PROJECT SUMMARY/ABSTRACT SEER data indicate that multiple myeloma is a major health problem. There are approximately 54,000 myeloma patients in the USA, 20,000 new patients will be diagnosed with myeloma in 2007, and nearly 11,000 patients succumb to their disease yearly. The cure rate and 10-year survival remains low indicating the need for new therapies. We have shown that chemo-resistant myeloma can be killed by killer-cell immunoglobulin- like receptor (KIR) ligand (-L) mismatched NK cells from a haplo-identical donor in vitro and in a clinical trial. However, we could find a KIR-L mismatched donor for only 30% of patients. We propose to use a 3-pronged approach to: a) apply NK cell therapy in the autologous setting making therapy possible for all patients and b) enhance the clinical efficacy of NK cells. We hypothesize that we can overcome the inhibition of autologous NK cells induced by HLA-class I on myeloma cells by activating and expanding the NK cells and by modulating the interaction between NK cell effectors and myeloma targets. In Specific Aim 1 we will determine if NK cell dose and potency can be reliably increased by expanding and activating NK cells from myeloma patients. Expansion of NK cells is important if we are to overcome the myeloma burden. Without expansion, there will be too few NK cells to eradicate all myeloma. `Supercharging' of the NK cells will overcome any inhibitory signals delivered by autologous myeloma. We will stimulate the NK cells with K562 cells transfected with membrane-bound IL15 and the co-stimulatory molecule 4-1BB-L. In Specific Aim 2 we will evaluate whether the action of activated autologous NK cells can be enhanced by flagging myeloma cells with a humanized antibody to CS1. CS1 is a CD2 receptor family molecule expressed by myeloma but not by normal tissues, therefore conferring myeloma-specific killing. This antibody will effectively `flag' myeloma cells for ADCC-mediated killing by NK cells. In Specific Aim 3 we will ascertain if the action of activated autologous NK cells can be increased by down regulating inhibitory ligands on myeloma by proteasome inhibition. NK cells do not normally kill autologous myeloma due to the interaction between HLA class I on myeloma cells with inhibitory receptors on NK cells. We have demonstrated that we can down regulate HLA-class I on myeloma in vitro and in vivo after treatment with the proteasome inhibitor bortezomib and that this translates into killing of myeloma by autologous NK cells. Hence, we will evaluate the existence of potential synergistic or additive effects when combining bortezomib with activated NK effectors. This clinical approach can be applied to patients with standard-risk myeloma to obtain even better growth control and more durable remissions once we have demonstrated the efficacy of enhanced NK cell therapy in patients with high-risk or relapsing myeloma. In addition, this research could lead to more efficacious treatment for other NK cell sensitive malignancies. PROJECT NARRATIVE Multiple myeloma is a form of bone marrow cancer that is currently incurable. There are approximately 54,000 myeloma patients in the USA. This grant proposal describes 3 new ways in which the patient's own immune cells can be used to destroy the cancer. Such treatment may also be useful to treat other cancers.