US movie studio MGM Holdings is exploring a sale, a person familiar with the matter told Reuters on Monday. The movie studio behind the James Bond franchise has tapped investment banks Morgan Stanley and LionTree LLC and started a formal sale process, the source said, asking not to be identified. The company has a market value of around 5.5 billion dollars, based on privately traded shares and including debt, the source added. The development was reported earlier by the Wall Street Journal. MGM Holdings said it had no comment.