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A gene found in abundance in 20% of breast cancers increases the number of stem cells suspected of fuelling a tumour’s growth and spread, according to a new study.
HER2 has been found to cause cancer stem cells to multiply and spread. Scientists say this explains why HER2 has been linked to a more aggressive type of breast cancer and to metastatic disease – where cancer has spread beyond the breast.
The study in the journal Oncogene showed that the drug Herceptin, which is used to treat HER2-positive breast cancer, was found to target and destroy the cancer stem cells.
Study author Dr Max S Wicha, from the University of Michigan Comprehensive Cancer Center, said: “This work suggests that the reason drugs that target HER2, such as Herceptin and Lapatanib, are so effective in breast cancer is that they target the cancer stem cell population. This finding provides further evidence for the cancer stem cell hypothesis.”
The cancer stem cell hypothesis says that tumours originate in a small number of cells, called cancer stem cells, and that these cells are responsible for fuelling a tumour’s growth. These cells represent fewer than 5% of the cells in a tumour.
In the current study, researchers found that breast cancer cells overexpressing the HER2 gene had four to five times more cancer stem cells, compared to HER2-negative cancers. In addition, the HER2-positive cells caused the cancer stem cells to invade surrounding tissue, suggesting that HER2 is driving the invasiveness and spread of cancer.
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