The top oncologist at the center of disgraced Assembly Speaker Sheldon Silver’s corruption case has been given the boot from his job as head of a non-profit research center. Dr. Robert Taub, until Friday the director of the Columbia University Mesothelioma Center, got $500,000 in state funding for the center in exchange for funneling sick patients to the Silver-affiliated law firm Weitz & Luxenberg, which in turn gave the allegedly crooked pol $3 million in referral fees, prosecutors said.