Stem cell mutation triggers fibroid tumours

Researchers have for the first time identified the molecular cause of fibroid uterine tumours, which affect millions of women causing irregular bleeding, anemia, pain and infertility. Despite the high prevalence of the tumours, which occur in 60 percent of women by age 45, the molecular trigger has been unknown. Now, a new North-western Medicine preclinical research has identified a single stem cell that develops a mutation, starts to grow uncontrollably and activates other cells to join its frenzied expansion, as the key player of the disease. “It loses its way and goes wild,” said Serdar Bulun, MD, the chair of obstetrics and gynaecology at North-western University Feinberg School of Medicine and North-western Memorial Hospital. “No one knew how these came about before. The stem cells make up only 1 and a half percent of the cells in the tumour, yet they are the essential drivers of its growth,” he explained. The stem cell initiating the tumour carries a mutation called MED12. Recently, mutations in the MED12 gene have been reported in the majority of uterine fibroid tissues. Once the mutation kicks off the abnormal expansion, the tumours grow in response to steroid hormones, particularly progesterone. For the study, researchers examined the behaviour of human fibroid stem cells when grafted into a mouse, a novel model initiated by North-western scientist Takeshi Kurita, a research associate professor of obstetrics and gynaecology. The most important characteristic of fibroid stem cells is their ability to generate tumours. Tumours originating from the fibroid stem cell population grew 10 times larger compared to tumours initiated with the main cell population, suggesting a key role of these tumour stem cells is to initiate and sustain tumour growth. “Understanding how this mutation directs the tumour growth gives us a new direction to develop therapies,” said Bulun, also the George H. Gardner Professor of Clinical Gynaecology.