US STOCKS-Wall Street flat as growth concerns breed caution
* AstraZeneca rejects sweetened Pfizer offer
* AT&T to buy DirecTV for $48.5 billion
* Indexes: Dow off 0.05 pct, S&P up 0.11 pct, Nasdaq up 0.46 pct (Updates to market open, adds quote)
By Chuck Mikolajczak
NEW YORK, May 19 (Reuters) - U.S. stocks were little changed on Monday, on the heels of back-to-back weekly declines for the S&P 500, as investors exercised caution over valuations after a run of mixed economic data.
U.S.-listed shares of AstraZeneca slumped 9.6 percent to $72.60. The British drugmaker rejected a sweetened and "final" merger offer from Pfizer which would have created the world's largest pharmaceuticals group. Pfizer shares advanced 1.5 percent to $29.56.
AT&T lost 1.7 percent to $36.12 after the telecom company said it will acquire DirecTV for $48.5 billion, as it seeks fresh avenues of growth beyond the maturing U.S. cellular business. DirecTV shares lost $1.81 at $84.37.
Equities have come under pressure, with consecutive weekly declines for the first time since January, as investors have become leery about growth prospects. Last week, readings on retail sales and consumer sentiment fell shy of expectations while labor and housing data provided reason for optimism. Continuación...