Scanning electron micrograph of a cluster of
breast cancer cells showing visual evidence of
programmed cell death (apoptosis) in yellow.
Credit: Annie Cavanagh (cellimagelibrary.org)
Nowadays there are quite a few compounds in clinical trials to assay their potential as breast cancer treatments. Some of them are the so called “PARP inhibitors”. These inhibitors work very well in tumours that have a deficiency in DNA repair because PARP proteins are involved in that process. However, a group of researchers working on a different type of breast cancer without any problem in DNA repair has discovered that, unexpectedly, PARP inhibitors can kill the cells of this other type of breast cancer as well.
Breast cancer is not just “one” cancer. It can be the result of different mutations; therefore there will be different types of breast cancer. One of them is called “BRCA deficient tumour”. This tumour has a defect in BRCA proteins. These proteins are part of one of the DNA repair mechanisms, the Homologous Recombination (HR). Cancer cells with a deficient HR cannot repair their DNA properly leading to a higher genomic instability. This instability is an important survival factor for the tumour and DNA repair mechanisms are good targets for antitumor therapy.