US STOCKS-Wall St dips with S&P 500's record high in sight
* Isis shares jump on drug results; Biogen up
* G Asset Management offers to buy stake in Barnes & Noble or Nook
* Groupon shares drop after company forecasts loss
* U.S. home resales fall to 18-month low in January
* Dow off 0.2 pct; S&P 500 down 0.2 pct; Nasdaq off 0.1 pct
By Rodrigo Campos
NEW YORK, Feb 21 (Reuters) - U.S. stocks slipped on Friday on options-related trading, with the S&P 500 facing resistance as it flirts with its record high even as economic data continues to underwhelm.
Shares declined late in the session due in part to trades related to options expiration, according to market participants.
U.S. home resales, also known as existing home sales, fell more than expected in January and hit an 18 month-low as the combination of cold weather and a lack of housing stock sidelined potential buyers. Continuación...