U.S. stock indexes edged mostly lower in afternoon trading Monday, giving back some of the market's solid gains from last week. Investors eased into trading ahead of a highly anticipated meeting between the U.S. and China's leaders later this week. The world's two largest economies have been embroiled in a trade war that has taken the market on a volatile roller-coaster ride this year and Wall Street is hoping for a deal. Health care stocks led the losers as pharmaceutical giant Bristol-Myers Squibb and its buyout target Celgene stumbled. Consumer discretionary stocks and banks also helped pull the market lower.