4 MIN. DE LECTURA
* Oil prices fall for sixth day in a row
* Freeport, Caterpillar, DuPont drop
* McKesson, Celgene slump on weak profit forecasts
* Alcoa to kick off earnings season after close
* Indexes down: Dow 0.1 pct, S&P 0.36 pct, Nasdaq 0.63 pct (Updates to early afternoon)
By Abhiram Nandakumar
Jan 11 (Reuters) - Wall Street struggled for gains in volatile trading on Monday, weighed down by healthcare stocks and oil prices hitting fresh 12-year lows, ahead of the start of corporate earnings season.
The S&P energy sector down 2.23 percent, and materials sector, off 1.6 percent, faced the brunt of a near 6 percent slide in oil prices.
The health sector was down 1.38 percent, dragged down by Celgene and McKesson. The utilities sector's 0.65 percent gain led the four advancing S&P sectors.
U.S. stocks opened higher, coming off their worst-ever start to a year on mounting investor concerns about declining oil prices and a China-led slowdown in global growth.
Even strong December U.S. nonfarm payrolls data on Friday failed to boost investor optimism.
"None of us know what the future is, but given this moment, where we've gotten very conflicting data, it makes investors nervous," said Kim Forrest, senior equity research analyst at Fort Pitt Capital Group in Pittsburgh.
"I think the final coup de grâce is the Federal Reserve and its tightening phase has made them even more nervous."
At 12:43 p.m. ET (1743 GMT), the Dow Jones industrial average was down 16.43 points, or 0.1 percent, at 16,330.02.
The S&P 500 was down 6.85 points, or 0.36 percent, at 1,915.18 and the Nasdaq Composite index was down 29.17 points, or 0.63 percent, at 4,614.46.
Celgene fell 5.8 percent to $102.66 and McKesson dropped 9.9 percent to $164.38 after both companies gave disappointing profit forecasts.
Exxon and Chevron were both off nearly 2 percent on weak oil prices. Exxon was the biggest drag on the S&P.
Among materials stocks, Freeport-McMoRan tumbled 17 percent, while Caterpillar and DuPont were down nearly 3 percent, weighing the most on the Dow.
Alcoa, down 0.5 percent at $8.04, is scheduled to report fourth-quarter results after the close, unofficially starting the earnings season.
The aluminum producer's performance is regarded as a barometer of results from other materials and industrial companies.
Energy and materials companies are expected to be main drivers behind U.S. corporate earnings moving into a recession - two quarters of falling profits - in the fourth quarter.
Overall, quarterly corporate earnings are expected to decline 4.2 percent, according to Thomson Reuters I/B/E/S.
Apple was up 1 percent at $97.99 on reports that its music streaming service hit the 10 million-subscriber mark in six months. The stock gave the biggest boost to the S&P 500 and Nasdaq.
Macy's was up 4.7 percent at $37.57 after Starboard Value urged the company to enter into joint ventures for its stores.
Under Armour was down 8.3 percent to $68.74 after Morgan Stanley cut its rating and price target on the stock.
Declining issues outnumbered advancing ones on the NYSE by 2,011 to 965. On the Nasdaq, 1,741 issues fell and 980 rose.
The S&P 500 index showed one new 52-week high and 96 new lows, while the Nasdaq recorded 11 new highs and 329 lows. (Reporting by Abhiram Nandakumar in Bengaluru; Editing by Savio D'Souza)