some tumours. And our experiments show clearly that PRKD1 does for this salivary gland cancers.

Q: What is most interesting about this particular cancer gene?

A: Probably that it is so strongly associated with a single tumour type. This gene is mutated in this tumour the vast majority of the time (about 70 per cent), which highlights just how prevalent or frequent this mutation is. With this tumour type we were able to understand very efficiently, effectively and completely because it turns out to be driven by this single gene. This allows us to take a tumour type that was almost completely uncharacterized and move very far down the path of characterization. This is a big contrast to most cancer genes, which are found in just a small fraction of cases.

Q: When can we see this in the clinic?

A: It is basically ready. It is a simple single sequencing process that pathology labs can now do routinely if they wish. If a patient is thought to have salivary gland cancer this test can be used immediately to help confirm or refute the diagnosis and inform the course of treatment.

This interview has been edited for clarity and length.