Also scheduled to take part in the telethon are Matt Damon, Michael Douglas, Jessica Biel, Jeremy Renner, Seth Rogen, Emma Stone, Simon Baker, Jordana Brewster, Diem Brown, Dana Delany, Chelsea Handler, Marg Helgenberger, Rashida Jones, Minka Kelly, Joe Manganiello, Jillian Michaels, Masi Oka, Ana Maria Polo, Alison Sweeney and SU2C co-founder Katie Couric.
Performers include Taylor Swift, Coldplay, Alicia Keys and Tim McGraw.
"I'm honored to be working with such talented artists who are lending their voice to SU2C's mission," said Gallen in a statement. "As we continue to plan the 2012 show, there's a hopeful energy building that the groundbreaking research we help fund will make an enormous impact in the fight against cancer."
The telethon will be broadcast on ABC, CBS, FOX and NBC as well as BIO, E!, ENCORE, HBO, HBO Latino, ION Television, LMN (Lifetime Movie Network), Logo, MLB Network, mun2, Palladia, SHOWTIME, Smithsonian Channel, STARZ, STYLE, TBS and VH1.
For more information, visit StandUp2Cancer.org.