(Updates prices, adds Boston Scientific)

NEW YORK, Sep 22 (Reuters) U.S. stock futures pointed to a second straight day of losses on Friday on concern about weakening economic growth after KB Home warned of tough conditions in the housing market.

Shares of KB Home, the fifth largest U.S. home builder, fell 4.1 percent in Europe after it said conditions in formerly strong markets weakened and the home-building market was unlikely to improve in the foreseeable future. For details, see ID:nN21395214.

That outlook added to worries about growth from the previous session when the Philadelphia Federal Reserve Bank's business index showed factory activity in the mid-Atlantic states unexpectedly shrank in September for the first time in more than three years.

''The last piece of economic information the market had was that Philly Fed number yesterday, so there's nothing out there to really turn around the mood in the market,'' said Paul Mendelsohn, chief investment strategist at Windham Financial Services in Charlotte, Vermont.

''We knew housing was weak here, but we didn't think manufacturing was going to fall off a cliff.'' Standard&Poor's 500 futures were down 2.8 points, barely above fair value, a mathematical formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract.

Dow Jones industrial average futures were down 16 points, and Nasdaq 100 futures were down 3.75 points.

Shares of Boston Scientific Corp. slid 8.3 percent to before the bell a day after the company issued preliminary sales and earnings below Wall Street expectations. Analysts at Prudential, Morgan Stanley and UBS cut their ratings on the company on Friday, according to MarketWatch and theflyonthewall.com. ID:nN21409340 Shares of Cablevision Systems Corp. slipped almost 1 percent in European trading after a regulatory filing revealed the cable operator awarded options to an executive after his 1999 death, backdating them so that they appeared to have been granted while he was still alive. ID:nN21208686 Shares of Dow component General Motors Corp. fell 1 percent in Europe after newspaper reports said two months of talks between the automaker, Renault and Nissan Motor had resulted in little progress toward a possible alliance. ID:nT275188 But on the upside, shares of Nike Inc. jumped 4.3 percent to .01 in early electronic trading after the world's No. 1 sport shoe and apparel maker, posted quarterly earnings above Wall Street targets.

REUTERS PKS HT1725