Found: a new drug mix to nix breast cancer

The new compound, when combined with conventional drugs, has shown promising early results in the treatment of some types of breast cancer, tests on mice showed.

Combining a special anti-cancer compound with conventional cancer-fighting drugs can slow down the growth of the most common form of breast cancer and can even cause some tumours to disappear completely, a new study has found.

The study, conducted by researchers from the Walter and Eliza Health Institute (WEHI) and published today in the journal Cancer Cell, centred on aggressive oestrogen receptor-positive (ER-positive) breast cancers. ER-positive tumours account for approximately 70% of breast cancers.

The researchers conducted tests on mice that had been implanted with breast cancer cells taken directly from humans, a lab method known as xenografting.

They found that mixing an anti-cancer agent called BH3-mimetics with the common breast cancer drug tamoxifen stopped or delayed tumour growth in the mice.

BH3-mimetics are currently already being trialed in leukaemia treatment, meaning the compound may be on the market within years.

How it works

BH3-mimetics work by targeting a compound in breast cancers called BCL-2. BCL-2 normally serves to ‘immortalise’ cancer cells by keeping them alive and protecting them from conventional treatments.

Combining BH3-mimetics with the conventional breast cancer drug tamoxifen provided “significant improvement in tumour response using xenograft models of primary invasive ER-positive breast cancer. This targeting strategy induced complete pathological remission in one of the tumour models,” the researchers wrote in their paper.

“The concept is that the treatment is neutralising a molecule that normally acts as a lifeline for tumour cells. By neutralising this lifeline, BCL-2, we are turning it into an Achilles heel,” said lead researcher Professor Geoff Lindeman from WEHI’s Breast Cancer Laboratory.

“I am hopeful that over the next two to three years we will see some early phase clinical studies involving breast cancer patients,” he said.

If those studies go well, the drug might be available for use within a five to 10-year timeframe, Professor Lindeman said.

“It is always hard to predict whether a new drug will be successful in the clinic. However I am quietly optimistic, given the promising findings to date,” he said.

The new research was was supported by the National Health and Medical Research Council, the Victorian State Government, the Australian Cancer Research Foundation, the National Breast Cancer Foundation and the Qualtrough Family Bequest.

New opportunities

Professor John Forbes, a breast cancer expert from the School of Medicine and Public Health at University of Newcastle, welcomed the new findings.

“This is an exciting, world-leading discovery that can lead to better outcomes for many women diagnosed with a specific type of breast cancer,” said Professor Forbes, who was not involved in the study.

“It creates a new era of opportunities for molecular targeted treatments specific for individual women and for understanding molecular processes in breast cancer.”

Caution required

However, Dr Brendon Coventry, Associate Professor of Surgery at University of Adelaide and another cancer expert, said that “most of these type of findings in mouse models need to be interpreted very cautiously as very few of them actually translate into clinically useful therapies.”

“Although the findings presented are interesting, they represent contrived models in immunodeficient mice (without immune systems) and therefore it is far too early to get too excited by such preliminary findings. The findings might be useful, but down the track, especially for breast cancer types where useful therapies do not exist, or have failed,” said Associate Professor Coventry, who was not involved in the study.

“It is a real conundrum for researchers today, because ‘early publicity’ is needed for funding, capital raising and professional kudos, but not too helpful for the public who then think that an immediate cure might be just around the corner,” he said.

“The public is so jaded by cancer research media attention at the moment that they just do not believe ‘breakthroughs’ are occurring any more. And let’s face it, rather embarrassingly, most claimed ‘breakthroughs’ are not proving to significantly advance cancer therapies.”