* J.C. Penney jumps after Citi upgrade
* Copper prices fall to lowest since July 2010
* Indexes off: Dow 0.29 pct, S&P 0.32 pct, Nasdaq 0.26 pct
NEW YORK, March 11 (Reuters) - U.S. stocks fell in afternoon trading on Tuesday after swinging between gains and losses for most of the session as the lack of major corporate earnings or market-affecting data kept trading directionless.
U.S. wholesale inventories rose more than expected in January, as companies built up stocks of autos and machinery, but sales posted their largest decline in nearly five years.
Retailers in the news included American Eagle and Urban Outfitters, their shares down sharply after disappointing outlooks.
"When you get a slow data week, markets tend to get a little jittery and slow," said Quincy Krosby, market strategist at Prudential Financial in Newark, New Jersey. "The market has been up very quickly and is sort of waiting for a next catalyst."
The Dow Jones industrial average fell 46.93 points or 0.29 percent, to 16,371.75, the S&P 500 lost 6.04 points or 0.32 percent, to 1,871.13 and the Nasdaq Composite dropped 11.349 points or 0.26 percent, to 4,323.099.
Urban Outfitters dropped 5 percent to $35.65 after it reported lower-than-expected quarterly sales and said it was "very cautious" on its current quarter. American Eagle Outfitters slumped 6.4 percent to $13.30 after it forecast earnings for the current quarter that were short of expectations.
The S&P retail index slipped 0.4 percent.
Dick's Sporting Goods Inc advanced 4.6 percent to $56.84 after the company posted fourth-quarter earnings and gave its first-quarter outlook.
Copper prices on the London Metal Exchange hit their lowest level since July 2010 under pressure from rising inventories of the metal and slow demand. Freeport-McMoRan Copper & Gold fell 1 percent, bringing the decline in the past four sessions to 8.4 percent.
Myriad Genetics Inc lost 8.7 percent to $34.46. The diagnostics company said a U.S. court denied a motion that would have stopped rival Ambry Genetics Corp from selling a similar version of Myriad's cancer test.
Men's Wearhouse said it would acquire rival Jos. A. Bank Clothiers for about $1.8 billion, ending a five-month saga that started with Jos. A. Bank offering to buy its larger menswear rival. Men's Wearhouse shares rose 5.4 percent to $57.56 and Jos. A. Bank added 4 percent to $64.31.
"M&A activity has been picking up, and it tends to offer a halo effect on sectors and subsectors involved," said Krosby, pointing to a broad support to the market coming from mergers and acquisitions lately.
J.C. Penney Co Inc jumped 5.8 percent to $8.91 after Citigroup raised the stock to a "buy" and boosted its price target to $11 per share.
Boyd Gaming Corp jumped 16 percent to $13.69 a day after hedge fund Elliott International disclosed a 4.99 percent stake in the gaming company.
La Jolla Pharmaceutical Co surged 66.5 percent to $18.15 after the company said its lead experimental drug to treat chronic kidney disease met the main goal of improving kidney function in a mid-stage study.