June 9 (Reuters) - U.S. stock indexes opened slightly higher on Wednesday, although a lack of clear catalysts kept trading slow, with investors awaiting fresh cues from inflation data this week and an upcoming Federal Reserve meeting. The Dow Jones Industrial Average rose 26.3 points, or 0.08%, at the open to 34626.16. The S&P 500 rose 5.7 points, or 0.14%, at the open to 4232.99, while the Nasdaq Composite rose 55.3 points, or 0.40%, to 13980.231 at the opening bell. (Reporting by Shashank Nayar in Bengaluru; Editing by Maju Samuel) Our Standards: The Thomson Reuters Trust Principles.