Seth Rogen's latest movie '50/50' was inspired by his friend's battle with cancer.

The actor wrote the screenplay for the film - which he stars in alongside Joseph Gordon-Levitt, Anjelica Huston, Anna Kendrick and Bryce Dallas Howard - after learning of Will Reiser's diagnosis.

Seth - who describes the motion picture as "art imitating life" - explained he "felt like crap" when he heard about Will's condition as "a bunch of us had been giving Will such a hard time about looking so lousy all the time.

"We had no idea he was sick, so when we found out it was really sh***y - but, of course, a lot sh***ier for him."

Will - who also had a hand in writing the screenplay - told the Chicago Sun Times: "It took a long time, but we got it done.

"Of course, there are things that I've fictionalized. For Example, my father does not have Alzheimer's [as does the dad of Gordon-Levitt, the character based on Will], but many of the scenes are very spot-on, including how hovering Anjelica's character is. My mom was just like that. I truly had to send her away."