The invention provides for the production of several humanized murine antibodies specific for the 
antigen LK26, which is recognized by the 
murine antibody LK26. This 
antigen is expressed in all choriocarcinoma, teratocarcinoma and renal 
cancer cell lines whereas it is not expressed on 
cell lines of leukaemias, lymphomas, neuroectodermally-derived and epithelial tumour 
cell lines (excepting a small subset of epithelial cell lines). Furthermore, whereas renal 
cancer cell lines express the LK26 
antigen, normal renal epithelial cells do not. Similarly, with the exception of the 
trophoblast, all normal adult and fetal tissues tested are negative for the LK26 
phenotype. The invention also provides for numerous 
polynucleotide encoding humanized LK26 specific antibodies, expression vectors for producing humanized LK26 specific antibodies, and host cells for the recombinant production of the humanized antibodies. The invention also provides methods for detecting cancerous cells (
in vitro and 
in vivo) using humanized LK26 specific antibodies. Additionally, the invention provides methods of treating 
cancer using LK26 specific antibodies.