A method of treating a tumor or enhancing survival of a subject having a tumor. The method includes (i) administering to a subject in need thereof an effective amount of a humanized monoclonal antibody or a fragment thereof, wherein the antibody or the fragment thereof has all complementarity determining regions of murine monoclonal antibody BAT (mBAT-1) and a framework region (FR) from an acceptor human immunoglobulin, or modified therefrom; and (ii) administering to the subject an effective amount of at least one chemotherapeutic agent selected from the group consisting of: 5-fluorouracil, cytarabine, oxaliplatin, paclitaxel and combinations thereof. The humanized antibody is administered between 1 and 30 days after commencing chemotherapy or substantially simultaneously or concurrently or according to an overlapping schedule with the at least one chemotherapeutic agent to thereby treat the tumor or enhance the survival of the subject having the tumor.