New clues to aggressive breast cancer

(Medical Xpress)—Queensland scientists have identified a genetic "switch" which indicates whether a woman's breast cancer will spread.

Teams from QIMR Berghofer Medical Research Institute and the Institute of Molecular Bioscience (UQ) have found that a particular RNA (Ribonucleic acid) molecule goes missing in aggressive cancers.

QIMR Berghofer's Dr Nicole Cloonan said the finding could provide a clearer prognosis for breast cancer patients, and ultimately open the door for new treatments.

"Essentially, this particular gene fragment, or microRNA, normally acts like an emergency brake in our genetic program, ensuring our cells continue to reproduce normally," Dr Cloonan said.

"But we've identified that this "emergency brake" fails in invasive, aggressive tumours. Its sudden absence in cancer tests would be a clear marker that a tumour is likely to spread.

"And we know that primary breast cancer rarely kills; it is those aggressive tumours that spread, or metastasise, which result in poor outcomes," Dr Cloonan said.

Breast cancer is the most common cancer in women. Survival can depend on when the cancer is diagnosed; once it has metastasised there is a five-year survival rate of only 21%.

"But this research has wider implications too. Although we focussed on breast cancer, it's clear this microRNA is also missing in aggressive liver, stomach, brain and skin cancers, and potentially others too. What we've uncovered seems to be a common cellular process which could be a new drug target," Dr Cloonan said.

"These microRNAs were once thought the "junk" of our genetic programs, something that finetuned pathways but that was all.

"But in recent years, we've come to appreciate the driving role they play in cancer, and as this work shows, a key role in preventing breast cancer cells from migrating throughout a person's body."