"I love Luke and I just wanted to show up and make sure that he understood that I love him and know that if there's anything I can do for him and his wife, sign me up," Cook toldPeople in a Wednesday report.
"Luke, Michael Johns, Jason Yeager and myself, we kind of buddied up one day at Hollywood week," Cook told People. "We called ourselves the four horsemen. Any time one of your own is going through something as horrible as that, it makes everything else seem a little bit insignificant."
Cook is familiar with supporting a loved one with cancer -- as his older brother Adam has been battling brain cancer for 10 years.
"Cancer is a very big part of my existence," Cook told People. "I'm excited to be put in [the spotlight] where I can hopefully do something to help other people."