Gene profiling to try and unlock the causes of breast cancer

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Gene profiling to try and unlock the causes of breast cancer in New Zealand

New research from the University of Auckland has found gene expression profiles, which are a sensitive measure of underlying tumour biology, showed no clear difference between breast tumours from New Zealand patients and those from patients overseas.

This suggests that other factors may contribute to the high and increasing breast cancer incidence in New Zealand compared to international populations, and more research needs to be done into our high rates of breast cancer, particularly the poor breast cancer survival of New Zealand Māori women.

The study, Gene expression profiling of breast tumours from New Zealand patients, was led by Dr Anita Muthukaruppan, Dr Annette Lasham, Professor Cris Print and Professor Andrew Shelling, of the University’s Faculty of Medical and Health Sciences and published in the New Zealand Medical Journal.

It is the first that analyses the gene expression of breast tumours from New Zealand women and also included academics from the University of Otago.

Breast cancer is the most common cancer among women and is the leading cause of cancer death in women worldwide. It is a cancer that can be caused by a multitude of factors, which can differ substantially between patients. There are different genetic, endocrinological, environmental and lifestyle factors involved in the development of breast cancer. New Zealand has one of the highest breast cancer incidences in the world, with approximately 92 cases per 100,000 people.

There has been a steady increase in breast cancer cases from 1978-2004, most likely due to improved rates of breast cancer screening. Although breast cancer mortality rates in New Zealand have declined over the last 20 years, breast cancer remains a significant cause of cancer mortality in New Zealand women, killing about 20 women per 100,000, more than in Australia, despite the similarity in health care systems between the two countries.

The study collected breast tumour samples from 106 female breast cancer patients, 47 female patients in Auckland and 59 from Christchurch.

The expression of approximately 30,000 genes in the tumours were analysed on a gene expression microarray chip, a laboratory tool used to detect the expression of thousands of genes at the same time.

The study has resulted in a robust gene expression dataset from 106 breast tumours from New Zealand women.

The study compared the gene expression profiles of New Zealand breast tumours with those from women recruited in similar large studies from Sweden, Singapore, France and the UK.

Overall analysis has showed that there were no significant biological differences between breast tumours from New Zealand patients and those from patients overseas.

Professor Shelling says numerous studies published on breast cancer specific to the population of New Zealand have been mainly directed at the epidemiology, health system inequalities, and the identification of various lifestyle factors, ethnic and socio-economic associations for breast cancer risk in New Zealand women. There are a limited number of studies that have attempted to elucidate the biology behind the pathogenesis of breast cancer specific to New Zealand, and have mostly utilised clinico-pathological parameters, survival data and other relevant, available retrospective breast cancer patient data.

“It would appear from this study that the higher rates of breast cancer in New Zealand women are not due to any obvious underlying biology,” Professor Shelling says.

The small number of studies that have attempted to investigate any differences in breast cancer biology between the various ethnic populations such as between New Zealand Māori and New Zealand European women have been contradictory and inconclusive;
albeit with small patient numbers for robust investigation.

“In the future, carefully designed and adequately powered genomic studies, using census-compatible ethnicity data may be able to exclude or confirm whether there are indeed biological factors associated with poor breast cancer survival of New Zealand Māori women,” Professor Shelling says.

The research was funded by Breast Cancer Cure, New Zealand with the support of the Cancer Society of New Zealand.

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