Katie Couric is returning to the "Today Show" for the first time in two years -- and she, along with ABC anchor Charles Gibson and NBC anchor Brian Williams -- is announcing a groundbreaking, all-networks cancer research fundraiser scheduled for September. Couric holds the cause close to her heart - she lost both her husband and sister to cancer.

"Stand Up to Cancer" will include a slew of star appeals and musical appearances -- including breast cancer survivor Melissa Etheridge, who today broke the news that she would appear on the show. "I hope I'll be performing 'I Run for Life,' which is my cancer song," says Melissa.

Now "Extra" is backstage with the anchors, as Katie and Charles joke around with each other. "We can't stand each other," says Gibson, to which Couric replied, "That's not true, don't say that! They'll pick that up and it'll go everywhere -- don't you know how modern media works?"

Joking aside, producer Laura Ziskin promises an evening to remember. "Imagine that you can do a television show that you could save one life with," said Ziskin, adding, "We will save many lives."