Nov 2 (Reuters) - U.S. stock indexes opened mixed on Tuesday as investors were cautious ahead of a Federal Reserve meeting where policymakers are expected to start scaling back bond purchases. The Dow Jones Industrial Average rose 21.27 points, or 0.06%, at the open to 35,935.11. The S&P 500 opened lower by 0.33 points, or 0.01%, at 4,613.34, while the Nasdaq Composite dropped 11.93 points, or 0.08%, to 15,583.99 at the opening bell. (Reporting by Devik Jain in Bengaluru; Editing by Maju Samuel)