Breast cancer breakthrough

City scientist, researchers decode genetic makeup of deadliest type

VANCOUVER

– Scientists from Edmonton, British Columbia and England have decoded the complex genetic makeup of the hard-to-treat, deadliest form of breast cancer.

Study leader Dr. Sam Aparicio of the BC Cancer Agency and 58 other researchers published their findings about triple negative breast cancer (TNBC) in the prestigious journal Na

ture on Wednesday. The scientists took about 18 months to examine more than 100 human tumours and found huge variations among them, with an unprecedented number and type of genetic and biological abnormalities.

“This paper results from having a world-class tumour bank in which Albertan women participated, and in our strong collaborations with the UBC team,” Dr. John Mackey of the Cross Cancer Institute wrote in an email Wednesday. “We have been working on these types of studies for years, and the technology is just now to the point that we can truly begin to understand the complexities of human cancer.”

Mackey’s colleague at the Cross, Dr. Sambasivarao Damaraju, said in a email he wanted to thank patients who consented to participate by donating the tumour tissues left over from their diagnostic procedures.

“It is imperative that we as a province should invest in this key tumour bank project for many more years to come as the technology is just mature to start giving dividends for an investment of this kind.”

TNBC accounts for about 16 per cent of all breast cancers, but 25 per cent of all deaths from breast cancer. It derives its name from the fact that it is missing a trio of surface cell hormone, steroid and protein receptors — estrogen, progesterone and herceptin. When the receptors are present, treatments — such as anti-estrogen therapy — can be used in a bid to inhibit tumour cell growth.

Anti-estrogen drugs interfere with the receptors, which prevents the hormone from attaching or landing on the tumour. In the case of estrogen, it appears to encourage the growth of some types of breast tumours.

But in cancers such as TNBC, where the tumour is not a ected very much, or at all, by estrogen to begin with, antiestrogen treatment has little or no benefit.

Steven Jones, co-author of the study and head of bioinformatics research at the BC Cancer Agency, said scientists expected to see genetic similarities in the tumours when they mapped their genomes. But they didn’t find the similarities they expected.

“Seeing these tumours at a molecular level has taught us we’re dealing with a continuum of di erent types of cancer here, not just one.”

A news release issued by the journal elaborates: “Some tumours only display a few mutations, and involve a limited number of molecular pathways that are implicated in disease progression, whereas multiple mutations and pathways are involved in other tumours,” referring to the findings that will most certainly convince experts that in order to do better research and improve the effectiveness of treatment, each tumour is so different that they should probably all be genetically sequenced so treatment can be tailored to each patient.

Genetic sequencing is not the standard of care in Canada and other countries yet, largely because of cost and other resource issues.

The study says TNBCS are still treated as if they were one type of disease even though the latest research shows that these types of breast cancers “do not behave as a single entity in response to current therapies,” Jones said, adding the findings show doctors cannot presume that one therapy can treat all tumours under the TNBC umbrella.

“The genetic diversity of these tumours, even though they’re clinically similar, probably explains why they are so di cult to treat.”