Structure/Function Characterization of S100B Inhibitors at Sites 2/3 within Malignant Melanoma

S100B is not merely a prognostic indicator within Malignant Melanoma (MM), but it promotes the degradation of p53 through a calcium‐dependent protein‐protein interaction. It is also now known that small molecule inhibitors of S100B (known as SBiXs) and RNA interference of S100B expression restore both p53 protein levels and normal transcriptional activation/apoptosis activities in MM, which typically has wild‐type p53. For these reasons, we aim to specifically inhibit the S100B‐p53 interaction as a potential therapy for MM. Our efforts at probing the binding surface of S100B revealed three persistent binding sites (Sites 1, 2, and 3), and efforts to discover/synthesize SBiXs which simultaneously bind all three sites are underway. Using a combination of structural biology techniques (X‐ray crystallography and NMR), in vitro binding, and cellular assays, the structure/function characterization of SBiXs binding Sites 2 and 3 were investigated. The SBiXs, which exhibit dissociation constants ranging from 40 nM to 100 μM, are compared and their ability to be extended into Site 1 are discussed. Such inhibitors may also have therapeutic value as early stage lead compounds for treating other cancers such as astrocytoma, renal tumors, and some forms of leukemia that also have elevated S100B.