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Novel genetic approaches to study breast cancer

Final Activity Report Summary - NOVEL BREAST CANCER (Novel genetic approaches to study breast cancer)

Cancer care will be revolutionised over the next decade by the introduction of novel therapeutics that target the underlying molecular mechanisms of the disease. With the advent of human genetics, a plethora of genes have been correlated with human diseases such as cancer the SNP maps. Since the sequences are now available, the next big challenge is to determine the function of these genes in the context of the entire organism. Genetic animal models have proven to be extremely valuable to elucidate the essential functions of genes in normal physiology and the pathogenesis of disease. Using gene-targeted mice our group has previously identified RANKL as a master gene of bone loss in arthritis, osteoporosis, and cancer cell migration and metastases (Nature, 1999; Nature 1999b; Cell 2000; Nature 2006) and genes that control heart and kidney function (Nature 2002; Cell 2002; Nature 2006); wound healing (Nature 2006); diabetes (Cell 2007); or lung injury (Nature 2005; Nature Med. 2005; Cell 2008). Based on impact factors, his laboratory has been ranked as one of the 10 best laboratories in the world. After 13 years in North America, the European Union Excellence has allowed Prof. Penninger and his group to accept an offer to come to Vienna to continue his work at IMBA, a new Centre of Excellence founded by the Austrian Academy of Sciences.

A primary goal was to generate a platform for the development and application of functional genomics in order to understand the pathogenesis of malignancies and to provide new animals models to test and develop novel therapies. These animal models are invaluable to identify the function of such genes in the whole organism and to test whether and how these genes cause cell transformation, invasion, and cancer metastases. Moreover, his group developed novel high throughput and innovative gene targeting strategies directly linked and integrated with state-of-the art technologies in fly genetics, that is, the use of whole genome tissue-specific in vivo RNAi Drosophila libraries to identify essential and novel pathways for cancer pathogenesis. Identification of new cancer disease genes will allow us to design novel strategies for cancer treatment and the creation of European-based biotechnology companies. The knowledge gained from these studies should ultimately impact on the basic understanding of cancer and human health in the future.

With the support of the European Union Excellence grant Josef Penninger's group has now performed a whole genome systems genetics screen in Drosophila to identify novel cancer genes, they developed new gene targeting strategies using novel ES cells and injection technologies and finally they generated multiple novel mouse models to study cancer in a complex system in vivo. For instance, we have been shown that the key osteoclast differentiation system RANKL-RANK appears to be a key soil factor for metastases of epithelial tumours into bones (Nature, 2006). Based on the basic physiology and the phenotypes of mutant mice, RANKL-RANK might be also novel targets that relay hormone stimulation to transformation and breast cancer. Our experiments are designed to provide definitive proof whether RANKL-RANK play a direct and cell autonomous role in breast cancer formation. Based on this, clinical trials are underway whether RANKL inhibition might allow reduction of metastases in breast and prostate cancer. Surprisingly, we also found an entirely novel function for RANKL-RANK, i.e. the system controls inflammation induced fever in the brain (Nature, 2009). His group has also identified novel key cancer genes termed HACE1. HACE1 mutant mice develop multiple tumours including breast cancer and our data suggest that HACE1 is downregulated in ~ 50 % of primary human cancer. Thus, HACE1 is a novel tumour suppressor gene and a strong candidate gene for the previously described 6q21 tumour suppressor locus (Nature Medicine, 2007).

Most human disease genes identified have been shown to have conserved orthologues in Drosophila. We developed a high throughput assay for tumour invasion and metastases in Drosophila. Using this assay, we screened 10 777 transgenic RNAi lines corresponding to 6 566 genes which show a significant degree of conservation with human genes for their role in Ras1V12 triggered tumour development. Based on our initial in vivo Drosophila screen we have identified 46 candidate target genes of cancer growth and cancer metastases. Data on one of these novel hits called TSPAN6 showed that TSPAN6 expression in the primary mammary gland tumour correlates with lung metastases at high significance suggesting that TSPAN6 constitutes a novel 'candidate lung metastasis gene'. Thus, we have identified multiple novel cancer genes in our fly screen that appear to have direct relevance for human cancer biology and metastases.