WHO: Platinum-selling singer, songwriter and actor Jesse McCartney sold more than 1.5 million copies of his first album, “Beautiful Soul,” and most recently re-released his third album, “Departure: Recharged.” When he’s not recording and writing songs for Toni Braxton and Leighton Meester, McCartney can be seen or heard (previously and now) on the big and small screens in “All My Children” (’98-’99), “Law and Order: SVU” (2008) and as the voice of Theodore in “Alvin & the Chipmunks” and its upcoming “Squeakquel.”

WHAT: City of Hope, one of the nation’s leading research and treatment for cancer, diabetes and other life-threatening diseases. Designated as a Comprehensive Cancer Center, City of Hope’s research and treatment protocols advance care throughout the nation.

WHY: “Bob Cavallo (chairman of the Disney Music Group and) the head of Hollywood Records, which has been my record label for the last six years, introduced me to City of Hope. Once I had the chance to really study the center and all of the things that they do, especially with their pediatric programs, I became a little obsessed.” Besides frequenting the Duarte, Calif.-based center, McCartney recently took to the Nokia Theater stage with Miley Cyrus and Demi Lovato for the second annual Concert for Hope, raising funds for the center’s cancer research efforts.

WHAT’S NEXT: McCartney plans to continue fund-raising for City of Hope, which is in the final construction stages of a new facility, the Arnold and Mabel Beckman Center for Cancer Immunotherapeutics and Tumor Immunology, opening in early 2010.