Breast cancer affects 1 in 9 New Zealand women. Anti-estrogens such as tamoxifen have been used to treat estrogen receptor positive (ER+) breast cancer and reduce the annual death rate by approximately one-third. However, a significant proportion of patients fail to respond to these drugs. Currently, there are still no clear methods to distinguish tumours that will or will not respond to these drugs. We have identified a novel protein called SHON, which plays an important role in breast cancer. By immunohistochemistry, we have shown that SHON protein expression in breast tumours predicts a favourable response to anti-estrogen treatment. We will generate a SHON-specific antibody and use it to analyse independent sets of breast cancer samples at different hospitals to validate the utility of SHON as a prognostic biomarker for predicting patient response to anti-estrogen drugs, thus prompting effective treatments and ensuring survival from the disease.