Dow Jones Industrial Average Tumbles Nearly 300 Points With American Express Company (AXP) Dropping 4%

U.S. stocks closed sharply lower Friday, with the Dow Jones Industrial Average tumbling as much as 357 points in afternoon trading Friday, amid jitters over Greece's debt crisis and concerns over regulations in China. Investors also weighed the strengthening dollar's drag on corporate profits during earnings season. All sectors were negative Friday, with financials, energy and technology among the biggest laggards.