Antibody validation rewrites the story of Estrogen Receptor beta
A new study by Cecilia Williams (KTH/ SciLifeLab) and colleagues uncovers that the notion of estrogen receptor beta playing a role in breast cancer is based on analyses with inadequate antibodies. The results show that other proteins are mistakenly identified as ERβ, which cannot even be detected in breast cancer tissue when using the only antibody with sufficient specificity.
The current paper, published this week in Nature Communications, sheds light on how using non-validated antibodies can lead a whole research field astray. The estrogen receptor is known to be responsible for the effects of the female hormone estrogen, and is also the target of the most successful breast cancer therapies to date (e.g. Tamoxifen). This receptor was the first and most important biomarker in breast cancer and can predict which patients respond to anti-estrogen treatment. However, almost half of tumors that express the estrogen receptor, do either not respond well to the treatment or develop resistance with time. When a second estrogen receptor, named ERbeta, was discovered 20 years ago this changed the paradigm of our understanding of estrogen signaling, and the new receptor was thought to be a very promising candidate for complementary breast cancer treatment.
Many groups have since studied this receptor in breast cancer, finding various levels of it, and various correlations to clinical parameters, however this has not led to any clinical advances. It has been thought that ERbeta has an opposite effect to that of the original receptor, now called ERalpha, and that ERbeta should not be blocked but instead activated in breast cancer, and that this would improve survival. Massive research has been performed and clinical trials recently initiated, in order to activate ERbeta in breast cancer patients. However, Williams and colleagues now show that other proteins are mistakenly identified as ERbeta by non-validated antibodies. After thorough antibody validations, they find that only one antibody is sufficiently specific. Using this one on breast cancer samples, the group do not find that ERbeta is expressed. To the identify the tissue-wide expression pattern of this receptor, they screen the full human tissue atlas and find expression in a limited number of normal tissues and cancers, including some reproductive and lymphoid organs and cancers.
“Our study contributes to improved reproducibility within research using biologics (antibodies), and clarifies earlier controversies within the field of estrogen and breast cancer, thus helping the field forward. In the end, we hope our study will help save both research funding and research time.” said Cecilia Williams.
Anna Asplund, who led major parts of the study within the scope of the Human Protein Atlas in Uppsala, emphasises that the present study is very timely:
“The significant problems due to poor validation of antibodies have recently been brought to the headlines by major journals, including Nature. We hope that our study, together with other on-going antibody validation efforts, will lead to a better quality of antibodies and antibody-based research.” she said.