Investigating the molecular mechanisms of micrometastasis and tumour dormancy in pediatric sarcoma

Sarcomas are an aggressive type of childhood cancer arising from bone or soft tissue. Despite advances in cancer treatment, sarcomas remain a deadly disease because of their tendency to spread throughout the body (metastasis). Following cancer surgery to remove a malignancy, remnant sarcoma cells are often able to remain dormant in the body for months or years, in spite of efforts to eradicate them with chemotherapy. When such therapies are ineffective, these hibernating cells may revive and regrow as deadly metastases. Under laboratory conditions, cultured cancer cells are able to survive for long periods in the form of multi-cellular clusters called “”spheroids””. Interestingly, these spheroids also appear to enter a hibernation state, with cancer cells trading away their ability to grow rapidly in favour of the ability to survive for long periods. The cells use their “oncogenes” to suppress the expression of their growth-promoting genes, despite the fact that oncogenes are normally known for their cancer-promoting properties. It is believed that cancer cells and their oncogenes target a new set of genes to drive this hibernation. Tony Ng is screening all human genes for ones important in maintaining this hibernation. Using a technique called gene expression profiling, he will determine which genes become more active when cancer cells hibernate. He is also studying two genes, TXNIP and YB-1, which appear to be important for spheroid survival and dormancy. Laboratory results will be validated using clinical samples of dormant tumour cells from childhood cancers. Ng hopes that the genes identified in these studies will become the basis of chemotherapies to specifically kill these hibernating cells, resulting in therapies that are more effective and less toxic to patients.