Keyhole limpet hemocyanin (KLH) is a large, multi subunit and oxygen-carrying metalloprotein which can provide T-cell help required for antibody production. KLH is used in a variety of cancer vaccines which contain non-Hodgkins lymphoma, cutaneous melanoma, breast and bladder cancer. In these vaccines, the specific tumor-associated antigens conjugated to KLH to stimulate anti-tumor immune responses which can destroy tumor cells. The potential in therapeutic vaccines for cancer and the documented efficacy of KLH as a superior carrier protein for cancer vaccines are creating a significant biopharmaceutical market for KLH formulations.