Breast cancer drug shown to accelerate tumour growth in lab tests

A certain type of breast cancer drug may actually be causing cancer cell growth to accelerate under some circumstances, according to new research.

Scientists from the UK's Francis Crick Institute, King's College London and Barts Cancer Institute at the Queen Mary University of London have discovered that the breast cancer drug lapatinib - which is designed to shrink tumours - can sometimes cause them to grow under laboratory conditions.

This is a result of the effect lapatinib has on HER2, a protein that encourages cell growth and is often found in elevated amounts among breast cancer patients. The drug is supposed to switch this protein off, but sometimes it can cause HER2 to partner with another protein, HER3, resulting in greater tumour growth than would have occurred without the drug.

Lapatinib has been successfully used in combination with other therapies to treat advanced breast cancer, but has failed clinical trials as a standalone treatment. These findings may explain why, and could suggest this drug may not be suitable for all women.

Study leader Dr Jeroen Claus, from the Francis Crick Institute, said: "If certain breast cancer drugs can cause cancer cells to grow more rapidly in particular circumstances in the lab, we need to evaluate carefully if that might happen in subsets of patients as well."ADNFCR-2094-ID-801846509-ADNFCR