An objective of the present invention is to provide antibodies that bind to Prominin-1 and have ADCC activity and/or CDC activity, and pharmaceutical compositions containing those antibodies as an active ingredient. To achieve a solution to the above-mentioned objective, the present inventors produced recombinant antibodies by cloning a nucleotide sequence of the AC133 antibody variable region, discovered that the ADCC/CDC-inducing effect which does not exist in the original AC133 antibody is imparted to the recombinant antibodies, and thereby completed the present invention. In the human chimeric antibody/human effector cell combination, the chimeric antibody whose constant region sequence had been converted to human IgG1/º was found to induce strong ADCC. Furthermore, the present inventors produced humanized antibodies prepared by grafting the AC133 antibody CDRs to a human antibody sequence, and further produced humanized antibodies having binding activities equivalent to the activity of the chimeric antibody by introducing amino acid substitutions into the humanized L chain sequence. The present invention provides unlabeled AC 133 human chimeric antibodies and humanized antibodies having antitumor effects.
