Breast Cancer Drug Offers New Hope Breakthrough: Breast cancer researchers Delphine Merino, Francois Vaillant, Geoff Lindeman and Jane Visvader. Anti-cancer drugs in clinical trials for some types of leukaemia could prove effective in treating the most common type of breast cancer, according to Australian researchers. A team from the Walter and Eliza Hall Institute have found that a drug known as BH3-mimetics, when combined with another breast cancer drug called tamoxifen, effectively treats some types of breast cancers. Known as aggressive oestrogen receptor-positive, or ER-positive, they represent about 70 per cent of breast cancers. Medical oncologist Geoff Lindeman, the joint head of Walter and Eliza Hall's breast cancer laboratory, said that in animal trials the drug combination had either delayed tumour growth or resulted in the tumour disappearing. "For breast cancer it looks as though you need to have the two working together," he said. The drug by itself does not appear effective, but certainly with the conventional breast cancer drug tamoxifen it changes things significantly. The researchers used tumour samples taken from breast cancer patients and implanted them in mice whose immune system was unable to reject the tissue. The mice were then treated with the drug combination. "This meant the responses that we saw were in real human breast cancers," he said. We're all very excited by this. Professor Lindeman said the findings also had potential implications for other types of tumour-based cancers. The common thread between these breast cancer types and some types of leukaemia is the molecule BCL-2. This molecule, which is expressed in up to 85 per cent of ER-positive breast cancers, serves as a kind of lifeline for cancer tumours. "BCL-2 can make tumours more resistant to chemotherapy," Professor Lindeman said. So in a sense we have turned this lifeline into an Achilles heel because we're able to switch off the survival pathways of this specific molecule. Professor Lindeman said this made cancer cells less likely to survive treatment, when combined with the breast cancer drug tamoxifen. Improved targeting of treatments, as opposed to the "one size fits all" approach of chemotherapy, also has the potential to reduce side effects in patients. The work, by a research team including Jane Visvader, Francois Vaillant and Delphine Merino, is published in the journal Cancer Cell on Tuesday. Human clinical trials could begin within a few years, Professor Lindeman said.