Kind-hearted singer Rihanna has launched an appeal for a bone marrow donor, after learning of a leukaemia-ridden New York mum-of-two's ongoing cancer battle. The Umbrella star has joined forces with DKMS - the world's largest non-profit marrow donor centre - to encourage people to help save the lives of others. And Rihanna was so moved by the desperate plight of Lisa Gershowitz Flynn, she's working tirelessly to locate a suitable donor before the ailing New Yorker loses her battle with the deadly disease. She tells, "When I heard about Lisa's plight, my heart broke. I said, 'I need to get the word out about Lisa right away.'" Rihanna, insists her own charity Believe - which helps out children with diseases like leukaemia - can work in conjunction with DKMS to ensure families aren't torn apart by the fatal illnesses. She adds, "My own charity, Believe, works specifically with children in need. Children need their mothers more than anything else in the world. Lisa has two children. My charity will continue to work with DKMS, because in finding a way to save Lisa's life, we will in turn be saving her children's lives." Flynn, who is the mother of a five-year-old son and three-year-old daughter, is overwhelmed by Rihanna's efforts in trying to find a donor match for her. She says, "For Rihanna to even be thinking about helping others and putting herself out there when she is so busy with her career is tremendous."