A compound extracted from the Christmas berry primrose plant may help stop the growth a rare and aggressive eye cancer, a study claims. In half of cases, uveal melanoma (UM) metastasises to the liver. For these patients treatment options are scarce, according to the study published in the journal Molecular Cancer Research. "I'm very optimistic," said Jeffrey Benovic, a professor at the Thomas Jefferson University in the US. "If the results are confirmed in animal models and eventually humans, it could offer a new way to treat metastatic uveal melanoma patients down the road," Benovic said. UM is the most common eye cancer in adults. The cancer forms in melanocytes, the cells that make skin and hair pigment. Although the condition differs from melanoma of the skin, both cancers are lethal, researchers said. UM accounts for about five per cent of all melanoma cases. Surgery or radiation is the go-to treatment for patients with primary UM that has not spread to other parts of the body. However, metastasis occur in about half of cases. The cancer most often travels to the liver. Once the cancer has spread, patients often only have a year or so to live as no effective therapies yet exist. The researchers tested whether a compound derived from an ornamental plant in the primrose family known as Ardisia crenata, might be able to fight the disease. The compound, dubbed FR900359, or simply FR, was discovered 30 years ago from the plant's leaves. FR works by blocking a particular type of G protein that sits on a cell's membrane, called Gq - an important signalling molecule. However, a subset of these proteins are mutated in UM, turning on a molecular pathway that leads to cancer growth. Dominic Lapadula, a graduate student in Benovic's lab, grew three different types of UM cells that have the cancer-spurring mutations in the lab. Then he treated the cells with FR. "We didn't expect it would work because previous research suggested a related compound called YM-254890 did not inhibit the mutated forms of the proteins found in uveal melanoma," said Lapadula. "FR very effectively blocked the growth of the uveal melanoma cells," he said. When the UM cells were treated with small amounts of FR, the cells appeared to revert from cancer cells to typical melanocytes. "FR appears to be able to help reset the cells back to their normal state. Ideally that's what you want," Benovic said. Higher doses of FR killed the cells. The results suggest the compound could be an effective drug to treat UM one day, the researchers said. "I'm hopeful FR and related compounds will reset the cancer cells in the mouse model as it did in the cells we grew in the lab," Benovic said, "getting it one step closer to testing in humans."