Actor Irrfan Khan, who shared the screen with Deepika Padukone in "Piku", says Deepika is the biggest star and he is glad Amitabh Bachchan thinks the same.Recently, Amitabh Bachchan said that people watched "Piku" only because of Deepika Padukone. Irrfan, asked for his reaction on the same, said: "I don39t want to react on that. If he is saying so then there is some truth to it. Deepika is the biggest star and she was the diamond in the whole montage of actors and I am glad he acknowledged Deepika39s work."Meanwhile, Irrfan is busy promoting his film "Madaari" and he says the definition of commercial cinema should be broadened.He says, "We are trying to redefine commercial cinema and commercial cinema39s definition should be broadened."Miraj Entertainment and Bharat Shah in association with EaseMyTrip.com are presenting "Madaari", a Paramhans Creations production. The film is directed by Nishikant Kamat and is all set to release on July 15.