MGM Resorts shares rally after BetMGM venture's raised outlook

** Shares in casino operator MGM Resorts MGM.N rise 8% on Monday, for the stock's biggest one-day percentage gain since early April after BetMGM, its U.S. sports-betting joint venture with Entain ENT.L raised its annual revenue and core earnings forecast

** The forecast pushed London-traded Entain shares up 15.3%

** MGM, which hit its highest level since mid-May, last traded at $34.27. The stock was the biggest gainer in the S&P 500 consumer discretionary index .SPLRCD, which was last up 1.2% on the day