An object of the present invention is to prepare an
antibody that targets CAPRIN-1 specifically expressed on the surface of
cancer cells and is superior in
antitumor activity to conventional antibodies and to provide use of the
antibody as a therapeutic and / or preventive agent for
cancer. The present invention provides use of an
antibody targeting an identified
cancer antigenic protein specifically expressed on the surface of cancer cells as a therapeutic and / or preventive agent for cancer, specifically, a pharmaceutical composition for treatment and / or prevention of cancer, comprising as an
active ingredient an antibody or a fragment thereof which has immunological reactivity with a CAPRIN-1
protein, the antibody or the fragment thereof comprising a
heavy chain variable region comprising
amino acid sequences represented by SEQ ID NOs: 5, 6, and 7 and a light chain variable region comprising
amino acid sequences represented by SEQ ID NOs: 9, 10, and 11.