Film stars John Cusack and Joan Cusack were among the attendees at "Roger Ebert: A Celebration of Life," a memorial held at the Chicago Theatre.

The brother-and-sister actors, who are from Evanston, Ill., took part in Thursday's event alongside Ebert's wife Chaz, independent filmmakers Gregory Nava and Julie Dash, director Andrew Davis, Sony Pictures Classics co-president Michael Barker, activist and comic Dick Gregory, and film critics Todd McCarthy and Scott Foundas, The Hollywood Reporter said.

"Roger Ebert is probably the most influential film critic in the world," Barker said. "He was a poet of the people."

"He reeked of integrity," John Cusack said.

The memorial also featured performances by the chorus Soul Children of Chicago, The Hollywood Reporter said.

Ebert, 70, was a Pulitzer Prize-winning movie reviewer who began writing for the Chicago Sun-Times in 1967. He later gained national celebrity status as the host of the TV programs "Coming Soon to a Theater Near You," "Sneak Previews," "At the Movies," "Siskel & Ebert & The Movies" and "Ebert & Roeper."

It was during his television career that he began the trademark thumbs-up or thumbs-down signs used to recommend or pan thousands of movies.

Ebert slowed down during a battle with thyroid cancer, which began in 2002. Although he had been unable to speak or eat solid foods since 2006, due to complications from the disease and reconstructive surgeries, he kept writing right up to his death last week.