US STOCKS-S&P 500, Dow futures drop on investor caution

* Doubts about recent market bounce surface

* Dow Chemical misses profit estimates

* Existing home sales, jobless claims on tap

* Ford posts wider-than-expected quarterly loss

By Ellis Mnyandu

NEW YORK, July 24 (Reuters) - The S&P 500 and Dow stock futures fell on Thursday as investors doubted stocks' recent bounce could be sustained and Dow Chemical (DOW.N: Quote, Profile, Research, Stock Buzz) said its profit missed Wall Street expectations, blaming higher energy prices.

Nasdaq stock futures were little changed, gaining some support from Amazon.com Inc (AMZN.O: Quote, Profile, Research, Stock Buzz) whose shares jumped nearly 7 percent before the bell a day after the Internet retailer beat Wall Street's profit forecasts.

Automaker Ford Motor Co (F.N: Quote, Profile, Research, Stock Buzz) posted a wider-than-expected quarterly loss amid declining sales of large pickup trucks and sport utility vehicles in North America. For details, see [ID:nN24301386].

U.S. stocks have been in rebound mode since the broader market made a new 2008 low about a week ago, driven mainly by a drop in oil prices and earnings from banks, beginning with Wells Fargo (WFC.N: Quote, Profile, Research, Stock Buzz) and including JPMorgan (JPM.N: Quote, Profile, Research, Stock Buzz), the third-largest U.S. bank.