NEW YORK ( TheStreet) -- Stocks turned negative on Thursday, after posting gains earlier in the session. Health care stocks surged on the heels of a Supreme Court ruling, while shares of Humana (HUM) jumped after reports surfaced that Aetna (AET) was close to acquiring the health care giant.

The S&P 500 lost 0.20%, the Dow Jones Industrial Average fell 0.31%, and the Nasdaq gave up 0.23%.

Bloomberg reported Aetna was closing in on an acquisition of Humana and could reach a deal as early as this weekend. Humana shares rose almost 7% after being halted earlier for volatility.

Meanwhile, health care stocks such as Aetna and UnitedHealth (UNH) gained following the 6-3 Supreme Court ruling that determined subsidies should be available in states where health care exchanges weren't created. Hospital operators also rose sharply; HCA (HCA) jumped 8%, while Tenet Healthcare (THC) rose almost 13%, making it the best-performing stock in the S&P 500. Community Health (CYH) added 12%.

"Health care is no longer a defensive sector, it's a growth sector," Mary Ann Bartels, chief investment officer of portfolio solutions at Merrill Lynch Wealth Management, told TheStreet TV. "We have 10,000 baby boomers turning 65 who will need health care going into retirement. [The Supreme Court ruling] is another positive point for the health care sector."

Crude oil slipped below $60 a barrel, falling more than 0.9% to $59.74.

Greek's leaders and the country's creditors met in Brussels on Thursday. After a three-hour meeting, no deal was reached, according to The Guardian. Greece's latest debt payment is due to the International Monetary Fund on June 30. Greece is reluctant to agree to austerity measures.

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