"Join me & @cityofhope in the fight against terminal diseases this summer. #BritneyArmy -- Let's do this! #summerofhope," Britney Spears tweeted on June 21.
The Summer of Hope campaign seeks to spread awareness of those suffering from terminal diseases, while City of Hope (ranked as one of "America's Best Hospitals" in cancer by U.S.News & World Report) is a leading research and treatment center for cancer, diabetes and other life-threatening diseases.
Rob Light, managing partner and head of music at uber agency CAA, heads up this unprecedented digital awareness campaign, which has already reached 328 million people on Twitter and Facebook.
Other participating artists include Selena Gomez, Adam Levine, Pitbull, David Guetta, PSY, One Direction, Rita Ora, Gavin Rossdale, Nicole Scherzinger and Jared Leto.