Cancer Sunnybrook Magazine - Spring 2016

MicroRNA: Tiny molecules, big risk factor


The Odette Cancer Centre’s latest groundbreaking research in identifying prostate cancer risk and, most importantly, prognosis, goes beyond genes to non-coding RNA (ribonucleic acid) molecules, known as microRNAs, that silence other genes.

“Our aim,” says Dr. Arun Seth, director of Molecular Diagnostics at Sunnybrook and a senior scientist at Sunnybrook Research Institute, “has been to identify microRNA sequences which can distinguish more aggressive cancers from those that are indolent [slowgrowing].”

The big issue in prostate cancer, he explains, “is identifying which tumours will have recurrence or spread.”

Dr. Seth is collaborating with Dr. Robert Nam, a urological oncologist at the Odette Cancer Centre and a Sunnybrook Research Institute associate scientist.

MicroRNAs can’t be seen, even under a microscope, so the sequencing to determine the precise order of nucleotides (the building blocks of DNA/RNA) per molecule undertaken by Dr. Seth’s lab was no small feat. More than 2,000 microRNAs in the human genome were examined in tumour samples for associations with prostate cancer progression. The research discovered five microRNAs strongly associated with prostate cancer. These five can be used to determine a patient’s microRNA risk score. Patients with a high microRNA risk score have a significantly higher rate of metastasis and of recurrence compared to those with a low score.

In other words, there’s hope that this microRNA research could lead to the establishment of another useful marker to detect a patient’s cancer risk and decide which course of treatment is best.

Dr. Seth explains: “We think these microRNAs could be used for prognosis, to better distinguish which cancer patients require immediate treatment and which can be monitored with active surveillance.” (Active surveillance is the continued monitoring of men with low risk of developing prostate cancer, with the option of treatment if risk increases.)

Photograph at top by Doug Nicholson