The present invention provides in one aspect novel fusion partner cells that ectopically express one or more genes that alter the phenotype of a hybrid cell made from a fusion of the fusion partner cell and a fusion cell, hybrid cell lines produced using the fusion partner cells. The invention in another aspect provides antibodies produced by certain hybrid cell lines, and compositions containing one or a combination of such antibodies or antigen-binding fragments thereof. The invention also provides in another aspect methods of using the antibodies or antigen-binding fragments thereof for diagnosis and treatment of diseases characterized by the antigens specifically bound by the antibodies.