Breast cancer is the most dangerous for women.

Now a team at McGill University (Montreal, Canada) has discovered a potential drug for up to 40% of breast cancers. The chemical could block an enzyme that boosts the growth of tumors.

Tested on mice, the drug delayed the evolution of tumors sensitive to the drug Herceptin, but other breast cancer types, too, could be affected. The team focused on the enzyme PTP1B, which enhances cell division, boosting the tumor growth. Roughly 40% of human breast cancers are linked to extremely high levels of this enzyme.

The team used mice which were vulnerable to breast tumors due to an overactive HER-2 gene, the cause of breast cancer in about 25 % of the cases and it is a cancer type stopped by the drug called Herceptin.

The erasure of PTP1B in these mice caused a prolonged delay in the development of the tumors and impeded the secondary development of tumors in the lungs. Over-expression of PTP1B had been linked by many researches to diabetes and obesity, turning off the insulin receptors. Many drugs were made to shut off its action.

The team also gave to other mice a PTP1B-blocker, which was also found to delay the growth of breast tumors and impede lung cancer. The treatment lasted just two weeks, but the drug's health benefits acted for two months. As mice were HER-2 positive, combining Herceptin and a PTP1B-blocker could help many women.

"This study is very exciting for cancer patients. However it won't cure cancer alone. It's another tool to tackle cancers, perhaps particularly for HER-2 positive tumors. Combined with Herceptin, it may provide a 'two-way kill'." said lead researcher Professor Michael Tremblay.

"As other research had suggested a greater proportion of breast cancers had an over-expression of PTP1B than responded to Herceptin treatment, other women could also benefit." he added.

Other types of cancer, like bone marrow tumors, also display significantly increased PTP1B, so they too could benefit from the new potential treatment.

"Drugs that block PTP1B may be useful in treating the disease, but they will first need to be carefully tested in human clinical trials. Blocking PTP1B could boost the effects of existing drugs that work like Herceptin." said Ed Yong, of Cancer Research UK.