The investment company owned by Kirk Kerkorian, who died last year, has begun to sell its stake in MGM Resorts International, under the terms of Kerkorian’s will. The company, called Tracinda Corp, will sell an initial 20 million shares for about $500 million to reduce its stake in MGM Resorts, according to a filing with the U.S. Securities and Exchange Commission on Monday. Tracinda Corp held a total of about 91 million shares, equivalent to a 16 percent stake, in MGM Resorts according to a filing last June. MGM Resorts last month said it would buy out Boyd Gaming’s stake in Atlantic City’s Bogata and take sole ownership of the city’s outperforming casino.