US STOCKS-S&P 500, Dow end up after late rebound; Apple, Pfizer lift
(Updates close with jump in Agenus; adds Gogo's shares down after the bell)
* Pfizer works on next move in takeover bid for Astrazeneca
* Amazon.com leads Nasdaq's loss
* Bank of America drops after suspending dividend increase, buyback plan
* Dow up 0.5 pct; S&P 500 up 0.3 pct; Nasdaq down 0.03 pct
By Caroline Valetkevitch
NEW YORK, April 28 (Reuters) - The S&P 500 ended higher on Monday after a volatile session, as gains in Apple and Pfizer helped offset another round of selling in some high-growth tech shares.
The Dow also managed to end the session with a modest gain, while the Nasdaq closed slightly lower after rebounding from a fall of over 1 percent. Leading the Nasdaq down was Amazon.com , which extended Friday's sharp drop a day after its earnings report.
A flurry of merger and acquisition activity in the pharmaceutical sector increased speculation of further deal-making. Shares of Pfizer gained 4.2 percent to $32.04 after the U.S. drugmaker was said to be working on its next move in a potential bid to take over Britain's AstraZeneca Plc. Continuación...