Antibodies and antigen binding fragments that specifically bind to clusterin are described. In some embodiments, the antibodies block the biological activity of clusterin and are useful in composition in certain cancers, more particularly in cancers, such as endometrial carcinoma, breast carcinoma, hepatocellular carcinoma, prostate carcinoma, a renal cell carcinoma, ovarian carcinoma, pancreatic carcinoma, and colorectal carcinoma. The invention also relates to cells expressing the humanized or hybrid antibodies. Additionally, methods of detecting and treating cancer using the antibodies and fragments are also disclosed.