Shares of MGM Resorts International /zigman2/quotes/209932643/composite MGM -0.69% rose 4% in the extended session Wednesday after the hotel and casino operator said Chief Executive Jim Murren will step down before his contract expires. Murren will continue to serve as chairman and CEO until a successor is appointed, and MGM's board has formed a search committee. That committee is working with an executive search firm "to promptly identify and evaluate candidates" for the CEO role, the company said. Murren has led MGM since 2008. MGM shares rose 3% in the regular trading session.