John Stamos Says He’s ‘Proud’ of Dave Coulier Remaining ‘So Positive’ amid Cancer Diagnosis (Exclusive)

John Stamos is showing solidarity with his “optimistic” friend Dave Coulier amid the latter’s recent cancer diagnosis.

“I’ve never seen anybody with cancer that is so positive, so optimistic,” Stamos, 61, exclusively told PEOPLE during the Invisible Raptor premiere at Landmark Sunset Theater in Los Angeles on Wednesday, Dec. 4.

“I truly believe he’s going to make it through,” he says of his former Full House costar, adding that he “flew to see” Coulier, 65, “a couple of weeks ago.”

Stamos also revealed at the event that his longtime friend is helping other cancer patients.

“He’s really dedicated to helping people that are going through the same thing that he is,” the actor shares. “I’m proud of him for what he’s doing.”

Coulier revealed his stage 3 non-Hodgkin lymphoma diagnosis exclusively to PEOPLE on Nov. 13. He shared that an upper respiratory infection resulted in swelling of his lymph nodes, which led him to get tested.

“My doctors called me back and they said, ‘We wish we had better news for you, but you have non-Hodgkin’s lymphoma and it’s called B cell and it’s very aggressive,’ ” the actor said at the time.

“This has been a really fast roller-coaster ride of a journey,” he added of the diagnosis.

This was not the first time Stamos has shown support for Coulier. On Nov. 18, the former costars posted a joint carousel of images to Instagram of Stamos sporting a bald cap in solidarity with his friend.

“Nothing like throwing on a bald cap and flexing some Photoshop skills to show some love and solidarity with my bro @dcoulier,” the Fuller House star’s caption on the images began.

“You’re handling this with so much strength and positivity — it’s inspiring. I know you’re going to get through this, and I’m proud to stand with you every step of the way,” he added.

Stamos also addressed the negative backlash that the pictures received at Wednesday’s event, telling PEOPLE, “There’s a lot of anxiety in this world right now. And I think people are looking to fuel it wherever they can for that brief, shiny moment.”

“But come on … I honestly didn’t get it,” he adds of the negativity.

Just hours after Coulier’s cancer diagnosis was initially made public via his PEOPLE interview, Stamos posted a message to social media, promising his friend that he would “be by your side through it all.”