WASHINGTON (Reuters) - A drug used to treat bone marrow cancer may also help treat osteoporosis by stimulating stem cells, U.S. researchers reported on Friday. They found that Velcade, made by Millennium Pharmaceuticals Inc to treat multiple myeloma, activated stem cells that differentiate into bone. Tests in mice showed it apparently helps regenerate bone tissue and be may be a potential treatment for osteoporosis, a team at Massachusetts General Hospital and the Harvard Stem Cell Institute reported in the Journal of Clinical Investigation.