The London-based insurance brokerage Willis Group Holdings will make the name change official Thursday with a ceremony at the downtown Chicago skyscraper. Willis is leasing 140,000 square feet and moving 500 employees to the building.

The new name isn’t the only recent change at the tower.

Last month, owners announced a $350 million greening effort, along with plans for a 50-story luxury hotel. For tourists, glass-bottomed enclosed balconies on the 103rd floor were opened earlier this month.

Sears Roebuck and Co. was the original tenant before leaving in 1992. A real estate investment group now owns the 1,450-foot, 110-story skyscraper.